IQ testing: time to
move on?
Jenny Webb
Consultant Clinical Psychologist
jenny.webb@agencyandaccess.co.uk
An early question ...
“IQ as a score is inherently meaningless and not
infrequently misleading as well. ‘IQ’ has outlived
whatever usefulness it may once have had and
should be discarded ... Combined scores such as
the ‘Index Scores’ in Wechsler batteries may also
obscure important information
obtainable only by examining
discrete scores”
(Lezak et al, 2004:22)
Mapping the territory
History
Reliability
IQ testing
Validity
Alternatives
Purpose
Context
The First World War
• Wechsler was an army test administrator
• Used Alpha, Beta & Army Performance
tests in selection of recruits
• 1.7 M men tested
• 1916 Terman devised IQ score, based
on ratio of mental to chronological age
And after the war ...
• Post-war use of tests in schools and acceptance
of idea of fixed, inherited intelligence, in both US
and Britain
• Wechsler repackaged army tests for
psychiatric patients in asylums, with
new method of computing IQ scores
• The birth of the IQ test as
we now know it in 1939 with
publication of the Wechsler-Bellevue
But what was being measured?
• “to demand ... that one who would measure intelligence
should first present a complete definition of it, is quite
unreasonable ... Electrical currents were measured long
before their nature was well understood” (Terman, 1916)
• “Intelligence is what the
intelligence tests test”
(Boring, 1929)
• “Statistical norms and values become incorporated within the
very texture of conceptions of what is today’s psychological
reality.” (Rose, 1991)
Wechsler’s concept of intelligence
• 1944: The “capacity of the individual to act
purposefully, to think rationally, and to deal effectively
with his environment”
• 1981: “an overall competency or global capacity”
“Multi-faceted and multi-determined”
“A function of the personality as a whole – responsive
to factors other than cognitive abilities” (‘conative’
variables)
• (what IQ tests measure) “is not something which can
be expressed by one single factor alone, say ‘g’”
(Wechsler, quoted in Tulsky et al, 2003)
And in the WAIS-IV ...
What it does ...
• Validity established by extent to which results correlate with
those of earlier intelligence tests, and correlations between
result on subtests which comprise the four indexes
What it says ...
• Validity refers to the degree to which evidence supports the
interpretation of test scores for the intended purpose ... As a
result, examination of a test’s validity requires an evaluative
judgement by the tester
• Evolving conceptualizations of validity no longer speak of
different types of validity but speak instead of different types
of validity evidence, all in service of providing information
relevant to specific intended interpretation of test score.
(American Educational Research Association, in WAIS-IV Manual, 2008)
What does DSM-V say?
• The definition of LD is largely unchanged
• But a proposal has been made to locate it within a
group of conditions labelled ‘Neurodevelopmental
Disorders’. ‘Mild mental retardation’ is to be
placed at one end of a single spectrum that
includes people with autistic spectrum disorders
(Andrews et al, 2009).
• Very few references taken from the LD literature
What does the BPS say?
• In its response, the BPS recognised that the
diagnostic systems for mental illness “fall short of
the criteria for legitimate medical diagnoses”.
• But as far as LD is concerned, the BPS said
that:“the use of diagnostic labels has greater
validity, both on theoretical and empirical
grounds” (BPS, 2011).
• No changes were suggested
What does it mean to ask about
construct validity?
• Based on the assumptions that:
– the construct ‘really’ exists
– it forms part of a theoretical network of propositions
which yield falsifiable predictions (Boyle, 2001; Popper, 1963)
• These assumptions are problematic, in the case
of both intelligence, and hence with learning
disability, which piggy-backs on the construct of
intelligence
Theories of intelligence and LD
• The definition of intelligence is still disputed.
