Carbon dioxide as a reinforcer in escape conditioning

The effects of varying CO₂ concentration, and intervals between CO₂ presentations, were determined from the performance by five pigeons of a learned motor act which eliminates CO₂ from the inspired air. The length of time from the onset of an externally-produced increase in inspired CO₂ to the performance of the learned motor response terminating the CO₂ presentation was inversely related to the CO₂ concentration presented (3 per cent and 5 per cent) and directly related to the inter-trial interval (3 minutes and 1.5 minutes). Chemoreceptors on the ventrolateral surfaces of the medulla are postulated to be the initial site of stimulation in the chain of events leading to the behavioral bioregulation of inspired CO₂ concentration.     

Stimulus correlates of visual pattern discrimination by monkeys: Multidimensional analyses

Fourteen monkeys were presented with a series of simultaneous discrimination problems, each problem consisting of two visual metric patterns, and Ss’ performance was analyzed with respect to several physical dimensions of the patterns. Proficiency of discriminative performance was found to be directly and almost exclusively related to the extent to which the two patterns, when translated, had unique parts.