Stimulus enhancement in greylag geese: socially mediated learning of an operant task

We recently observed the spreading of a novel tradition in a flock of semiferal greylag geese, Anser anser:
an increasing number of individuals began to bite and chew the stems of butterbur, Petasites hybridus.
Because this behaviour spread particularly fast within families, social learning seemed to be involved. We
therefore designed an experiment with hand-reared goslings, which were socially imprinted on humans,
to investigate whether and how the observation of an experienced tutor affects the acquisition of a novel
skill. Goslings had to open the gliding lid of a box to get at a food reward. To each of seven hand-reared
observers a human tutor demonstrated where and how to open the lid, whereas seven controls remained
untutored. All observers learned to perform the task but only one of the controls succeeded. The observers
explored more often at the position shown by the tutor than elsewhere and seemingly learned by trial
and error. In contrast, control birds explored primarily at positions that did not allow them to open the
box. These results indicate that in greylag goslings the observation of an experienced model facilitates the
learning of an operant task. We conclude that stimulus enhancement followed by operant conditioning
were the mechanisms involved, which may have accounted for the fast spread of the stem-chewing
tradition between family members.