Figure 1.

Stimulus design and preliminary results from Experiment 1. (A) Illustration of task procedure. Participants passively viewed dot arrays with no explicit task instructions except to press a button when the array was presented in red, which happened on 5% of all the trials. (B) Numerosity of a dot array is inherently related to its intensive (IA and Spar) and extensive properties (TA and FA). An orthogonal dimension to numerosity can be constructed as a combination of IA and TA, which is referred to as the dimension of “size (in area).” Another orthogonal dimension to numerosity can be constructed as a combination of Spar and FA, which is referred to as the dimension of “spacing.” Construction of these 2 axes allows us to realize that the entire parameter space can be represented as a function of the 3 orthogonal axes: numerosity, size, and spacing. Sets of dot arrays were constructed to span a range of numerosity and other visual properties, as represented in orange dots in this parameter space. See Materials and Methods for details. (C) Grand-averaged ERPs for all the trial conditions collapsed from Experiment 1. Topographic maps show averaged ERPs within a 50-ms time window centered on the specified latencies.