Effects of Dot Pitch and Dot Size on the Discriminability of Dotted Lines in Braille Graphics

Abstract

The present study aimed to clarify factors that would make it easier for persons reading Braille graphics to discriminate 2 lines by analyzing effects of dot pitch and dot size on the number of trials needed to complete tasks requiring discrimination of 2 lines and on participants' performance time. The overall results suggested that dot pitch and dot size affect the discriminability of embossed dotted lines. Study 1 examined effects of dot pitch on the discriminability of embossed dotted lines. In Braille graphics, a difference in the pitch of 2 dotted lines that was more than 3mm was required for easy discrimination when the 2 lines were composed of medium-size points (1.5mm in diameter). Study 2 examined the affect of dot size on the discriminability of embossed dotted lines. Only between 1 and 3 of the 8 participants were able to complete the tasks when points that were the same distance apart were either medium (1.5mm diameter) or large (1.7mm diameter), which suggests that points of those sizes may not be appropriate for use in lines in Braille graphics when a discrimination between 2 lines is required. The largest points (1.7mm diameter) were relatively discriminable from the smallest ones (0.7mm diameter).