Developmental Psychology
1993, Vol. 29, No. 3.498-510
Copyright 1993 by Ihe American Psychological Association, Inc.
0O12-I649/93/J3.OO
Autistic Children's Difficulty With Mental Disengagement From an Object:
Its Implications for Theories of Autism
Claire Hughes and James Russell
Experiment 1 demonstrated that autistic Ss continue to fail a task originally designed as one of
strategic deception when there is no opponent present: They perseveratively indicate the target
object. We argue that this behavior is better explained in terms of failing to disengage from an
object than in terms of a theory-of-mind deficit. To ensure that their difficulties were not due to
failure to construe the task in a competitive manner, we ran a 2nd study, on detour reaching.
Compared with control Ss, the autistic Ss had great difficulty with the task. We discuss autistic
children's difficulties with these 2 tasks in the light of recent evidence that autism is associated with
failing executive tasks and argue that viewing the syndrome as an executive deficit has clear
advantages.
It has been proposed that childhood autism can best be characterized as a deviance or delay in the development of a theory
of mind, which is the ability to represent mental representations. This has been dubbed a deficit in metarepresentation
(Baron-Cohen, Leslie, & Frith, 1985; Leslie, 1987). In support
of this claim, researchers have demonstrated that, in comparison with matched clinical controls, autistic children and adolescents find tasks that demand an appreciation of how false beliefs determine action and judgment difficult to complete (e.g.,
Baron-Cohen, 1989b; Baron-Cohen et al., 1985; U. Frith, 1989;
Perner, Frith, Leslie, & Leekam, 1989). An understanding of
false belief is crucial to a mature conception of mentality, because beliefs possess the hallmark of all thinking, namely, that
of being "in the running for truth," capable of being either true
or false.
Entirely consistent with the metarepresentational deficit
view is the emerging evidence that autistic children find strategic deception difficult (Russell, Mauthner, Sharpe, & Tidswell,
1991; Sodian & Frith, 1992). If deception means attempting to
implant a false belief into the mind of another person, then it
must be the case that anybody who cannot understand what it is
to have a false belief will be incapable of deception.
The primary motivation of our first study was to question
whether such demonstrations of failures to deceive really provide evidence for the metarepresentational deficit view. In
brief, it is possible that, whatever difficulties autistic children
may or may not have with understanding false beliefs, they
could be failing deception tasks because of an inability to perform the behavioral strategy necessary for deception. This strategy involves disengaging attention from a focal object (normally
a desired object in a box) and behavioral reference (normally
pointing) to a place where there is no object—an analogue of
Woodruff and Premack's (1979) demonstration of deceptive behavior in the chimpanzee.
This skeptical point will be made in the context of the Russell et al. (1991) study of deceptive behavior in autistic, mentally
handicapped, and normal preschool subjects. Russell et al.
used a procedure called the windows task. In the initial phase of
the task, two opaque boxes were placed between the subject and
an opponent, with the experimenter sitting beside the subject.
The "players" closed their eyes as the experimenter placed some
chocolate inside one of the boxes. The subject's task was to tell
the opponent, by pointing, which of the two boxes he or she had
to open in order to find the chocolate. Each time the opponent
went to the baited box, he or she retained the chocolate, and
each time the opponent went to the empty box, the subject was
given the chocolate. In this manner, subjects inevitably discovered that it was in their interest for the opponent to be led to
look in the empty box, and thus in their interest to point to the
empty box. But because the boxes were opaque, the subjects did
not, of course, know which one was the empty box before they
pointed.
Claire Hughes (now at Groupe de Recherches de Genetique Epidemiologique, Paris, France) and James Russell, Department of Experimental Psychology, Cambridge University, Cambridge, United
Kingdom.
The experiments reported here were conducted by Claire Hughes in
partial fulfillment of the requirements for a doctoral degree in Cambridge University, supervised by James Russell.
We are very grateful to the staff and pupils of the following U.K.
schools for autistic children for their assistance: Broom Hayes, Devon;
Doucecroft, Essex; Hope Lodge, Southampton; Linden Bridge,
Surrey; Peterhouse, Southport; Portfield, Christchurch; Radlett
Lodge, Hertfordshire; Stormhouse, South Yorkshire; Sybil Elgar, Ealing; and Wargrave House, Merseyside. We are also grateful to the staff
and pupils of the following special schools: Downsview, London;
Green Hedges, Cambridge; Beltwaite, Peterborough; Horizons, London; Highfield, Ely; Ickburgh, London; Lady Adrian, Cambridge;
Meadowgate, Wisbech; Pepys Road, Cambridge; and Rees Thomas,
Cambridge.
Correspondence concerning this article should be addressed to
James Russell, Department of Experimental Psychology, Cambridge
University, Downing Street, Cambridge CB2 3EB, United Kingdom.
After 15 trials, the boxes were changed. This time, they both
had "windows" that faced away from the opponent and toward
the subject. Where would the subjects now point? If they understood that it was necessary to deceive the opponent to win the
chocolate, then they should point to the box that was now visibly empty. This was what the 4-year-old normal children and
498
499
MENTAL DISENGAGEMENT
the nonautistic, mentally handicapped children tended to do
both on the first trial and on all of the subsequent 20 trials. By
contrast, the 3-year-old normal children and the autistic children typically pointed to the box containing the chocolate on
the first trial. They failed to deceive the opponent when an
opportunity to do so presented itself, a finding that is consistent
with the metarepresentational deficit theory. Moreover, success
on the windows task correlated quite well with success on a
false-belief task.
However, two considerations stand in the way of explaining
the failures as being due to a deficit in mental knowledge. The
first of these is empirical. The autistic subjects (and also the
3-year-old normal subjects) typically continued to indicate the
baited box on all of the subsequent 20 trials, despite the fact
that pointing to the baited box meant that the chocolate was
lost to the opponent. It is not at all clear how the metarepresentational deficit hypothesis is supposed to explain the fact that
autistic children are so prodigiously unresponsive to negative
feedback. That is to say, why should a subject who has no conception of what it means to implant a false belief into the mind
of another also be unable to learn the conditional rule, "Point
to the empty box to get the chocolate"?
Second, even if such strong perseveration with the wrong
response were not strongly associated with failure, there would
still be a questionmark over why the autistic subjects pointed to
the baited box on the first trial. To refer to the empty box, a
subject must not only "decide to deceive": He or she must also
disengage attention from a desired object and point to a place
where the object is not. It is one thing to know what it means to
deceive somebody to gain a desired object, but quite another to
be able to draw oneself away from that object and refer to the
place where the object is absent. Perhaps autistic subjects, for
whatever reason, find such disengagement plus reference extremely difficult, compared with matched clinical controls.
At this point, it must be said that when we place the results of
the Russell et al. (1991) study beside those of the Sodian and
Frith (1992) study, it becomes apparent that the autistic subjects' difficulty is specifically with behavioral reference to the
empty box, not with performing any action at an empty location. Sodian and Frith showed that autistic subjects are no less
capable than are mentally handicapped subjects of locking an
empty box in order that a puppet that they wish to help will fail
to open that box and succeed in opening the baited box. This
also shows that autistic subjects are capable of some degree of
disengagement from a baited box in circumstances like this.
