The role of working memory in spatial enumeration: patterns of selective interference in subitizing and counting.

Articulatory suppression (repeatedly pronouncing a syllable or word while carrying out another task) is thought to interfere selectively with the phonological store in working memory. Although suppression interferes with temporal enumeration (enumerating successive light flashes), to date there has been little evidence of such interference in spatial enumeration (enumerating units laid out in space at one time)--a finding with serious ramifications for theories of enumeration. Participants carried out a spatial enumeration task, enumerating 1-8 dots while listening to a metronome (baseline condition) or while carrying out a secondary task to the rhythm of the metronome (dual-task condition). There were four secondary tasks: simple articulation (saying a letter), complex articulation (alternating between two letters), simple tapping (tapping a finger), and complex tapping (alternating between two fingers). Interference varied with number of items, but the pattern differed from that observed with temporal enumeration.