Orientation biases for facial emotion recognition during childhood and adulthood.

Facial emotion recognition develops slowly, with continuing changes in performance observable up to 10 years of age and beyond. In the current study, we chose to examine how the use of specific low-level visual features for emotion recognition may change during childhood. Adults exhibit information biases for face recognition; specific spatial frequency and orientation sub-bands make a larger contribution to recognition than others. This means that depending on the specific task (e.g., identification, emotion recognition), participants will perform worse when some features are removed from the original image and better when those features are included. One example of such an information bias for face recognition is the differential contribution of horizontal orientation energy relative to vertical orientation energy; adult participants are better able to recognize faces and categorize their emotional expressions when horizontal information is included than when only vertical information is included. Although several recent studies have demonstrated various ways in which horizontal orientation energy (and so-called "bar-codes" for face appearance) contribute to adult face processing, there have been as yet no studies describing how such a bias emerges developmentally that may offer insight into the mechanisms underlying the slow development of facial emotion recognition. In the current study, we compared children's (5- and 6-year-olds and 7- and 8-year-olds) and adults' performance in a simple emotion categorization task using orientation-filtered faces to determine the extent to which horizontal and vertical orientation energy contributed to recognition as a function of age. We found that although all three participant groups exhibited a clear bias favoring the use of horizontal orientation energy, the nature of this bias differed as a function of age. Specifically, 5- and 6-year-olds exhibited a disproportionate performance cost when vertical orientation energy was all that was available relative to when stimuli were limited to horizontal orientation energy. One feature of the development of facial emotion recognition, thus, appears to be the capability to use suboptimal or weakly diagnostic information to support recognition.

Emotion recognition (sometimes) depends on horizontal orientations.

Face recognition depends critically on horizontal orientations (Goffaux & Dakin, Frontiers in Psychology, 1(143), 1-14, 2010): Face images that lack horizontal features are harder to recognize than those that have this information preserved. We asked whether facial emotional recognition also exhibits this dependency by asking observers to categorize orientation-filtered happy and sad expressions. Furthermore, we aimed to dissociate image-based orientation energy from object-based orientation by rotating images 90 deg in the picture plane. In our first experiment, we showed that the perception of emotional expression does depend on horizontal orientations, and that object-based orientation constrained performance more than image-based orientation did. In Experiment 2, we showed that mouth openness (i.e., open vs. closed mouths) also influenced the emotion-dependent reliance on horizontal information. Finally, we describe a simple computational analysis that demonstrates that the impact of mouth openness was not predicted by variation in the distribution of orientation energy across horizontal and vertical orientation bands. Overall, our results suggest that emotion recognition largely does depend on horizontal information defined relative to the face, but that this bias is modulated by multiple factors that introduce variation in appearance across and within distinct emotions.