Congruency effects in dot comparison tasks: convex hull is more important than dot area

J Cogn Psychol (Hove). 2016 Nov 16;28(8):923-931. doi: 10.1080/20445911.2016.1221828. Epub 2016 Aug 31.


The dot comparison task, in which participants select the more numerous of two dot arrays, has become the predominant method of assessing Approximate Number System (ANS) acuity. Creation of the dot arrays requires the manipulation of visual characteristics, such as dot size and convex hull. For the task to provide a valid measure of ANS acuity, participants must ignore these characteristics and respond on the basis of number. Here, we report two experiments that explore the influence of dot area and convex hull on participants' accuracy on dot comparison tasks. We found that individuals' ability to ignore dot area information increases with age and display time. However, the influence of convex hull information remains stable across development and with additional time. This suggests that convex hull information is more difficult to inhibit when making judgements about numerosity and therefore it is crucial to control this when creating dot comparison tasks.

Keywords: Dot comparison; congruency effects; magnitude representations; numerical cognition.

Grant support

This work was funded by a grant (RES-062-23-3280) from the Economic and Social Research Council, UK (CG and LC), a Royal Society Dorothy Hodgkin Research Fellowship (CG) and a Royal Society Worshipful Company of Actuaries Research Fellowship (MI).