Within-subjects experiments on blocking and facilitation in honeybees (Apis mellifera).

It has long been suspected in the vertebrate literature, but demonstrated only recently in work with honeybees (Apis mellifera), that the different treatments of nontarget stimuli in conventional between-groups blocking experiments may give the appearance of blocking independently of experience with the target stimulus. The same difficulty does not arise in within-subjects experiments, and in a series of such experiments with odors and colors free-flying honeybees gave no evidence of blocking; separate reinforced presentations of one element of a reinforced compound failed to reduce responding to the second. There was, however, clear evidence of facilitation; separate nonreinforced presentations of one element of a reinforced compound increased responding to the second. The implications of the results for further work on compound conditioning in honeybees and other animals are considered.