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We investigate simple mechanisms for social learning in an evolutionary simulation of food-preference copying in Norway rats. These animals learn preferences by interacting with conspecifics, but, unexpectedly, they fail to learn aversions after interacting with a poisoned demonstrator. They also follow each other to food sites. Simulation results show that failure to discriminate between sick and healthy demonstrators may be due to details of food toxicity in foraging environments. A seemingly complex instance of social information transmission is explained through the action of simple behaviours in an appropriately structured environment.

Decreased distractibility in young male chicks (Gallus domesticus) following the administration of testosterone esters was first described for search tests (Andrew and Rogers 1972). Two procedures were followed. In the first, food grains of two different colours (both of which were acceptable to the chick) were presented in clumps. Choise was biassed towards one type by previous training, in some cases by very brief exposure just before test. Testosterone-treated chicks (T’s) sustained search on a clump for longer, sometimes ending with a single peck on non-preferred food before shifting to another clump, when they at once resumed choice of the preferred food type. Controls shifted more readily between clumps as the preferred food was exhausted, but they also shifted more readily to sustained choice of the second food type. The second procedure showed this latter effect more clearly. Here the two types of food were presented against a distracting background of pebbles which matched in colour the preferred food type. Under these conditions, only T’s were able to sustain long runs on the preferred food, whilst controls took both types in an opportunistic way. Level of deprivation has no effect on the differences between T’s and controls: this and other appropriate control procedures are reviewed by Andrew (1972).