Look on the Bright Side: Positivity Bias Modulates Interference Effects in the Simon Task

Negative faces are detected more quickly but categorized more slowly than positive faces. Using a Simon task, we examined stimulus-and response-related processes of this dissociation: If negative stimuli are both processed and responded to more quickly than positive ones, they should elicit reduced Simon effects. Conversely, if negative stimuli are processed more quickly but responded to more slowly, enlarged Simon effects should occur. Consistent with the first possibility, negative stimuli showed reduced Simon effects. Unexpectedly, this reduction transferred to neutral stimuli (arrows and pointing hands) requiring the same response as negative faces. This pattern suggests that spatial attention became biased toward the side associated with a positive-face response and away from the side associated with a negative-face response, demonstrating that, similar to higher level cognitive decision processes, even early attentional processes can be subject to a positivity bias ("Pollyanna effect").