Abstract
It is known that judgments about objects’ distances are influenced by familiar size: a soccer ball looks farther away than a tennis ball if their images are equally large on the retina. We here investigate whether familiar size also influences judgments about the size of images of objects that are presented side-by-side on a computer screen. Sixty-three participants indicated which of two images appeared larger on the screen in a 2-alternative forced-choice discrimination task. The objects were either two different types of balls, two different types of coins, or a ball and a grey disk. We found that the type of ball biased the comparison between their image sizes: the size of the image of the soccer ball was over-estimated by about 5% (assimilation). The bias in the comparison between the two balls was equal to the sum of the biases in the comparisons with the grey disk. The bias for the coins was smaller and in the opposite direction (contrast). The average precision of the size comparison was 3.5%, irrespective of the type of object. We conclude that knowing a depicted object’s real size can influence the perceived size of its image, but the perceived size is not always attracted towards the familiar size.
Highlights
When interacting with the world around us, we use retinal size information to judge the distances and sizes of three-dimensional objects
The results of an example participant (Figure 2) show negative biases for the Soccer and Balls condition, which corresponds to a smaller image of a soccer ball looking as large as the other image
Familiar size affects size perception in the direction of assimilation: the size of an image of a soccer ball that is smaller than its real-world size is overestimated
Summary
When interacting with the world around us, we use retinal size information to judge the distances and sizes of three-dimensional objects. It is known that judged distance is influenced by familiar size: a soccer ball looks farther away than a tennis ball when their images are large on the retina [1] This illusion influences how we interact with such an object: if a matchbox looks like that of a brand that sells large matchboxes, one grasps it as if it were a larger box that is positioned farther away [2]. The issue of which question is answered might play a role in experiments on size perception: are participants reporting about the size of the object, the size of its retinal image (angular size), or a mixture of both?. Besides investigating how familiar size influences judgments of the size of images that are presented on a computer screen (is it assimilation or contrast?) we examined whether superadditivity plays a role in this judgement
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
