Background: Bistable images are visual stimuli that have the particular characteristic of being interpreted in two different ways. Due to their physical characteristics, these images, while being observed, encourage the observer to make perceptual alternations, in such a way that it is never possible to perceive the two possible percepts simultaneously. The defining lines and contours of a bistable image, along with all its characteristics, can influence its perception, as well as the areas of the image that are observed. Thus, the fixation points that direct attention to specific areas become modulating factors of the bottom-up type. This phenomenon applies to advertising logos of bistable type. Objective: the study aimed at establishing the influence that a fixation point shown previously can exert on the perception of two bistable logotypes. Thus, it was wanted to find if there is (or not) a bottom-up modulation effect caused by eye-fixations on a particular area of the images that might be related to one of the possible percepts of the bistable stimuli. Method: Using a fixed 120-Hz eye-tracking device, two bistable logos were observed by thirty-five participants in optimal mental health conditions. A fixation point was manipulated at the beginning of the observation of each logo to contrast the perceptions reported in that condition with the interpretations given when the logos were observed without any fixation point that could modulate the observer´s attention. An intrasubject design was conducted so that the two bistable logotypes used could be observed by all the participants. The presentation of bistable stimulus was counterbalanced so as to control the effect that the order of images could make. Results: The data was not distributed normally. By using a non-parametrical statistical test (U-MannWithney), it was found that the fixation point had a significant effect on the interpretation of the percept associated with the area where such point was placed. There is some evidence that lends support to the fact that the observed areas of a bistable stimulus have an impact on its interpretation. Conclusions: It is possible to influence the perception of a bistable logo by means of bottom-up modulators. The brain processes visual sensory information by focusing on specific features of bistable stimuli that can modulate the perception. By drawing the observer´s attention to areas that can influence visual perception, it is possible to direct bistable perception favoring one of the possible percepts to be perceived over the other one.
