Subtle predictive movements reveal actions regardless of social context

Abstract

Humans have a remarkable ability to predict the actions of others. To address what information enables this prediction and how the information is modulated by social context, we used videos collected during an interactive reaching game. Two participants (an “initiator” and a “responder”) sat on either side of a plexiglass screen on which two targets were affixed. The initiator was directed to tap one of the two targets, and the responder had to either beat the initiator to the target (competition) or arrive at the same time (cooperation). In a psychophysics experiment, new observers predicted the direction of the initiators' reach from brief clips, which were clipped relative to when the initiator began reaching. A machine learning classifier performed the same task. Both humans and the classifier were able to determine the direction of movement before the finger lift-off in both social conditions. Further, using an information mapping technique, the relevant information was found to be distributed throughout the body of the initiator in both social conditions. Our results indicate that we reveal our intentions during cooperation, in which communicating the future course of actions is beneficial, and also during competition despite the social motivation to reveal less information.

The ability to predict actions of others from distributed cues is still developing in six- to eight-year-old children

“…Previous studies have shown that adults predict the target of an action and make anticipatory eye movements to that location (Flanagan & Johansson, 2003). These predictions are likely based on kinematic cues (Cavallo et al, 2016;Diaz, Fajen, & Phillips, 2012) that are widely distributed across body of the actor (McMahon et al, 2019;Pesquita, Chapman, & Enns, 2016;Vaziri-Pashkam, Cormiea, & Nakayama, 2017). Adults can use this distributed information to make predictions even when the locus of the information is far from the body part performing the action.…”

“…These cues begin early in the actor's movement. For example, when asked to predict the target of the reach, participants are able to predict the target of the reach before the actor's finger had even lifted-off from the table (McMahon et al, 2019). When the movements prior to the finger's lift-off are occluded, participants are much slower at predicting the target of the reach (Vaziri-Pashkam et al, 2017).…”

“…Participants in this study performed a competitive reaching task similar to our previous studies (Vaziri-Pashkam et al, 2017;McMahon et al, 2019). The participants were always assigned the role of the "Blocker."…”

The ability to predict actions of others from distributed cues is still developing in 6- to 8-year-old children

“…Previous studies have shown that adults predict the target of an action and make anticipatory eye movements to that location ( Flanagan & Johansson, 2003 ). These predictions are likely based on kinematic cues ( Cavallo, Koul, Ansuini, Capozzi, & Becchio, 2016 ; Diaz, Fajen, & Phillips, 2012 ) that are widely distributed across the body of the actor ( McMahon, Zheng, Pereira, Gonzalez, Ungerleider, & Vaziri-Pashkam, 2019 ; Pesquita, Chapman, & Enns, 2016 ; Vaziri-Pashkam, Cormiea, & Nakayama, 2017 ). Adults can use this distributed information to make predictions even when the locus of the information is far from the body part performing the action.…”

“…These cues begin early in the actor's movement. For example, adults are able to predict the target of an actor's reach before the actor's finger had even lifted off from the table ( McMahon et al, 2019 ). When the movements prior to the finger's lift-off are occluded, participants are much slower at predicting the target of the reach ( Vaziri-Pashkam et al, 2017 ).…”