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Individual Differences

Tuesday 12/6/05

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Those traits that aid in survival or increase

the likelihood of reproductive access/success

tend to be propagated to a greater extent

than do traits that do not assist in survival orreproduction.

Selective breeding can mimic the process of

natural selection without the environmentalpressures of survival and reproductive

access.

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Tryon (1940)

Selective Breeding of Rats

Rats were selectively bred based on their

ability to learn complex mazes.

After 18 generations, two groups emerged: Maze-bright (MB) rats, which could learn to

navigate complex mazes very quickly and

accurately.

Maze-dull (MD) rats, which could learn to navigatecomplex mazes, but much more slowly and less

accurately.

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Cooper & Zubek (1958)Selective Breeding & Environment

Selectively bred rats to create a maze-bright

(MB) group and a maze-dull (MD) group.

All rats were reared in one of threeenvironments:

1. Restricted: in cages alone with no toys.

2. Normal: in cages with other rats but no toys.

3. Stimulating: in cages with other rats and lots of

toys, exercise equipment, and other movable

objects.

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Cooper & Zubek (1958)Selective Breeding & Environment

Results:

Restricted condition: poor learning in both MB

and MD rats.

Normal condition: same pattern as Tryon

(1940)--MB rats learned better than MD rats.

Stimulating condition: good learning in both MB

and MD rats.

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General conclusion from

selective rat breeding studies:

Tryon (1940) demonstrated that genetics can

influence specificlearning abilities in rats.

Expression of genetic differences in learning

abilities can depend on the conditions of the

rearing environment.

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Twin Studies

Identical & fraternal same-sex twins are

compared on many dimensions.

Any differences between the groups in thestrength of the relationships between the

abilities of the siblings are attributable to

genetic factors.

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Identical twins demonstrate a higher

correlation in recall ability than do fraternal

same-sex twins, (Thompson et al., 1991;Finkel & McGue, 1993).

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Age Differences in

Learning & Memory

The very old and very young do not respond

to classical conditioning as well as do those

individuals in intermediate age groups.

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Childhood Memory

Childhood amnesia: the inability to

remember early childhood experiences.

Average age of earliest memory is 3.5 years

(range: 2-7 years of age).

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Childhood amnesia may be the result of:

Encoding & retrieval incompatibilities (lack of

verbal skills during encoding)

Lack of preexisting knowledge structure

Insufficient working memory capacity

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Aging and Memory

Cognitive abilities in general (including

memory) tend to decline with age.

Some of the deficits in memory may be

attributable to a discrepancy betweenlearning and performance.

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Learning Disabilities

Most learning disabilities (dyslexia, ADHD,

etc.) affect only one stage, type, or function

of memory. Many common learning disabilities affect the

encoding stage.

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Pretty much done