All in the first glance: first fixation predicts individual differences in valence bias.

Surprised expressions are interpreted as negative by some people, and as positive by others. When compared to fearful expressions, which are consistently rated as negative, surprise and fear share similar morphological structures (e.g. widened eyes), but these similarities are primarily in the upper part of the face (eyes). We hypothesised, then, that individuals would be more likely to interpret surprise positively when fixating faster to the lower part of the face (mouth). Participants rated surprised and fearful faces as either positive or negative while eye movements were recorded. Positive ratings of surprise were associated with longer fixation on the mouth than negative ratings. There were also individual differences in fixation patterns, with individuals who fixated the mouth earlier exhibiting increased positive ratings. These findings suggest that there are meaningful individual differences in how people process faces.

Sensory uncertainty leads to systematic misperception of the direction of motion in depth.

Although we have made major advances in understanding motion perception based on the processing of lateral (2D) motion signals on computer displays, the majority of motion in the real (3D) world occurs outside of the plane of fixation, and motion directly toward or away from observers has particular behavioral relevance. Previous work has reported a systematic lateral bias in the perception of 3D motion, such that an object on a collision course with an observer's head is frequently judged to miss it, with obvious negative consequences. To better understand this bias, we systematically investigated the accuracy of 3D motion perception while manipulating sensory noise by varying the contrast of a moving target and its position in depth relative to fixation. Inconsistent with previous work, we found little bias under low sensory noise conditions. With increased sensory noise, however, we revealed a novel perceptual phenomenon: observers demonstrated a surprising tendency to confuse the direction of motion-in-depth, such that approaching objects were reported to be receding and vice versa. Subsequent analysis revealed that the lateral and motion-in-depth components of observers' reports are similarly affected, but that the effects on the motion-in-depth component (i.e., the motion-in-depth confusions) are much more apparent than those on the lateral component. In addition to revealing this novel visual phenomenon, these results shed new light on errors that can occur in motion perception and provide a basis for continued development of motion perception models. Finally, our findings suggest methods to evaluate the effectiveness of 3D visualization environments, such as 3D movies and virtual reality devices.