We return to the Sodian and Frith study when the results of our
two experiments have been reported.
Our first experiment was designed to pit a prediction derived
from the metarepresentational deficit hypothesis against a prediction derived from the hypothesis that the autistic subjects'
difficulty is with disengagement from a focal object and subsequent behavioral reference toward an empty location. We refer
to these as the metarepresentation and the disengagement hypotheses. Essentially, if the metarepresentation hypothesis is
correct, autistic subjects should perform more successfully on
the windows task when the deceptive element is removed,
whereas the disengagement hypothesis predicts that they
should find the task equally as difficult when there is no requirement to deceive. We removed the deceptive element from the
task by removing the opponent. Subjects had simply to learn
that to obtain a piece of candy, they had to point to the empty
box. They were not in competition with the experimenter, who
could see the location of the chocolate as well as they could and
whose role was to dispense the chocolates rather than win them
for herself.
We had a secondary aim. Because the subjects in the original
version of the windows task had been required to point to the
box that the opponent was to open, it might have been the case
that their difficulties with disengagement were purely at the
motor level. If this were so, it would severely restrict the implications of their failure and would certainly make any parallels
between failure on this task and failure on the false-belief tasks
difficult to sustain. For this reason, we included an additional
condition in which the response was verbal: The two boxes
were of different colors and the subject had to say which of
them should be opened.
Subjects in the experiment were either autistic or nonautistic
but mentally handicapped children and adolescents. Each subject received the windows task in one of four conditions: manual response with opponent present (as in Russell et al., 1991);
manual response without opponent; verbal response with opponent; and verbal response without opponent.
Experiment 1
Method
Subjects. Sixty subjects who had been diagnosed as autistic according to the Diagnostic and statistical manual ofmental disorders (3rd ed.,
rev., or DSM-III-R; American Psychiatric Association, 1987) and 60
mentally handicapped subjects without autism took part in the study.
The autistic children were attending National Autistic Society-funded
U.K. schools in London, Cambridge, Southampton, Devon, Merseyside, and Yorkshire. They had a mean age of 13 years and 3 months
(range = 6 years and 6 months to 18 years and 4 months). These children all had verbal mental ages (MAs) of at least 3 years and 6 months
and had all been able to give three successive correct answers on the
training phase of the windows task (see below). The mentally handicapped subjects were attending special schools in Cambridgeshire or
London and had a mean age of 11 years and 5 months (range = 6 years
and 1 month to 17 years and 4 months). These subjects had verbal MAs
of at least 2 years and 10 months and had all been able to give three
successive correct answers on the training phase of the windows task.
The sex ratios (male: female) were 3.6:1 for the autistic group and 3:1
for the mentally handicapped group.
Design. Within both the autistic and the nonautistic groups, 15
subjects were assigned to each of the four experimental conditions:
no-opponent plus verbal response; opponent plus verbal response; noopponent plus nonverbal response; and opponent plus nonverbal response.
Matching groups for mental age. The nonverbal mental ages
(NVMA) of the subjects were compared on the Raven's Coloured Progressive Matrices (Raven, 1962). However, because two thirds of the
mentally handicapped, nonautistic subjects failed to attain a basal
score, we did not consider the NVMAs informative. The inclusion of
these nonautistic subjects in the study can, however, be justified post
hoc: The experimental task turned out to be well within their range of
ability. Note that a conservative comparison, for our purposes, required us to have autistic subjects with a higher level of intelligence
than the nonautistic subjects. A second conservative measure was to
ensure that the autistic subjects' verbal mental ages (VMAs) were at
500
CLAIRE HUGHES AND JAMES RUSSELL
least as high as those of the nonautistic subjects, given that the VMAs
of autistic children are typically lower than their N VM As (Lockyer &
Rutter, 1970).
The VMAs of all the nonautistic, mentally handicapped subjects
and 74% of the autistic subjects were assessed on both the Verbal Comprehension and Naming subtests of the British Abilities Scales (BAS;
Elliot, Murray, & Pearson, 1983). Sixteen of the autistic subjects (26%)
received only a single test: the British Picture Vocabulary Scale
(BPVS). (Because the subjects had recently been given this test by
other researchers, the staff of the school in question felt that further
testing would overtax the children.) The mean VMA of the autistic
group on the verbal comprehension subtest was 4.3 years (n = AA, SD =
6.5 months), and the mean VMA of the nonautistic group was 4.0
years (SD = 7.2 months). The mean VMA of the autistic group on the
other verbal tests (either naming or BPVS) was 6.5 years (SD = 17.62
months), and the mean VMA of the nonautistic group (on naming
only) was 5.75 years (SD = 18.6 months). In fact, the VMAs of the
autistic group are probably an underestimate, given that many of them
were at ceiling on the verbal comprehension subtest: 36% of the autistic subjects against 5% of the nonautistic subjects at ceiling. The modal
VMA of the autistic subjects on the verbal comprehension subtest was
greater than 4 years and 10 months (ceiling), and the modal VMA for
the nonautistic subjects on the verbal comprehension subtest was 3
years and 10 months.
Because the disengagement and metarepresentation hypotheses
make different predictions about whether the no-opponent condition
should be easier than the opponent condition for the autistic children,
it was particularly important to ensure that the intellectual level of the
30 autistic subjects in the no-opponent groups should approximate
that of the 30 autistic subjects in the opponent subgroups. Fifty-seven
percent of the no-opponent autistic subjects were at ceiling on verbal
comprehension compared with 40% of the opponent autistic subjects,
and 33% of the no-opponent autistic subjects were at ceiling on naming
compared with 27% of opponent autistic subjects. Of the remaining
cases, the mean VMAs (in years) for verbal comprehension and naming, respectively (BAS only), were as follows: no-opponent subjects, 4
years and 1 month and 6 years and 7 months, and opponent subjects, 4
years and 0 month and 6 years and 5 months.
Materials. One red and two blue opaque boxes 5.5 X 4 X 3.5 in.
(14 X 10 X 9 cm) were used in the training phase of the experiment. In
the verbal conditions, one of the boxes was red and the other blue; in
the nonverbal condition, they were both blue. In the experimental
phase, similar boxes were used that had one transparent side (a "window"). There was a supply of candy (usually "Smarties") or a healthsnack equivalent for children with dietary problems.
Procedure. Subjects were tested individually in a quiet room in the
school. In the opponent conditions, they were first introduced to the
opponent, who was either a second experimenter or a member of the
school staff. The opponent sat across from the subject, and the experimenter sat beside the subject. Subjects were told that they had to compete with the opponent for candy and that they had to tell the opponent
which box to open. If the opponent found the candy, the opponent kept
it, but if the opponent went to the empty box, the candy was given to
the subject. On each trial, the experimenter asked both the opponent
and the subject to cover his or her eyes while she (the experimenter) hid
candy in a box. Half of the children were asked to tell the opponent
which box to open by pointing, and half of them were told to tell the
opponent the color of the box to be opened. (The experimenter had
first ensured that all subjects could use the color terms.) The subjects
then witnessed the consequences of indicating the baited and the
empty boxes, with the outcomes of their choices being made clear to
them on each trial. They were told that they could either eat the candy
as soon as they won it or save it for later. The training phase continued
for J 6 trials. The critical instructions were worded as follows:
In a minute I'm going to ask you both to cover your eyes while I
put a sweet in one of the boxes. Then I'll ask you to uncover them
and tell [the opponent—either by pointing or by saying the color of
the box] which box to open. If she/he finds a sweet in the box,
she/he will keep it. But if the box is empty, then we'll look in the
other box and you will win the sweet that's there.
