Grasp planning influences the face inversion effect

BACKGROUND Face perception relies on global processing, minimizing attention to individual features. Inversion disrupts this by impairing spatial configuration, shifting focus to local features¹. Motor planning also shapes perception: precision grips enhance local analysis, while power grips promote global processing². This study tests whether grip planning influences visual processing in an inversion paradigm. METHOD Twenty-eight adults completed an inversion task with upright and inverted stimuli (faces, bottles, houses), responding using either power or precision devices. Reaction times and accuracy were analyzed with a linear mixed-effects model using a Complex Random Intercepts³ structure to account for subject-specific variability across categorical conditions. RESULTS Orientation and stimulus type had significant effects, F(1, 53.89) = 27.28, p < .001; F(2, 54.00) = 3.69, p = .03, respectively, with a significant orientation × stimulus interaction, F(2, 107.04) = 7.82, p < .001. The grasping × stimulus interaction approached significance, F(2, 53.92) = 2.69, p = .077. Exploratory post-hoc contrasts revealed a stronger inversion cost for faces during power grasp planning (t(144) = 5.21, p < .0001) compared to precision grasp planning (t(143) = 3.72, p = .0017). CONCLUSION While orientation and stimulus type independently influence reaction times, their interaction amplifies the inversion cost for faces when a power grasp is planned. This dynamic interplay between action and perception highlights the need for further investigation into how motor planning shapes cognitive processing.