Cognitive Processes PSY 334 Chapter 14 – Individual Differences in Cognition

Gray Matter is Pruned Ages 5-20 Gogtay et al., 2004

White Matter Increases Ages 15 to 75 Prefrontal cortex Temporal lobe Bartzokis et al., 2001

What Changes?  Gray matter first thickens then thins as neurons are weeded out and most-used connections are strengthened. Development is sensory and motor first, then back-to-front with frontal areas last.  White matter increases with myelination of axons providing interconnections. This increases until age 50, then declines.  Both curves are quadratic, not linear.

What Develops  Two explanations for changes in children’s thinking: They think better – more working memory. They know better – more facts.  Probably both occur, due to neural changes: Increase in synaptic connections. Myelination increases neural transmission speed.

Empiricist vs Nativist Debate  Not exactly a nature-nurture debate but concerns where knowledge comes from.  Nativists argue that the most important knowledge is part of genetically programmed development.  Empiricists argue that virtually all knowledge comes from experience with the environment.  Implications for the potential to change.

Increased Mental Capacity  Case – memory-space proposal. Growing working memory development is the key to the developmental sequence.  Increased speed of neural function leads to increased working memory. Due to increased myelination  Kail – speed of mental rotation becomes faster with age (8-22 yo).

Increased Knowledge  Chi – developmental differences may be knowledge related. Children do worse than adults on most memory tasks. Where children are skilled at chess and adults are novices, children do better than adults.  Novice-expert comparisons can explain developmental differences. Children do not elaborate effectively.

Korkel’s Results GradeSoccer ExpertsSoccer Novices There was no effect of grade level, only expertise.

Cognition and Aging  Decreases in IQ performance scores occur after age 20: Related to speed of response on tests.  Older adults do better on jobs.  Age-related declines in brain function: Cell loss, shrinkage & atrophy. Compensatory growth of remaining cells. Brain-related degenerative disorders such as Alzheimer’s.

Mean WAIS-R IQ Declines Salthouse, 1992

Probability of a Philosopher’s “Best Book” Declines with Age Lehman, 1953

Ability to Hold Multiple Premises in Mind Declines Salthouse, 1992

Decline is NOT Disability  Note that substantial proportions of older individuals are able to write “best books” or do integrative reasoning even at 70.  Longitudinal and cross-sectional studies have problems: Age cohorts have different historical experiences (Great Depression, nutrition) Everyone declines from their own unique baseline, not relative to a group.

Use it or Lose It  With cognitive exercise: Number of neurons declines but number of synapses per neuron increases. Brain weight increases with age.  Without cognitive exercise: Number of neurons and brain weight both decline. Number of synapses per neuron declines.  Learn new things and stay active!

Psychometrics  Measures of performance of individuals on a number of tasks – examination of correlations across such tasks. IQ Tests – Binet, Stanford-Binet, Wechsler Mental age vs deviation IQ.  Factor analysis of performance scores: Crystallized intelligence – increases with age Fluid intelligence – decreases with age.

Distribution of S-B IQ Test Scores IQ ScoreTraditional Ranking System (~.25%)Genius or near genius Gifted Very Superior Intelligence Superior Intelligence Average/Normal Dullness Borderline deficiency Mild mental retardation 35-50Moderate mental retardation Severe mental retardation < 20Profound mental retardation (1%)

Kinds of Abilities  Reasoning ability: Sternberg connects psychometrics to the information-processing approach. People who score high on reasoning tests perform reasoning steps more quickly.  Verbal ability: Working memory capacity is related to verbal ability. People who recall words more rapidly do better on verbal ability tests.

Kinds of Abilities (Cont.)  Spatial ability: Rate of mental rotation is slower for those with lower spatial ability test scores. People with high spatial ability may choose to solve a problem spatially, not verbally.  Differences in abilities may result from differences in rates of processing and working-memory capacities. Unclear whether this is innate or a difference in practice (nature vs nurture).