Negative priming is an implicit memory effect in which prior exposure to a stimulus unfavorably influences the response to the same stimulus. It falls under the category of priming, which refers to the change in the response towards a stimulus due to a subconscious memory effect. Negative priming describes the slow and error-prone reaction to a stimulus that is previously ignored. [1] For example, a subject may be imagined trying to pick a red pen from a pen holder. The red pen becomes the target of attention, so the subject responds by moving their hand towards it. At this time, they mentally block out all other pens as distractors to aid in closing in on just the red pen. After repeatedly picking the red pen over the others, switching to the blue pen results in a momentary delay picking the pen out (however, there is a decline in the negative priming effect when there is more than one nontarget item that is selected against [2] ). The slow reaction due to the change of the distractor stimulus to target stimulus is called the negative priming effect.
Negative priming is believed to play a crucial role in attention and memory retrieval processes. When stimuli are perceived through the senses, all the stimuli are encoded within the brain, where each stimulus has its own internal representation. In this perceiving process, some of the stimuli receive more attention than others. Similarly, only some of them are stored in short-term memory. Negative priming is highly related to the selective nature of attention and memory.
Broadly, negative priming is also known as the mechanism by which inhibitory control is applied to cognition. This refers only to the inhibition stimuli that can interfere with the current short-term goal of creating a response. [3] The effectiveness of inhibiting the interferences depends on the cognitive control mechanism as a higher number of distractors yields higher load on working memory. Increased load on working memory can in turn result in slower perceptual processing leading to delayed reaction. Therefore, negative priming effect depends on the amount of distractors, effectiveness of the cognitive control mechanism and the availability of the cognitive control resources. [4]
There are a number of theories and models that try to explain the reason behind negative priming. They all try to reason negative priming's role in cognition and justify why it occurs. A few of the well-known models are presented below.
Distractor inhibition model is the oldest model that explains the negative priming effect as the result of selective attention to a target stimulus. When we pay attention to a particular stimulus, we perceive other stimuli surrounding the target as distractors in order to help focus. But when one of those distractors becomes the new target of attention, our response to the target is hampered due to immediate residual inhibition. [5] [6] Selective attention is the ability to respond to a specific object when there are other distractors that also compete for a response. To explain this selective attention, the distractor inhibition model proposes a dual mechanism involving excitation to boost target signal and inhibition to suppress distractors. This inhibition is triggered when there is a mismatch between the internal representations of the target and a distractor. Inhibition of the distractor's internal representation is a way of helping to selectively attend to the target stimulus. This inhibition decays gradually when the stimulus is no longer present to help with the next target. However, if a distractor stimulus is re-encountered as the target, the internal representation of the distractor stimulus may continue to be suppressed because it is too soon for the decay to dissipate already. This is referred to as the transient residual inhibition. This inhibition also impairs the processing of an appropriate response to the new target stimulus and results in greater reaction time. [5] [7]
There are a few problems associated with this inhibition model. This model accounts for negative priming only when the stimuli are repetitively ignored as distractors during a goal directed behavior of selecting the target stimulus. This model does not support negative priming effects found in cases short of goal directed behavior. Another issue is that negative priming effects have been found to be long-term contradicting to the proposed transient residual inhibition. [8] Long-term persistence of negative priming questions the validity of the distractor inhibition model.
The episodic retrieval model is the current popular model and explains that negative priming occurs due to memory retrieval. This model theorizes that each encounter with a stimulus is encoded and stored separately as an individual episode. Each episode includes perceptual details of both the stimuli and the response developed for that stimulus. When a stimulus is encountered the second time, the previous episode regarding that stimulus along with its tags of perceptual details, role in selective attention, and response given are all retrieved automatically. When the repetitively ignored distractor stimulus is encountered as the target, a tag associated with the response to the stimulus is also retrieved. This response tag of a distractor will likely be "do-not-respond" tag as opposed to the "respond" tag of the target stimulus. Retrieval of the previous "do-not respond" tag of the stimulus conflicts with the current "respond" tag. This presents a problem of whether to respond or not. Resolving this conflict takes time and produces negative priming effect. [1] [9]
Episode retrieval model has gained more popularity over the last decade compared to the distractor inhibition model due to the issues with long-term negative priming. Episode retrieval varies from the distractor inhibition model because it claims that the negative priming occurs only when the memory of the stimuli is retrieved and not during the encoding of the distractor stimuli. Recent findings lean towards this model but the model itself is not entirely complete. Its idea of association tags like the "do-not-respond" tag is vague and needs concrete evidence to support this model.
