Varying background colours reveals that enhanced short-term memory for angry faces is a valence and not an arousal effect

There is debate on whether the effect of stimulus emotionality on memory is a valence or an arousal effect. In a previous study, short-term memory (STM) was enhanced for angry compared to happy and neutral faces, and music-induced contextual arousal did not modulate this effect. The absence of such a contextual arousal effect could, however, have been due to the cross-modal nature of the study, as the contextual arousal was induced auditorily while the to-be-remembered stimuli were presented visually. In this study, we investigated the influence of visually-induced contextual arousal on the same STM task  to determine whether the angry face benefit in STM is a valence or an arousal effect. Contextual  arousal was successfully manipulated by presenting the background colours red, pink, and light pink. STM discrimination was enhanced for angry faces, and was not modulated by contextual arousal. High contextual arousal elicited by the red or pink backgrounds was accompanied by a more liberal response bias, regardless of facial expression. Because of this dissociation and because the effects of facial expression and background colour did not interact, it is concluded that the angry face benefit in STM is a valence and not an arousal effect. It is suggested that these stimulus valence and contextual  arousal effects have different underlying mechanisms.