Numerical discrimination by rats using sequential auditory stimuli

Abstract

Three rats were trained under a discrimination procedure in which responding was reinforced only following the repeated presentation of three bursts of white noise (S+). S− consisted of presentations of either two or four bursts of noise. All animals responded significantly more in the presence of S+ and, in two cases, showed lower response rates to both “2” and “4” stimuli. Responding by the third animal revealed differentiation between S+ and the stimulus “2,” but no reliable suppression to stimulus “4.” The present instances of discriminative control by the stimulus “3” replicate Fernandes and Church’s (1982) demonstration of control by sequential auditory stimuli in the rat. Moreover, because the present procedure involves adjacent S− values both greater as well as less than S+, these results extend our knowledge of the rat’s abilities with sequential auditory stimuli: Rats are capable of making intermediate numerical discriminations based upon something other than a simple many-versus-few dichotomy.