Abstract
Recent studies have shown that image memorability (the estimated probability that an image would be remembered) is a consistent image-specific trait. Several studies have recently found that during naturalistic encoding (when participants freely view images and are not aware of any task that may follow) physical stimulus properties such as image size, contrast, and presentation duration all influence memory such that images with higher levels of these physical properties are associated with higher memory and higher image memorability. Specifically, these studies used 160 images of faces, people, indoors and outdoors from LaMem dataset that were carefully selected to be balanced for memorability scores (as available from LaMem) across the physical stimulus manipulations they performed. During naturalistic encoding, image memorability was significantly affected by physical manipulations with higher levels of each physical property (bigger size, higher contrast, longer duration) leading to higher image memorability. Since the memorability of images was influenced by these physical manipulations to different degrees, here we were interested to examine whether image category contributed to this variability. Image memorability was modulated according to visual category and the specific physical modulation (size, contrast, presentation duration). Memorability of images from all categories was significantly influenced by the strongest vs weakest physical conditions (size of 24° vs 3°, contrast of 60 vs 7.5 RMS, or presentation duration of 2000 vs 250ms), and interestingly, images of people were influenced the most across all physical manipulations. Furthermore, images of people were also the most influenced between the two moderate levels of physical properties (size of 12° vs 6°, contrast of 30 vs 15 RMS, or presentation duration of 1000 vs 500ms), while face images the least. While multiple factors are likely to contribute to image memorability, our results suggest that the contribution of physical image properties to image memorability is likely category-dependent.