Feature integration theory
Encyclopedia
The feature integration theory, developed by Anne Treisman
and Garry Gelade since the early 1980s, posits that different kinds of attention are responsible for binding different features into consciously experienced wholes. The theory has been one of the most influential psychological model
s of human visual attention
.
__toc__
The second stage involved in perceiving an object is the focused attention stage. This stage involves integrating individual features in order to perceive the whole object, or recognize it if enough information is presented. If the object is familiar, associations are made between the object and prior knowledge in order to aid in recognition. Bálint's syndrome
sufferers, who as a consequence of parietal lobe
damage seem incapable of properly focusing attention, lend credence to this two-staged model of attention.
It was widely speculated that the saliency map could be located in early visual cortical areas, e.g. the Primary Visual Cortex (V1), though this is controversial. Wolfe's popular Guided Search Model offers a more up to date theory of visual search but is also problematic.
Treisman distinguishes between two kinds of visual search tasks, "feature search" and "conjunction search". Feature searches can be performed fast and pre-attentively for targets defined by only one primitive feature, such as color, shape, movement or orientation. Conjunction searches proceed serially for targets defined by a conjunction (two or more) of primitive features - it is much slower and requires conscious attention. She concluded from many experiments that color
, orientation
, and intensity
are primitive features, for which feature searches may be performed.
Research participant R.M., a Bálint's syndrome
sufferer who is unable to focus attention on individual objects, experiences illusory conjunctions when presented with simple stimuli such as a "blue O" or a "red T." For 23% of trials, even when able to view the stimulus for as long as 10 seconds, R.M. reported seeing a "red O" or a "blue T" . This finding is in accordance with feature integration theory's prediction of how one with a lack of focused attention would erroneously combine features.
However, if people use their knowledge or experience to perceive an object, it is less likely to make mistakes. Treisman did another experiment to explain this phenomenon – she presented three shapes to participants and illusory conjunctions persisted. Surprisingly, when she told participants that they were being shown a carrot, lake and tire (in place of the orange triangle, blue oval, and black circle, respectively), illusory conjunctions disappeared . Treisman maintained that prior-knowledge played an important role in proper perception. Normally, bottom-up processing is used for identifying novel objects; but, once we recall prior knowledge, top-down processing is used. This explains why people are good at identifying familiar objects rather than unfamiliar.
, which in this case, refers to a difficulty in separating a letter from the background .
Anne Treisman
Anne Marie Treisman FRS is a psychologist currently at Princeton University's Department of Psychology. She researches visual attention, object perception, and memory. One of her most influential ideas is the feature integration theory of attention, first published with G. Gelade in 1980...
and Garry Gelade since the early 1980s, posits that different kinds of attention are responsible for binding different features into consciously experienced wholes. The theory has been one of the most influential psychological model
Cognitive model
A cognitive model is an approximation to animal cognitive processes for the purposes of comprehension and prediction. Cognitive models can be developed within or without a cognitive architecture, though the two are not always easily distinguishable.In contrast to cognitive architectures, cognitive...
s of human visual attention
Attention
Attention is the cognitive process of paying attention to one aspect of the environment while ignoring others. Attention is one of the most intensely studied topics within psychology and cognitive neuroscience....
.
__toc__
Stages
According to Treisman, in the first stage of visual processing termed the preattentive stage, several primary visual features are processed and represented with separate "feature maps" that are later integrated into "saliency maps" that can be accessed in order to direct attention to the most conspicuous areas. During this stage, the object is analyzed with details such as shape, color, orientation and movement in mind. Each of these aspects is processed in different areas of the brain. The main idea that a processed object's features are automatically separated may seem counter-intuitive because we perceive the whole object instead of seeing each separate aspect; however, this analysis happens in the perceptual process before we are even conscious of the object.The second stage involved in perceiving an object is the focused attention stage. This stage involves integrating individual features in order to perceive the whole object, or recognize it if enough information is presented. If the object is familiar, associations are made between the object and prior knowledge in order to aid in recognition. Bálint's syndrome
Balint's syndrome
Bálint's syndrome is an uncommon and incompletely understood triad of severe neuropsychological impairments: inability to perceive the visual field as a whole , difficulty in fixating the eyes , and inability to move the hand to a specific object by using vision...
sufferers, who as a consequence of parietal lobe
Parietal lobe
The parietal lobe is a part of the Brain positioned above the occipital lobe and behind the frontal lobe.The parietal lobe integrates sensory information from different modalities, particularly determining spatial sense and navigation. For example, it comprises somatosensory cortex and the...
damage seem incapable of properly focusing attention, lend credence to this two-staged model of attention.
