Unpredictable singleton distractors in visual search can be subject to second-order suppression

Area of Science:

• Cognitive Psychology
• Neuroscience
• Visual Perception

Background:

• Attentional capture by salient distractors can impair visual search.
• Previous research suggested suppression of distractors was limited to predictable features (first-order suppression).
• The possibility of second-order suppression for unpredictable distractors remained unclear due to conflicting evidence.

Purpose of the Study:

• To investigate the conditions under which second-order suppression of salient distractors in visual search is effective.
• To re-evaluate previous findings on suppression limitations by manipulating feature variability.
• To demonstrate that second-order suppression can be applied to unpredictable distractors.

Main Methods:

• A multiframe letter-probe paradigm was used to measure performance in visual search tasks.
• Experiments manipulated the predictability and variability of distractor and target features (color).
• Observer performance was assessed by the frequency of reporting probe letters at distractor locations.

Main Results:

• A singleton suppression effect was observed when target and distractor colors were constant (Experiment 1).
• No suppression effect was found when target and distractor colors were swapped randomly (Experiment 2).
• A robust suppression effect reappeared when target and distractor colors had high variability (eight random colors) (Experiment 3).

Conclusions:

• First-order suppression is not universally applicable.
• Second-order suppression of salient distractors is possible under conditions of high feature variability.
• Suppression effects are independent of direct target-distractor competition.