Sensory input from the moving hand influences saccadic eye movements during reading.

Reading involves saccadic eye movements. Measured reading time and the number of mistakes made while reading reflect the speed and accuracy of the saccades in target localization, if all other factors influencing these parameters are kept constant. The observed phenomenon that reading a book is easier when it is held in an individual's hand than when it is not, especially when movement of the reading text occurs while travelling in a vehicle, raises the question of the role of sensory input from the moving arms in guiding saccades in the direction in which the text is moved. To address this question, 12 healthy subjects (6 males and 6 females), aged 19-21 years took part in this study where reading time and the number of mistakes made while reading a non-moving standardized printed text was noted. Similar printed texts were read by the subjects while mechanically moving them at different fixed speeds in the horizontal plane, with and without the subject's arms moving with the text. At each speed, the reading time recorded when the subject's arms moved with the text was significantly lesser than when they did not (P<0.05). The number of mistakes made were significantly more when not moving the arms than when moving them with the text, at higher speed of text movement (P<0.05). The results indicate that sensory input from the passively moving arms guided saccades in the direction of movement of the text during reading.