Pupil size and drag state in a reaction time task

Bradshaw, John L. · 1970 · OpenAlex-citations

DOI: 10.3758/bf03335723

archive: archived pipeline: cataloged verified

Get this paper ↗ (DOI — opens at the source; we link to it, we don't host it)

Summary

This study investigates the effects of drug-induced changes in arousal on pupillary responses and motor performance during an auditory reaction-time (RT) task. Motivated by the hypothesis that drugs influencing arousal levels would alter both pupillary baseline and peaking phenomena as well as RT performance, the research examined three conditions: normal, alcohol, and amphetamine. The study aimed to determine if these pharmacological interventions would produce distinct patterns in pupillary dilation and reaction times, potentially offering insights into the physiological correlates of cognitive and motor states. The experiment involved six subjects who sequentially experienced all three conditions in a randomized order. Under the alcohol condition, subjects consumed a dose equivalent to 48 cc of alcohol in a 20% solution 25 minutes before testing. For the amphetamine condition, subjects took 15 mg of amphetamine sulfate 75 minutes beforehand. Testing occurred at 9 a.m. on an empty stomach, with abstention from other stimulants. The apparatus monitored pupillary diameter changes while subjects performed an auditory RT task involving warning signals followed by either long (5.5 sec) or short (2.5 sec) foreperiods before the response signal. Each condition lasted 8.5 minutes, comprising 17 trials for each foreperiod length. Pupillary data were recorded at approximately 2.7 frames per second, and RT was measured to the nearest 1/100 second. The results indicated distinct effects for each drug. Amphetamine significantly increased pupillary baseline dilations compared to the normal condition (p < .05), but it did not significantly affect the shape or amplitude of the pupillary response peak, nor did it alter reaction times. In contrast, alcohol resulted in average pupillary baselines similar to the normal condition but caused considerably flattened response peaks (p < .001) and significantly increased reaction times. Statistical analysis confirmed that alcohol accounted for the significant drug effects on both pupillary peak shape and RT performance, while amphetamine and normal conditions did not differ significantly in these metrics. Long warning foreperiods resulted in fractionally faster performance than short foreperiods across conditions. The findings suggest that amphetamine primarily induces an increase in baseline pupillary dilation without improving motor performance, an effect comparable to a reduction in background light intensity. This indicates that amphetamine may increase arousal levels without enhancing the specific cognitive-motor processing required for the task. Conversely, alcohol’s depressant effects are manifested in slowed motor performance and altered pupillary peak dynamics, despite unchanged baselines. The study concludes that while amphetamine alters baseline arousal indicators, it does not facilitate performance in this RT task, whereas alcohol impairs both pupillary response characteristics and reaction speed. These results highlight the dissociation between baseline arousal levels and specific task-related pupillary and motor responses under different pharmacological influences.

Provenance

The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed.

Summary generated by qwen3.6-27b-prismaquant on 2026-06-26; verification: verified.

Topics

Ranked by relevance to this paper. Hover a topic for its definition.

• workload measurement

Information type

What kind of knowledge this paper contributes, grouped by family — independent of topic (what it is about) and method (how it was studied).

• Empirical Findings: behavioral performance data