The influence of odor on perception of emotional stimuli

Abstract

Emotion can play a major role on how we allocate our attention to relevant stimuli. Pereira et al. (2006) have shown longer reaction times, in a target detection task, when participants were exposed previously to unpleasant images; on the other hand, faster reactions times occurred when pleasant images were presented, suggesting an activation of appetitive motivational systems. The present study was aimed to investigate how odor affects performance in a 2-AFC paradigm proposed by Erthal et al. (2005). A central picture, taken from the International Affective Picture System (Lang, 1999), was presented briefly (200ms) flanked by two peripheral bars. The bars were located 10° to the right and left of the center of the screen with five possible orientations (0°, 6°, 11°, 22° and 45°). Participants (n=6) were asked to respond (key presses) whether or not the bars had the same orientation. The experiment consisted of three blocks; in each block a single type of picture (neutral, pleasant or unpleasant) was presented. There were two experimental sessions, control and appetitive odor (lemon oil). Experimental sessions were carried out in a counterbalanced way. Replicating Pereira et al. (2006), participants showed longer reactions times to trials in the unpleasant block in both sessions. However, participants were overall faster to respond during the appetitive odor session. This suggests that attentional resources are modulated both by positive pictures and appetitive odor resulting in an increased performance for this condition.