Subliminal stimuli

Subliminal stimuli (/sʌbˈlɪmɪnəl/) (the prefix sub- literally 'below, or less than'), contrary to supraliminal stimuli or 'above threshold', are any sensory stimuli below an individual's threshold for conscious perception. A 2012 review of functional magnetic resonance imaging (fMRI) studies shows that subliminal stimuli activate specific regions of the brain despite participants being unaware. Visual stimuli may be quickly flashed before an individual can process them, or flashed and then masked, thereby interrupting the processing. Audio stimuli may be played below audible volumes or masked by other stimuli. Subliminal stimuli (/sʌbˈlɪmɪnəl/) (the prefix sub- literally 'below, or less than'), contrary to supraliminal stimuli or 'above threshold', are any sensory stimuli below an individual's threshold for conscious perception. A 2012 review of functional magnetic resonance imaging (fMRI) studies shows that subliminal stimuli activate specific regions of the brain despite participants being unaware. Visual stimuli may be quickly flashed before an individual can process them, or flashed and then masked, thereby interrupting the processing. Audio stimuli may be played below audible volumes or masked by other stimuli. Applications of subliminal stimuli often base themselves on the persuasiveness of the message. Importantly, research on action priming has shown that subliminal stimuli can trigger only actions a receiver of the message plans to perform anyway. However, consensus of subliminal messaging remains unsubstantiated by other research. Most actions can be triggered subliminally only if the person already has the potential to perform a specific action.The following sections have more information on specific studies which investigate the effectiveness of subliminal stimuli. The threshold in subliminal stimuli research is the level at which the participant is not aware of the stimulus being presented. Researchers determine a threshold for the stimulus that will be used as the subliminal stimulus. That subliminal stimulus is then presented during the study at some point and measures are taken to determine the effects of the stimulus. The way in which studies operationally define thresholds depends on the methods of the particular article. The methodology of the research also varies by the type of subliminal stimulus (auditory or visual) and the dependent variables they measure. The objective threshold is found using a forced choice procedure, in which participants must choose which stimulus they saw from options given to them. Participants are flashed a stimulus (e.g. the word 'orange') and then given a few choices and asked which one they saw. Participants must choose an answer in this design. The objective threshold is obtained when participants are at chance level of performance in this task. The length of presentation that causes chance performance on the forced choice task is used later in the study for the subliminal stimuli. The subjective threshold is determined by when the participant reports that his or her performance on the forced choice procedure approximates chance. The subjective threshold is 30 to 50 ms slower than the objective threshold, demonstrating that participants are able to detect the stimuli is present sooner than their perceived accuracy ratings would indicate. In other words, stimuli presented at a subjective threshold have a longer presentation time than those presented at an objective threshold. When using the objective threshold, primes neither facilitated nor inhibited the recognition of a color. However, the longer the duration of the priming stimuli, the greater effect it had on subsequent responding. These findings indicate that the results of some studies may be due to their definition of below threshold. Perception without awareness can be demonstrated through the comparison of direct and indirect measures of perception. Direct measures use responses to task definitions as per the explicit instructions given to the subjects. Indirect measures use responses that are not a part of the task definition given to subjects. Both direct and indirect measures are displayed under comparable conditions except for the direct or indirect instruction. For example, in a typical Stroop Task, subjects are given the task of naming the color of a patch of ink. A direct measure is 'accuracy'—true to the instructions given to the participants. The popular indirect measure used in the same task is 'response time'—subjects are not told that they are being measured for response times. Similarly, a direct effect is the effect of a task stimulus on the instructed response to that stimulus, usually measured as accuracy. An indirect effect is an uninstructed effect of the task stimulus on behavior, sometimes measured by including an irrelevant or distracting component in the task stimulus and measuring its effect on accuracy. These effects are then compared on their relative sensitivity: an indirect effect that is greater than direct effect indicates existence of unconscious cognition. In order to study the effects of subliminal stimuli, researchers will often prime the participants with specific visual stimuli, often images, and determine if those stimuli elicit different responses. Subliminal stimuli have mostly been studied in the context of emotion, in particular, researchers have focused a lot of attention to the perception of faces and how subliminal presentation to different facial expression affects emotion. Visual subliminal stimuli has also been used to study emotion eliciting stimuli and simple geometric stimuli. A significant amount of research has been produced throughout the years to demonstrate the effects of subliminal visual stimuli. Attitudes can develop without being aware of its antecedents. Individuals viewed slides of people performing familiar daily activities after being exposed to either an emotionally positive scene, such as a romantic couple or kittens, or an emotionally negative scene, such as a werewolf or a dead body between each slide and the next. After exposure from something which the individuals consciously perceived as a flash of light, the participants gave more positive personality traits to those people whose slides were associated with an emotionally positive scene and vice versa. Despite the statistical difference, the subliminal messages had less of an impact on judgment than the slide's inherent level of physical attractiveness.