We are constantly exposed to multiple visual scenes, and while freely viewing them without an intentional effort to memorize or encode them, only some are remembered. It has been suggested that image memory is influenced by multiple factors, such as depth of processing, familiarity, and visual category. However, this is typically investigated when people are instructed to perform a task (e.g., remember or make some judgment about the images), which may modulate processing at multiple levels and thus, may not generalize to naturalistic visual behavior. Visual memory is assumed to rely on high-level visual perception that shows a level of size invariance and therefore is not assumed to be highly dependent on image size. Here, we reasoned that during naturalistic vision, free of task-related modulations, bigger images stimulate more visual system processing resources (from retina to cortex) and would, therefore, be better remembered. In an extensive set of seven experiments, naïve participants (n = 182) were asked to freely view presented images (sized 3° to 24°) without any instructed encoding task. Afterward, they were given a surprise recognition test (midsized images, 50% already seen). Larger images were remembered better than smaller ones across all experiments (∼20% higher accuracy or ∼1.5 times better). Memory was proportional to image size, faces were better remembered, and outdoors the least. Results were robust even when controlling for image set, presentation order, screen resolution, image scaling at test, or the amount of information. While multiple factors affect image memory, our results suggest that low- to high-level processes may all contribute to image memory.

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We are constantly exposed to multiple visual scenes, and without intentional effort to memorize or encode them, only some are remembered. It has been suggested that such nonintentional memory is influenced by the depth of processing, but it is unclear whether this applies to visual images. Here we reasoned that bigger images may entail deeper level of processing and will thus be remembered better. In a series of image-viewing experiments we found that larger images were better remembered, image memorability was proportional to image size, faces were better remembered, and outdoors the least. While multiple factors affect image memorability, here we show that under incidental exposure without an encoding task, a basic physical image dimension plays an important role. These results could have significant implications to multiple domains as learning, education, aging, medical care and policies, transport and others.