Date of Award


Document Type

Union College Only

Degree Name

Bachelor of Science



First Advisor

Erika Wells




synesthesia, memory, numbers, neurology, tasks


Synesthesia is a neurological condition whereby separate perceptions are linked producing a mixed perceptual experience (Simner, 2012). Number-form synesthesia occurs when the spatial representations of numbers are distorted. For example, non-synesthetes (who are sinistrodextral readers) will spatially represent numbers in a linear fashion from left to right in ascending order (Gertner, Henik, & Kadosh, 2009). The spatial representations of numbers in number-form synesthetes, however, include multiple depth planes and non-linear spatial arrays (Kadosh, Gertner, & Terhune, 2012). The present case study investigates the advantages and disadvantages of number-form synesthesia in tasks involving visuospatial flexibility, working memory capacity, and task switching. In the visuospatial task, participants judged the orientation of numbers or letters as either the normal orientation or a mirror image. Additionally, stimuli could be rotated on a central axis by 60 deg intervals. Working memory capacity was determined by creating a memory span test that was congruent or incongruent with a synesthete’s spatial representation of numbers. Results suggest that number-form synesthesia may present a visuospatial advantage in numerical mental rotation tasks, suggesting increased mental flexibility. A disadvantage for number-form synesthesia was found in working memory tasks, particularly when the memory span was incongruent with the synesthete’s spatial number-array. A task-switching study was also performed, which measured differences between a synesthete and controls in task switch cost, or the difference in reaction time between repeat trials and switch trials. Participants switched between two different tasks: one judging whether a number is near to or far from the number 5, and another judging whether a given letter is a vowel or consonant. No differences in task switch cost were found. Overall, both advantages and disadvantages were found in number-form synesthesia.