Memory sensitivity improves with larger image size during naturalistic encoding

We have recently found that people remember bigger images more than smaller images during naturalistic-like encoding. Since these findings were established with accuracy levels which may be confounded by response biases, and since memory performance was apparently low, here we addressed these issues. By reanalysing our old lab dataset (n = 101) and in new online experiments (n = 199), we estimated accuracy, dprime memory-sensitivity that accounts for potential response biases (criterion), and RT-based ROC measures. Consistently across experiments, we found that overall memory performance, as estimated by dprime and ROC-based analyses, was modest but significantly above chance, indicating that a certain level of image information was encoded and learnt. Larger images (in the 3°−12° range) were better remembered, as evident in dprime and accuracy. In the online experiments, memory for 1.5° images did not differ from that of 3° images and memory for images likely bigger than the screen size (24°) dropped, likely reflecting display size limitations. Memorability also increased with image size. Our findings provide converging measures that image size plays an important role in memory during naturalistic encoding for images in the size range of 3°−12°. Our study also emphasizes the importance of testing an effect across multiple measures and methods.