Explicit knowledge, higher order
thoughts, and hypnosis
Zoltan Dienes
University of Sussex
1. A hierarchy of ways in which knowledge can be
explicit
2. Highest level of explicitness <-> conscious
awareness
3. Explicitness and control
4. Three possible accounts of hypnosis
5. Relation to existing theories of hypnosis
What is implicit or explicit knowledge?
Dienes & Perner, 1999:
One can explicitly represent just parts of, or all of,
what it is to know a fact.
Consider the knowledge:
I see that it is a fact that the word in front of me has the
meaning butter
There is a hierarchy of making this knowledge explicit.
One might just explicitly represent:
i) the property
"butter”
ii) the predication of the property to an individual
"The word in front of me has the meaning butter“
iii) the proposition's factuality
"it is a fact that p“
Active representations that are not fact explicit are simply
taken to be true.
Considering different possible models of the world, past
and present states of the same object, explicit memory,
counterfactual reasoning all require representing factuality
explicitly.
iv) the mental attitude of knowing, seeing, etc
“I see that it is a fact that p“
Step (iv) is fully explicit knowledge; in previous steps the
knowledge is to some degree implicit.
Relation between explicit knowledge and conscious knowledge?
Higher order thought theory of Rosenthal:
a mental state is conscious if we are conscious of being in that
mental state;
we are conscious of being in a mental state when we have a
thought that we are in that mental state;
in sum, a mental state is a conscious mental state in virtue of the
person having a higher order thought that they are in that mental
state.
Fully explicit knowledge <-> conscious knowledge
A second order thought (e.g. “I see that the cat is black”)
makes one aware of the first order thought (“the cat is
black”) and hence makes the first order thought a
conscious thought.
The second order thought itself is not a conscious thought
until one becomes conscious of it – by a third order
thought (e.g. “I know that I am seeing that the cat is
black”).
It is the third order thought that makes one consciously
aware that it is *me seeing*.
Declarative representations
Declare what is the case.
i.e. must represent the full proposition explicitly AND represent that
it is a fact – fact explicit.
Imperative representations
“If Y, then do X”
“Do X”
X and Y cannot be taken to be true
i.e. must also be fact explicit
Norman & Shallice (1986):
Supervisory Attentional System (SAS) (attention
demanding, conscious control)
contention scheduling: selects according to level of
activation, which is determined by trigger conditions of
the schema and lateral inhibition/excitation between
schemata.
SAS can bias activation values and is needed for
1) planning or decision making
2) Troubleshooting
3) learning new actions
4) technically difficult actions
5) overcoming strong pre-existing response
Perner, 1998
Two types of control (SAS and contention scheduling) relate
to the implicit-explicit distinction.
All the executive tasks
e.g. following verbal instructions to implement new actions,
planning
involve declarative representation of schema content "If S1
do A1" OR “Do A1” as a goal (often: as something
desired).
(Conditionals and imperatives must be fact explicit.)
Technically difficult actions (4) also presumably refers to
strengthening difficult actions by declarative
representations.
Trouble shooting (2) and overcoming response (5) require
one forms a declarative representation of what is to
inhibited as well as what is to be achieved.

Executive function tasks require fact-explicit
representations of goals.
(Contention scheduling can use fact-implicit representations
of conditions, actions, and goals.)
Perner (2002)
Vehicle control:
Action schema comes to control behaviour because of its
vehicle properties i.e. degree of activation.
(predication implicit knowledge)
Content control:
Fact-explicit representation ("if condition C then do action
A" or "do A") determines which schema comes to control
behaviour (the schema with the conditions and action
described by this representation).
Contention scheduling requires only vehicle control
Executive tasks require content control.
Content control-based system (the higher system) sets
off action schemata, that then run according to vehicle
control; the higher system may or may not monitor the
results of the action schemata.
The higher system (a) can trigger the lower system; (b) and
monitor its successful performance
Either or both of the above can lead to the representation "I
am intending this action".
Sense of agency and intention comes from the higher order
thought “I am intending this action”;
The function of this HOT is to
(i) track initial content control and
(ii) track consistency of vehicle control with any previous
content control that may have set the vehicle control up
Hierarchy of voluntary action:
- Non-intentional: vehicle control produces an action
not set by the higher system.