Due to the issues found with the distractor inhibition model, Tipper and Houghton modified the distractor inhibition model to account for long-term negative priming effects. The original inhibition account proposed that inhibition occurs only when the distractors are suppressed. The Houghton–Tipper model revised this proposition and claims that inhibition occurs during both the encoding of distractors and the retrieval of that memory. The main reason for this change is to explain the long-term negative priming and justify it using the new combined model. When a repeated distractor becomes the target, processing of this stimulus automatically retrieves the memory of the stimulus being inhibited as a distractor. This model suggests that inhibition occurs when ignoring the distractor and during the memory retrieval of the previous ignorance of the stimulus. [5] Therefore, it incorporates the inhibition account in selective attention and the episode retrieval model.
This theory proposes that negative priming effect is the result of interference due to the target being located where the distractor was once located. [1] When the target stimulus and distractor stimulus are repeatedly placed in the same location, we know their respective location and pay attention more to the location of the target than the target itself. Our response to the target is also faster because we have already identified where to pay attention. This is called Simon effect, which refers our innate tendency to respond faster and more accurately when stimuli occur in the same location. This can be explained by neuroscience in terms of neural facilitation and short-term plasticity. However, if the positions of the stimuli are not the same as before, it is no longer easy to attend to the target as it once was. The feature mismatch hypothesis states that inhibition occurs when there is a mismatch between the target and its location. This theory is explains the effects of location specific negative priming but lacks in its justification of negative priming when location is not involved. [10] It deviates from the distractor inhibition model to describe location specific negative priming but has more loop holes than the other models.
Temporal discrimination model attempts to blend in both the selective attention and memory retrieval aspects of negative priming in a less complex model. It is based on the assumption that negative priming is caused only at the moment of response to a stimulus that was previously considered distractor. [11] This model explains negative priming as the delayed response due to confusion in classifying a stimulus as old or new. A new stimulus is immediately classified as new and undergoes perceptual processing. A repeated old stimulus is familiar and cues the automatic retrieval of the prior episode. A stimulus that has been repetitively ignored prior to becoming the target is neither entirely new nor old. This ambiguity slows down the processing of the stimuli. The temporal discrimination model points to this ambiguity as the cause of slowed categorization of the stimulus leading to negative priming effect. Like feature mismatch hypothesis, this model also claims that negative priming is not due to selective attention of the target or the inhibition of the distractor. This model argues that "negative priming is an emergent consequence of a discrimination process that is inherent to memory retrieval". Temporal discrimination model explains negative priming without reference to inhibition of distractors or the "do not respond" tag and by simple discrimination of "old", "new" and "in between" categories. [11]
Experiments on negative priming consist of two main components: prime and probe. Prime trial tries to mimic real life experiences of distractor stimuli in target selection but with more repetition to get quantifiable negative priming data. It comprises the initial presentation and the repetitive trials of the target and the distractor stimuli. It is set up such that a set of distractor stimuli are constantly ignored in the process of target selection. In the previous example provided, prime refers to the repeated perception of the blue pen as the distractor. Probe trial in an experiment refers to the actual testing for negative priming effects. In this trial, the repeated distractor of the prime trial is presented as the target. The reaction time of the response for the probe target (prime distractor) is measured to quantify the negative priming effect.
Some experiments may use additional interferences such as changing the position of the stimuli or presenting completely irrelevant stimuli during either of these trials. [3] The magnitude of negative priming effects are found to be higher with these interferences. Interferences are used to investigate how the response to the distractor changes under conditions of a third interfering stimulus.
The primary two stimulus modalities used for negative priming research are visual and auditory stimulus materials. The stimulus presented varied from objects or symbols in visual field to human voices or artificial sounds. Stronger negative priming effects are found for auditory stimulus but the standardized effect sizes between the modalities did not vary. [1] Evidence for negative priming has also been found across various modes of response including vocal naming, manual key press, and reaching. [3] Negative priming was observed for various types of judgment such as identification, categorization, matching, counting and localization. The tasks used to find evidence for negative priming includes Stroop color–word task, lexical decision task, identification, matching, and localization tasks. The Stroop color–word task utilizes the Stroop effect to observe the distractor suppression and negative priming. Identification tasks present a set of images, sounds, words, symbols, or letters and require the subject to select the prime target based a particular feature that differentiates the target from the distractor. Lexical decision utilizes semantic knowledge of the subject and tests the subject ability to remember the multiple meanings and uses of one word. For example, the word "bank" has multiple meanings and can be referred in different contexts such as "bank is a place where money is deposited" or "banks of a river". [3] Matching tasks require subjects to respond "same" or "different" by matching the target letters or shapes with the explicitly specified goal while ignoring the distractor. Localization tasks require some form of movement of subjects to respond to the location of the target stimulus. [12] This type of localization task is especially used to test the feature mismatch hypothesis as it provides evidence for negative priming during the mismatch of the location and target stimuli.
