Prime gesture and motor inhibition: Unveiling the mechanisms of motor interference effects caused by dangerous objects

Dangerous objects can inhibit prepared motor actions elicited by prime gestures, resulting in prolonged reaction times—a phenomenon termed the motor interference effect caused by dangerous objects. Previous research has emphasized that motor inhibition requires the affordance activation strength elicited by dangerous targets to exceed an inhibitory threshold. However, existing studies have confounded affordance activation levels with variations in multiple factors, including prime gestures, stimulus sizes, target orientation affordances, and low-level sharp-edge features. These methodological confounding factors have led to ambiguity regarding the necessary conditions for the emergence of motor interference effects. To address this issue, this study conducted five experiments using a prime-target grip congruency judgment task. Experiment 1 controlled for shape and grip-type differences between dangerous and neutral targets. Experiment 2 further matched target sizes in the precision-grip condition to those in the power-grip condition, which eliminated stimulus sizes as a contributing factor for motor interference effects. Experiment 3 manipulated prime gestures while using identical stimuli for power-grip and precision-grip targets (the area of power-grip targets was twice that of precision-grip targets). Results showed that motor interference effects in the power-grip target condition depended on the power-grip prime gesture. To further investigate potential confounds, Experiments 4 and 5 used target stimuli without handle features and manipulated the target grasping experience to exclude the influences of target orientation affordances and low-level sharp-edge features. Taken together, these findings clarify the prerequisite conditions for motor interference effects and enhance our understanding of their underlying motor control mechanisms.