Does subitizing require attention? A systematic review and meta-analysis
Whether enumeration of small number of objects requires attention remains controversial. Although most recent studies argue for a role of attention in subitizing, these studies include varied stimuli and different methods of manipulating attention. It is unclear if the observed attention effects in different studies are real effects. It is also unclear whether there is publication bias in these studies. To answer this question, a systematic review and meta-analysis was performed to evaluate the attention effects on enumeration of small numbers. A total of 14 studies (22 experiments, 35 comparisons) were included in a meta-analysis to compare the attention effects on subitizing. Results from the meta-analysis suggest that a manipulation of attention can evidently modulate the behavioural performance in the subitizing range (response time, accuracy and Weber fraction). These findings were consistently observed in various experimental designs and different stimuli (p < .010; p < .001; p < .001; respectively), suggesting attention does play a role in subitizing. A new model was proposed to explain the mechanism of subitizing and enumeration. Findings in this study may contribute to the understanding of “number module” in brain and contribute to models of numerical cognition in education. However, a publication bias was observed in this study, suggesting the observed effects might not be very accurate. To better estimate the effect of attention manipulations in the subitizing range, studies with larger samples, or future meta-analyses including unpublished outcomes and unpublished studies may be required.