• Psychiatric diagnoses in general do not meet the
criteria of construct validity given above
• The definition of LD includes reference to
adaptive function, which is one of the behaviours
that the intelligence test seeks to predict
• Poor reliability implies absence of validity
Reliability
• Poor reliability applies not just to cut-off point but
to standardisation in general including:
–
–
–
–
Method of recruitment of standardisation sample
Exclusion criteria
Very low numbers of people with LD in each age group
Assumption of normal curve, which probably does not
apply in the low IQ range
– Irregulaties in test administration by clinicians
– Arbitrary changes in test content
– Test items not standardised on PWLD
Ecological validity
• Intelligence as measure by IQ correlates with
academic performance, occupational
achievement (Sternberg et al, 2001; Dickerson Mayes et al, 2009),
and survival into old age (Deary et al, 2008)
• But relationship to measures of adaptive
behaviour only moderate (Whitaker, 2003)
• IQ in PWLD a less significant contributor to
self-determination than opportunity to make
choices (Wehmeyer & Garner, 2003)
Historical relativity
• We cannot assume that ‘learning disability’ equates with
earlier labels for people seen as having cognitive
impairments (Goodey, 2011). Abilities needed to function in
different eras vary
• The medicalisation of LD only occurred in the 19th Century
with the institutional ascendance of the medical profession
• There has also always been a political agenda, beginning with
concern about property rights in Middle Ages
• From 1961-1972 the definition of LD given by the AAMR
specified an IQ of one SD below the mean (ie IQ 85). In 1973
this was revised to raise the cut-off point to two SDs below
the mean (ie IQ 70)
Cultural relativity
ICD10 Diagnostic Criteria for Research
• Detailed diagnostic criteria cannot be specified for
mental retardation, since ‘low cognitive ability and
diminished social competence, are profoundly affected
by social and cultural influences’ (WHO, 1993: F70-7).
• Eg
– Kenya: intelligence defined as “the ability to do without
being told what needed to be done around the homestead”
– Brazilian street children: may fail maths at school, but run
successful street businesses
(Sternberg, 2001 on ‘Practical Intelligence’)
How is the WAIS used?
1. As a way of locating the person in relation to
the hypothesised normal distribution of
intelligence. They may then be labelled as
‘having’ or ‘not having’ a LD and services may
be allocated on this basis.
2. As a test of discrete cognitive functions eg
verbal expression, visuo-spatial ability,
though most of the tests involve multiple
cognitive functions.
Alternative models of
cognitive assessment
• Neuropsychological (localisation/functional
interconnections) (Lezak et al, 2004; Luria, 1970)
• Developmental (Hogg & Sebba, 1986)
• Developmental cognitive neuropsychology
(Karmiloff-Smith, 1995)
• Capacity to learn (Feuerstein R & Rand Y, 1998)
• Environmental demands/supports (AAMR, 1992)
• Central role of non-cognitive variables (Raven &
Raven, 2008)
Social implications
• Intelligence testing has always served a social function, at its worst
associated with labelling, stigma, discrimination, eugenic solutions,
racism, imprisonment and control of reproduction eg: “intelligence
tests ...will ultimately result in curtailing the reproduction of
feeblemindedness and the elimination of an enormous amount of
crime, pauperism, and industrial inefficiency” (Terman, quoted in
Minton, 1988).
• In my experience IQ score is currently used as way of rationing
services. ‘Mild’ LD is equated with low risk or mild problem. This is
regardless of the actual level of risk the person faces.
• A moral dimension attaches to this discrimination, so that certain
people are seen as not only ineligible but undeserving of services.
This is reminiscent of Victorian distinction between the deserving
and undeserving poor.
Stephen, aged 25
• Prospective father
• Born with cerebral palsy, and has hearing
impairment
• Has a troubled history
• Is very chatty and appears capable
• Refused service from both LD SS and Locality SS
team
• ABAS results:
– General Adaptive Composite
68-74 (per. rank 3)
Stephen’s WAIS results
Similarities
Digit Span
Vocabulary
Arithmetic
Information
Scaled Score
4
6
4
3
8
Scaled Score
Block Design
6
Matrix Reasoning
6
Symbol Search
9
Coding
4
Composite
Score
Verbal Comprehension Index 69-81
Perceptual Reasoning
72-84
Working Memory
64-78
Processing Speed
75-91
Full Scale IQ
68-76
Percentile
Rank
4
6
2
10
3
Stephen’s OT AMPS Assessment
(Assessment of Motor & Process Skills)
Standard score
*ADL Motor
^ADL Process
51
<45
Percentile rank
< 1.0
< 1.0
*Observable, goal-directed actions enabling a person to
move themselves or task objects
^Observable, goal-directed actions that are used to logically
organise & adapt behaviour in order to complete a task
Stephen’s OT Report
Difficulties in eg:
• Positioning body, reaching for objects,
manipulating & carrying objects, coordination,
walking
• Distraction, carelessness, organisation,
anticipating change & responding to problems,
learning from experience
Conclusions: safety issues; limited potential to learn
new skills; need for compensatory strategies
Stephen’s SALT Report,
after initial visit
•
•
•
•
Tangential conversation
Reluctant to say he does not understand
Literal interpretation
Difficulty in understanding negatives,
prepositions, reversible sentences, comparatives,
plurals, complex sentences
• Unable to tell the time
• Acquiescent, leading to frustration & anger
How should we report on
Stephen’s LD assessment?
