Serial learning in the pigeon in a free correction procedure: role of reinforcing values

Pigeons were shown four chromatic stimuli simultaneously (A, B, C, D) in daily 15-min sessions. A free correction procedure was used: production of the series A-->B-->C resulted in food delivery and ended a trial, while incorrect colour pecks had no consequences. The learning criterion (five consecutive correct series) was not achieved after 50 sessions, although the number of correct responses increased progressively. From around session 10, birds produced primarily transitions between items B and C or A and C and repeats on items B and C (BC 35%, AC 15%, BB 10%, CC 25%). Despite the low rate of the previously acquired A-->B transition (6%), its production was highly correlated with that of the A-->B-->C series. On the other hand, item C was predominantly pecked and a recency effect occurred for this item. These data extend previous findings indicating that acquisition of series in pigeons involves the formation of associative links between stimuli according to direct and indirect reinforcing values.