Abstract:The basic patterns of inheritance of learning ability in animals have been delineated. Summaries of strain differences in learning rate, responses to selective breeding for learning, heritabilities of learning phenotypes, and heterosis and overdominance are presented. In addition, the patterns of inheritance are shown to vary with the early environment.The causes of genetic differences have received much attention, but much of the research is inconclusive. Both general learning ability and task-specific abilities are important, but their relative importance is not known for most learning tasks. Strain differences have been found to vary widely in response to variations in stimulus parameters, motivational levels, temporal spacing of trials, and pharmacological manipulations. However, in only a few cases have strain differences in learning actually been shown to be attributable to differences in sensory capacities, motivation, memory or activity levels. The physiological bases for differences are totally unknown. The pathways of gene action on learning also await discovery.Although some researchers have claimed to study the adaptive value of learning, their exclusive utilization of laboratory populations precludes meaningful interpretation of their results.Several methodological shortcomings of various experiments are considered, and important areas for future research are suggested.
Article:Learning is a phenotype which has engaged the interests of numerous researchers seeking genetic bases for behavioral differences. In fact, much of the earliest research identifiable as behavior genetics dealt with some aspect of learning in animals (Bagg, 1916;Yerkes, 1916;Tolman, 1924). Ensuing experimentation was performed primarily by psychologists using genetically ill-defined populations. The rather recent appearance of standardized inbred mouse strains with widespread availability has led to renewed interest in the genetic analysis of learning, as well as other phenotypes. Several sophisticated quantitative genetic tools are now readily available for the study of learning. Examples of the application to learning research of selective breeding, the classical cross, the diallel cross, sib analysis, parent-offspring regression, and single-gene analysis have appeared recently.A central motive for compiling the present review is the author's opinion that the increase in genetic sophistication has not been paralleled by a similar growth in the sophistication of measures of learning. In many studies it appears that learning was selected as a phenotype of convenience and general interest.Similarly, the questions about learning investigated have tended to be simplistic and of little interest to those concerned with the nature of the learning process itself. Many recent studies have raised issues that were presented in the earliest research and therefore have contributed little to progress in the area. This is an unfortunate situation in view of the potential power of genetic techniques to answer important questions abou...