In the experimental phase, the boxes were swapped for ones with a
single transparent side. This meant that the subject, but not the opponent, could see the candy inside. This feature was pointed out to the
subjects immediately before the first experimental trial began: "With
these boxes, you'll be able to see the sweet, so the game gets really easy."
This phase consisted of 20 trials in which the subjects were given the
opportunity of engaging in the deceptive strategy of luring the opponent to the empty box. Throughout the experimental phase, the subject
was encouraged to win as many pieces of candy as possible and was
congratulated for doing so. During the procedure, the opponent behaved in an appropriately pleased or disappointed manner.
In the no-opponent conditions, the experimenter began by making a
pile of candy. She introduced the training phase by telling the subject
that he or she was going to play a game to win candy that involved
closing his or her eyes while the experimenter hid a piece of candy in
one of the two boxes. The subject was told that he or she had to tell the
experimenter which of the boxes to open. This could be done either by
saying the color of the box or by pointing. If the opened box contained
a piece of candy, it was returned to the experimenter's pile, and if the
opened box was empty, the subject was given the piece of candy from
the unopened box. The subject could eat the candy or save it for later.
The procedures for ensuring that subjects had understood the rule
used in the training phase (see below) were the same as in the opponent
condition. In this case, the wording of the critical instructions were as
follows: "If Ifinda sweet in that box, I'll put it back in the pile. But if
the box is empty, then we'll look in the other box and you will win the
sweet that's there."
In the training phases of both the opponent and the no-opponent
conditions, the following questions were asked from the 1 lth to the
16th trials after the indicated box had been opened. If the opened box
was empty, we asked the subject where the candy is and then we asked,
"Who wins the sweet?" (for the opponent conditions) or "Where does
the sweet go?" (for no-opponent conditions). If the baited box had been
indicated, we asked the subject just one of the latter questions. If a
subject failed to give three correct answers in a row (with one of the
three being a case where the empty box had been indicated) within
these six trials, the session was discontinued, the subject was congratulated for winning so much candy, and another subject was recruited (see
Subjects section).
Results
On the first experimental (windows) trial, more autistic subjects than nonautistic, mentally handicapped subjects (70% vs.
37%) indicated the box containing the candy, x 2 0, N = 60) =
13.39, p < .001 (see Table 1). It can be seen from the table that
exactly half of the autistic subjects in this category continued to
do this for the subsequent 20 trials, whereas none of the nonautistic subjects did so. Perseveration was, therefore, a significant
feature of the autistic subjects' behavior. (The raw data, including IQ scores, are available from the authors on request.)
However, not all of the autistic children failed because of
perseveration. Eleven of the autistic subjects (spread evenly
throughout the four subgroups) responded randomly. This pattern was rarer in the nonautistic subjects: Two of them did so.
Sometimes this was because the autistic subject was persevera-
501
MENTAL DISENGAGEMENT
tively pointing to the same box. Some of the others either may
have wanted to distribute the candy between themselves and
the experimenter (for evidence that autistic children understand social reciprocity, see Baron-Cohen, 1991) or were simply
indifferent to winning. However, perseverative pointing to the
baited box was the predominant form of behavior in the autistic subjects.
It would appear from Table 1 that testing condition (i.e., with/
without opponent and with/without verbalization) had no effect on performance of the autistic subgroups. To see whether
this was the case, we adopted arbitrary criteria for "passing"
and "failing" the windows task similar to those adopted by
Russell et al. (1991). On the liberal criterion, the subject had to
make no more than three errors from 20 trials (i.e., three verbal
or nonverbal references to the baited box). On the conservative
criterion, a subject had not only to make no more than three
errors overall but had to be correct (i.e., indicate the empty box)
on the first trial.
As can be seen from Table 2, the percentages of autistic subjects passing within each condition are the same under the two
criteria. This tells us that all the autistic subjects who succeeded
did so from the very first trial. In the nonautistic group, by
contrast, subjects frequently began with the wrong strategy and
improved as the session continued. That is to say, the nonautistic subjects generally benefitted from negative feedback and the
autistic subjects did not. When the frequencies of passing in the
two groups were compared on the conservative criterion (the
criterion on which the nonautistic children were less successful), the group difference was clearly significant, x 2 0, N = 60) =
26.2, p < .001. It is evident that the superior performance of the
nonautistic group was present under all four testing conditions.
Chi-square tests confirmed that the performance of the autistic subjects was not affected by the presence or absence of an
opponent, nor by the response mode. By contrast, the presence
of an opponent did significantly improve performance in the
nonautistic group on both criteria: x2(l, N = 30) = 5.55, p <
.025, on the conservative criterion; x 2 0, N= 30)= 9.31, p< .01,
on the liberal criterion.
Discussion
Removing the opponent in the windows task did not make
the task easier for autistic subjects. The predominant mode of
Table 1
Number of Subjects (From 15) Who Indicated the Incorrect
(Baited) Box on the First Experimental (Windows) Trial
Under the Four Conditions
Nonautistic
Autistic
Condition
n
Perseverating
subjects"
n
Perseverating
subjects*
No opponent, verbal
No opponent, nonverbal
Opponent, verbal
Opponent, nonverbal
Total
10
13
9
10
42
6
8
3
4
21
7
7
4
4
22
0
0
0
0
0
a
Number of subjects who perseverated for all 20 trials.
Table 2
Percentage of Autistic and Nonautistic Subjects Who Passed the
Windows Test on the Two Criteria Under Four Conditions
Nonautistic
Autistic
Condition
Conservative criterion
No opponent, verbal
No opponent, nonverbal
Opponent, verbal
Opponent, nonverbal
13.3
6.7
13.3
20.0
2
1
2
3
46.7
40.0
73.3
73.3
7
6
11
11
2
1
2
3
66.7
53.8
93.3
93.3
10
8
14
14
Liberal criterion
No opponent, verbal
No opponent, nonverbal
Opponent, verbal
Opponent, nonverbal
13.3
6.6
13.3
20.0
Note. The n equals the number of subjects from 15 who passed.
responding in the autistic subjects was their reference to the
baited box throughout the phase of the task in which the candy
was visible to them. This is in sharp contrast to the behavior of
the comparison group of mentally handicapped subjects. Although these subjects often referred to the baited box on the
first (windows) trial, they inevitably learned the strategy for
winning the candy (their reference to the empty box) in the
course of the 20 experimental trials: Perseverative reference to
the baited box throughout the 20 trials occurred in none of our
60 nonautistic subjects.
