Experimental evolution of prepared learning

Abstract

Animals learn some things more easily than others. To explain this so-called prepared learning, investigators commonly appeal to the evolutionary history of stimulus-consequence relationships experienced by a population or species. We offer a simple model that formalizes this long-standing hypothesis. The key variable in our model is the statistical reliability of the association between stimulus, action, and consequence. We use experimental evolution to test this hypothesis in populations of Drosophila. We systematically manipulated the reliability of two types of experience (the pairing of the aversive chemical quinine with color or with odor). Following 40 generations of evolution, data from learning assays support our basic prediction: Changes in learning abilities track the reliability of associations during a population's selective history. In populations where, for example, quinine-color pairings were unreliable but quinine-odor pairings were reliable, we find increased sensitivity to learning the quinine-odor experience and reduced sensitivity to learning quinine-color. To the best of our knowledge this is the first experimental demonstration of the evolution of prepared learning.

The evolution of cognitive mechanisms in response to cultural innovations

“…The assumption of no change requires us to posit a lack of genetic variance in learning mechanisms, which runs counter to substantial evidence (39,(41)(42)(43)(44)(45), or else to explain how the selection regime was miraculously unaffected by the new social niche. The assumption of evolutionary change may also be viewed as scientifically more productive, as it encourages further research (46).…”

“…In reality, of course, unlike in the beak example, learning mechanisms are not necessarily constrained to be uniform across all domains; there is plenty of evidence for adaptive specialization in associative learning mechanisms (e.g., refs. [38][39][40].…”

A social insect perspective on the evolution of social learning mechanisms

“…Experimental evolution paradigms provide evidence that environments where particular cue types are reliably useful for decision-making select for changes to the attentional or perceptual mechanisms that determine stimulus salience. For example, Drosophila lines for which learning about olfactory stimuli is the best method of identifying a good brood host develop enhanced sensitivity to such cues and ignore visual alternatives, and vice versa (36). In a social context, the question of whether social cues are especially salient has rarely been directly addressed [with the exception of Galef et al (64)], but a number of bee studies touch upon the topic, with mixed results.…”

“…These latter two alternatives-that bees are particularly sensitive to social CSs when learning about where to find food, or that they are particularly likely to learn positive social CS-sucrose combinations-are qualitatively different traits. Theory correspondingly predicts that they should evolve under different circumstances (36,71). To visualize the difference, consider again the Garcia effect (35).…”

“…In other words, whereas there may be little evidence to support a polarized view of asocial-and social learning processes, it does not follow that the ability to learn socially is simply a useful byproduct of the fundamental ability to learn asocially that has remained untouched by natural selection. There is clear empirical evidence that natural selection can fine-tune associative processes to particular tasks (34)(35)(36).…”