Response–stimulus interval (RSI) is another form of data that is used to quantify negative priming. RSI is the time difference between the response to prime target and the onset of probe trial. Negative priming effects are observed for delays of 20 millisecond to 8000 millisecond between the prime trial and the probe trial. Several experiments found that negative priming decays rapidly during this delay between prime and probe trials. [3] Many studies have tried to find a rate of this decay but have not been successful. [9] [13] Researchers of both the distractor inhibition model and episode retrieval model use varying results of the RSI effects to justify the decay as a part of their model. More globally accepted research is needed to determine concrete RSI data and establish short-term and long-term negative priming limits.
Neurological evidence of negative priming effects is being researched to help understand the physiological aspects and to develop more accurate models. The most common method to find such neurological evidence is by neuroimaging the brain using fMRI while subjects go through experiments of tasks that prompt negative priming effects. The two primary bases for neurological evidence are the internal representations of stimuli and memory retrieval. Most significantly activated regions of the brain are the left temporal lobe, inferior parietal lobe, and the prefrontal cortex of the frontal lobe. [14] Evidence for internal representations are found in the left anterior temporal cortex, which has been associated with abstract semantic knowledge representations. [15] The left anterolateral temporal cortex was found to be directly related to the magnitude of negative priming effect. [16] The inferior parietal lobe is connected to the shifts in attention that occurs when attending to the distractors and the target. The inferior parietal cortex activated whenever attention shifted from the distractor to target stimulus or vice versa. [14] Another significant area of activation was found in the prefrontal cortex. The superior, inferior, and medial frontal gyri, and the medial prefrontal cortex exhibited activation during the negative priming tasks. [17] Activations in the frontal lobe has been associated with inhibitory network and selective attention. Similarly, evidences for semantic representations and temporal lobe activations are used to support the episode retrieval model. In an fMRI meta-analysis, in addition to the right middle frontal gyrus, left superior temporal gyrus and precuneus, the anterior cingulate cortex was revealed across fMRI studies. Whether the cingulate cortex is directly involved in negative priming processes or due to the contrast between congruent and mismatching stimuli is still up for debate. [18] Additional investigations of the neurophysiological data of negative priming are necessary to further clarify the relationship between selective attention and memory in negative priming.
Negative priming is identified as one of the cognitive process necessary for goal directed behaviors. It is associated with many cognitive processes such as inhibition, selective attention, encoding, memory retrieval, and short-term memory. Neuropsychiatric disorders may be due to problems with some of the above-mentioned areas of cognition. Currently, schizophrenia, obsessive compulsive disorder, and Tourette syndrome are being studied with reference to negative priming. [17] [19] Understanding the paradigm of negative priming can lead to the use of negative priming tasks as diagnosing tools to identify the disorders. Knowledge about the physiological basis of negative priming can also help in designing therapies or treatment for neuropsychiatric disorders.
Among the four theories, the feature mismatch hypothesis and the temporal discrimination model lack solid evidence and are inadequate. These two models differ slightly from the distractor inhibition model and episode retrieval model respectively and can be incorporated into the latter two. The distractor inhibition model was the dominant model until recent contradicting findings pointed to a retrieval mechanism in negative priming. [1] The episode retrieval model is gaining more support for the memory based negative priming but lacks in its explanation of the association tags. Perhaps, further research exploring both these models may help to better understand the role of negative priming in attention, memory and cognition.
In psychology, the Stroop effect is the delay in reaction time between congruent and incongruent stimuli.
Executive functions are a set of cognitive processes that are necessary for the cognitive control of behavior: selecting and successfully monitoring behaviors that facilitate the attainment of chosen goals. Executive functions include basic cognitive processes such as attentional control, cognitive inhibition, inhibitory control, working memory, and cognitive flexibility. Higher-order executive functions require the simultaneous use of multiple basic executive functions and include planning and fluid intelligence.
