Processing of facial expressions has been shown to potentiate orienting of attention toward the direction signaled by gaze in adults, an important social-cognitive function. However, little is known about how this social attention skill develops. This study is the first to examine the developmental trajectory of the gaze orienting effect (GOE), its modulations by facial expressions, and its links with theory of mind (ToM) abilities. Dynamic emotional stimuli were presented to 222 participants (7-25 years old) with normal trait anxiety using a gaze-cuing paradigm. The GOE was found as early as 7 years of age and decreased linearly until 12-13 years, at which point adult levels were reached. Both fearful and surprised expressions enhanced the GOE compared with neutral expressions. The GOE for fearful faces was also larger than for joyful and angry expressions. These effects did not interact with age and were not driven by intertrial variance. Importantly, the GOE did not correlate with ToM abilities as assessed by the "Reading the Mind in the Eyes" test. The implication of these findings for clinical and typically developing populations is discussed.

Early face encoding, as reflected by the N170 ERP component, is sensitive to fixation to the eyes. Whether this sensitivity varies with facial expressions of emotion and can also be seen on other ERP components such as P1 and EPN, was investigated. Using eye-tracking to manipulate fixation on facial features, we found the N170 to be the only eye-sensitive component and this was true for fearful, happy and neutral faces. A different effect of fixation to features was seen for the earlier P1 that likely reflected general sensitivity to face position. An early effect of emotion (~120 ms) for happy faces was seen at occipital sites and was sustained until ~350 ms post-stimulus. For fearful faces, an early effect was seen around 80 ms followed by a later effect appearing at ~150 ms until ~300 ms at lateral posterior sites. Results suggests that in this emotion-irrelevant gender discrimination task, processing of fearful and happy expressions occurred early and largely independently of the eye-sensitivity indexed by the N170. Processing of the two emotions involved different underlying brain networks active at different times.

The current study investigated the effects of presentation time and fixation to expression-specific diagnostic features on emotion discrimination performance, in a backward masking task. While no differences were found when stimuli were presented for 16.67 ms, differences between facial emotions emerged beyond the happy-superiority effect at presentation times as early as 50 ms. Happy expressions were best discriminated, followed by neutral and disgusted, then surprised, and finally fearful expressions presented for 50 and 100 ms. While performance was not improved by the use of expression-specific diagnostic facial features, performance increased with presentation time for all emotions. Results support the idea of an integration of facial features (holistic processing) varying as a function of emotion and presentation time.

Recent evidence suggests that liking and wanting of food rewards can be experimentally dissociated (e.g., Berridge, 1996); this dissociation extends to attenuated neophobia in the present study. Rats tend to eat less of a novel food than a familiar food, a phenomenon called neophobia. The present experiments evaluated whether attenuation of neophobia by prior exposure reflects enhanced liking of the flavor using the Taste Reactivity (TR) test. In Experiment 1, rats given five 10 sec TR trials with water or various concentrations of saccharin solution (0.1%, 0.2%, 0.5%) did not show a change in the number of hedonic reactions displayed across trials. However, in a subsequent consumption test from a bottle containing 0.25% saccharin solution, rats with no prior saccharin exposure (group water) consumed less than rats with prior saccharin exposure; that is they displayed neophobia. In Experiment 2, whether rats received five 10 sec TR trials with water or 0.5% saccharin solution, they did not display a difference in hedonic reactions to 0.25% saccharin solution in two 5 min TR test trials. These results suggest that the attenuation of neophobia is evidenced as an increase in the tendency to approach a bottle containing the flavored solution (wanting), but not as an enhanced liking of that solution.

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