Exploring the role of visual selective attention in synesthesia
Individuals with grapheme-color synesthesia perceive colors, called concurrents, when processing alphanumeric stimuli. Concurrents may arise from cross activation between cortical language and color processing areas. Two experiments used an attentional blink (AB) paradigm to test whether production of concurrents is an automatic or attention-demanding process. Two experiments used a visual-short-term-memory paradigm to test whether working memory (WM) representations of concurrents are capacity demanding. When target color was incongruent with concurrent color but color did not define targets, a synesthete (S1) showed delayed AB recovery compared to controls. When color defined targets and target color was congruent with concurrent color, the ABs of S1 and controls were similar. It appears that concurrent production is involuntary (automatic), but requires resources (attention demanding). WM capacity of S1 and controls was similar. WM representations including concurrents required no more capacity than representations without concurrents. Thus, although production of concurrents requires resources, maintenance does not.