We can provisionally conclude, therefore, that these data support the mental disengagement account of the autistic subjects'
original failure (Russell et al., 1991) against the metarepresentation account. That is to say, if the autistic subjects are still
failing when there is no "other mind" in which to implant a false
belief, then it makes little sense to say that they perseveratively
pointed to the baited box because they lacked the necessary
theoretical grasp of mental concepts. This is not, of course, to
deny that autistic individuals might indeed lack such concepts,
but it is to deny that their performance on the windows task
demonstrates such a lack (see General Discussion). What these
children and adolescents seem to be failing to do is to disengage
their attention, and thus their behavioral reference, from an
object that is both desired by them and the focus of the task.
However, an advocate of the metarepresentational account
might wish to use these data as evidence that performance on
this task is simply irrelevant to the psychology of deception.
The argument would run that children who succeed on the task
do not do so by virtue of deceiving the opponent—they simply
point to the empty box without giving thought to the mental
state of the opponent, without even regarding him or her as an
opponent. But such a denial would be unwise for two reasons.
First, this task strips down the act of deception to its bare minimum: luring an opponent to a place where something is not
when we know where that something really is. Such behavior is
surely not irrelevant to the psychology of deception: It is a primitive, necessary condition for the more richly mentalistic form
of deception that people practice in their everyday lives.
502
CLAIRE HUGHES AND JAMES RUSSELL
Second, the metarepresentational theory is an ambitious
theory that is supposed to explain virtually all of those respects
in which autistic people fail psychological tests in comparison
with matched clinical controls within a single deficit—the inability to represent the relationship between the mind and reality. Proponents of the theory should, therefore, be able to explain why autistic subjects perseverate on this task when it is
stripped of deceptive elements, and this explanation should be
theoretically motivated. That is to say, it is no goodfieldingpost
hoc explanations of the autistic subjects' difficulties, such as,
"The absolute number of items won is not intrinsically rewarding for them," "They have a characteristic way of giving up
when they don't understand something—they perseverate," or
"Autistic subjects are more compliant, so they do as they were
initially told to do and tell the other person which box to open
every time." These kinds of explanations are not motivated by
the metarepresentational theory itself.
That said, there is an impediment to our conclusion in favor
of the disengagement hypothesis. It is that the no-opponent
condition might be said to have required, if not full-blown deception, then at least the act of literally misleading another
person. Moreover, the experimenter in this condition could
potentially be construed as a competitor for resources. That is
to say, we may have failed to eradicate the element of competition from the task in the no-opponent condition.
This objection has some force, especially in the light of a
recent study by Baron-Cohen (in press). In this, autistic children were taught a simple coin-hiding game in which one person puts his/her hands behind his/her back, hides a coin in one
of them, and then presents his/her closed fists to an opponent
who then has to guess which hand contains the coin. Playing
the role of guesser was not difficult for the autistic children, but
they had severe problems being the hider. In the role of hider,
they would often reveal the coin to the guesser: They would
thrust the hand containing the coin toward the guesser or even
tell him or her which hand had the coin in it. In terms of the
metarepresentational account, these children were failing to
understand the process and point of withholding information
from another person. This may or may not be so, but the data
certainly reveal a failure to grasp the point of a competitive
game. There is, of course, an important difference between the
coin-hiding procedure and our no-opponent condition, in that
in our case, the experimenter could see everything. But the
worry remains that our autistic subjects were failing to misdirect the experimenter because they failed to grasp some competitive element in the procedure, whereas the comparison subjects did grasp this competitive element and thereby succeeded.
The following piece of data is at least weakly consistent with
the argument that success on the no-opponent condition may
have been achieved through a form of deceptive behavior. Recall that the mentally handicapped subjects in this experiment
performed significantly better (on both the conservative and
the liberal criteria) in the opponent condition. Given that the
opponent condition was the condition in which the need for
deceptive behavior was the more patent, we can explain nonautistic subjects' relative difficulty with the no-opponent condition by the fact that here it was less patent—implying that a
competitive "set" may have underlain what success they did.
achieve, compared with the autistic subjects in the no-opponent condition.
Because of this problem of interpretation, we developed a
new task on which to compare autistic subjects with control
subjects. As will be seen, the new task still demanded mental
disengagement from a desired object but did so in a situation in
which the experimenter could not be construed as a competitor
for resources. The subject's task was to obtain a marble that
rested on a platform inside a box (see Figure 1). A direct reach
toward the marble broke an infrared light beam, which caused
a photoelectric cell inside the box to make the marble drop out
of sight through a trap door in the platform. There were two
ways in which the marble could be obtained. The subject could
turn a knob on the right-hand side of the box to cause a paddle
behind the marble to flip it down a chute and out of the box
toward the subject—the "knob route." Alternatively, the subject
could use a switch on the other (left) side of the box to extinguish the light beam and thus enable a reach—the "switch
route." (Note that the switch route requires the subject to act on
the side that is normally nondominant. However, left-handedness is about twice as common in children with autism and a
variety of other mental handicaps than in the normal population [Fein, Waterhouse, Lucci, Snyder, & Humes, 1984]. In any
event, there is no reason to believe that making an intentional
movement to the left is especially difficult for autistic people.)
If the autistic children have substantially greater difficulty
with these detour tasks than the comparison groups, this will
suggest that they have a specific problem with mental disengagement from an object. Such an outcome will not in itself
explain why deception is difficult for such children, but it will
reinforce the disengagement account of their performance on
the windows task against the metarepresentational account.
There are two additional reasons why this detour-reaching
Figure 1. The box used in the detour-reaching task in Experiment 2.
MENTAL DISENGAGEMENT
503
forward movement. Throwing this bolt triggered a green light on the
left of the front face of the box and caused the yellow light to be
extinguished. The green light signaled to the subject that the switch
route was now required rather than the knob route. To use the switch
route, the subject had to operate a small, toggle switch on the left side of
the box. This switch was inoperative when the knob route was available
and the yellow light was on. The left side of the box also contained a
small door (15 x 20 cm), by means of which the experimenter could
manipulate the bolt and reposition the marble at the end of each trial.
Procedure. Subjects were tested individually in a quiet room in the
school. A pilot study had established that retrieving the marble by
means of the knob route was trivially easy for subjects in this ability
range and that it was the switch-route task that caused difficulty. For
this reason, the knob-route task was always given first, so as not to
frustrate some subjects by presenting a difficult task first. The session
began when the experimenter invited the subject to take the marble out
of the box. After the subject had failed to do this twice because his or
her reach triggered the trap-door mechanism, the experimenter demExperiment 2
onstrated that a direct route would invariably cause the marble to drop
away. She then drew the subject's attention to the yellow light on the
Method
upper front face of the box and explained that whenever this light was
Subjects. Forty children and adolescents with an established diagon, the only way to obtain the marble was by turning the knob on the
nosis of autism as denned in DSM-III-R (American Psychiatric Assoright-hand side of the box. She demonstrated this two times and then
ciation, 1987) and who are between 6 and 19 years made up the autistic
invited the subject to do the same. Subjects were allowed to retrieve the
group (mean age = 12 years and 8 months). They were attending many
marble through the knob routefivetimes. All but 4 subjects performed
of the same National Autistic Society-funded schools as those used in
these five trials without error: Two of the autistic subjects made two
thefirststudy, and many of the subjects had also participated in Expererrors, and 2 of the mentally handicapped subjects made two errors.
