Tonal frequency shifts and gaps in acoustic stimulation as reflex-modifying events

When a relatively weak signal, such as a mild tone, precedes an intense reflex-eliciting stimulus by an appropriate interval (about 100 msec), the amplitude of the elicited reaction is often reduced. It was found that in student volunteers a brief gap in a steady pure tone that occurred 150 msec prior to a mild tap to the glabella (the flat region between the eyebrows) could inhibit the eyeblink elicited by the tap. It was also found that a shift in tonal frequency across a gap in a tone was more inhibitory than a gap with no frequency shift, but it was no more inhibitory than the onset of the short second tone alone. The final study determined the minimum amount of frequency shift required to produce an additional inhibitory effect above that of a gap alone. The findings are discussed in terms of various aspects of sensory processing.     

Induction by reinforcer schedules.

Traditional strategies for determining whether a reinforcer schedule enhances the occurrence of an activity are reviewed and critically evaluated. A basic assumption underlying these strategies is that it is possible to isolate the effect of reinforcer intermittency on schedule induction. It is concluded that this is not, in fact, possible. An alternative approach is proposed that emphasizes the inductive effects of the reinforcer schedule as a unit and the effects of particular aspects of the reinforcer schedule (e.g., interreinforcer interval, repetition of the reinforcer, reinforcer magnitude).