While viewing a visual stimulus, we often cannot tell whether it is inherently memorable or forgettable. However, the memorability of a stimulus can be quantified and partially predicted by a collection of conceptual and perceptual factors. Higher-level properties that represent the "meaningfulness" of a visual stimulus to viewers best predict whether it will be remembered or forgotten across a population. Here, we hypothesize that the feelings evoked by an image, operationalized as the valence and arousal dimensions of affect, significantly contribute to the memorability of scene images. We ran two complementary experiments to investigate the influence of affect on scene memorability, in the process creating a new image set (VAMOS) of hundreds of natural scene images for which we obtained valence, arousal, and memorability scores. From our first experiment, we found memorability to be highly reliable for scene images that span a wide range of evoked arousal and valence. From our second experiment, we found that both valence and arousal are significant but weak predictors of image memorability. Scene images were most memorable if they were slightly negatively valenced and highly arousing. Images that were extremely positive or unarousing were most forgettable. Valence and arousal together accounted for less than 8% of the variance in image memorability. These findings suggest that evoked affect contributes to the overall memorability of a scene image but, like other singular predictors, does not fully explain it. Instead, memorability is best explained by an assemblage of visual features that combine, in perhaps unintuitive ways, to predict what is likely to stick in our memory.
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