Time-sharing in rats: effect of distracter intensity and discriminability

Interruptions (gaps) and unfamiliar events (distracters) during a timed signal delay the timed response of humans and other animals. To explore this phenomenon, we manipulate the intensity of auditory distracters (Experiment 1), and we dissociate the role of distracter intensity, distracter similarity with the intertrial interval, and dissimilarity from the timed auditory signal (Experiment 2). When the intertrial interval and the timed signal were silent, the delay in response after an auditory distracter increased with its intensity: Rats ignored (ran through) a 40-dB distracter, stopped timing during a 75-dB distracter, and reset after a 100-dB distracter. However, when timing was signaled by a 70-dB noise, rats reset both for 40- and 100-dB distracters, stopped for both 55- and 85-dB distracters, and run for the 70-dB distracter. Data are accounted for by a time-sharing model assuming 2 concurrent processes-time accumulation and memory decay controlled by the discriminability of the interrupting event-whose interplay results in a continuum of responses, from run to reset.