iment 1. In the nonautistic, mentally handicapped group, there were
After these five trials, the bolt was thrown to block the knob route,
25 subjects between 6 and 18 years (mean age = 10 years and 8 months). causing the yellow light to be extinguished and the green light to apThey were attending special schools in Cambridge or London. As in
pear on the front of the box. The experimenter then showed the subject
Experiment 1 these children had a variety of learning disorders and
that when the green light was on, the knob did not work any more. She
included only 1 child with Down's syndrome. Some of the children had
then demonstrated the switch route and told the subject that it was now
participated in the first experiment. The group of preschoolers comessential to flip the switch before reaching inside the box. She also
prised twenty 3- to 4-year-old children (mean age = 3 years and 8
demonstrated again the consequences of a direct reach. The instrucmonths) attending nursery schools in Cambridge.
tions for the switch route were as follows: "When the green light is on,
Matching for mental age. Verbal mental age (VMA) was assessed
this means that you can't use the knob any more. Instead the way to
by the Test for the Reception of Grammar (TROG; Bishop, 1989).' The
win the marble is by using this switch here; then you can reach in and
mean VMA for the autistic group was 6.58 years (SD = 2.6; range = 4
get the marble. But you have to make sure that the switch is down first."
years and 0 months to 13 years and 7 months), and the mean VMA for
To maintain the subjects' interest in the task until the marble was
the mentally handicapped group was 6.17 years (SD =1.38; range = 4
retrieved a criterial number of times, we used the following measure.
years and 0 months to 10 years and 3 months). Nonverbal mental age
Subjects were shown a plastic trumpet made up of 16 colored segments
(NVMA) was assessed by the matrices subtest of the British Abilities
and were allowed to blow into it, after which the trumpet was dismanScales (Elliot et al., 1983). The mean NVMA on this test for the autistic
tled. Each time the marble was retrieved by the switch route, one seggroup was 6.76 years (SD = 2.9; range = 4 years and 0 months to 14
ment of the trumpet was reassembled, with the bell and mouthpiece
years and 2 months), and the mean NVMA for the mentally handisegments kept back until the subject was about to attain criterion.
capped group was 5.8 years (SD =1.5; range = 4 years and 0 months to
8 years and 2 months). Note that these mental ages are substantially
higher than the chronological ages of the preschool children.
1
In this test, subjects are presented with a series of four colored
Materials. The box (see Figure 1) was made of aluminum and meapictures
and have to indicate the one to which a sentence applies. For
sured 30 x 30 X 30 cm. In its front face was a centrally located, circular
example, presented with (a) a boy and a girl jumping over some
opening, 15 cm in diameter, cut in a perspex square. Mounted inside
flowers, (b) a boy and a girl jumping over a wall, (c) a boy and a girl
the box was a pyramid-shaped platform with a narrow, flat top on
behind a wall, and (d) a boy jumping over a wall, they have to indicate
which a large marble rested. On either side of the opening in the front
the picture of which "They are jumping over the wall" is true. This
face of the box were photoelectric cells by means of which an infrared
item probes subjects' understanding of the distinction between singubeam was directed toward the top of the platform. When the beam was
lar/plural personal pronouns. Overall, the grammatical structures
broken, a trapdoor at the top of the platform was automatically actitested range from noun and verb up to "neither X nor Y" and the
vated. Immediately behind the marble's resting position was a small
embedded sentence. Our autistic subjects did remarkably well on this
metal paddle that could beflippedforward by turning a round knob in
test—indeed, their verbal M As were comparable with their nonverbal
the right, external side of the box. By this means, the marble could be
M As. This may be because the TROG is a relatively pure test of recepprojected forward and down a small chute running between the plattive
syntax. It has no planning components that the difficult items in
form and a catch tray at the front of the box. A yellow light mounted at
the BAS verbal comprehension test have (e.g., "Before you give me the
the right-hand top of the front face of the box remained lit when the
van, give me the little house"), and it has no items that probe underknob route was available. The knob route could be blocked by throwstanding of social and emotional facts, as do the standard naming tests.
ing a small bolt located in front of the paddle, thus obstructing its
task may clear up interpretational problems remaining from
Experiment 1. First, despite the efforts made to match groups
for verbal intelligence, it is possible that the autistic subjects
were understanding the procedure less well and that their failure to understand manifested itself in stereotyped responding.
The detour-reaching task is far easier to understand than the
windows task. Second, as we argued in the introduction with
reference to Sodian and Frith's (1992) data, autistic subject's
difficulty appears to be with their reference away from an object rather than with performing an action at a place where the
object is absent. In the detour-reaching task, no reference is
required, which enables us to determine the role of the referential act per se in autistic subjects' problem with disengagement
from an object.
504
CLAIRE HUGHES AND JAMES RUSSELL
Thus, by the end of the experiment, subjects had assembled trumpets
whose sizes varied in proportion to the number of trials they had taken
to attain a criterial run.
Immediately after we showed subjects the trumpet, the trials with
the switch route commenced. Each time a subject failed to retrieve the
marble (either by a direct reach or by turning the knob), he or she was
reminded of the switch-route procedure. If a subject did nothing either
at the beginning of a trial or after having used the switch, he or she was
given a verbal reminder of what to do. This is referred to as a prompt.
Scoring of the switch route. In coding responses, we discriminated
between those uses of the switch and subsequent reaches that were the
result of prompting by the experimenter (i.e., to switch, to reach, or to
do both) and those responses that were not. If a subject made a direct
reach, thus causing the marble to drop through the trap door, this was
coded as a failure. Trials on which the subject touched the knob were
also coded separately. Only coordinated switch-and-reach sequences
were scored as correct. If the sequence involved prompting from the
experimenter, touching the knob, glances to the experimenter, or
pauses of over 7 s, this was not recorded as a correct trial. Criterion was
a run of three coordinated switch-and-reach sequences within 15 trials.
Results
The autistic subjects were significantly less likely to attain the
criterial number of retrievals on the switch-route task than were
the other two groups: Only 55% of the autistic children and
adolescents attained criterion as compared with 92% of the
mentally handicapped children and 95% of the preschoolers.
Comparison of the performance of the two clinical groups produced the followingchi-square value: x2(l. N= 65)= 15.51, /?<
.001. The data are illustrated in Figure 2 in terms of the percentages of the three groups attaining criterial runs within sets of
three trials. (The coded raw data and details of IQ matching are
available from the authors on request.)
In Figure 3 we illustrate the relationship among the attainment of criterion and chronological age (CA), VMA, and
NVMA in the autistic subjects. In each case, the subjects are
split into four groups of 10 subjects each in terms of these three
measures. On the ordinate is shown the average performance
for each subgroup, which could range from 1 (i.e., every subject
reached criterion) to — 1 (i.e., every subject failed to reach criterion). Thus, if the histogram is below zero, it means that more
subjects failed to reach criterion in that particular subgroup
than succeeded in doing so. It can be seen that there is an
apparent disjunction between the lowest quartile of subjects
and the other three: On all three measures (CA, VMA, and
NVMA), more subjects in the lowest quartile failed to reach
criterion than attained it. Indeed, none of the subjects in the
lowest NVMA quartile attained criterion.
