Subliminal Gestalt grouping: Evidence of perceptual grouping by proximity and similarity in absence of conscious perception

•Previous studies supported perceptual grouping outside the focus of attention.•Our work provides direct evidence of subliminal perceptual grouping processes.•Grouped patterns by proximity and by similarity were displayed as masked primes.•The results showed a reliable priming effect in absence of prime awareness.•Our data support that Gestalt grouping can occur under subliminal conditions. Previous studies making use of indirect processing measures have shown that perceptual grouping can occur outside the focus of attention. However, no previous study has examined the possibility of subliminal processing of perceptual grouping. The present work steps forward in the study of perceptual organization, reporting direct evidence of subliminal processing of Gestalt patterns. In two masked priming experiments, Gestalt patterns grouped by proximity or similarity that induced either a horizontal or vertical global orientation of the stimuli were presented as masked primes and followed by visible targets that could be congruent or incongruent with the orientation of the primes. The results showed a reliable priming effect in the complete absence of prime awareness for both proximity and similarity grouping principles. These findings suggest that a phenomenal report of the Gestalt pattern is not mandatory to observe an effect on the response based on the global properties of Gestalt stimuli.