Tryon's Rat Experiment
Tryon's Rat Experiment is a psychology experiment conducted by Robert Tryon in 1940 and published in the Yearbook of the National Society for Studies in Education.[1]
Experiment set-up
[edit]Prior to Robert Tryon’s study of selective rat breeding, concluded in 1942, many psychologists believed that environmental, rather than genetic, differences produced individual behavioral variations. Tryon sought to demonstrate that genetic traits often did, in fact, contribute to behavior. To do so, Tryon created an experiment that tested the proficiency of successive generations of rats in completing a maze. He initiated the experiment by exposing a genetically diverse group of rats to the maze, labeling those who made the fewest errors “bright”, and those with the most errors “dull”. Tryon then mated the “bright” males with “bright” females, and “dull” males with “dull” females. After their children matured, Tryon repeated the maze test with them, and again separated the “bright” and the “dull”, again breeding “bright” with “bright” and “dull” with “dull”. Tryon continued this process for seven generations, creating two distinct breeds of “bright” and “dull” rats. In order to demonstrate that behavior had little effect on the genetically selectively bred rats, and lessen the chance of error when making his conclusions, Tryon cross-fostered the rats—that is, he had a “dull” mother raise “bright” children, and vice versa. The independent variables in his experiment were the parental pairings, the choice of environment and parents for upbringing, and number of rats put through the maze. The dependent variable was the number of errors made by the rats in 19 trials of the maze.[2]
Implications and conclusions
[edit]While Tryon's results showed that the “bright" rats made significantly fewer errors in the maze than the “dull" rats did, the question exists of what other sensory, motor, motivational, and learning processes also influenced the results of the experiment. A common misconception of this experiment and other similar experiments is that the observed change in the performance in the maze directly correlates with general learning ability. This is not the case. Rather, it has become a widely accepted belief among behavior geneticists that the superiority of the bright rats may have been confined to Tryon’s specific test; thus, it is not necessarily due to a difference in learning capacity between the two groups of rats. Genetic variation, such as better peripheral vision, can make some rats “bright” and others “dull”, but does not determine their intelligence.[3] Nonetheless, Tryon’s famous rat-maze experiment demonstrated that the difference between rat performances was genetic since their environments were controlled and identical.[4]
See also
[edit]- Behavioural genetics
- Nature and nurture
- Artificial selection
- Gene-environment interaction
- Selective breeding
References
[edit]- ^ Tryon, R. C. (1940). Genetic differences in maze-learning ability in rats. Yearbook of the National Society for Studies in Education, 39, pp. 111-119
- ^ Gray, Peter. Psychology. 6th ed. New York: Worth, 2007. Print.
- ^ Martinez, Joe and Raymond Kesner. Neurobiology of Learning and Memory. Massachusetts: Elsevier Inc., 2007. Print.
- ^ Cooper, R. M. and Zubek, J. P. (1958). "Effects of enriched and restricted early environments on the learning ability of bright and dull rats". Canadian Journal of Psychology 12 (3): 159–164. PMID 13573245
Further reading
[edit]- Cooper & Zubek 1958, "Effects of Enrich and Restricted Early Environments on the Learning Ability of Bright and Dull Rats"
- Davis & Tolman 1924, "A Note on the Correlations Between Two Mazes"
- Hirsch & Tryon 1956, "Mass Screening and Reliable Individual Measurement in the Experimental Behavior Genetics of Lower Organisms"
- Krechevsky 1933, "Hereditary Nature of 'Hypotheses'"
- Hall 1951, "The Genetics of Behavior" (inHandbook of Experimental Psychology', Stevens 1951)
- McClearn 1959, "The Genetics of Mouse Behavior in Novel Situations"
- McClearn 1962, "The Inheritance of Behavior"
- Hirsch et al 1967, _Behavior-Genetic Analysis_
- McClearn 1970, "Behavioral Genetics"
- Rosenthal, R, & Fode, K. (1963). "The effect of experimenter bias on the performance of the albino rat". Behavioral Science, 8, 183-189.
- Stone & Nyswander 1927, "The Reliability of Rat Learning Scores from the Multiple-T Maze as Determined by Four Different Methods"
- Tolman & Jeffress 1925, "A Self-Recording Maze"
- Tolman & Nyswander 1927, "The Reliability and Validity of Maze-Measures for Rats"
- Tolman 1924, "The Inheritance of Maze-Learning Ability in Rats"