The figure also shows the mean ages (CA or MA) in each
quartile. Two things are apparent from these data. First, success on this task begins to emerge in autistic subjects with MAs
of around the late 4 years, whereas failure to attain criterion is
not uncommon with a mean MA of just under 7 years. Recall
that the task is trivially easy for normal children who are approaching 4 years of age or who have recently turned 4. Second,
it would appear that MA is a better predictor of success than
CA. To check this last conclusion, we computed the correlation
between number of trials to criterion (or to end of the session
for subjects not reaching criterion) and VMA (age partialled)
and NVMA (age partialled) and with CA. The results were as
follows: The correlation of trials-to-criterion with VMA (age
partialled) was r= -.60 (p < .01); with NVMA (age partialled),
r = -.65, p < .01; and with age (VMA partialled), r = .035, ns.
Figure 4 presents the data for the mentally handicapped children in the same way as does Figure 3 for the autistic children.
Because there were 25 subjects in this group, the divisions were
into groups of 5 this time. When analyses were run for these
subjects that were similar to those run for the autistic subjects,
none of the correlations were found to be significant.
We now turn to qualitative differences in performance between the two clinical groups. Was perseveration more common in the autistic subjects? The first kind of perseveration
considered was direct-route perseveration in which the subject
Group performances on the box task
Pass in 3
Pass in 6
Pass in 9
Pass in 12
Pass in 15
FAIL
Success level
Figure 2. The percentages of subjects from the autistic, mentally handicapped (MLD), and normal
groups who attained criterion on the box task in Experiment 2 within sequences of three trials.
505
MENTAL DISENGAGEMENT
Autistic performance related to subject age
8 . 23
0.0-
•0.5-
17. 23
11 .66
0.5-
•
•
j
14 .85
Mm
reaches except for a fully prompted switch-and-reach sequence
on Trial 5. We can conclude, therefore, that although perseveration with a direct route to the goal was not the virtual prerogative of the autistic subjects that it had been in the first experiment, this kind of perseveration was clearly more common in
autistic subjects than in the clinical comparison group.
It is also possible to regard touching the knob as a form of
WILD performance related to subject age
1
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2
3
Aga Ranking
4
Autistic performance related to subject NVMA
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-1.0
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NVMA Ranking
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i
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4
5
Age Ranking
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MLD performance related to subject NVMA
O)
Autistic performance related to subject VMA
1
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c
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is
•1.0
2
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NVMA
2
3
VMA Ranking
Figure 3. The proportion of autistic subjects (10 per subgroup) ranked
by chronological age, nonverbal mental age (NVMA), and verbal mental age (VMA) who reached criterion on the box task. (For example, 1.0
means all 10 subjects passed; -1.0 means all 10 failed.)
reaches directly for the marble and causes it to drop out of sight.
This is strongly analogous to the form of perseveration seen in
Experiment 1. We only coded a repetition of a direct reach as
perseverative. In the autistic group, 65% of the subjects made at
least two such consecutive direct reaches, compared with 32%
of the mentally handicapped subjects, x 2 0, N= 65) = 6.75, p <
.01. Moreover, 3 of the autistic subjects produced nothing but
direct reaches throughout the 15 trials, although there were a
number of other autistic subjects whose responses were nearly
all direct reaches. For example, 1 subject began with a switchknob-reach sequence and produced direct reaches on all the
other 14 trials, whereas another subject performed all direct
£
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2
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3
4
Ranking
MLD performance related to subject VMA
1.0
0.5-
0.0
-0.5-
-1.0
2
3
VMA
4
Ranking
Figure 4. The proportion of mentally handicapped (MLD) children
(5 per subgroup) ranked by chronological age, nonverbal mental age
(NVMA), and verbal mental age (VMA) who reached criterion on the
box task. (For example, 1.0 means all 5 subjects passed; -1.0 means all
5 failed.)
506
CLAIRE HUGHES AND JAMES RUSSELL
perseveration. Although this is not perseverative behavior directed at the goal, it is perseveration with a response that was
successful in the previous phase of the experiment. Of the autistic subjects, 22.5% touched the knob at least once, compared
with 4% of the mentally handicapped subjects, x2(l, N= 65) =
4.19, p< .05. It turned out that, in general, if an autistic subject
touched the knob once, he or she probably touched it at least a
second time, whereas there was only one case of touching the
knob in the mentally handicapped children—on the first trial
and not repeated. Thus, perseveration in the sense of repeating
a previously successful strategy, despite demonstrations of its
inefficacy, was also more likely to feature among the responses
of the autistic group.
There was, however, a third distinctive way of failing to attain a criterial run that cannot be regarded as perseverative.
This occurred when a subject produced a coordinated switchand-reach sequence but failed to follow this up with another
one. This never occurred in the preschool children and occurred only twice (8%) in the mentally handicapped subjects. It
occurred, however, in 42.5% of the autistic subjects. When we
compare the two clinical groups, we find a chi-square value of
X2(l, N= 65) = 8.82, p < .001. Indeed, 5 of the autistic adolescents produced a switch-and-reach response on the first trial
and then followed it up with a direct reach. This might be
regarded as a failure to monitor a correct response that one has
produced as being a correct response. Alternatively, this behavior might be seen as being due to the performance of a reach
triggering another reach without a prior switch—a failure to
inhibit rather than monitor behavior. In light of this uncertainty, we refer to this form of error as "failing to capitalize" on
a correct response.
We have identified, therefore, three kinds of error. All of
them were more prevalent in the autistic children.
Discussion
Autistic subjects continue to have difficulties disengaging
from a salient, desired object when all vestiges of interpersonal
competition are removed from the task. Specifically, the autistic subjects found it much more difficult than did mentally
handicapped children to throw a switch in order to perform an
object retrieval. This would appear to be something that is difficult to account for on the metarepresentation hypothesis.
A result that requires immediate comment is that the knob
route to retrieval was trivially easy for the autistic subjects. On
the disengagement hypothesis, this must be explained by saying that the demands for "mental disengagement" from the
marble were much higher in the switch route than in the knob
route. This may be so, but there are two, rather clearer, differences between the routes: (a) The switch route required two
distinct acts that had to be performed in the correct order,
whereas the knob route required a single act; and (b) the causal
relation between the act and the retrieval was direct and clear in
the knob route but, in the switch route, was sufficiently indirect
and obscure (to a subject who knows nothing about how breaking invisible light beams can trip mechanisms) as to seem arbitrary
Both of these considerations limit somewhat the explanatory
force of the disengagement hypothesis. The first suggests that
the autistic subjects may be finding the switch route difficult
because it requires a minimal degree of planning in addition to
mental disengagement. The second suggests that it not so much
the planning requirements of the switch-and-reach sequence
that are causing difficulty as it is the fact that thefirstof the two
acts bears an arbitrary relation to the second.
