Effect of expectation on face perception and its association with expertise - Neural and Behavioural Data

Mares, Inês

Birkbeck Schools and Research Centres > School of Science > Psychological Sciences

Participants completed a battery of tasks during including 1) a behavioral task, where participants learnt the association between a color and an object category (faces or cars), followed by 2) an EEG task where participants observed stimuli of these two categories preceded by a fixation cross matching the learned association or not, 3) a measure of face expertise, the Cambridge Face Memory Test -long form, and 4) a broadly matched measure of object expertise, the Cambridge Car Memory Test.
The behavioral association task was presented using the Gorilla.sc platform, starting with a training block during which participants learned to consistently associate a colour cue (red or blue, counterbalanced between participants) with one of two categories (i.e. faces or cars, 30 trials each).
Trials started with a predictive cue, a fixation cross with a color matching the trial category (750 ms), followed by an empty frame of the same color (500 ms).
The target image was then briefly displayed inside the frame for 250 ms. Participants were asked to categorise the image as a face or a car, with a button press.

In the testing blocks, participants completed a similar categorization task, where the target was consistent with the predictive colour cues in 75% of trials (i.e. 120 trials in each category, 90 trials with the expected image, 30 trials with an unexpected image).
60 trials (30 cars and 30 faces), were presented without any learned association, using a black fixation cross and frame, not previously associated with any condition. In these blocks the target image appeared for a shorter period (only 100 ms), and visual noise was added to the images.
Participants completed a total of 300 trials of the test phase over 4 blocks.

The main EEG task was presented using the E-prime software (Version 2.0).
Participants were asked to attend to the target stimuli (faces and cars) while searching for a letter (an 'A' or 'K'), presented centrally in catch trials (40 trials, around 7.7% of total trials).
Trials started with a black fixation cross (duration 900-1200 ms, pre-allocated randomly to the trial list in steps of 25 ms), followed by a predictive cue, a fixation cross of a colour associated to one of the stimuli categories (750 ms), and then by the target stimuli (500 ms).
As before, to maintain the predictive contingency, the target was consistent with the predictive colour cues in 75% of trials (i.e. 240 trials were presented for each category of which 180 trials displayed an image of the predicted category while 60 trials presented an image of the unexpected category).

At the end of the session participants completed the CFMT+ and the CCMT.

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