Grip-Force Modulation During Action Word Reading: An RSVP Paradigm with Bayesian Temporal Analysis

Grip force provides a behavioral index of motor engagement during action language processing, but prior studies have relied on auditory presentation and fixed analysis windows. We adapted grip force methodology to Rapid Serial Visual Presentation (RSVP) and used a Time-resolved Bayesian Evidence Display (TBED) to characterize motor resonance without predefined time windows. We tested two boundary conditions on language-induced motor activation: grammatical aspect (present vs. inceptive constructions) and conscious imagery ability (typical imagery vs. aphantasia). In participants with typical imagery, present-tense action sentences elicited higher grip-force modulation, in line with previous studies. Inceptive constructions showed no reliable motor resonance, with Bayesian evidence supporting the absence of effects. Direct comparisons revealed stronger motor modulation for present-tense than inceptive actions, with inceptive actions patterning like non-action sentences. Participants with aphantasia showed no motor resonance for either construction, although interpretation is limited by increased noise associated with the smaller sample size. Methodologically, RSVP affords fine temporal control but may be associated with greater signal variability; TBED complements this approach by distinguishing evidence of absence from absence of evidence in time-resolved data.