Visual Enumeration: Subitizing and Its Nature

217 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2004.To examine the role of subitizing in ongoing visual enumeration processes, three experiments were conducted using saccade-continent display change technique and peripheral preview paradigm. The results shows that numerical information of up to 3 or 4 items can be quickly enumerated from an extrafovea display and be used in the following enumeration process when the display comes into fovea in the next fixation. While a valid peripheral preview facilitates enumeration speed, invalid preview information causes a penalty in both accuracy and response time. This difference only occurs for small set enumeration; for large set sizes, enumeration speed is facilitated whether information from the peripheral preview is valid or invalid. These findings suggest subitizing as part of the object perception processes. A surprising difference between two display-change conditions in which one item was either inserted in or removed from the display during a saccade to the stimulus pattern further suggests that subitizing is explained well by the object-file/visual-index theories. The nature of small and large set enumeration processes and their interaction is discussed in the last chapter.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD