Social induction of malleability in ducklings: sensory basis and psychological mechanism

Abstract Abstract. At the organismic level, the first step in the pathway to evolutionary change is a deviation from species-typical behaviour. The present experiments examined how social rearing can foster species-atypical behaviour. Social rearing fosters such an extreme degree of malleability in mallard ducklings that when socially reared mallard ducklings are exposed to the chicken maternal call, they come to prefer it to the mallard maternal call in simultaneous auditory choice tests. Social isolates do not develop a preference for the chicken call. The present experiments were designed to elucidate the sensory features of the social situation that are essential to malleability and to determine what these sensory features do that creates a psychologically malleable state in the socially reared duckling. The experimental results indicate that tactile contact is the sensory basis of malleability and such contact is effective even if provided by stuffed ducklings. Tactile isolation, even in ducklings that can see and hear other ducklings, engenders such a high degree of arousal that malleability is absent when ducklings are tactually isolated from one another. Tactile contact affords an optimum low level of arousal that is essential to malleability.