INDIVIDUAL VERSUS SOCIAL-LEARNING - EVOLUTIONARY ANALYSIS IN A FLUCTUATING ENVIRONMENT

A model for haploid asexual inheritance of social and individual learn ing is proposed. Animals of one genotype, individual learners (IL), be have optimally for the current environment and, except for a fixed cos t due to learning errors, have the optimal fitness in that environment . Animals of the other genotype are social learners (SL) each of whom copies a random individual from the previous generation. However, the phenotype of a social learner depends on whom it copies. If it copies an IL or a correctly behaving SL, it has the ''correct'' phenogenotype , SLC. Otherwise, its behavior is wrong and we call its phenogenotype SLW. Different models for the environmental fluctuation produce differ ent dynamics for the frequency of SL animals. An infinite state enviro nment is such that when it changes, it never reverts to an earlier sta te. If it changes every generation, social learning can never succeed. If, however, a generation in which the environment changes is followe d by L-1 generations of environmental stasis and l greater than or equ al to 3, some fitness sets do allow the maintenance of social learning . Analogous results are shown for a randomly fluctuating environment, and for cyclic two-state environments. In a second type of model, each animal can learn individually with probability L. We examine the evol utionary stability properties of this probability in the infinite stat e environment. When a generation of change is followed by L-1 generati ons of stasis, fitness parameters can be found that produce an evoluti onarily stable nonzero probability of social learning. In all of the m odels treated, the greater the probability of environmental change, th e more difficult it is for social learning to evolve.