What Eye Fixation Patterns Tell Us About Subitizing

Abstract

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.

Subitizing and counting in typical and atypical development

“…Trick and Pylyshyn (1993, 1994a, 1994b proposed that subitizing is based on the existence of a limited number of index tokens (FINST; fingers of instantiation) in the visual system that allow the parallel tagging of a small (up to four) amount of items during pre-attentive visual processing. Note, however, that a number of recent studies have challenged the view that subitizing is not influenced by attentional limitations (Railo, Koivisto, Revonsuo & Hannula, 2008;Sophian & Crosby, 2008;Vetter, Butterworth & Bahrami, 2008).…”

Developmental and individual differences of gazing processes underlying the enumeration of small numbers

“…Subitizing or enumerating small numbers of items by adults has traditionally been considered to be a spatially parallel and preattentive process (e.g., Trick & Pylyshyn, 1993;Trick & Pylyshyn, 1994). However, recent studies have raised doubts about this view, because the enumeration of small sets has been observed to also be affected by attentional limitations, although it is less dependent on attentional processes compared with the processing of large sets (Pincham & Szuücs, 2012;Sophian & Crosb, 2008;Railoa et al, 2008). These studies in adults indicate that enumeration of both small and large numbers share the same processes of counting, and the former process (i.e., subitizing)…”

“…Several previous studies in adults examined differences in attentional processes during enumeration of small versus large numbers of items (Railoa, Koivistoa, Revonsuoa, & Hannulae, 2008;Sophian & Crosb, 2008;Trick & Pylyshyn, 1993;1994;Watson, Maylor, & Bruce, 2007). These studies have consistently suggested that subitizing for small number ranges in adults does not require serial attention, unlike counting for large number ranges.…”

“…Trick & Pylyshyn (1993;1994) investigated RTs and examined the different levels of visual processing between subitizing and counting, including the spatially parallel, preattentive stage of visual analysis (i.e., feature registration or grouping) for subitizing, and the spatially serial, attentive stage of visual analysis for counting. Recent studies have investigated eye movements during dot counting as an indicator of parallel preattentive or serial attentive processes (Sophian & Crosb, 2008;Watson et al, 2007). Sophian & Crosb (2008) reported that eye fixations were less likely to be located in arrays of ≤ 3 items than in arrays of ≥ 4 items, and that the fixation times for arrays of large numbers increased as a function of the number of dots.…”

“…Recent studies have investigated eye movements during dot counting as an indicator of parallel preattentive or serial attentive processes (Sophian & Crosb, 2008;Watson et al, 2007). Sophian & Crosb (2008) reported that eye fixations were less likely to be located in arrays of ≤ 3 items than in arrays of ≥ 4 items, and that the fixation times for arrays of large numbers increased as a function of the number of dots. These eye-movement data confirmed that the enumeration of very small sets in adults requires parallel preattentive process and do not depend on serial attentive processes of counting.…”