The study reported here examined the role of expertise in the composite face effect which constitutes better recognition of the top half of a face when in composite with a congruent vs. an incongruent (in terms of response required) bottom half. Experiment 1a (n=96) used prototype-defined artificial stimuli (checkerboards) to investigate the composite effect. The advantage of using these stimuli is that expertise can be fully controlled. Experiment 1b (n=96) aimed to replicate the composite effect in face stimuli which served as a control and provided a direct comparison of the composite effect between face and checkerboard stimuli. A full experimental design including congruent/incongruent aligned and misaligned composites was used in both experiments to measure the composite effect. Experiment 1a revealed that the composite effect could not be obtained in checkerboard composites. Experiment 1b confirmed the robust composite face effect. We interpret our results as suggesting that expertise/perceptual learning does not contribute to the composite effect for faces.

We report the results from two experiments (n=192) examining the congruency effect (better performance for congruent vs incongruent stimuli) for prototype-defined checkerboard composites. We used a complete matching task design as that used to study a robust index of face recognition i.e., the composite face effect. The results from both experiments reveal an effect of order of presentation for congruent and incongruent trials. Critically, participants presented with incongruent first and then congruent trials revealed a significant congruency effect. In contrast, participants presented with congruent first and then incongruent trials showed no congruency effect. These results contribute to the composite effect literature by reporting the first evidence of a congruency effect for artificial non-face stimuli which do not have a predefined orientation. Also, they provide evidence in support of test order as a determining factor potentially modulating the composite effect.

In the present study, we tested the effects of anodal tDCS deliveredover the Fp3 (for 10mins at 1.5mA) on the face inversion effect(better recognition for upright vs inverted faces) while participantsperformed an old/new recognition task. We recruited three groupsof participants (n=72) and randomly assigned them toexperimental conditions. In the anodal Study Phase conditionparticipants received the tDCS stimulation during the learningphase only. In the anodal Recognition Phase condition,participants received the anodal stimulation during the recognitiontask only. In the control group participants received shamstimulation (during the study or recognition phase). Consistentwith previous research, the results showed that anodal stimulationreduced the inversion effect by impairing recognition of uprightfaces. Critically, in both anodal conditions the inversion effect wassignificantly reduced compared to sham, and no difference wasfound between the two anodal conditions. Upright faces in eachanodal condition were recognized significantly worse than sham.This suggests that the tDCS-induced effects on face recognitionare immediate and affect both learning and performance. Weinterpret the results based on the account of perceptual learningand previous work on tDCS and the inversion effect.

In this study we show that a particular form of neuro-stimulation can affect face recognition skills impairing participantsperformance on a face recognition task without affecting the composite face effect. Using a Face-Matching task (n=48)traditionally used to study the composite face effect (better recognition of the top half of an upright face when in compositewith a congruent vs and incongruent bottom half) we confirm that anodal transcranial Direct Current Stimulation (tDCS;double-blind and between subjects study) delivered over the left DLPFC at Fp3 (10 mins at 1.5mA) affects overall facerecognition performance for upright faces. But no effect of the tDCS was found on the composite face effect itself. Weinterpret our results in the light of previous literature on the tDCS effects on perceptual learning and face recognition,suggesting that different mechanisms are involved in the face inversion effect and the composite face effect.