Acquisition and retention in compound matching with hue and peck number elements

Pigeons learned and retained compound samples composed of hue (red vs. green) and peck number value fixed-ratio (FR) 5 vs. FR 20] in a modified matching-to-sample (MTS) task. For different groups both FR and hue were relevant, or hue alone or FR value alone were relevant. Both acquisition and short-term retention of the samples were assessed. The rate of acquisition differed among the groups, with hue/FR > hue > FR. For groups hue/FR and hue, sample FR influenced the rate of learning, with larger sample FRs promoting faster learning. Sample FR also influenced working memory. When both hue and sample FR were relevant, and when FR alone was relevant, pigeons displayed better retention of the smaller (FR 5) sample—the “choose-small” effect. This dissociation of sample FR effects during acquisition and retention could be taken to indicate differences in the sources of immediate and delayed stimulus control.