Images and other stimuli contain both local features (details, parts) and global features (the whole). Precedence refers to the level of processing (global or local) to which attention is first directed. [1] Global precedence occurs when an individual more readily identifies the global feature when presented with a stimulus containing both global and local features. [2] The global aspect of an object embodies the larger, overall image as a whole, whereas the local aspect consists of the individual features that make up this larger whole. Global processing is the act of processing a visual stimulus holistically. Although global precedence is generally more prevalent than local precedence, local precedence also occurs under certain circumstances and for certain individuals. [3] Global precedence is closely related to the Gestalt principles of grouping in that the global whole is a grouping of proximal and similar objects. Within global precedence, there is also the global interference effect, which occurs when an individual is directed to identify the local characteristic, and the global characteristic subsequently interferes by slowing the reaction time.
Global precedence was first studied using the Navon figure, where many small letters are arranged to form a larger letter that either does or does not match. [2] Variations of the original Navon figure include both shapes and objects. [4] Individuals presented with a Navon figure will be given one of two tasks. In one type of task, participants are told before the presentation of the stimulus whether to focus on a global or local level, and their accuracy and reaction times are recorded.
Consistent | Neutral | Conflicting |
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TTTTTTTTTTTT TTTTTTTTTTTT TTTT TTTT TTTT TTTT TTTT TTTT | ++++++++++++ ++++++++++++ ++++ ++++ ++++ ++++ ++++ ++++ | SSSSSSSSSSSS SSSSSSSSSSSS SSSS SSSS SSSS SSSS SSSS SSSS |
In another type of task, participants are first presented with a target stimulus, and later presented with two different visuals. One of the visuals matches the target stimulus on the global level, while the other visual matches the target stimulus on the local level. In this condition, experimenters note which of the two visuals, the global or local, is chosen to match the target stimulus. [2]
In general, reaction time for identifying the larger letter is faster than for the smaller letters that make up the shape. [2] Navon directed participants to focus either globally or locally to stimuli that were consistent, neutral, or conflicting on the global and local levels (see figures above). [2] Reaction time for global identification was much faster than for local identification, showing global precedence. [2] Additionally, global interference effect, which occurs when the global aspect is automatically processed even when attention is directed locally, causes slow reaction time. [2] Navon's study global precedence and his stimuli, or variations of it, are still used in nearly all global precedence experiments.
When presented with a Navon figure, there is a slight local preference for Caucasians, but East Asians show an obvious global preference and are faster and more accurate at global processing. [5] The inclination towards global precedence is also evident in second generation Asian-Australians, but the correlation is weaker than that of recent immigrants. This could stem from the physical environment of East Asian versus Western cities, as the level of visual complexity varies across these environments. [5] The tendency of Caucasians to process information "analytically" and Asians "holistically" has also been attributed to differences in brain structure. [6]
For some cognitive scientists, the stark contrast in cognitive processing trends across cultures and races suggests that all studies on cognitive perception should report participants’ races to ensure valid theoretical conclusions. Especially in experiments involving spatially distributed stimuli, neglected racial or cultural differences in visual perception could skew results. [5]
Global precedence is not a universal phenomenon. [3]
When Navon figure stimuli are presented to participants from a remote African culture, the Himba, local precedence is observed although the Himba show the capabilities for both global and local processing. [3]
This difference in precedence for Navon figure stimuli can be attributed to cultural differences in occupations, or in the practice of reading and writing. This finding dispels the idea that local precedence is a consequence or symptom of disorders, since the Himba is a normally functioning society capable of both global and local processing. [3]
Stimuli are either meaningful or meaningless. For example, letters and familiar objects, like a cup, are meaningful, while unidentifiable and non-geometric forms are not. In both types of stimuli, the global advantage is observed, but the global interference effect only occurs with meaningful stimuli. [4] In other words, when the global object is meaningful, the reaction time for identification of the local feature increases. [4]
This supports the theory that within global precedence, global advantage and global interference rely on two separate mechanisms. Global-local interference occurs as a result of automatic processing of global objects. The theory is that the global precedence effect has a sensory mechanism active in global advantage, whereas automatic and semantic processes are active in the interference effect. [4]
Cognitive processing varies across different age groups, and several studies have been done using Navon-like figures to examine the correlation between precedence and age.
