Facing fear: the effect of emotional expressions on visual short-term memory for faces

Visual short-term memory (VSTM) is capacity-limited, with most people able to keep no more than 3 – 4 simple items in VSTM at any given time (Luck & Vogel, 1997). Notably, as the complexity of stored items increases, capacity seems to decrease suggesting that this range may represent the upper limit of VSTM capacity (Alvarez & Cavanagh, 2005). Is there anything that can offset the trade-off between stimulus complexity and VSTM capacity? Recent studies using face stimuli — which are visually complex — suggest that our extensive experience with faces translates into a VSTM advantage for upright but not inverted faces (Curby & Gauthier, 2007). Here, we connect this line of research to a large body of research showing that emotion can benefit memory. Although such memory-emotion studies have typically pertained to long-term memory, we investigate whether faces signaling emotion have a VSTM advantage over those that are more neutral, and if so whether this effect depends on encoding time (as might be suggested based on work by Maljkovic & Martini, 2005). We measured VSTM capacity for faces with either neutral or fearful expressions under long (4000 ms) or short (1000 ms) encoding durations. To control for basic perceptual differences between the fearful and neutral faces while decreasing the salience of emotional expression, we also tested the same faces in an inverted orientation. Results revealed that VSTM for emotional faces was larger than that for neutral faces, but that this VSTM advantage was limited to upright faces and was equivalent across long and short encoding conditions. In order to clarify the nature of this main finding, we report additional studies probing the impact of more limited encoding durations on this VSTM advantage.