Haptic perception of the horizontal by blind and low-vision individuals

We examined haptic perception of the horizontal in visually impaired people . Blind people (late blind and congenitally blind), persons with very low v ision, and blindfolded sighted individuals felt raised-line drawings of jar s at four angles. They had to demonstrate their understanding that water re mains horizontal, despite jar tilt, by selecting the correct raised-line dr awing given four choices. Low-vision subjects, with near perfect scores, pe rformed significantly better than the other groups of subjects. While the l ate-blind and blindfolded sighted subjects performed slightly better than t he congenitally blind participants, the difference between the late-blind a nd congenitally blind groups was nonsignificant. The performance of the con genitally blind subjects indicates that visual experience is not necessary for the development of an understanding that water level stays horizontal, given container tilt.