Tactile mental rotation in blindfolded and congenitally blind subjects

Abstract

Mental rotation is the process of imagining an object rotated into a di erent orientation in space. This well-known visual phenomenon may be used to understand the cognitive processing by applying it to the tactile modality. Linear correlation between response times and angular orientations of the explored objects shows the mental rotation e ect. Twelve sighted, 12 congenitally blind subjects participated in this study. All subjects were right handed. Gender and age were balanced. The sighted were blindfolded through the experiments. Two tactile L-shaped objects were glued on cardboards as pairs rotated at ve orientations (0o, 45o, 90o, 135o, 180o). A passive touch method was developed, subjects' hands were steady on a platform and objects were placed and lifted with a lever. Subjects used their palms to passively touch the objects. The subjects were instructed to explore the objects tactually and decide if the pairs were same or di erent di erent meaning mirror as known to the experimenter. Response times and accuracies were recorded. Correlation analysis and ANOVA were performed using Matlab. Results showed that both the blindfolded and congenitally blind subjects used mental rotation process during tactile exploration of the stimuli. The results support the idea that an analog representation is used in the cortex which totally lacked visual input. The data presented in this study, combined with the literature further supports the hypothesis that spatial properties of the objects are encoded similarly for touch and vision.|Keywords : Object recognition, blindness, touch.