Evolutionary thinking in the history of the comparative psychology of learning

Darwin's theory of evolution initially inspired researchers to search for intelligence in animals. The early work was dominated by the assumption that intelligence is qualitatively the same in all species, and that it is meaningful to compare all species in the same situation or situations. This assumption persisted through the "learning theory" era, even when interest had faded in species comparisons. Even today there has not yet been an adequate test of the assumption that intelligence is qualitatively the same across species and situations. Interest has returned, however, to a second implication of evolution: We should expect to find not only similarities among species, but also divergences and adaptation to specific problems. Some speculations are offered regarding implications for human intelligence.