When presented with a global-local task, children and adolescents exemplify a local bias. [7] Younger children respond slower to different types of stimuli compared to older children, and thus local precedence seems more prevalent than global precedence in perceptual organization, at least until adolescence, when the transition to globally oriented visual perception begins. [7] The ability to encode a global shape, which is necessary for efficiently recognizing and identifying objects, increases with age. However, it has also been found that there is a bias towards global information during infancy, which may be based upon high spatial frequency information, as well as limited vision. Therefore, global precedence during the early years of life may not be upwards but rather a U-shaped development. [7]
There is a decline of global precedence in older subjects. [8] When presented with a Navon-like figure, young adults demonstrate global precedence enhancement in that when the number of local letters forming the global letter increases, their global precedence increases. On the other hand, there is no precedence effect or enhancement for older subjects when presented with the same task. [8] This links global precedence to the Gestalt principles of Proximity and Continuity, and suggests that Gestalt-related deficiencies, such as decline in perceptual grouping, may underlie the decline of global precedence in older subjects. [8]
Global precedence decline may also relate to hemispheric specialization. The spatial frequency theory proposes that global versus local information is processed through two “channels” of low (global) versus high (local) spatial frequencies. [9] spatial frequency measures how often a stimulus moves through space. Based upon this theory, the double frequency theory links the left hemisphere with high spatial frequencies, leading to a global precedence effect, and the right hemisphere with low spatial frequencies, leading to a local precedence effect. This suggests neuropsychological factors behind global precedence decline in there may be faster aging in the right than the left hemisphere. [8]
Studies regarding mood have shown that positive and negative cues can influence global versus local attention during image-based tasks.
Some studies have shown that positive priming decreases local response time, demonstrating a lessening effect of global precedence, while negative priming increases local response time. [10] Mood dictates one's preferences for processing type. [10]
The result that negative priming reduces flexibility correlates to the Psi theory states that negative emotion inhibits one’s access to extension memory, reducing cognitive flexibility. This also supports the theory that positive affect increases cognitive flexibility. [10]
Positive mood priming also increases cognitive flexibility when prime words do not have individualistic specificity and when primes are visual. [11] Positive affect does not simply promote local processing, but rather improves one’s abilities in his non-preferred dimension. [11] For example, one preferring the local aspect of stimuli would show increased performance in identifying the global aspect and vice versa. This further supports the cognitive flexibility theory.
However, many studies regarding global processing and affect conflict with each other. One particular study showed that individuals in happy moods are more likely than those in sad moods to identify images based on global attributes rather than local ones, contrary to other studies that have been conducted. [12] Paying attention to global features is the standard strategy for visual processing. Therefore, if positive feelings are more frequent than negative feelings, and thus positive feelings are more accessible, then positive feelings should instigate global processing more than negative feelings because the global strategy is similarly more accessible. [12] From a more worldly application, positive affect might aid in understanding the larger meaning of stimuli like literature or art, whereas negative affect might aid understanding more minute details within those stimuli, like particularly rhythmic words or the nuance of colors. [12]
Priming with Navon figures aides the recognition of faces, a holistic task, when the response elicited from the figure matches the precedence of the figure. [13] For example, if the stimulus has local precedence and the participant is cued to respond with the local feature identification, his accuracy in facial recognition improves. The same occurs when global responses are asked of global stimuli. [13]
When a facial task requires local processing for identification, participants’ facial recognition improves when they must respond to global precedence stimuli with local responses and vice versa. [13] They are forced to show cognitive flexibility in their responses to the Navon figure primes.
One theory explains that normal facial recognition requires automatic processes, whereas special facial recognition requires controlled processes. [13] Automatic processes are aided by correlative stimuli and responses, while controlled processes are aided by stimuli and responses that do not correlate. This indicates that facial recognition depends on type of attention, automatic or controlled, rather than focus on global or local features.
When identifying inverted faces, those showing stronger global precedence show a more prominent [14] Those showing a stronger global precedence also have a greater deficit in identification abilities when the faces are inverted; their identification abilities decrease more from upright identification to inverted identification than weak global precedence individuals. [14]
This correlates to the theory that upright faces are processed holistically, or with a special mechanism. [14] Those with stronger global precedence should perform better at holistically processing a face upright. Stronger global precedence should show a greater decrease in accuracy of identification of inverted faces because the task relies on local processing.
