Attentional modulation of face expression perception

Abstract

Previous studies in our lab have shown that the attentional state (attending versus ignoring) that is applied when initially exposed to a novel face can determine later how that face will be evaluated on social emotional scales. Specifically, faces that are ignored in difficult attention tasks are later seen as less trustworthy than attended faces. A possible explanation for attentional modulation of affective appraisal of faces is that prior active ignoring subtly alters subsequent sensitivity to face expression. To test this possibility, we made careful psychometric measurements of face expression perception using face morphs (e.g., angry-neutral; happy-neutral) of the same individuals expressing different expressions. Participants judged faces with a range of morph values as neutral versus expressive. The resultant psychometric curves (% “expressive” response plotted as a function of % face expression intensity) were used to select approximately equivalently intense expressions for each face and expression dimension in the stimulus set. Faces with these values were then used in the main experiment. Here, observers engaged in a simple but demanding visual search task (to control their attention state) using neutral faces only. Immediately after each search trial, they made by a face expression judgement (using the morph values derived from our psychometric measurements) on a face that was either a prior target or distractor. The post-search psychometric functions were then used to reveal whether prior attention modulated the slope or shifted the expression sensitivity functions laterally. The former indicates sensitivity change whereas the latter reflects a biasing mechanism. Results for both happy and angry expression will be discussed in terms of attentional modulation of perception in other stimulus domains.