EEG and Eye Tracking Signatures of Target Encoding during Structured Visual Search

Area of Science:

• Cognitive Neuroscience
• Human Factors
• Psychology

Background:

• Visual search involves target detection and memory encoding.
• Eye-tracking and electroencephalography (EEG) measures, including fixation duration, pupil size, and saccade-related potentials (SRPs), can reflect cognitive processes during visual search.
• Previous research indicates these variables differentiate between fixating on targets versus non-targets.

Purpose of the Study:

• To investigate whether eye-tracking and EEG variables differentiate between correctly identified targets (hits) and missed targets (misses).
• To explore the complementary roles of eye-tracking and EEG in understanding visual search and memory encoding failures.

Main Methods:

• Participants performed a visual search task with varying numbers of targets per trial.
• A concurrent auditory math task (high load) was used to induce memory encoding failures, compared to a low load condition.
• Eye-tracking (fixation duration, pupil size) and EEG (SRPs) data were recorded.

Main Results:

• More targets were missed under high cognitive load compared to low load.
• Eye-tracking features (larger pupil size, shorter fixation duration for missed targets) better distinguished hits from misses than targets from non-targets.
• SRP features (larger P300 waveforms for targets) better distinguished targets from non-targets than hits from misses.

Conclusions:

• Eye-tracking and EEG measures provide complementary information about visual search processes.
• Eye-tracking variables may indicate encoding failures, while SRPs may reflect target relevance.
• These findings suggest potential applications for monitoring observer attention and memory in search tasks.