The degree of global precedence one demonstrates has been found to differ in relation to the variable of an individual's field dependence. [15] Field dependency is the amount that one relies on Gestalt laws of perceptual organization. High field dependency corresponds to a greater bias toward the global level, while field independence corresponds to a lesser dependency on the global level. [15]
This indicates that individual characteristics have an effect on the prevalence of global precedence and that global and local processing exist on a continuum. [15]
Neuropsychological evidence based on PET scans suggests that the global aspect of visual situations activates and is processed preferentially by the right hemisphere, whereas the local aspect of visual situations activates and is processed preferentially by the left hemisphere. [16] The classical view of Gestalt psychology also suggests the right hemisphere is involved in the perception of wholes and thus plays a stronger role in global processing, whereas the left hemisphere involves separate local elements and therefore plays a stronger role in local processing. [16]
However, hemispheric specialization is relative because it depends on the experimental setting as well as the individual’s “attentional set.” [16] In addition, stimulus type may influence the neural structures underlying hemispheric specialization. Global processing is the default strategy for most individuals, but local stimuli are often more perceptually demanding to recognize and identify, showing the effect of stimuli on visual processing. [16]
The Navon figure has been used in relating theories regarding processing to assessing cognitive learning disabilities, such as developmental dyslexia, dyscalculia, obsessive-compulsive personality disorder, and autism.
When given a Navon figure test, people with dyslexia have difficulty automatically identifying graphemes with phonemes, but not with identifying numbers with magnitudes. [17] On the other hand, people with dyscalculia have difficulty automatically identifying numbers with magnitudes, but not letters and with phonemes. This suggests a dissociation between subjects with dyslexia and dyscalculia. These developmental learning disabilities do not cause general problems with identifying symbols to their mental representations, but rather create specific challenges. [17]
Obsessive-compulsive personality disorder (OCPD) subjects are prone to be distracted by the local aspects of stimuli when asked to identify global aspects of figures such as the Navon figure. [18] This is likely because individuals with OCPD characteristically have sharp, detail-oriented attentions, and tend to focus more on specifics rather than the larger context. [18]
There are correlations between global or local performance on a task and the abilities to identify emotion and canine age for autistic children. [19] In both cases, global responses correlate to better identification. [19] In general, autistic children demonstrate much weaker global precedence than those without the disorder. [19] Within the group of autistic children, those who respond more globally to a discrimination task perform better on emotion and canine age tasks. [19]
One explanation is a possible biological dysfunction in the brain region where facial processing occurs. Research indicates that global processing, facial recognition, and emotional expression recognition are all linked to the right hemisphere. [19] A defect in that area would explain the characteristics of autism. For further information on facial recognition and processing in individuals with autism see the autism and facial recognition section of face perception.
Wishful thinking is the formation of beliefs based on what might be pleasing to imagine, rather than on evidence, rationality, or reality. It is a product of resolving conflicts between belief and desire. Methodologies to examine wishful thinking are diverse. Various disciplines and schools of thought examine related mechanisms such as neural circuitry, human cognition and emotion, types of bias, procrastination, motivation, optimism, attention and environment. This concept has been examined as a fallacy. It is related to the concept of wishful seeing.
The McGurk effect is a perceptual phenomenon that demonstrates an interaction between hearing and vision in speech perception. The illusion occurs when the auditory component of one sound is paired with the visual component of another sound, leading to the perception of a third sound. The visual information a person gets from seeing a person speak changes the way they hear the sound. If a person is getting poor-quality auditory information but good-quality visual information, they may be more likely to experience the McGurk effect. Integration abilities for audio and visual information may also influence whether a person will experience the effect. People who are better at sensory integration have been shown to be more susceptible to the effect. Many people are affected differently by the McGurk effect based on many factors, including brain damage and other disorders.
Facial perception is an individual's understanding and interpretation of the face. Here, perception implies the presence of consciousness and hence excludes automated facial recognition systems. Although facial recognition is found in other species, this article focuses on facial perception in humans.
Associative visual agnosia is a form of visual agnosia. It is an impairment in recognition or assigning meaning to a stimulus that is accurately perceived and not associated with a generalized deficit in intelligence, memory, language or attention. The disorder appears to be very uncommon in a "pure" or uncomplicated form and is usually accompanied by other complex neuropsychological problems due to the nature of the etiology. Affected individuals can accurately distinguish the object, as demonstrated by the ability to draw a picture of it or categorize accurately, yet they are unable to identify the object, its features or its functions.
The lexical decision task (LDT) is a procedure used in many psychology and psycholinguistics experiments. The basic procedure involves measuring how quickly people classify stimuli as words or nonwords.
Affect, in psychology, refers to the underlying experience of feeling, emotion, attachment, or mood.
