Images are often used for instructing, illustrating, identifying, providing variation, authority, and information as a supplement to text and sound. In addition, images are used for content that is important, difficult to understand, and new to the readers. The effectiveness of any visual depends on the medium, on the type of information, and on the amount of time subjects are allowed to interact with the material. Images can also be affective and provide participants with entertainment, and underline an experience both positive and negative.
Subliminal images or images below the threshold of human perception can trigger subconscious associations and influence emotions and attitudes, especially in movies and television. Subliminal images can be used to persuade, compliment, tease, disgrace, scare, and even seduce the audience. In advertising especially, images may carry subliminal messages. Advertisements for liquor or cigarettes, for instance, sometimes use sex symbols. Images can be compensatory, making it easier for poor viewers to understand, learn, and remember things they read in text.
Proponents of subliminal vision claim it is capable of scanning ongoing structures and gathering more data than an alert examination lasting thousand times longer. With impartial sharpness our unconscious vision registers minute details irrespective of whether they belong to the figure or to the background. But it usually tends to retract the conscious preference for the shape and pays more attention to textural and backdrop elements.
Although solid research evidence suggests that our attitudes may be susceptible to subliminal visual information, those same research findings make clear the limits on such influence. Firstly, in laboratory studies of subliminal image effects, experimenters have to work hard to ensure that subjects focus closely on the region in which subliminal stimuli are presented. In the usual confusion of everyday environments, such dedicated focusing is unlikely, and so the messages probably would not receive even minimal processing.