Searching in space and in time.

Our conception of attention is intricately linked to limited processing capacity and the consequent requirement to select, in both space and time, what objects and actions will have access to these limited resources. Seminal studies by Treisman (Cognitive Psychology, 12, 97-136, 1980) and Broadbent (Perception and Psychophysics, 42, 105-113, 1987; Raymond et al. Journal of Experimental Psychology: Human Perception and Performance, 18, 849-860, 1992) offered the field tasks for exploring the properties of attention when searching in space and time. After describing the natural history of a search episode we briefly review some of these properties. We end with the question: Is there one attentional "beam" that operates in both space and time to integrate features into objects? We sought an answer by exploring the distribution of errors when the same participant searched for targets presented at the same location with items distributed over time (McLean et al. Quarterly Journal of Experimental Psychology, 35A, 171-186, 1982) and presented all at once with items distributed over space (Snyder Journal of Experimental Psychology; 92, 428-431, 1972). Preliminary results revealed a null correlation between spatial and temporal slippage suggesting separate selection mechanisms in these two domains.