Neuroscience 20a – Intelligence

Anil Chopra

1.Define intelligence as a psychological concept

2.Describe some common tests used to measure intelligence and the differences between them

3.Understanding the use and application of the WAIS

4.Evaluate the strengths and limitations of IQ tests

5.Understand psychometric approaches to intelligence

6.Give examples of how heredity and environment influence intelligence

Intelligence is defined as aproperty of mind that encompasses many related mental abilities, such as the capacity to

reason

plan

solve problems

think abstractly

comprehend ideas and language

learn

To an extent the definition of intelligence is culturally shaped because different practices tend to recognised different social intellectual qualities.

Measuring Intelligence

Mental Age: this is a test developed for children of different age groups. A child’s ability was expressed as a mental age (MA) corresponding to the level of ability of a particular chronological age (CA) that they matched.

IQ – Intelligence Quotient: the average intelligence quotient is 100 and is assessed by their mental age/chronological age x 100. IQ has a bell-shaped normal distribution with a standard deviation of around 15 points.

IQ tests are used in the clinic for selection, diagnosis and evaluation and take the form of questions that test verbal and non-verbal intelligence.


The current test used for children is the Weschler Intelligence Scale for Children (WISC/WISC-III) and is split into:

Verbal IQ - facility for symbolic thought and language

  • General knowledge
  • Comprehension
  • Mathematical and arithmetic ability
  • Associations and similarities between word
  • Vocabulary
  • Contains questions on digit span.
  • Sequences – numbers and letters.

Performance IQ - symbolic nonverbal thought and processing speed.

  • Picture completion
  • Digit-symbol coding
  • Block design
  • Matrix reasoning
  • Picture arrangement
  • Object assembly
  • Symbol search.

They are used in neuropsychological diagnosis and produce 4 indices:

1) Verbal comprehension: Thinking in language, a left hemisphere ability

2) Perceptual organisation: Thinking in visual images, predominantly a right hemisphere function

3) Working memory: Ability to hold and manipulate items in memory to solve problems, involving the frontal lobes

4) Processing speed:Time to apprehend, scan, retrieve, and respond to stimuli

Premorbid IQ

This can be used to in neurodegenerative conditions. Whilst patients may not be able to give definitions, their ability to pronounce a word can signify familiarity. Two tests are used:

  • National Adult Reading Test-Revised (Nelson)
  • Wechsler Test of Adult Reading (Wechsler)

Validity of IQ:

»Correlates about 0.6-0.7 with school grades

»Useful in targeting children at either extreme of the scale

»Valid when comparing people of the same culture, not valid when looking between cultures or minorities within a culture

»A powerful predictor of job performance and occupational achievement

»Evaluates areas of intelligence important in a literate industrialised society

Limits of IQ Tests

IQ tests came about due to social, educational and political need.

Tests are not based on cognitive and brain models.

They do not assess creativity or interpersonal skill.

There is a cultural bias – white middle class people perform better.

Serpell (1979) asked Zambian and English children to reproduce patterns in three media: wire models, clay models, or pencil and paper. Zambian children excelled in the wire medium. English children were best with pencil and paper.

Psychometric Approaches

The most common tests were those that assessed general intelligence – g. Spearman showed that generally scores on individual tasks were correlated i.e. that being good at one activity generally made patients good at another.

There were other tests that assessed specific abilities – s. These included verbal/numerical tests and spatial/mechanical tests.

Cattell later proposed the ideas of fluid and crystallised intelligence:

  • Fluidintelligence: assess the ability to process information and approach novel problems - gf
  • Crystallisedintelligence: assess individual’s store of knowledge, much of which is learned form culture –gc

Recent Factor analysis shows that there is a 3 level hierarchy to intelligence:

a general factor

primary abilities

specific abilities

Pros and cons of psychometric approach:

The predictive ability of IQ tests are impressive

They can identify, but not explain the underlying processes

More specific factors such as those above in the Cattell model do not relate to neurophsychological concepts

Longitudinal studies show that specific factors change with age while “g” all round cognitive ability is insensitive to change and different developmental trajectories

Information Processing Approach:

-Aims to determine the underlying processes and the different cognitive operations used in thinking

-Processes include:

  • Speed of processing – strong correlate to IQ
  • Knowledge base – amount stores in long-term memory, they way it is organised and ease of accessibility
  • Ability to acquire and apply cognitive strategies – e.g. mnemonics and formulas for solving maths

Multiple Intelligences

Gardener Later put forward the theory that there were 7 kinds of intelligences:

  • musical
  • bodily/kinaesthetic as in athletes and dancers
  • spatial as in mental maps
  • Linguistic/verbal
  • logical/mathematical
  • intrapersonal- self understanding
  • interpersonal - social skills

Evidence for Theory:

  • Each skill can be isolated with its own rules, procedures and memory systems
  • Savants = individuals with pockets of superior ability against a background of disability
  • Prodigies = people who can write music before read – i.e. musical IQ independent of verbal ability
  • Differental childhood develop courses

He concluded that each of these develops separately, with its own rules, procedures and memory systems. He also examined additional types of intelligence such as naturalist intelligence i.e. being able to assess features of the environment, existential intelligence i.e. concerning ultimate issues, and moral intelligence i.e. associated with the rules, behaviours and attitudes of life.

Limitations to “Multiple Intelligence” Theory

-does not take into account any general abilities

-difficult to measure

-there is a potential for intelligence sub-categories

-some of the so-called intelligences may be just talents

Determination of IQ

»Piaget proposed that intelligence develops through the addition of information into an existing structure.

»Vygotsky proposed that intellectual abilities are social in origin.

»There is a certain amount of hereditary association with intelligence:

  • Gene activation requires an environment, often an interpersonal or environmental one.
  • A sizable part of the variation in intelligence test scores isassociated with genetic differences among individuals.
  • The figures are misleading because most tests are done on children.

»There are number of biological variables

  • Malnutrition (esp. in childhood).
  • Blood lead levels.
  • Foetal alcohol syndrome
  • Prenatal exposure to aspirin and antibiotics.

»The average IQ has increased in the last 50 years, most probably due to richer cultural environment, nutrition and artefact.

»There are no differences in overall IQ between males and females however:

  • Males better on visual-spatial tasks like mental rotation and spatio-temporal tasks like tracking a moving object through space
  • Females better on some verbal tasks including synonym generation and verbal fluency.

Learning Disabilities

MILD 50-70

No demonstrable CNS abnormality

Social class bias, predominantly in lower classes

Concerns 1 million in UK

SEVERE <50

CNS aetiology - chromosomal - Down’s syndrome

No social class bias

Psychological training greatest gains in this group

Concerns 150,000 in UK

Left Handedness:

  • 12% of the population are left handed, most are normal but left handedness is more common in neurological disorders
  • 20% of mentally retarded are left handed, also common in epilepsy, autism and learning disorders
  • The majority of right handed have language in the left hemisphere, in left handed it is more commonly bilateral or in the right hemisphere
  • Left handedness with right hemisphere language sometimes shows evidence of early left hemisphere brain damage.