title: Modulating attentional load affects numerosity estimation: evidence against a pre-attentive subitizing mechanism.
abstract: Traditionally, the visual enumeration of a small number of items (1 to about 4), referred to as subitizing, has been thought of as a parallel and pre-attentive process and functionally different from the serial attentive enumeration of larger numerosities. We tested this hypothesis by employing a dual task paradigm that systematically manipulated the attentional resources available to an enumeration task. Enumeration accuracy for small numerosities was severely decreased as more attentional resources were taken away from the numerical task, challenging the traditionally held notion of subitizing as a pre-attentive, capacity-independent process. Judgement of larger numerosities was also affected by dual task conditions and attentional load. These results challenge the proposal that small numerosities are enumerated by a mechanism separate from large numerosities and support the idea of a single, attention-demanding enumeration mechanism.
authors.affiliation: Institute of Cognitive Neuroscience, University College London, London, United Kingdom. p.vetter@ucl.ac.uk
authors.forename: Petra
authors.initials: P
authors.lastname: Vetter
authors.forename: Brian
authors.initials: B
authors.lastname: Butterworth
authors.forename: Bahador
authors.initials: B
authors.lastname: Bahrami
mesh_terms: D000328:Adult; D001288:Attention; D004193:Discrimination Learning; D005260:Female; D006801:Humans; D008297:Male; D008433:Mathematics; D008606:Mental Processes; D008962:Models, Theoretical; D009949:Orientation; D010364:Pattern Recognition, Visual; D011930:Reaction Time; D015203:Reproducibility of Results; D014785:Vision, Ocular; D014796:Visual Perception