Physically Implied Surfaces

This page contains demos and stimuli for Little, P. C. & Firestone, C. (2021). Physically Implied Surfaces. Psychological Science.

Here are a few demonstrations of the phenomenon we sought to capture:

What object is the man interacting with?

What angle is the surface that the disc is bouncing off of?

What is the shape of the container that these discs are in?

And here is a loop of sample displays from Experiment 1:

In the experiment, participants' task was to report whether the black line was horizontal or vertical, as quickly as possible, while disregarding the movements of the actor (whose behavior was non-predictive of the line's orientation). Even so, when his actions were "congruent" with the line that followed, participants gave facilitated responses to its orientation.

Links to the three experiments:

Experiment 1 - an actor interacting with an invisible surface

Experiment 2 - a simulated disc bouncing off of an invisible surface

Experiment 3 - a simulated disc bouncing off of an invisible surface (no delay)

Data, stimuli, and other materials are available at

Want to interact with invisible surfaces yourself? Find the inspiration for our experiments here.

Questions? E-mail Pat Little ( or Chaz Firestone ( You can also visit the homepage of the JHU Perception and Mind Laboratory.