The Ebbinghaus illusion (a.k.a. Titchener circles) is a robust optical illusion discovered more than 100 years ago. Two identically-sized* circles are presented, one is surrounded by large circles, the other by small circles. The one surrounded by small circles looks bigger.
In 2012, a research group from Purdue University, the Max Planck Institute and the University of Virginia wondered if the illusion might have practical applications – say, for sportspersons. They reasoned that :
“Bigger targets feel as if they should be easier to hit, so people may feel more confident when aiming for a bigger target.”
Leading to the question of whether golfers might find putting easier if the Ebbinghaus illusion was employed to make the hole look bigger? Their experiments supported their hypothesis :
“Participants putted more successfully to the perceptually bigger hole. As outlined in the introduction, this result suggests a link between perceived size and performance.”
See: Witt, J. K., Linkenauger, S. A., & Proffitt, D. R. (2012). Get me out of this slump! Visual illusions improve sports performance. Psychological Science, 23, 397-399. (full copy here)
Their findings have, however, recently been questioned. This time, a team from Université de Franche-Comté and Université Paris-Est Créteil performed three Ebbinghaus-assisted putting experiments, and in general found very little, if any, advantage.
“One practical implication of the present study is that sportsmen, coaches and teachers should not rush to embrace training techniques that rely on the Ebbinghaus illusion to improve sports performance in novices, unless they are prepared to accept little or no benefit.”
See : Maquestiaux, F., Arexis, M., Chauvel, G. et al. Ebbinghaus visual illusion: no robust influence on novice golf-putting performance. Psychological Research, 2020. (full copy here)
* Note : Yes, we’ve checked, they are.