Exhibition Program

Science of Human


What is a "straight" ball?

Physical and perceptual attributes of a pitched ball


Athletes' perceptions are extraordinarily sensitive, but they do not necessarily capture the physical world as it is. We accurately quantified the physical characteristics of pitched baseballs, and then investigated how batters perceived them. In the physical measurement, we devised a technique to easily measure the 3D rotation characteristics of the ball using a single camera. In the perceptual measurement, we found that the batters’ perception of the ball’s horizontal movement in the trajectory was systematically biased, even though they discriminated small differences in the movement. Moreover, we found that the direction of their bias was reversed, depending on the pitcher’s handedness. In sports science, physical measurement tends to be emphasized, and the gap between the physical characteristics and players’ perception is at issue. Combining physical and perceptual measurement to identify the cause of such a gap could lead to a dramatic revolution in training and coaching.


  1. D. Nasu, T. Kimura, M. Kashino, “Do baseball batters perceive straight ball trajectory as straight?” in Proc. 2020 Conference on North American Society for Psychology of Sport and Physical Activity, 2020.


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Daiki Nasu / Kashino Diverse Brain Research Laboratory