• Say he has not ‘got’ a learning disability?
• Produce a long and
nuanced report?
• Fiddle the results?
A different direction?
• Leave definition of ID to the
psychiatrists and redefine LD
in a clinically meaningful way
• There are several suggestions which we can draw
on. These mostly include the concepts of:
– age of onset
– cognitive function
– adaptive function
– risk
– vulnerability
Alternative definitions of LD
• Flynn (2000) suggests the use of direct tests of impaired adaptive
behaviour to assess intellectual disability.
• Greenspan & Switzky (2006) suggest defining ID in terms of
deficits of conceptual, practical and social intelligence that result
in a need for supports in order to succeed in culturally relevant
roles
• Greenspan et al (2011) suggest that impairments are
demonstrated by the person’s history of academic, practical and
social risk
• Whitaker’s (2008) definition links competence, environmental
demands, intellect, risk and distress.
• Raven & Raven (2008) suggest finding out what interests the
person, and then how good they are at the cognitive functions
needed for this task.
Another suggestion ...
“The learning disabled are those people who,
due to cognitive deficits beginning at birth or
during childhood, are unable to fulfil social
roles in a way that is expected in a particular
society at a particular time, and hence are
considered to be at risk, practically, physically,
socially or emotionally.”
(Webb, 2014)
Link between LD definition,
formulation and intervention
BPS Good Practice Guidelines on Formulation:
recent moves within Clinical Psychology to
begin to "develop coherent, credible
alternative forms of categorisation which are
based on psychological theory and which have
direct implications for both aetiology and
intervention" (BPS, 2011)
Whatever we decide ...
I hope we will not collude in withholding of
services to very vulnerable people by
continuing to use a definition of learning
disability which is theoretically &
methodologically unsound.
I hope that today we can begin to seek a
definition which is both meaningful and
helpful to our very vulnerable clients
Selected references re definition
BPS (June 2011) Response to American Psychiatric Association: DSM-V
Development
Flynn J R (2000) The hidden history of IQ and special education
Psychology, Public Policy and Law, 6, 1, 191-8
Greenspan S & Switzky N (2006) What is Mental Retardation? Ideas for an
evolving disability in the 21st Century Washington DC: AAMR
Greenspan et al (2011) Intelligence involves risk-awareness and
intellectual disability involves risk-unawareness: implications of a
theory of common sense Journal of Intellectual and Developmental
Disability 36, 246-57
Raven J & Raven J eds (2008) The Uses & Abuses of Intelligence NY: Royal
Fireworks Press
Webb J (2014) A guide to psychological understanding of people with
learning disabilities: eight domains and three stories London:
Routledge
Whitaker S (2008) Intellectual disability: a concept in need of revision?
British Journal of Developmental Disabilities 54(1) 3-9
Other references
Andrews G et al (2009) Exploring the feasibility of a meta-structure for
DSMV and 1CD11: could it improve utility and validity?
Psychological Medicine 39, 1992-2000
Boyle M (2000) Schizophrenia: a Scientific Delusion?
BPS (2011) Good Practice Guidelines on the Use of Psychological
Formulation Leicester: BPS
Feuerstein R & Rand Y (1998) Don’t Accept Me As I Am Arlington
Heights: Skylight
Flynn J R (2000) The hidden history of IQ and special education
Psychology, Public Policy and Law, 6, 1, 191-8
Goodey CF (2011) A History of Intelligence and Intellectual Disability:
the shaping of Psychology in early modern Europe Farnham:
Ashgate
Luria A R (1970) The functional organisation of the brain Scientific
American 222 (3) 66-78
Other references cont’d
McKenzie K, Murray G C &Wright J (2004) Adaptations and
accommodations: the use of the WAISIII with PWLD Clinical
Psychology 43, 23-6
Murdoch S (2007) IQ testing: the brilliant idea that failed London:
Duckworth Overlook
Popper K (1963) Conjectures and refutations London: Routledge
Russell E W (2010) The ‘obsolescence’ of assessment procedures
Applied Neuropsychology 17, 60-67
Sternberg R J et al (2001) The predictive value of IQ Merrill-Palmer
Quarterly 457(1), 1-41
Wehmeyer M L & Garner N W (2003) The impact of personal
characteristics of people with intellectual and developmental
disability on self-determination and autonomous functioning
Journal of Applied Research in Intellectual Disabilities 16, 255-65