The mismatch negativity (MMN) or mismatch field (MMF) is a component of the event-related potential (ERP) to an odd stimulus in a sequence of stimuli. It arises from electrical activity in the brain and is studied within the field of cognitive neuroscience and psychology. It can occur in any sensory system, but has most frequently been studied for hearing and for vision, in which case it is abbreviated to vMMN. The (v)MMN occurs after an infrequent change in a repetitive sequence of stimuli For example, a rare deviant (d) stimulus can be interspersed among a series of frequent standard (s) stimuli. In hearing, a deviant sound can differ from the standards in one or more perceptual features such as pitch, duration, loudness, or location. The MMN can be elicited regardless of whether someone is paying attention to the sequence. During auditory sequences, a person can be reading or watching a silent subtitled movie, yet still show a clear MMN. In the case of visual stimuli, the MMN occurs after an infrequent change in a repetitive sequence of images.
Repetition priming refers to improvements in a behavioural response when stimuli are repeatedly presented. The improvements can be measured in terms of accuracy or reaction time, and can occur when the repeated stimuli are either identical or similar to previous stimuli. These improvements have been shown to be cumulative, so as the number of repetitions increases the responses get continually faster up to a maximum of around seven repetitions. These improvements are also found when the repeated items are changed slightly in terms of orientation, size and position. The size of the effect is also modulated by the length of time the item is presented for and the length time between the first and subsequent presentations of the repeated items.
Echoic memory is the sensory memory that registers specific to auditory information (sounds). Once an auditory stimulus is heard, it is stored in memory so that it can be processed and understood. Unlike visual memory, in which our eyes can scan the stimuli over and over, the auditory stimuli cannot be scanned over and over. Since echoic memories are heard once, they are stored for slightly longer periods of time than iconic memories. Auditory stimuli are received by the ear one at a time before they can be processed and understood. For instance, hearing the radio is very different from reading a magazine. A person can only hear the radio once at a given time, while the magazine can be read over and over again. It can be said that the echoic memory is like a "holding tank" concept, because a sound is unprocessed until the following sound is heard, and only then can it be made meaningful. This particular sensory store is capable of storing large amounts of auditory information that is only retained for a short period of time. This echoic sound resonates in the mind and is replayed for this brief amount of time shortly after being heard. Echoic memory encodes only moderately primitive aspects of the stimuli, for example pitch, which specifies localization to the non-association brain regions.
In cognitive psychology, the Eriksen flanker task is a set of response inhibition tests used to assess the ability to suppress responses that are inappropriate in a particular context. The target is flanked by non-target stimuli which correspond either to the same directional response as the target, to the opposite response, or to neither. The task is named for American psychologists Barbara. A. Eriksen & Charles W. Eriksen, who first published the task in 1974, and for the flanker stimuli that surround the target. In the tests, a directional response is assigned to a central target stimulus. Various forms of the task are used to measure information processing and selective attention.
Indirect memory tests assess the retention of information without direct reference to the source of information. Participants are given tasks designed to elicit knowledge that was acquired incidentally or unconsciously and is evident when performance shows greater inclination towards items initially presented than new items. Performance on indirect tests may reflect contributions of implicit memory, the effects of priming, a preference to respond to previously experienced stimuli over novel stimuli. Types of indirect memory tests include the implicit association test, the lexical decision task, the word stem completion task, artificial grammar learning, word fragment completion, and the serial reaction time task.
Priming is a phenomenon whereby exposure to one stimulus influences a response to a subsequent stimulus, without conscious guidance or intention. For example, the word NURSE is recognized more quickly following the word DOCTOR than following the word BREAD. Priming can be perceptual, associative, repetitive, positive, negative, affective, semantic, or conceptual. Research, however, has yet to firmly establish the duration of priming effects, yet their onset can be almost instantaneous.
There is evidence suggesting that different processes are involved in remembering something versus knowing whether it is familiar. It appears that "remembering" and "knowing" represent relatively different characteristics of memory as well as reflect different ways of using memory.
In neuroscience, the lateralized readiness potential (LRP) is an event-related brain potential, or increase in electrical activity at the surface of the brain, that is thought to reflect the preparation of motor activity on a certain side of the body; in other words, it is a spike in the electrical activity of the brain that happens when a person gets ready to move one arm, leg, or foot. It is a special form of bereitschaftspotential. LRPs are recorded using electroencephalography (EEG) and have numerous applications in cognitive neuroscience.
Task switching, or set-shifting, is an executive function that involves the ability to unconsciously shift attention between one task and another. In contrast, cognitive shifting is a very similar executive function, but it involves conscious change in attention. Together, these two functions are subcategories of the broader cognitive flexibility concept.
Inhibitory control, also known as response inhibition, is a cognitive process and more specifically, an executive function – that permits an individual to inhibit their impulses and natural, habitual, or dominant behavioral responses to stimuli in order to select a more appropriate behavior that is consistent with completing their goals. Self-control is an important aspect of inhibitory control. For example, successfully suppressing the natural behavioral response to eat cake when one is craving it while dieting requires the use of inhibitory control.
