Introduction
to Psychology (Spring 2009)
Stimulus
Response Paper for January 29, 2009
By
Halford H. Fairchild
Gazzaniga, M.S. (1967). The split brain in man. Scientific American, 217, 24-29.
Stimulus. This article reviews the research on the specialized functions of the left and right cerebral hemispheres. In studies where the hemispheres have been separated (by cutting the bundle of nerve fibers that connect them, the corpus callosum), and by constructing specialized experimental situations (where stimuli may be presented to one hemisphere but not the other), researchers have found: (1) the left hemisphere controls the ability to use language; (2) the right hemisphere is more involved in spatial relationships (including artistic activities); (3) although the right hemisphere could think about and analyze objects, it could not verbalize those thoughts (placing language functions, again, in the left hemisphere); and (4) emotional reactions were experienced in both hemispheres, but verbalizations were accessible only to the left.
Response(s). These experiments are very interesting. However, too much may be made of these hemispheric specializations because, in the real world, with normal people (people who have not had their hemispheres separated—the vast majority), the two hemispheres communicate with each other almost simultaneously. That is, these specializations can only be demonstrated in the most unusual of circumstances.
On the other hand, Gazzaniga suggested that communication between hemispheres may not be so complete, in normal people; and other research has found that females have greater hemispheric communication than men.
It may be that a fully integrated
brain (one where the two hemispheres communicate well) can perform additional
cognitive tasks – in a gestalt, where
the whole is greater than the sum of its parts.
As Levy (1985) noted, no human activity uses only one side of the
brain. “
Rosenzweig, M.R., Bennett, E.L., & Diamond, M.C. (1972). Brain changes in response to experience. Scientific American, 226, 22-29.
Stimulus. This article reviews research on the effects of “enriched” or “impoverished” environments on the brains of laboratory rats. “Enriched” rats were handled more and had “toys” in their cages. Findings supported the idea that the brains of the “enriched” rats were more developed (heavier and thicker; and greater number of glial cells with larger neurons). The “enriched rats had a higher level of chemical activity in their brains. Synapses, too, were larger. When they studied wild deer mice placed in the “enriched” laboratory cages, and compared them to mice in a more natural environment, the “enriched” environments were deemed impoverished relative to the real-world environments. The authors make cautious statements about possible generalizations to humans. They suggested, for example, that malnutrition could be detrimental to cerebral development.
Related research: Even the brains of adult animals, reared in impoverished conditions, could improve when placed in an enriched environment. The visual cortex of blind persons are less developed (less convoluted and thinner) than persons with normal sight. Implications for humans: stimulation is good (use it or lose it).
Responses. This line of research has been cited by scientific racists, who have suggested that the environments of poor people – impoverished – may be linked to their lower intelligence. Interestingly, researchers found that the home environments of poor people is exceedingly stimulating (lots of people and sounds and sights) – and they concluded that there may be too much stimulation in these homes.
The “typical” American middle-class home isn’t.
How do you “humanely” sacrifice the animals?
“Enriched” and “impoverished” – the language of finances.
Just because a synapse is bigger doesn’t make it better. Does it?
Generalizing across species should be done with great caution.
Bourchard, T., Lykken, D., McGue, M., Segal, N., & Tellegen, A. (1990). Sources of human psychological differences: The Minnesota study of twins reared apart. Science, 250, 223-229.
Stimulus: The studies of monozygotic twins reared apart (vs. reared together) concludes that many attributes are genetically determined.
Responses: This line of research is fundamentally flawed for its pseudo-experimental nature. There is no random assignment, and sampling is haphazard.
It suffers from experimenter (researcher) biases.
This line of research has been castigated as contributing to scientific racism. It reaches the same conclusions of highly disputed research by Sir Francis Galton and Arthur Jensen. The hidden agenda may be to accept racial inequality as inevitable.
"Who are you" is reminiscent of the Twenty Statements Test.
We almost always attribute our personalities to environmental causes, with perhaps an exception being homosexuality.
Physical attributes (height, skin color, etc.) are genetically determined, sure, but they interact with the social environment. Being cute has its advantages.
Nature and nurture are inextricable and always operate together.
A "sense of humor" gene? Ya gotta be kidding. Multiple genes always are determinative.
Nature is 100% determinative (we could have the genetics of a fruit fly, for example); as is environment. Both are 100% important. Ball of clay.
The correlation of human attributes (and genes) and those of monkeys is greater than zero.
Researchers should compare their correlations with people who are completely unrelated.
Thought experiment: Clone 16 HHFs and put them in radically different environments. You'll get radically different outcomes.