Abstract
In synesthesia the presentation of alphanumeric characters can result in an automatic perception of color, called a “photism”. An object-substitution masking (OSM) paradigm was used to investigate the role of photisms in target identification. In OSM, a target surrounded by four dots is presented among a number of distractors and quickly removed while its surrounding dots remain. The dots can be an effective mask when they share the target's color. In two experiments, participants reported which of two targets (2 or 5) was present among non-digit distractors arranged on an 8.4° diameter ring (allowing attention to be distributed along the ring). All display items were surrounded by dots; the target disappeared after 20ms. We tested synesthetes (projector and associator) and ≥ 30 control subjects (for a population estimate). In Experiment 1 controls' error increased with set size (2 – 8; p < .01). In Experiment 2 set size was constant (8 items); across counterbalanced blocks target duration varied in 6 steps between 20 and 40 ms. Controls' error decreased with longer display durations (p < .01). In both experiments, synesthetes performed within the same range as controls indicating that their photisms did not improve performance. Indeed, synesthetes reported they did not experience photisms during the task. We suggest that under some conditions of display configuration, brief exposure, and masking, shape information may survive without the generation of photisms. An experiment in progress examines whether focal attention is necessary for synesthetes to perceive and benefit from photisms.
NSF BCS: 0418179 to Mary A. Peterson, UA SBSRI grant to Abrie Schroeder