Same-different reaction times studied with a flash masking technique

Saito, M. · 1982 · OpenAlex-citations

DOI: 10.3758/bf03204191

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 time course of visual pattern discrimination by measuring reaction times (RTs) for same-different judgments under flash masking conditions. The research addresses the "fast same" phenomenon, where subjects typically respond faster to identical stimuli than to different ones, a finding that challenges certain analytic models of perception. Previous studies often used continuous masking or identification tasks; this work employs a brief flash mask to temporarily degrade target contrast, allowing for a more precise examination of the temporal dynamics of perceptual processing. The study comprises two experiments using letter pairs (N and Z) presented simultaneously. In Experiment 1, subjects judged whether two letters were the same or different. The target remained visible until response, while a 50-msec flash mask was presented at varying stimulus-onset asynchronies (SOAs) ranging from 0 to 200 msec, with high or low luminance. Experiment 2 increased task difficulty by manipulating the number of letters: subjects judged either two letters or four letters (where "different" meant three identical and one distinct). The same masking parameters were used, but only high-intensity masks were employed. Experiment 1 revealed a significant luminance-dependent masking effect, where higher intensity masks increased RTs, particularly at short SOAs. However, no significant difference was found between "same" and "different" response times, indicating an absence of the "fast same" effect in this simple discrimination task. Experiment 2 produced a significant three-way interaction among letter number, response category, and SOA. A weak "fast same" effect emerged only when task difficulty was increased (four-letter condition) and specifically at intermediate SOAs (e.g., 100 msec), where "same" judgments were faster than "different" judgments. At short or long SOAs, or in the two-letter condition, this effect disappeared. The findings support Krueger’s (1978) "noisy operator theory," which posits that internal noise creates spurious feature mismatches, requiring more processing checks for "different" judgments. The study suggests that the "fast same" phenomenon is not inherent to the comparison process itself but depends on task difficulty and the level of perceptual noise. Simple tasks with high contrast differences do not trigger the phenomenon, whereas difficult tasks with reduced figure-ground contrast (due to masking) amplify noise, leading to slower "different" responses. These results challenge two-process theories that assume fixed identity and serial processors, suggesting instead that perceptual matching is sensitive to noise levels and stimulus complexity.

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 2026-06-25; verification: verified.

Topics

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

• inattentional change blindness