-Intentional: higher system sets up the lower system;
when appropriate conditions are met, the schema executes the
appropriate action.
- absent-minded intentional action: lower
system runs unmonitored, producing actions appropriate to
plan.
- fully content-controlled intentional action:
Higher system triggers and continuously monitors execution
of action schema, over-riding when necessary.
fully content-controlled intentional action
-without HOT: unconscious performance of
executive function tasks??
-fully voluntary action, i.e. performed with HOT
("I intend to perform this action")
(and typically with 3rd order thought, making you aware
of your intention "I know I am intending to perform this
action").
Hypnosis. Three possible mechanisms:
1 Content control without a HOT.
2 HOTs without first order states.
3 Different "I" representations.
Content control without a HOT?
a) Suggestion to forget the number "four": "1,2,3,5,6,.." must be content control, but person claims ignorance of
doing anything strange => no second order thought.
b) Spanos, Radtke, and Dubreuil (1982): highs suggested to
forget certain words in any type of task given to them
produced those words at a below baseline level in a word
association test. Content control, because the existing
associations that would be produced by vehicle control
must be suppressed.
In general, virtually any arbitrary behaviour can be
hypnotically suggested despite the fact that such behaviour
might be novel to the person, and many hypnotic suggestions
require the person ignore some salient aspect of the situation
(e.g. amnesia or analgesia suggestion) => many hypnotic
responses are under content control.
Highs are especially good at dissociating HOTS from fact
explicit representations?
Bowers and Woody (1996): (after hypnosis) highs could NOT
think of their favourite car for 2 minutes more effectively
than lows
How is the normal ascent from fact-explicitness to
attitude explicitness prevented?
According to HOT theory, HOTS are just thoughts
and so their occurrence will be sensitive to the same
influences as other thoughts (Rosenthal, 2001). That
is, consistent with the socio-cognitive approach, a
HOT about intention might not occur because of
Beliefs and expectations: the expectation that the
act will occur involuntarily prevents HOTS of
intending from occurring.
Highs are especially able to control HOTs with
expectations?
 If tell highs to expect a state of affairs they should be
more likely to consciously perceive it than lows.
Naish (1983): In a signal detection task (detect 300ms
tones amongst 360ms tones), when subjects were told the
signal would be more likely, the change in bias was
higher for highs than lows
(based on verbal report: perceptual experience changed
not just response tendency).
(cf Karlin, 1977; Dolby & Sheehan, 1977)
Assume: Third order HOTs (TOTs “I know I am intending
to do X”) are easier to suppress than second order HOTs
(SOTs “I am intending to do X”).
Maybe very highly hypnotizable subjects can suppress
SOTs – so can do “forget 4” task.
Mediums can only suppress TOTs. The second order
thought is still there making them aware of content of
content control (“do not say 4”), making them aware of 4.
So couldn’t do forget 4 task – or analgesia, amnesia, etc.
But could do other tasks e.g. arm levitation (would not be
aware of intending the arm to rise, so would appear
involuntary.)
=> Order of difficulty of hypnotic tasks (cognitive harder
than motor) explained?
2 HOTs without first order states.
Rosenthal (2000, 2001) : One can have a second order thought
that one is in a certain first order state, without actually being
in that state. It will seem to one that one is e.g. experiencing
pain even though in fact one is not!
=> mistaken HOTs could produce many of the experiences
brought about by hypnotic suggestion?
Such mistaken second order thoughts should be most likely to
occur if one strongly expects the first order state to occur.
If expectations operate directly on HOTs, hypnotic
hallucinations would not facilitate implicit perceptual tasks.
If expectations operate via suppressing intentions to
imagine (i.e. the first mechanism: content control without
HOTs), hypnotic hallucinations would involve brain
pathways involved in perception.
Kosslyn et al (2000): PET scan indicated highs having
visual hallucination had active visual pathways.
=> In this case, content control without HOT is a better
explanation than HOT without first order content.
Speculation: dissociation between HOTs and first order
states is brought about by expectations.
Consistently:
Kirsch (1985, 1991): Hypnotic experiences are the
outcome of expectations .
Or is there some other mechanism by which or state in
which HOTs are suppressed?? Are there individual
differences in the mechanism/extent to which expectations
can determine HOTs independently of first order content?
