Cardiac orienting and startle blink modification in novel and signal situations.

Abstract

ABSTRACTPrior work, has shown that reflex blinking can be facilitated by directing attention to the reflex stimulus. It was assumed that if facilitation were due to sensory enhancement, blinking would also be facilitated by novelty‐induced orienting prior to the reflex‐eliciting stimulus. The assumption was tested by establishing an expectancy for weak tactile stimulation to be followed by an acoustic reflex stimulus and then introducing, without announcement, trials on which weak acoustic or visual stimuli occurred and were followed by the reflex stimulus. Interspersed control trials of the reflex stimulus alone provided baseline data. Novel trials did produce the expected facilitation of reflex latency and magnitude. Similar effects were obtained when the same stimuli were presented to a different group of subjects with instructions to judge duration of the reflex stimulus on control trials and when warned by the weak acoustic and visual stimuli. In both experiments, blink latency but not magnitude was facilitated by the irrelevant tactile stimuli, thus supporting previous suggestions of a dissociation between these measures of reflex strength. A third group of subjects, receiving identical stimulation, was instructed to attend to the weak acoustic and visual lead stimuli but to perform no task. Attending to the lead stimuli did not produce facilitation of either blink magnitude or latency.