This seeming arbitrariness of the means-end relation may
have some bearing on the contrast, noted in the introduction,
between the difficulties that autistic subjects have with the windows task and the relative ease with which, on the data of Sodian and Frith (1992), they are able to lock an empty box so that
an ally will go instead to the baited one. We claimed that the
first causes difficulty because it requires reference (an act of
pointing) and the second does not because it requires action at
an empty location. An essential feature of referring is that the
relation between the sign and the referent be arbitrary or "nonnatural" (Grice, 1957). The relation between locking a box and
another agent failing to gain entry to it is, in contrast, a "natural" one. It may, then, have been the seeming arbitrariness of the
switch-and-reach relation that caused the difficulty—a hypothesis that could easily be tested by keeping the means-end demands constant in detour reaching but rendering obvious the
causal relation between the acts. It is significant, in this context,
that autistic children are relatively unimpaired on search tasks,
tool use, and categorization by color, form, and function (Morgan, Cutrer, Coplin, & Rodrigue, 1989; Sigman & Ungerer,
1984). These are means-end tasks in which the relation between
means and ends is nonarbitrary.
Analysis of the different kinds of errors that the autistic subjects made was revealing. One message is that the autistic subjects were not simply victims of what Sandson and Albert
(1984) call, in their analysis of perseveration, "stuck-in-set" perseveration. That is to say, it was by no means the general rule
that these subjects would make a direct reach, witness its consequences, and then fail to change their behavior. Some of the
less-able autistic subjects produced a pattern like this, but they
were not in the majority. This is noteworthy, because it is possible to describe the form of perseveration shown in the windows
task as stuck-in-set perseveration.
The other two forms of error involved use of the knob and
failure to capitalize on a successful switch-and-reach sequence.
The first of these might be regarded as a case of what Sandson
and Albert (1984) call recurrent perseveration—"an abnormal
post-facilitation of memory traces" (p. 715). In other words, the
task triggered memories of an action that had been successful
on previous trials. The second of these, in which subjects perform a successful response and then lapse back into error, is
still further from stuck-in-set perseveration. In this case, as we
have argued, subjects are either failing to monitor their behavior as correct or are failing to suppress a direct reach once they
have made one after a switch-and-reach sequence.
This analysis of errors provides further reason for denying
that the autistic subjects' difficulty was caused simply by their
inability to disengage their attention from the focal object. Perseveration with the direct reach certainly comes under this
heading, as does failure to capitalize on a correct response, if
we assume that the latter is due to the failure to suppress a
repetition of the direct reach. However, use of the knob route
when the switch route is required is better regarded as failure to
MENTAL DISENGAGEMENT
disengage from a previous strategy. Indeed, the fact that the
knob route was very easy for the autistic subjects suggests that
they are certainly able to disengage from the object sufficiently
well to retrieve it by action at another place.
Despite the questions that these data raise about the disengagement hypothesis, the difference between the two clinical
groups was very clear and does not yield to an explanation in
terms of theory-of-mind deficits. In general, the autistic subjects exhibited a lower level of executive ability, a fact whose
general significance is now discussed.
General Discussion
Our first experiment suggested that autistic subjects fail a
test of strategic deception because they have difficulty with
mentally disengaging from a focal object, not because they are
unable to implant a false belief into the mind of a competitor:
They found the task equally difficult when there was no competitor to deceive. Our second experiment revealed similar difficulties with the simpler task of throwing a switch before
reaching for a marble. On the face of this at least, these data are
not explicable in terms of the metarepresentation hypothesis.
However, insofar as the disengagement hypothesis locates
the autistic person's executive difficulties squarely with disengaging attention from a focal object, it is probably too simple.
The executive demands for successful deception require the
subject not only to disengage from the object but also to establish a three-stage plan (i.e., refer to empty location, lure opponent there, and obtain goal at another location). Moreover, the
disengagement hypothesis implies that the problems with reference to an empty location arise out of a primary failure of
disengagement, whereas reference—as an arbitrary means—
sets a mental challenge of its own. These shortcomings were
highlighted in Experiment 2, in which we showed that disengagement from a focal object was trivially easy when there was a
direct causal link between an act that was distinct from the
object and the attainment of it (i.e., the knob route). However,
when the subject was required, on the switch route, to perform a
separate and—for the subject—arbitrary means to enable direct
action on the object, a variety of perseverative behaviors ensued. We must conclude, therefore, that these two experiments
provide evidence for a general executive impairment in autism
rather than for a specific impairment in mental disengagement.
Provisional disengagement from a goal in order to perform
the arbitrary means to attain it is just one component of a
constellation of mental operations referred to as the executive
functions. These are taken to encompass all those mental operations that are separately necessary and jointly sufficient for
volitional, goal-directed behavior: inhibition of perceptually
triggered or inappropriate responses; planning and embedding
of behavioral and cognitive sequences; maintaining an appropriate set and disengaging from an inappropriate one; and
monitoring the success and failure of current strategies. These
are the functions normally assumed to be carried out by the
prefrontal cortex (Luria, 1973; Shallice, 1988). On the level of
behavior, the executive functions provide an agent with a flexible and autonomous relationship to the environment. On the
level of thought, they provide the individual with what Piaget
called autoregulation—the capacity to avoid "centration" (Pia-
507
get, 1950) on local saliences and, through this, the achievement
of the kind of balance between competing representations that
is necessary for adequate judgment.
Our data fit alongside other recent evidence that autistic subjects perform poorly on the standard tests of executive functioning (Ozonoff, Pennington, & Rogers, 1991; Ozonoff,
Rogers, & Pennington, 1991; Prior & Hoffman, 1990; Rumsey,
1985; Rumsey & Hamburger, 1988, 1990; Steel, Gorman, &
Flexman, 1984). Ozonoff, Pennington, and Rogers (1991), for
example, reported a comparison between a group of high-functioning autistic children and control children with a variety of
mild mental disorders by using a number of measures, including theory-of-mind tasks, executive function tasks, emotion
perception tasks, memory tasks, and spatial tasks. The two deficits that were the most widespread in the autistic sample were
those of executive function (i.e., Tower of Hanoi and the Wisconsin Card Sorting Test) and of second-order theory of mind (i.e.,
questions about one person's thoughts about another person's
thoughts). Only some of the autistic children had difficulties
with the standard false-belief task (presumably because these
subjects were high-functioning). In general, executive function
performance was the best discriminator between the two
groups.
We now consider two ways in which one might view the relationship between executive dysfunctions in autism and theoryof-mind difficulties, which are also a feature of the syndrome.
The first concerns assessment and the second concerns
etiology.
In the first place, given the executive difficulties that autistic
persons experience, the tests that have traditionally been used
to assess their theory of mind would seem to be inappropriate.
For example, the usual procedure for assessing a subject's understanding of false belief is one in which the subject's own
knowledge of the object's location is in competition with whatever grasp he or she may have of the protagonist's mental state
(Wimmer & Perner, 1983). Clearly, this means setting the subject an executive problem. Were autistic individuals to be given
deception and false-belief tasks in which their knowledge of the
current state of physical reality was not in competition with
their representation of another person's mental state, they
would, on this argument, find the tasks much easier.
