Subliminal perception of complex visual stimuli.

Rationale: Unconscious perception of various sensory modalities is an active subject of research though its function and effect on behavior is uncertain. Objective: The present study tried to assess if unconscious visual perception could occur with more complex visual stimuli than previously utilized. Methods and
Results: Videos containing slideshows of indifferent complex images with interspersed frames of interest of various durations were presented to 24 healthy volunteers. The perception of the stimulus was evaluated with a forced-choice questionnaire while awareness was quantified by self-assessment with a modified awareness scale annexed to each question with 4 categories of awareness. At values of 16.66 ms of stimulus duration, conscious awareness was not possible and answers regarding the stimulus were random. At 50 ms, nonrandom answers were coupled with no self-reported awareness suggesting unconscious perception of the stimulus. At larger durations of stimulus presentation, significantly correct answers were coupled with a certain conscious awareness. Discussion: At values of 50 ms, unconscious perception is possible even with complex visual stimuli. Further studies are recommended with a focus on a range of interest of stimulus duration between 50 to 16.66 ms.