Selective attention in pigeon temporal discrimination

Cues can vary in how informative they are about when specific outcomes, such as food availability, will occur. This study was an experimental investigation of the functional relation between cue informativeness and temporal discrimination in a peak-interval (PI) procedure. Each session consisted of fixed-interval (FI) 2- and 4-s schedules of food and occasional, 12-s PI trials during which pecks had no programmed consequences. Across conditions, the phi (phi) correlation between key light color and FI schedule value was manipulated. Red and green key lights signaled the onset of either or both FI schedules. Different colors were either predictive (phi = 1), moderately predictive (phi = 0.2-0.8) or not predictive (phi = 0) of a specific FI schedule. This study tested the hypothesis that temporal discrimination is a function of the momentary conditional probability of food; that is, pigeons peck the most at either 2 s or 4 s when phi = 1 and peck at both intervals when phi < 1. Response distributions were bimodal Gaussian curves; distributions from red- and green-key PI trials converged when phi 0.6. Peak times estimated by summed Gaussian functions, averaged across conditions and pigeons, were 1.85 and 3.87 s; however, pigeons did not always maximize the momentary probability of food. When key light color was highly correlated with FI schedules (phi 0.6), estimates of peak times indicated that temporal discrimination accuracy was reduced at the unlikely interval, but not the likely interval. The mechanism of this reduced temporal discrimination accuracy could be interpreted as an attentional process.