Abstract: In the classical exogenous cue-target paradigm, when a target is presented in the same location as a cue within a stimulus onset asynchrony (SOA) of 250 ms or less, target detection is facilitated. However, when the SOA is extended to more than 250 ms, target detection is slowed at the cued location. This phenomenon is called inhibition of return (IOR). IOR is generally assumed to be an adaptive mechanism which enhances the chance of success or survival by maximizing the chance of detecting important information in visual search during human evolution. If so, the time course and/or magnitude of IOR may be affected by biological information of the cue. If a cue provides information relevant to individual’s survival, then attention may not be inhibited from reorienting to the cue. However, previous evidence concerning this issue is controversial. This study is to further examine whether IOR is modulated by emotional valences of face, which convey important biological and social information. We hypothesized that emotional information conveyed through supraliminally presented face cues may not differentially affect the IOR effect, because this information could be suppressed by the top-down control settings demanding no interference from emotion, whereas emotional information conveyed through subliminally presented face cues may affect pattern of the IOR effect, because this information is processed automatically and it escapes from top-down suppression.
A total of 32 undergraduate students participated in Experiments 1 and 2, which manipulated the number of simultaneously cued locations. Faces with different emotional valences (happy, angry and neutral) were as uninformative peripheral cues, supraliminally in Experiment 1 and subliminally in Experiment 2, while the participants were instructed to make detection responses to the target, which was presented at one of the cued locations or at an uncued location, as quickly and accurately as possible. Experiment 1 obtained an overall IOR effect but the magnitude of this effect was not affected by the emotional valences of face cues. Experiment 2 obtained a significant IOR effect, but only for the neutral face cues. These findings are consistent with our hypothesis, suggesting that IOR can be modulated by the property of biologically important cues. The evolutionary significance of the IOR mechanism was discussed.

Key words: supraliminal emotion cue, subliminal emotion cue, emotional valence, inhibition of return