Early postural dynamics reveal the rapid processing of fake social cues for deceptive actions in sports.

Deceptive actions such as head fakes are a hallmark of interactive sports, yet it is not well understood how decisions and whole-body responses to head fakes unfold over time. In the present study, participants viewed video sequences of a basketball player passing to the left or right, either with or without a head fake. In the buzzer task, participants moved laterally to press a response button as if to intercept the pass. In the vocal task, they verbally indicated pass direction. Reaction times (RTs), movement times (MTs), and medio-lateral center-of-pressure (CoP) displacements were recorded to investigate whether motor output is rapid and stimulus-driven or rather requires continuous integration of fake and pass cues. Further, we investigated whether the mere observation of a basketball player leads to overt micromovements even if no response movement is intended. The data analysis shows that head fakes increased RTs in both the buzzer and vocal tasks. In the buzzer task, head fakes induced an initial, small erroneous CoP shift, which was then rapidly corrected. When CoP trajectories were aligned by head orientation, fake and non-fake trajectories diverged shortly after movement onset. In the present dynamic sport-related context, this pattern is more compatible with the early integration of head and pass information than with a strictly sequential prime-target account, although the paradigm differs from classic Rapid Chase Theory designs with discrete primes and target events. In the vocal task, participants were not instructed to move, yet CoP traces showed tiny but systematically lateralized micromovements with a temporal structure resembling that in the buzzer task, albeit without an initial erroneous shift for head fakes. These postural fluctuations are consistent with action-observation-related motor activation, although they do not uniquely identify motor resonance and may also reflect attentional or generalized embodied response tendencies. A clear deceptive response conflict at the postural level emerged only when a lateralized action was prepared.