Time-based visual selection with emotional faces

Abstract

The biological and behavioural importance of the face has led to the proposition of several mechanisms dedicated to highly efficient specialized processing (e.g., M.H. Johnston, 2005). This is reflected in the attentional properties attributed to facial stimuli, especially when they contain affective information (e.g., R. Palermo & G. Rhodes, 2007). This thesis examines those attentional properties via a modified version of the visual search paradigm (i.e. the preview search task; D.G. Watson & G.W. Humphreys, 1997), which proposes that observers can intentionally suppress items seen prior to a full search array, for effective search performance (i.e. the preview benefit; D.G.Watson & G.W. Humphreys, 1997, 1998). The findings from this thesis show that it is possible to deprioritize previewed facial stimuli from search, although only a partial preview benefit was shown. Emotional valence of previewed faces had little impact on this effect, even when preview duration was extended from 1000-3000ms. However, when duration was reduced to 250-750 ms, negatively valenced faces were more difficult to suppress than positively valenced faces. In addition, when previewed faces changed expression concurrently with the onset of the full search array, the preview benefit was abolished, irrespective of the direction of the expression change (i.e. neutral to positive, or neutral to negative). A search advantage for negative face targets was demonstrated throughout all of the investigations in this thesis. These findings are consistent with previous work establishing preferential detection of, and selectively impaired disengagement from, negative faces (e.g., J.D. Eastwood, D. Smilek, & P.M. Merikle, 2001; E.Fox, R. Russo, R.J.Bowles, & K. Dutton, 2001). However, they also suggest the sensitivity of the visual marking mechanism to ecological considerations (such as the nature of the stimulus), and the overall relevance of emotional face stimuli to the visual system