ABSTRACT
Many human characteristics have been studied with the goal of determining the relative contributions of heredity and environment. The methods employed are necessarily less direct than the techniques of animal studies. R. B. Lockard found that rats with different genotypes reared in the same environmental conditions differ also in light-contingent bar-pressing activity. A number of theories of personality and temperament propose a relationship between the need for sensory stimulation and emotional functioning. Generally, both features are regarded as strongly genetically determined. However, environmental factors also are claimed to contribute to their development. Emotional reactivity also was examined during avoidance reaction training. Psychologists study the behavior of so-called lower animals with the hope of finding principles that can be generalized to the behavior of humans. The general assumption is that principles derived from animal research can be used as hypotheses for human behavior.
