Subitizing reflects visuo-spatial object individuation capacity

• Published in: Cognition Vol. 121; no. 1; pp. 147 - 153
• Main Authors: Piazza, Manuela, Fumarola, Antonia, Chinello, Alessandro, Melcher, David
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.10.2011; Elsevier
• Subjects: Adult; Attention - physiology; Biological and medical sciences; Capacity limits; Cognition; Cognitive Processes; Computation; Concept Formation; Estimation; Evidence; Female; Fundamental and applied biological sciences. Psychology; Human; Humans; Individuality; Individuation; Law; Learning. Memory; Male; Mechanization; Memory; Memory, Short-Term - physiology; Neuropsychological Tests; Pattern Recognition, Visual - physiology; Photic Stimulation; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Space Perception - physiology; Spatial Ability; Subitizing; Visual Perception - physiology; Visual Stimuli; Visuo-spatial attention; Visuo-spatial working memory; Capacity limits; Visuo-spatial attention; Visuo-spatial working memory; Subitizing; Individuation; Human; Visual memory; Spatial attention; Cognition; Space perception; Memory capacity; Stimulus identification; Working memory; Counting; Spatial memory
• ISSN: 0010-0277; 1873-7838; 1873-7838
• DOI: 10.1016/j.cognition.2011.05.007

► Subitizing may reflect a capacity limited mechanism for multiple object individuation. ► We compare capacity in enumeration and in visuo-spatial short term memory tasks. ► Capacity in the two tasks correlate across subjects and is reduced in dual task conditions. ► Results are predicted assuming a common mechanism for individuation. Subitizing is the immediate apprehension of the exact number of items in small sets. Despite more than a 100 years of research around this phenomenon, its nature and origin are still unknown. One view posits that it reflects a number estimation process common for small and large sets, which precision decreases as the number of items increases, according to Weber’s law. Another view proposes that it reflects a non-numerical mechanism of visual indexing of multiple objects in parallel that is limited in capacity. In a previous research we have gathered evidence against the Weberian estimation hypothesis. Here we provide first direct evidence for the alternative object indexing hypothesis, and show that subitizing reflects a domain general mechanism shared with other tasks that require multiple object individuation.