Evidence:
1) General responsiveness of hypnotic subjects to demand
characteristics
2) For suggestions given with no induction, correlation between
expectation of response and response = 0.53 (Braffman &
Kirsch, 1999)
3) Post-induction, expectation of number of suggestions that
will be experienced correlates highly with number of
hypnotic suggestions experienced, r = .64 (Council et al,
1986).
4) Subjects pass more suggestions after an induction rather than
without an induction only to the extent that they expect to
(Braffman & Kirsch, 1999).
3. Different "I" representations
Kihlstrom (1997): subject creates an additional
"Hypnotic I". Because the hypnotic I's intentions (causes
of hypnotic responding) are not linked to the normal "I"
the person does not experience himself as intending the
actions to occur.
Possible mechanism, but complex.
Cannot be the basis of most hypnotic responding - it
predicts a hidden observer, and a fully fledged hidden
observer only occurs for about 5% of the population.
Content control is presumably easier with relevant HOTs to
support it, they can add to and support the controlling
activation.
Therefore, to engage in content control without HOTs, one
must be good at content control.
Prediction: Highs should be better than lows at content
control. Is this true?
YES – on a range of different type of cognitive tasks
Relatedly, with brain imaging techniques Crawford has
argued highs respond to hypnotic suggestions with increase
in blood flow in anterior frontal cortex (location of SAS).
1) Graham & Evans (1977): Highs better than lows at
random number generation (failure to replicate:
Crawford et al 1993)
2) Naish (1983): Highs can bias perceptual schemata
more strongly than lows.
3) Dienes (1987): When hearing simultaneous lists of
words, highs can select on the basis of representational
content (semantic category) to a greater degree than
lows, but they cannot filter according to purely sensory
features any better than lows.
(cf Karlin, 1977; Dolby & Sheehan, 1977)
4) Dixon & Laurence (1992): Highs have greater strategic
control over reversing the Stroop effect than lows.
5) Some evidence highs can maintain attentional focus
better than lows (Das, 1964; Gur, 1974; Smyth & Lowry,
1983; Wallace & Patterson, 1984).
6) Some evidence that highs can co-ordinate the
processing of multiple simultaneous information sources
better than lows (Sigman, Phillips, & Clifford, 1985).
7) Some evidence that highs have faster reaction times to
complex decision-making tasks than lows (Crawford,
Horton, & Lamas, 1998).
Comparison with existing theories of hypnosis:
- Like socio-cognitive perspective (e.g. Spanos), our view
emphasizes strategic nature of hypnotic responding
BUT we regard the lack of voluntariness as real;
- like neo-dissociation theory (Hilgard), the "executive
ego" (SAS) is involved in responding
BUT there is not two streams of consciousness
- Bowers and Woody(1994): hypnosis involves a
weakening of frontal lobe function and thus contention
scheduling controls behaviour (hence the feeling of
involuntariness):
frontal lobe function must be less efficient without the
HOTs to support it
BUT hypnotic responding cannot be based simply upon
contention scheduling. Bowers and Woody’s theory fails to
get to grips with the highly strategic and, when necessary,
content-controlled nature of hypnotic responding.
like Bowers and Woody, control is split off from
consciousness, BUT the SAS is still involved.
Kirsch & Lynn (1997): hypnotic responding is based on
contention scheduling, and the generalized intention to
perform action x whenever it is suggested; this
"implementation intention" produces an automatic
response (action x) whenever its satisfaction conditions
(i.e. the suggestion) are obtained.
However, one cannot automatically perform tasks
requiring content control, not even with generalized
implementation intentions: One must specifically form
the right fact-explicit representation and this goes
beyond contention scheduling.
Conclusions
1. Executive function (content control) requires less
explicit representation than conscious awareness (fact
explicit vs attitude explicit)
2. Hypnotic responding often requires content control, but
subjects do not have relevant higher order thoughts
(attitude explicit representations) to make the content
control conscious
3. The theories of Hilgard and Spanos - that hypnotic
subjects respond strategically and with executive
function – seem right. The analysis in (1) shows there is
no need to try to force hypnotic responses into being
based on contention scheduling to account for the lack of
conscious intentions.