Long-term visual experience recalibrates human orientation perception

Sensory neural reorganization occurs as a result of visual experience in the adult as well as early in life. Here we report and quantify a misperception of visual orientation: when alphanumeric characters that are commonly tilted clockwise were presented with a clockwise tilt, they were perceived as less tilted than the same stimulus horizontally inverted. In contrast, subjective perception of tilt magnitude for horizontally inverted non-alphanumeric stimuli was similar to that for non-inverted stimuli. Therefore, misassessment of tilt of alphanumeric characters probably reflects a persistent sensory recalibration of orientation perception as a result of previous long-term visual experience.