Behavioral and electrophysiological evidence for valence-space congruency effect of emotional pictures in a spatial Stroop task

Abstract

Previous studies have shown that people implicitly associate the emotional valence of abstract words with vertical position (i.e., positive words up, negative words down), resulting in the so-called valence-space congruency effect. Research has demonstrated that there is a valence-space congruency effect when it comes to emotional words. It's interesting to see that whether the emotional pictures with different levels of valence are mapped to distinct vertical space positions. Here, the event-related potential (ERP) and time-frequency techniques were employed to investigate the neural basis of the valence-space congruency effect of emotional pictures in a spatial Stroop task. Firstly, this study showed that the reaction time of the congruent condition (i.e., positive pictures in the top and negative pictures in the bottom of the screen) was significantly shorter than that of the incongruent condition (i.e., positive pictures in the bottom and negative pictures in the top of the screen), suggesting that exposure to stimuli with positive or negative valence, regardless of whether these stimuli were comprised of words or pictures, would be enough to invoke the vertical metaphor. Moreover, we found that the congruency between the vertical position and the valence of emotional pictures could significantly modulate the amplitude of the P2 component and the Late Positive Component (LPC) in ERP waveforms, as well as the post-stimulus alpha-ERD in the time-frequency plane. This study has conclusively demonstrated the presence of a space-valence congruency effect in emotional pictures and has elucidated the underlying neurophysiological mechanisms associated with the valence-space metaphor.