Investigating stages of information processing and attentional capacity: Contributions of startle eyeblink modification and measures of signal detection

A stage and a capacity model of information processing were investigated, employing startle blink modification and measures of signal detection. Pitch discrimination difficulty and task demands were manipulated in four experiments in order to depict individual stages of processing and to index attentional resource allocation,;In the first three experiments, subjects were presented identical stimuli, consisting of a standard 1 s tone, followed 6 s later by a test tone, either higher or lower than the standard, and 2 or 4 s duration. The startle eyeblink reflex was elicited 120, 240, or 3000 ms following test tone onset. The test tone was either easy or difficult to discriminate in pitch compared to the standard tone. Subjects in Experiment One were instructed to attend to the pitch and duration of the prestimuli; in Experiment Two they attended only to pitch; and in Experiment Three only to duration. Experiment Four involved a signal detection task. Three measures, reaction time, confidence ratings, and d;Predictions involving Experiments One, Two, and Three were based on previous studies in which startle blink modification has been associated with attentional processing. As predicted, Experiment One revealed significant startle blink inhibition compared to baseline. Contrary to predictions, no differences were seen in startle blink inhibition as a function of attention or due to pitch discrimination difficulty. It was concluded that previous studies in which subjects were required to make absolute judgments concerning prestimuli required sufficient attentional resources to reveal differential startle blink inhibition. The present study, involving relative stimulus judgments, presumably required fewer attentional resources.;Predictions concerning startle blink facilitation later during processing were not revealed. Failure to obtain significant startle blink facilitation was most likely due to increased subject variability in the presence of prestimuli compared to in their absence.;Measures of signal detection were largely uncorrelated with startle blink modification. These findings also may be due to differences between absolute and relative stimulus judgments.;Based on findings from Experiment One, additional predictions involving early attentional processing for Experiments Two, Three and Four were introduced. I propose future experiments to address these findings in more depth.