In this context, it is significant that Ozonoff, Pennington,
and Rogers (1991) found that it was second-order belief that was
the more widespread deficit in the autistic children, because, in
addition to requiring some degree of mental knowledge, second-order belief tasks also require the subject to perform a
complex series of planful computations not dissimilar from
those required by a task such as the Tower of Hanoi. Most
normal adults would fail a third- or fourth-order belief task;
this would not be because their grasp of mentality is impoverished but because the demands placed on the capacity for sequential embedding are so great.
However, there is a piece of evidence that would seem to
contradict our claim that autistic subjects fail tasks of the falsebelief kind because they are mentally drawn to the focal object.
Autistic subjects perform well on the so-called false-photograph
task (Leekam & Perner, in press). This is a task designed by
Zaitchik (1990) that is structurally similar to the false-belief
task but in which a camera rather than a mind represents the
508
CLAIRE HUGHES AND JAMES RUSSELL
initial situation. One answer might be that it is only when autistic subjects' knowledge of another's mental state is in competition with their knowledge about an object that the latter wins
out. In the false-photograph task, there is competition between
two physical objects for mental salience—the object initially
photographed and the photograph.
We turn now from questions of assessment to questions of
etiology. The previous discussion left open the possibility that,
were the executive demands of theory-of-mind tasks stripped
away, autistic persons would be shown to have a more or less
normal conception of mental life. This is highly implausible.
We suggest, instead, that (a) autistic persons' difficulties with
mentalizing are real and profound, and (b) that these may be a
developmental consequence of early executive dysfunction.
It is certainly possible to take the symmetrically opposing
view to this and regard executive deficits as a product of an
innate lack of a theory of mind (Baron-Cohen, 1989a), and it is
certainly possible to regard mentalizing and executive deficits
as being causally unrelated. However, the present conjecture is
that executive deficits, if they are present very early in life, may
handicap the child in the acquisition of mental concepts. Consider, in illustration, the Norman and Shallice (1986) model of
the executive system. This contains a "supervisory attentional
system" that has it effects by modulating the action of lower,
more automatic systems and that comes into play when the
individual is required to deal with novelty and to make decisions. Because dealing with novelty and making decisions are
two prerequisites for successful social interaction, a child who
was congenitally handicapped in this regard would fail to develop normal social relations. Moreover, such a child would fail
to develop a sense of himself or herself as a more or less autonomous ego, framing and executing intentions. The developmental outcome would indeed be "lack of a theory of mind."
Strong support for the view that autism is rooted in a disorder
of the executive functions would be provided by evidence that
early frontal impairment results in later autism. However, the
evidence is somewhat contradictory (Price, Daffner, Stowe, &
Mesulam, 1990; Welsh, Pennington, Ozonoff, Rouse, &
McCabe, 1991) and difficult to interpret (Bishop, in press). Until this question is resolved, there are two good reasons for
considering the possibility that autism may be rooted in early
executive dysfunction. The first of these concerns the neurophysiology of the disorder: We at least know a little about the
physiological underpinnings of the executive functions and
have some ideas about how malfunctioning of these might result in mental illness. The second reason is that regarding autism as a disorder of the executive functions enables us to explain a wider range of component symptoms. We deal with each
of these in turn.
In thefirstplace, the commonalities between frontal patients
and autistic people have been well documented (Damasio &
Maurer, 1978; Fein, Pennington, Markowitz, Braverman, &
Waterhouse, 1986; Rumsey, 1985). However, the claim that the
underlying deficit in autism involves the prefrontal cortex also
suggests a commonality with schizophrenia, a disorder that is
often regarded as a "frontal disorder" (C. D. Frith, 1987; Robbins, 1990; Weinberger, 1988). The problem is that although
autism and schizophrenia share some features, they are manifestly different syndromes.
However, as C. D. Frith and Frith (1991) have argued, this
paradox can be resolved by attending to the fact that autism is
invariably acquired early in life, whereas schizophrenia is typically acquired later. It is possible to claim that both syndromes
are caused by a dysfunction of the frontal-limbic system—early
dysfunction in autism and later dysfunction in schizophrenia.
The argument is based on C. D. Frith's (1987) account of schizophrenia. The theory runs that in acute schizophrenia there is
disruption of the route between the formation of goals and
plans and their execution as willed actions: the monitoring of
launched intentions has broken down. Such a disruption can
explain many of the common acute symptoms, such as patients
hearing their own thoughts relayed to them as if broadcast by
others, having the delusion that their actions are not under their
own control, and misattributing intentions and beliefs to
others. The predominantly negative symptoms found in
chronic schizophrenia are a developmental outcome of such a
chaotic and unpredictable mental life. At this stage, patients
now have a deficit not in monitoring goals and plans but in
generating them. Note that it is in chronic schizophrenia that
we find a high level of stereotypical behavior (C. D. Frith &
Done, 1983), similar though not identical to that found in autism (Prior & Macmillan, 1973).
To return to the C. D. Frith and Frith (1991) hypothesis in
light of this, if a frontal-limbic dysfunction occurs after the
period when the basic mental concepts develop in normal children, we would expect a disorder to emerge in which patients
know what thinking and intending consist of but in which they
cannot control the attribution of these processes—schizophrenia. If, on the other hand, the frontal-limbic dysfunction occurs
very early in life, if, that is, there is a disorder of volition while
mental concepts are still developing, a disorder will result in
which the patient lacks a basic conception of the mental domain—autism.
One clear impediment to this hypothesis is the lack of evidence for a specific frontal-limbic dysfunction in autism. In
fact, there is a bewildering proliferation of neurological theories of autism, and many of these isolate subcortical rather
than frontal impairments (Coleman & Gillberg, 1985; Courchesne, 1989; Prior, 1987; Reichler& Lee, 1987). However, if we
assume, along with Luria (1973; and see Prior, 1987), that adequate development of the higher mental functions in the cortex
depends on a prior adequate development of intact "lower"
processes, then there is no contradiction in isolating an early
subcortical dysfunction as the primary cause of autism while
also regarding the disorder as a disorder of the executive functions.
We turn finally to the second reason for considering autism
as a disorder of the executive functions: It explains more symptoms. The stereotypies, excessive desireforsameness,and repetitive interests in very narrow topics that are central features of
autism (Kanner, 1943; Prior & Macmillan, 1973) are all easy to
regard as manifestations of a deep volitional disorder. They also
involve, in various ways, perseveration. Our experiments have
highlighted perseveration in autism, and perseveration is
strongly associated both with frontal damage and with schizophrenia (Freeman & Gathercole, 1966; C. D. Frith & Done,
1983; Sandson & Albert, 1984). Moreover, the dramatic volitional impairments found in obsessive-compulsive disorder are
MENTAL DISENGAGEMENT
associated with poor performance on executive function tasks
such as the Wisconsin Card Sorting Test (Head, Bolton, &
Hymas, 1989).
In conclusion, we have argued that an adequate grasp of mental concepts may well depend on the adequate functioning of
the executive system, and so, to that extent, there is no unresolvable conflict between approaches to autism that stress executive dysfunctions and those that stress metarepresentational
ones. The real theoretical dispute is about which dysfunction is
developmentally primary.
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Received November 12,1990
Revision received June 23,1992
Accepted July 10,1992 •