Target-distractor discriminability in visual search
DOI: 10.3758/bf03208228
archive: archived pipeline: cataloged verified
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Summary
This paper addresses the mechanisms underlying target-distractor discriminability in visual search, specifically aiming to resolve ambiguities in previous research where discriminability was manipulated between blocks or subjects. Such prior designs allowed participants to anticipate difficulty levels, making results consistent with various competing models. Harold Pashler investigates whether trial-by-trial variation in the number of confusable distractors affects performance, thereby preventing strategic anticipation and isolating the cognitive processes involved in search. The study employed two experiments using speeded detection tasks with capital letter stimuli. In Experiment 1, nine subjects searched for a target letter (C) among distractors, with the number of similar distractors (Gs) varying unpredictably from 0 to 5 per trial. In Experiment 2, eighteen subjects searched for one of two targets (C or E), with distractors similar to either target (Gs for C, Fs for E) varying in number. Reaction times (RTs) and error rates were recorded. A control condition in Experiment 2 verified that effects were due to similarity rather than intrinsic stimulus difficulty. The results demonstrated that increasing the number of target-confusable distractors significantly increased RTs for both "yes" (target present) and "no" (target absent) responses, with larger effects on "no" trials. Crucially, in Experiment 2, distractors similar to one target slowed the detection of the other target to a similar degree as distractors similar to the present target. This cross-target interference persisted even when subjects could not anticipate the specific distractor composition. Error rates showed modest increases in both misses and false alarms. These findings indicate that decision noise, rather than feature-specific inhibition or perceptual competition, is the primary source of latency effects in visual search. The data contradict models proposing that decisions are based on evidence integrated across all display positions (the integration model), as such models would predict that similar distractors facilitate detection by adding evidence. The results also challenge the independent-channels model without modification. Instead, the data are broadly consistent with models hypothesizing parallel search followed by slow serial checking, such as Hoffman’s (1978) model. The study concludes that visual search performance is heavily influenced by the statistical likelihood of false alarms arising from decision noise when discriminability is low, rather than by perceptual interference between similar items.
Provenance
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| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | OpenAlex-citations | — | — | 1 | 2026-06-17 |
| archive | success | unpaywall | — | — | 2 | 2026-06-25 |
| extract | success | pdftotext | — | — | 2 | 2026-06-26 |
| clean | success | clean | — | — | 1 | 2026-06-26 |
| chunk | success | chunk | — | — | 1 | 2026-06-26 |
| embed | success | embed | Qwen/Qwen3-Embedding-8B | — | 1 | 2026-06-26 |
| enrich | failed | — | — | — | 5 | 2026-07-05 |
| promote | success | — | — | — | 1 | 2026-06-17 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 1 | 2026-06-25 |
| tag | success | vector_similarity | — | — | 6 | 2026-06-26 |
| verify | success | — | — | — | 1 | 2026-06-26 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-25; verification: verified.
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