Subliminal Image

[Chanelle Kirksey]

In1957, the American cinematographer James Vicary claimed to have increased the sales of Coca-Cola by inserting in his cinema's movies some frames with "Drink Coca-Cola!" written on it. Five years later, however, he admitted to having inflated his results somewhat by including certain data that were labeled scientifically unreliable.[3] However, Vicary's claim increased scientific interest in subliminal messages.

Indeed, subliminal stimulation is now accepted as a legitimate research field in the scientific literature. A 2012 review of functional magnetic resonance imaging (fMRI) studies showed that subliminal stimuli activate specific regions of the brain despite participants' unawareness,[4] a result corroborated in a meta-analysis from 2023[5] concerning subliminal stimulation in post-traumatic stress disorder (PTSD). Visual stimuli may be quickly flashed before an individual can process them, or flashed and then masked to interrupt processing. Audio stimuli may be played below audible volumes or masked by other stimuli.

Applications of subliminal stimuli are often based on the persuasiveness of a message. Research on action priming has shown that subliminal stimuli can only trigger 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 is already prepared to perform a specific action.[6]

The context that the stimulus is presented in affects their effectiveness.[7] For example, if the target is thirsty then a subliminal stimulus for a drink is likely to influence the target to purchase that drink if it is readily available.[7] The stimuli can also influence the target to choose the primed option over other habitually chosen options.[7] If the subliminal stimuli are for a product that is not quickly accessible or if there is no need for it within a specific context then the stimuli will have little to no effect.[7] Subliminal priming can direct people's actions even when they believe they are making free choices.[6] When primed to push a button with their off-hand, people will use that hand even if they are given a free choice between using their off-hand and their dominant hand.[6] However, a meta analysis of many strong articles displaying effectiveness of subliminal messaging revealed its effects on actual consumer purchasing choices between two alternatives are not statistically significant;[8] subliminal messaging is only effective in behaviour in very specific present intentions and contexts, which means they do not have visible results for mischievous results. It is suggested, however, that subliminal stimuli can bias acting decisions, including internally and freely generated ones, but, since that effect remains along with the aforementioned intentions and contexts, any impact on the choice of action are not mischievous but rather appropriate and adaptive.[6][7][8]

In subliminal stimuli research, the threshold is the level at which the participant is not aware of the stimulus being presented.[9] Researchers determine a threshold for the stimulus that is used as the subliminal stimulus. That 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 subjective threshold is determined when the participant reports that their performance on the forced-choice procedure approximates chance. The subjective threshold is 30 to 50 ms slower than the objective threshold, demonstrating that participants' ability to detect the stimuli is earlier than their perceived accuracy ratings would indicate; that is, stimuli presented at a subjective threshold have a longer presentation time than those presented at an objective threshold. When using the objective threshold, priming stimuli neither facilitated nor inhibited the recognition of a color. However, the longer the duration of the priming stimulus, 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.[9]

Some stimuli supposed to elicit a specific emotional reaction (e.g., spider pictures shown to a spider-fearful person) could fail to elicit it even if consciously perceived.[10] This sounds apparently obvious: even if one is arachnophobic, the spider picture could be too brief to elicit a fear reaction. However, this is not obvious at all from the perspective of a phobic person, who is typically afraid even by the mere thought of the phobic stimulus. This lack of emotional response induced by very brief phobic pictures that were nonetheless emerged to awareness has brought to the definition of emotionally-subliminal stimuli as stimuli that do not induce the expected emotional reaction even if consciously perceived.[10]

Similarly, a direct effect is the effect of a task stimulus on the instructed response to it, and is 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.[12] These effects are then compared on their relative sensitivity: an indirect effect that is greater than a direct effect indicates that unconscious cognition exists.[11][12]

However, a debate was raised in the scientific literature because of the heterogeneity of paradigms to make stimuli subliminal and to assess their effectiveness: the best solution has been proposed to be a trial-by-trial assessment of each stimulus' conscious detection.[13][14] Despite its rigorousness, this assessment can be problematic in studies comparing the brain responses to detected versus undetected stimuli, as the resulting differences could be attributed to the act of answering (e.g., pressing a button) rather than to the (un)conscious processing: in these cases, a no-report paradigm could be preferable.[15]

In order to study the effects of subliminal stimuli, researchers often prime participants with specific visual stimuli, and determine if those stimuli elicit different responses.[16][17] Subliminal stimuli have mostly been studied in the context of emotion; in particular, researchers have focused a lot of attention to the face perception and how subliminal presentation to different facial expression affects emotion.[18][19][20][21] Visual subliminal stimuli have also been used to study emotion eliciting stimuli and simple geometric stimuli.[22][23][24][25] A significant amount of research has been produced throughout the years to demonstrate the effects of subliminal visual stimuli.[26]

Attitudes can develop without being aware of their antecedents[definition needed].[16] 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 exhibited 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.[16][27]

Individuals show right amygdala activity in response to subliminal fear, and a greater left amygdala response to supraliminal fear.[17] In a 2005 study, participants were exposed to a subliminal image flashed for 16.7 milliseconds that could signal a potential threat and again with a supraliminal image flashed for half a second. Furthermore, supraliminal fear showed more sustained cortical activity, suggesting that subliminal fear may not entail conscious surveillance while supraliminal fear entails higher-order processing.[17]

A seminal article published in 1994 found that subliminal phobic pictures elicited specific electrodermal reactions even if not consciously perceived.[28] This study paved the way to a prolific research field investigating the psychophysiological and behavioral correlates of emotionally-relevant stimuli made subliminal.[13][29][5]

A subliminal sexual stimulus has a different effect on men compared to women. In a study by Omri Gilliath et al., men and women were subliminally exposed to either a sexual or a neutral picture, and their sexual arousal was recorded. Researchers examined the accessibility of sex-related thoughts after following the same procedure with either a pictorial judgment task or lexical decision task. The results revealed that the subliminal sexual stimuli did not have an effect on men, but for women, lower levels of sexual arousal were reported. However, in conditions related to accessibility of sex-related thoughts, the subliminal sexual stimuli led to higher accessibility for both men and women.[22]

Laboratory research on unconscious perception often employs simple stimuli (e.g., geometric shapes or colors) in which visibility is controlled by visual masking.[24] Masked stimuli are then used to prime the processing of subsequently presented target stimuli. For instance, in the response priming paradigm, participants have to respond to a target stimulus (e.g. by identifying whether it is a diamond or a square) which is immediately preceded by a masked priming stimulus (also a diamond or a square). The prime has large effects on responses to the target: it speeds responses when it is consistent with the target, and slows responses when it is inconsistent. Response priming effects can be dissociated from visual awareness of the prime, such as when prime identification performance is at chance, or when priming effects increase despite decreases in prime visibility.[24]

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