Visual search: efficiency continuum or distinct processes?

Whether visual search involves two distinct processes--traditionally referred to as serial and parallel--or a single process operating on a continuum of efficiency or speed, is an issue with a long history in the study of attention. On the basis of the unimodality of search slope distributions in a very large data set, Wolfe (1998) argued for a continuum model. Reanalysis of this data set using statistical procedures more appropriate for adjudicating between continuous and discontinuous models supports the existence of two distinct processes.