Grouping Strategies in Numerosity Estimation between Intrinsic and Extrinsic Grouping Cues

Abstract

The number of items in an array can be quickly and accurately estimated by dividing the array into subgroups, in a strategy termed “groupitizing.” When attempting to remember a telephone number, it is better to do so by dividing the number into several segments. Different forms of visual grouping can affect the accuracy of the enumeration of a large set of items. Previous studies have found that when groupitizing, enumeration accuracy is improved by grouping arrays using visual proximity and color similarity. Based on Gestalt theory, Palmer (1992) divided perceptual grouping into intrinsic (e.g., proximity, similarity) and extrinsic (e.g., connectedness, common region) principles. Studies have investigated groupitizing effects of intrinsic grouping. However, to the best of our knowledge, no previous study has explored groupitizing effects for extrinsic grouping cues. Therefore, this study explored whether extrinsic grouping cues differed from intrinsic grouping cues for groupitizing effects in numerosity estimation. The results showed that both extrinsic and intrinsic grouping cues improved enumeration accuracy. The extrinsic grouping cues were more accurate in terms of sensory precision of the numerosity estimation than were the intrinsic grouping cues.