The following is a summary of “Motion information plays only a secondary role in sex identification of walking persons in frontal view,” published in the February 2023 issue of Ophthalmology by Bobbert, et al.

On the basis of movies with only point lights, observers had a success rate above chance when determining the sex of walking people. It had been suggested that spectators heavily relied on motion information when making decisions. For a study, researchers sought to determine how motion information, instead of merely form information, brings value to the frontal plane. 

In the first experiment, 209 viewers were tasked with determining whether frontal-plane still images of point lights depicting six male and six female walkers represented either gender. They employed two different kinds of point-light images: cloud-like images that only included point lights and skeleton-like images with connected point lights. Observers had a mean success rate of 63% when using still images that resembled clouds; however, they had a higher mean success rate of 70% when using still images that resembled skeletons (P< 0.001). In the second experiment, 273 participants were asked to categorize the sex of skeleton-like still photos and skeleton-like movies of eight complete walking strides. 

According to movies, there was a 73% total success rate. The success rate based on still images for observers who were initially shown still images was 68%, whereas the success rate based on still images for observers who were first shown movies was 74%, which was identical to the success rate based on movies (P > 0.05). The interpretation was that once the meaning of the point lights was made obvious, motion information was useless. 

As a result, they concluded that motion information only had a minor impact on the frontal plane sex identification of walking individuals.

Reference: jov.arvojournals.org/article.aspx?articleid=2785391