Sense modality switching and serial leaming

This investigation examined the effect of sense modality switching ofinformation at various positions of a serial learning task. Different numbers of flashes of light and different numbers of “blips” ofa pure tone were used as signalsin a four-position serial learning task. The design of the study involved a switch in sense modality at each one of the four possible positions in the series. Thus, it was possible to determine if the transmission of information through one sense modality makes it progressively more difficult or more time consuming to switch to another source of information transmitted through another modality. The results generally supported the contention that, as information is received through a particular modality, there is a build-up of the disruption involved in switching sense modality.     

Signalled and unsignalled free-operant avoidance in the pigeon

Pigeons were trained to depress a lever to avoid electric shock under free-operant avoidance schedules without a warning signal, or with a warning signal that could be terminated only by a response. Most birds in the signalled avoidance procedure terminated more than 50% of the warning signals before shock. In the unsignalled avoidance procedure, several birds formed a temporal discrimination and received relatively few shocks; other birds responded only in post-shock bursts, and received many more shocks.     

Time limits for completing fixed ratios

Two experiments investigated how the addition of time limits affected fixed-ratio behavior. In Exp. 1, pigeons obtained food only if they completed the ratio within a specified time after the end of the preceding ratio. In Exp. 2, they obtained food only if they took longer than a specified time. Failures to meet the time criteria produced brief timeouts. The times taken depended on the requirements in both experiments. In Exp. 1, progressively briefer time criteria resulted in faster ratios, and in Exp. 2, longer time criteria increased the time taken in each ratio. The pigeon's sensitivity to the temporal variable, a property of the entire period extending from the first opportunity to respond to the end of the ratio, indicated that performance involved a behavioral unit encompassing both the post-reinforcement pause and the responses comprising the ratio.