Reaction times in discriminations of varying difficulty: decision modulated by arousal.
Pigeons discriminated the hue of a spot of light that appeared in discrete trials. A green spot always signaled food ("green S+") and so did a red spot of constant hue ("red S+"), but on most trials a different red hue appeared and no food was given for pecks ("red S-"). The hue of red S- stayed the same during blocks of up to twelve sessions, but it changed from block to block. During a final group of sessions red S- was omitted and the percent reinforcement to the two S+ stimuli was varied. Major findings were that (1) percent response (Pct(R)) to S- varied with S+/S- similarity, describing a typical ogival psychometric function; (2) Reaction times (RTs) to both red and green S+s were minimal when the red discrimination was impossible (that is, when red S+ and S- were identical); (3) RTs to red S+ were greatest during discriminations of intermediate difficulty; (4) as Pct(R) declined during the learning of a difficult discrimination, RTs increased to red S+ as well as red S-. Most aspects of the data were reproduced by simulations with a quantitative model that incorporated reinforcement-based decision and arousal processes.
Blough
Donald S
DS
Brown University, Providence, RI 02912, USA. donald_blough@brown.edu
D000818:Animals; D001143:Arousal / Q000502:physiology*; D001245:Association Learning / Q000502:physiology; D003118:Color Perception / Q000502:physiology; D010856:Columbidae; D004193:Discrimination Learning / Q000502:physiology*; D005260:Female; D008959:Models, Neurological; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D011594:Psychometrics; D011930:Reaction Time / Q000502:physiology*