It was widely speculated that the saliency map could be located in early visual cortical areas, e.g. the Primary Visual Cortex (V1), though this is controversial. Wolfe's popular Guided Search Model offers a more up to date theory of visual search but is also problematic.
Treisman distinguishes between two kinds of visual search tasks, "feature search" and "conjunction search". Feature searches can be performed fast and pre-attentively for targets defined by only one primitive feature, such as color, shape, movement or orientation. Conjunction searches proceed serially for targets defined by a conjunction (two or more) of primitive features - it is much slower and requires conscious attention. She concluded from many experiments that color
Color
Color or colour is the visual perceptual property corresponding in humans to the categories called red, green, blue and others. Color derives from the spectrum of light interacting in the eye with the spectral sensitivities of the light receptors...
, orientation
Orientation (geometry)
In geometry the orientation, angular position, or attitude of an object such as a line, plane or rigid body is part of the description of how it is placed in the space it is in....
, and intensity
Intensity (disambiguation)
-In colloquial use:*Strength *Amplitude*Level *Magnitude -Physics:*Intensity , power per unit area *Field strength of electric, magnetic, or electromagnetic fields...
are primitive features, for which feature searches may be performed.
Experiments
In order to test the statement that features are independent in the early preattentive stage, Treisman and Schmidt (1982) designed an experiment in which participants are shown a picture involving four shapes and two black numbers for one-fifth of a second. After the display, a random-dot masking field appeared on screen to eliminate “any residual perception that might remain after the stimuli were turned off” . The task of participants was to report the black numbers first, followed by what colored shapes they saw at four locations.The results of this experiment verified Treisman and Schmidt's hypothesis. In 18% of trials, participants reported seeing shapes “made up of a combination of features from two different stimuli” , even when the stimuli had great differences. This is an illusory conjunction, an often occurring illusion people experience during visual search. While people can typically remember the presence of an object, they often forget its location or color. They occur in various situations; for example, you may identify a passing person wearing a red shirt and yellow hat and very quickly transform him or her into one wearing a yellow shirt and red hat. Feature integration theory can explain illusory conjunctions – in Treisman’s words, features are “free floating” so they may be incorrectly combined .Research participant R.M., a Bálint's syndrome
Balint's syndrome
Bálint's syndrome is an uncommon and incompletely understood triad of severe neuropsychological impairments: inability to perceive the visual field as a whole , difficulty in fixating the eyes , and inability to move the hand to a specific object by using vision...
sufferer who is unable to focus attention on individual objects, experiences illusory conjunctions when presented with simple stimuli such as a "blue O" or a "red T." For 23% of trials, even when able to view the stimulus for as long as 10 seconds, R.M. reported seeing a "red O" or a "blue T" . This finding is in accordance with feature integration theory's prediction of how one with a lack of focused attention would erroneously combine features.
However, if people use their knowledge or experience to perceive an object, it is less likely to make mistakes. Treisman did another experiment to explain this phenomenon – she presented three shapes to participants and illusory conjunctions persisted. Surprisingly, when she told participants that they were being shown a carrot, lake and tire (in place of the orange triangle, blue oval, and black circle, respectively), illusory conjunctions disappeared . Treisman maintained that prior-knowledge played an important role in proper perception. Normally, bottom-up processing is used for identifying novel objects; but, once we recall prior knowledge, top-down processing is used. This explains why people are good at identifying familiar objects rather than unfamiliar.
Reading
When identifying letters while reading, not only are there shapes picked up but also other features like their colors and surrounding elements. Individual letters are processed serially when spatially conjoined with another letter. The locations of each feature of a letter are not known in advance, even while the letter is in front of the reader. Since the location of the letter's features and/or the location of the letter is unknown, feature interchanges can occur if one is not attentively focused. This is known as lateral maskingLateral masking
Lateral masking is a problem for the human visual perception of identical or similar entities in close proximity. This can be illustrated by the difficulty of counting the vertical bars of a barcode....
, which in this case, refers to a difficulty in separating a letter from the background .