In neuroscience, the visual P200 or P2 is a waveform component or feature of the event-related potential (ERP) measured at the human scalp. Like other potential changes measurable from the scalp, this effect is believed to reflect the post-synaptic activity of a specific neural process. The P2 component, also known as the P200, is so named because it is a positive going electrical potential that peaks at about 200 milliseconds after the onset of some external stimulus. This component is often distributed around the centro-frontal and the parieto-occipital areas of the scalp. It is generally found to be maximal around the vertex of the scalp, however there have been some topographical differences noted in ERP studies of the P2 in different experimental conditions.
The visual N1 is a visual evoked potential, a type of event-related electrical potential (ERP), that is produced in the brain and recorded on the scalp. The N1 is so named to reflect the polarity and typical timing of the component. The "N" indicates that the polarity of the component is negative with respect to an average mastoid reference. The "1" originally indicated that it was the first negative-going component, but it now better indexes the typical peak of this component, which is around 150 to 200 milliseconds post-stimulus. The N1 deflection may be detected at most recording sites, including the occipital, parietal, central, and frontal electrode sites. Although, the visual N1 is widely distributed over the entire scalp, it peaks earlier over frontal than posterior regions of the scalp, suggestive of distinct neural and/or cognitive correlates. The N1 is elicited by visual stimuli, and is part of the visual evoked potential – a series of voltage deflections observed in response to visual onsets, offsets, and changes. Both the right and left hemispheres generate an N1, but the laterality of the N1 depends on whether a stimulus is presented centrally, laterally, or bilaterally. When a stimulus is presented centrally, the N1 is bilateral. When presented laterally, the N1 is larger, earlier, and contralateral to the visual field of the stimulus. When two visual stimuli are presented, one in each visual field, the N1 is bilateral. In the latter case, the N1's asymmetrical skewedness is modulated by attention. Additionally, its amplitude is influenced by selective attention, and thus it has been used to study a variety of attentional processes.
N2pc refers to an ERP component linked to selective attention. The N2pc appears over visual cortex contralateral to the location in space to which subjects are attending; if subjects pay attention to the left side of the visual field, the N2pc appears in the right hemisphere of the brain, and vice versa. This characteristic makes it a useful tool for directly measuring the general direction of a person's attention with fine-grained temporal resolution.
In the psychology of perception and motor control, the term response priming denotes a special form of priming. Generally, priming effects take place whenever a response to a target stimulus is influenced by a prime stimulus presented at an earlier time. The distinctive feature of response priming is that prime and target are presented in quick succession and are coupled to identical or alternative motor responses. When a speeded motor response is performed to classify the target stimulus, a prime immediately preceding the target can thus induce response conflicts when assigned to a different response as the target. These response conflicts have observable effects on motor behavior, leading to priming effects, e.g., in response times and error rates. A special property of response priming is its independence from visual awareness of the prime.
Pre-attentive processing is the subconscious accumulation of information from the environment. All available information is pre-attentively processed. Then, the brain filters and processes what is important. Information that has the highest salience or relevance to what a person is thinking about is selected for further and more complete analysis by conscious (attentive) processing. Understanding how pre-attentive processing works is useful in advertising, in education, and for prediction of cognitive ability.
Cognitive inhibition refers to the mind's ability to tune out stimuli that are irrelevant to the task/process at hand or to the mind's current state. Cognitive inhibition can be done either in whole or in part, intentionally or otherwise. Cognitive inhibition in particular can be observed in many instances throughout specific areas of cognitive science.
The neurocircuitry that underlies executive function processes and emotional and motivational processes are known to be distinct in the brain. However, there are brain regions that show overlap in function between the two cognitive systems. Brain regions that exist in both systems are interesting mainly for studies on how one system affects the other. Examples of such cross-modal functions are emotional regulation strategies such as emotional suppression and emotional reappraisal, the effect of mood on cognitive tasks, and the effect of emotional stimulation of cognitive tasks.
In cognitive psychology, intertrial priming is an accumulation of the priming effect over multiple trials, where "priming" is the effect of the exposure to one stimulus on subsequently presented stimuli. Intertrial priming occurs when a target feature is repeated from one trial to the next, and typically results in speeded response times to the target. A target is the stimulus participants are required to search for. For example, intertrial priming occurs when the task is to respond to either a red or a green target, and the response time to a red target is faster if the preceding trial also has a red target.