What eye fixation patterns tell us about subitizing

Differences between the enumeration of very small (1-3) versus larger (4-6) numerosities were examined by investigating where people fixate when they are enumerating different numbers of items. Overall, fixations were more likely to be located in regions of the array that contained target items when the array contained 4 or more targets than when it contained 3 or fewer, a result that is consistent with previous research indicating that the enumeration of very small sets is less dependent on attentional processing than is the enumeration of larger sets. However, both the pattern of fixations across different distractor conditions and an analysis of the temporal course of fixations in the absence of distractors were inconsistent with a dichotomous distinction between pre-attentive and attentional forms of enumeration. Rather, our results suggest that, irrespective of numerosity, enumeration entails some attentional processing of target items, but attentional processing plays a markedly greater role in the enumeration of 4 or more items than in the enumeration of 3 or fewer.