The Enumeration Of Real-World Objects Depends On Their Perceived Size But Not Their Conceived Size

The capacity to quickly and accurately enumerate objects in our environment appears to be a core cognitive ability: it emerges early in human development, and has dedicated neural substrates. We can learn about the mechanisms of enumeration by studying which factors influence enumeration accuracy. For example, when estimating the number of circles in a briefly presented display, people overestimate the number of physically small circles (e.g., diameter = 0.5 inches) relative to the number of physically large circles (e.g., diameter = 4 inches). Here we explored whether the familiar size of objects will have a similar effect on enumeration: would people overestimate the number of pennies relative to the number of cars, even if they were the same size on the screen? On each trial, 3-10 objects were displayed for 500 ms, followed by a checkerboard "mask" displayed for 250 ms.The task was to indicate how many objects were seen. The images presented varied in physical size (big versus small on the screen), as well as familiar size (large versus small in the world, e.g., cars vs. pennies). The manipulation of physical size and familiar size was counterbalanced across images. The results showed a significant effect of physical size: observers overestimated the number of objects when they were physically small than when they were physically big. However, there was no effect of familiar size on enumeration. Thus, the number of objects we see depends on their perceived size, but not their conceived size.