Image size effect on memory generalizes to deeper encoding and cannot be explained by perceptual measures

We have recently found that during shallow (“naturalistic”/incidental) encoding larger images are better remembered. However, it is unclear whether this reflects a genuine influence of image size on mnemonic processes or an epiphenomenal consequence of its influence on perception, and whether this effect robustly generalizes to deeper encoding. Here, we tested these in three experiments (n = 189) differing in encoding depth: naturalistic (freely viewing the images without being informed a memory test will follow), intentional memorization (freely viewing while memorizing the images since a memory test was to follow), or perceptual encoding (reporting for each image whether there was a person in it and whether it was taken indoors or outdoors, without being informed a memory test will follow). During encoding in the perceptual experiment, participants viewed 160 images of different sizes (3°-15.5°) followed by an old-new recognition memory test of 320 images (half “old”). While perceptual measures were at ceiling, memory improved with image size, presenting a dissociation between perception and memory and indicating that the effect of image size on memory is not a mere reflection of limited perception for smaller images. Additionally, the effect of image size on memory generalized to all encoding tasks such that memory improved for larger images (as evident by accuracy and d’), regardless of average memory performance increasing with encoding depth. These findings suggest that image size operates as a genuine sensory-based modulator of memory encoding, beyond perceptual sensitivity, pointing to a broader role of low-level visual properties in shaping memory representations.