The variable spatial resolution is compensated by tip of the tongue tracing in pattern recognition


Pamir, Z., Canoluk, M. U., Jung, J. - H., & Peli, E. (2019). The variable spatial resolution is compensated by tip of the tongue tracing in pattern recognition. Investigative Ophthalmology & Visual Science , 60 (9), 3310-3310. Copy at


The tongue has been suggested to be an ideal platform for visual sensory substitution devices because of its high spatial resolution and high sensitivity. However, inhomogeneities in resolution and sensitivity across its dorsal surface have been reported. In the present study, using the BrainPort Vision Pro, we investigated how the inhomogeneity in the spatial resolution affects letter recognition performance of normally sighted and blind individuals. Stimuli were 26 computer-generated English alphabet capital letters streamed directly to the intra-oral device (IOD), not through the camera. Stimulation intensity was adjusted to be above threshold at the lowest resolution (back of the tongue). We compared three display conditions; static, drawing, and tracing with the tip of the tongue. In the static condition, the complete letter was displayed on the tongue at once and participants were not allowed to move their tongue. In the drawing condition, the letter was divided into smaller parts and sequentially presented as in the case of hand lettering. In the tracing condition, the letter is presented at once, as in the static, but participants were encouraged to trace the pattern with their tip of the tongue. In all conditions, participants were required to name the letter. Data was collected from 10 participants. Recognition performance was significantly better for the tracing condition (M=67%, SEM=8.54) compared to both static (M=38%, SEM =5.07) and drawing (M=33%, SEM =5.93) conditions. There was no difference between the static and drawing conditions. The performance was well above chance (3.84%) for all conditions. There was no significant difference in time required to recognize a letter across conditions, and between normally sighted and blind participants’ performance. Tracing the spatial pattern with the tip of tongue provides far better performance in recognizing letters. The results suggest that inhomogeneity in spatial resolution reduces the recognition performance through aliasing when the spatial pattern is presented across the inhomogenous tongue surface; and the higher resolution at the tip enables motor tracing for recognition. This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019. Individual (N: Normally sighted, B: Blind) and mean percent correct responses for letter recognition in static, drawing and tracing conditions. The horizontal red line shows chance level (1/26). Error bars show SEM. * p < 0.001.