Visual search is a type of perceptual task requiring attention that typically involves an active scan of the visual environment for a particular object or feature among other objects or features. Visual search can take place with or without eye movements. The ability to consciously locate an object or target amongst a complex array of stimuli has been extensively studied over the past 40 years. Practical examples of using visual search can be seen in everyday life, such as when one is picking out a product on a supermarket shelf, when animals are searching for food among piles of leaves, when trying to find a friend in a large crowd of people, or simply when playing visual search games such as Where's Wally?
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.
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.
Priming is the idea that exposure to one stimulus may influence a response to a subsequent stimulus, without conscious guidance or intention. The priming effect refers to the positive or negative effect of a rapidly presented stimulus on the processing of a second stimulus that appears shortly after. Generally speaking, the generation of priming effect depends on the existence of some positive or negative relationship between priming and target stimuli. For example, the word nurse might be recognized more quickly following the word doctor than following the word bread. Priming can be perceptual, associative, repetitive, positive, negative, affective, semantic, or conceptual. Priming effects involve word recognition, semantic processing, attention, unconscious processing, and many other issues, and are related to differences in various writing systems. Research, however, has yet to firmly establish the duration of priming effects, yet their onset can be almost instantaneous.
The superior temporal sulcus (STS) is the sulcus separating the superior temporal gyrus from the middle temporal gyrus in the temporal lobe of the brain. A sulcus is a deep groove that curves into the largest part of the brain, the cerebrum, and a gyrus is a ridge that curves outward of the cerebrum.
Visual object recognition refers to the ability to identify the objects in view based on visual input. One important signature of visual object recognition is "object invariance", or the ability to identify objects across changes in the detailed context in which objects are viewed, including changes in illumination, object pose, and background context.
A Navon figure is made of a larger recognisable shape, such as a letter, composed of copies of a smaller different shape. Navon figures are used in tests of visual neglect. David Navon's research demonstrated that global features are perceived more quickly than local features. Jules Davidoff also performed research, but in a remote culture, finding opposite results; the participants more readily identified the local features. Patients with simultanagnosia have difficulty identifying global features, and when presented with a Navon figure will identify only the local features. A 2010 study comparing global-local processing in different races, found that East Asians demonstrated significantly stronger global processing than Caucasians.
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.
Subliminal stimuli are any sensory stimuli below an individual's threshold for conscious perception, in contrast to supraliminal stimuli. A 2012 review of functional magnetic resonance imaging (fMRI) studies showed that subliminal stimuli activate specific regions of the brain despite participants' unawareness. 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.
Emotion perception refers to the capacities and abilities of recognizing and identifying emotions in others, in addition to biological and physiological processes involved. Emotions are typically viewed as having three components: subjective experience, physical changes, and cognitive appraisal; emotion perception is the ability to make accurate decisions about another's subjective experience by interpreting their physical changes through sensory systems responsible for converting these observed changes into mental representations. The ability to perceive emotion is believed to be both innate and subject to environmental influence and is also a critical component in social interactions. How emotion is experienced and interpreted depends on how it is perceived. Likewise, how emotion is perceived is dependent on past experiences and interpretations. Emotion can be accurately perceived in humans. Emotions can be perceived visually, audibly, through smell and also through bodily sensations and this process is believed to be different from the perception of non-emotional material.
Verbal overshadowing is a phenomenon where giving a verbal description of sensory input impairs formation of memories of that input. This was first reported by Schooler and Engstler-Schooler (1990) where it was shown that the effects can be observed across multiple domains of cognition which are known to rely on non-verbal knowledge and perceptual expertise. One example of this is memory, which has been known to be influenced by language. Seminal work by Carmichael and collaborators (1932) demonstrated that when verbal labels are connected to non-verbal forms during an individual's encoding process, it could potentially bias the way those forms are reproduced. Because of this, memory performance relying on reportable aspects of memory that encode visual forms should be vulnerable to the effects of verbalization.
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.
Amodal completion is the ability to see an entire object despite parts of it being covered by another object in front of it. It is one of the many functions of the visual system which aid in both seeing and understanding objects encountered on an everyday basis. This mechanism allows the world to be perceived as though it is made of coherent wholes. For example, when the sun sets over the horizon it is still perceived as a full circle, despite occlusion causing it to appear as a semi-circle. Another example of this is a cat behind a picket fence. Amodal completion allows the cats to be seen as a full animal continuing behind each picket of the fence. Essentially amodal completion allows for sensory stimulation from any parts of an occluded object we can not directly see.