The BallGame

As part of my doctoral research at the department of neurophysiology and pathophysiology, University Medical Centre Hamburg-Eppendorf, I conducted two experiments on experiential and movement dynamics during social interactions: the BallGame and the MirrorGame. Here, I present the basic setup of the BallGame.

In the BallGame experiment, two players took their seat in adjacent EEG laboratories, and used their index finger movements to steer a shared virtual ball around obstacles towards as many targets as possible. Parallel to the game, we recorded finger- and eye-movements, asked participants to rate their experience, and used high-density electroencephalography to observe their brain activity.

The BallGame experiment. Fig. A left: screenshot of the game environment. Fig. A right: lab camera view on one of the participants playing the game, seated in the EEG chamber. Fig. B left: the relationship between hand- and ball-movement. Fig. B right: interface participants used to give feedback about their experience during the game. Fig. C: experimental protocol – preparations (written and verbal instructions to the game, mounting and calibrating the recording equipment), baseline EEG recordings, individual and joint play, post-game baseline EEG recordings, and a individual interviews after the game. Figure 1 from the manuscript (see below).

This video illustrates the game environment and the relationship between finger- and ball movement. Note that here, different from the actual experimental setup, all 9 obstacles present in the game environment are visible – in the real game, only 6 of 9 obstacles were visible to each player. Note also that it shows individual play only – in the experiment I conducted, players started out with individual play, and then moved to joint play, during which the movement of the ball reflects players’ integrated finger-movements: when A steers ‘west’ and B steers ‘east’, the ball does not move at all; when A steers ‘north’ and B steers ‘east’, the ball moves into ‘north-east’ direction at intermediate speed, etc. The board and handles visible in the video only serve to orient the hands in line with the axis of ball movement they control: in this case, the left hand (index finger) steered the ball left-and-right, while the right hand was controlling up-and-down movement. The goggles and the markers in the corners of the screen form part of the system that records participants’ eye movements. Note also that compared to the actual experimental setup, this demonstration does not include brain activity recording (seated outside of the EEG chamber, without EEG cap).

Participants played 40 trials of joint play. During half of the trials, they could see exactly the same six obstacles. During the other half, they had complementary views: three obstacles were visible to both players, three only to player A, and three only to player B. After every three to four trials, we asked players for feedback about their engagement in the game, how predictable they felt their partner was behaving (could they understand what the other person was doing?), as well as the level of agreement they sensed with their partner (players could not talk but only had the movement of the ball to coordinate with their partner).

We are in the process of submitting a manuscript about this experiment and our findings to be published as part of a frontiers research topic on sensorimotor foundations of social cognition.