Recent from talks
Knowledge base stats:
Talk channels stats:
Members stats:
Interindividual differences in perception
Interindividual differences in perception describes the effect that differences in brain structure or factors such as culture, upbringing and environment have on the perception of humans. Interindividual (differing from person to person) variability is usually regarded as a source of noise for research. However, in recent years, it has become an interesting source to study sensory mechanisms and understand human behavior. With the help of modern neuroimaging methods such as fMRI and EEG, individual differences in perception could be related to the underlying brain mechanisms. This has helped to explain differences in behavior and cognition across the population. The present study using MRS provides direct evidence showing that the excitatory process in the suprasensory areas is linked to the individual differences in visual motion perception. The neurotransmitter concentration in the higher areas that execute cognitive functions is related to the interindividual variability in the perception of visual motion. Common methods include studying the perception of illusions, as they can effectively demonstrate how different aspects such as culture, genetics and the environment can influence human behavior.
A motion quartet is a bistable stimulus - it consists of two dots that change their position from frame to frame. This position change can either be interpreted as horizontal or vertical movement by viewers, and this experience can switch during viewing between interpretations. Depending on the aspect ratio of the two dots' positions, one or the other state is perceived longer or more often. At an aspect ratio of one, the illusion is biased towards the vertical perception. The reason for this might be the way the human brain processes the signals from both eyes in the visual system. The right half of an eye's field of view is processed by the left hemisphere, and the left half by the right hemisphere. A stimulus moving vertically only involves one field of view and so one hemisphere, while a stimulus moving vertically from one field of view to the other involves both hemispheres, and requires communication between them. The delay caused by this additional signalling might be the cause for the bias. There are also individual differences in the way the motion quartet is perceived: Some people require a different aspect ratio to perceive both axes of movement than others. A study using diffusion tensor imaging further showed differences in the structure of the corpus callosum, the primary connection between the two hemispheres, might be the origin of these differences.
There exist a variety of illusions that make objects appear bigger or smaller compared to their real size. Two such illusions are the Ebbinghaus and the Ponzo illusions. The Ebbinghaus illusion makes a dot seem bigger because it is surrounded by smaller dots, while the Ponzo illusion exploits human perspective processing by making a dot appear bigger because it seems farther away. Schwarzkopf et al. found that the size of the primary visual cortex (V1) has an effect on the magnitude of these illusions. The larger the subject's V1 surface area was, the less the subjects fell for the illusion. This is hypothesized to be due to the fact that a larger V1 dedicated to the same portion of the visual field means a lesser effect of later, fixed-size visual areas (which are the ones that are responsible for the illusion effect).
The McGurk effect is an auditory illusion in which people perceive a different syllable when incongruent audiovisual speech is presented: an auditory syllable "ba" is presented while the mouth movement is "ga". As a result, the listener perceives the syllable "da". However, according to Gentilucci and Cattaneo (2005), not everyone perceives this illusion; only about 26% to 98% of the population are susceptible to this illusion. One of the psychological models that explains the interindividual differences in speech perception is the fuzzy logic model of speech perception According to this model, a categorization process is carried out when processing speech sounds. When listening to a stimulus, the features of the acoustic signal are analyzed. Subsequently, this signal is compared with the features that are stored in the memory; finally the sound is classified into the category that best fits. However, this classification may have a blurred boundary respectively to the category which the sound belongs to. As a result, the final decision may depend on integration of multiple sources of information. When the McGurk effect is presented the auditory and visual components of the speech are separately evaluated before being integrated. In those who perceive the McGurk effect, the visual information has a higher influence on the perception of the ambiguous audiovisual information and thus the sound is classified as "da".
Many studies have concluded that the area responsible for the perception of this phenomenon is the left superior temporal sulcus(STS). This area is critical for the multisensory integration of visual and auditory information during speech perception. Moreover, there is a correlation between the activation of the STS and the perception of the McGurk effect. In that sense, if the left STS correctly integrates the mismatched audiovisual information, a McGurk effect is perceived; if the left STS is not active, the visual and auditory information are not integrated and thus a McGurk effect is not perceived.
In one study blood-oxygen-level dependent functional magnetic resonance imaging (BOLD fMRI) was used to measure the brain activity in perceivers and non-perceivers of the McGurk effect while presented with congruent audiovisual syllables, McGurk audiovisual syllables (auditory "ba" + visual "ga" producing perception of "da"), and non-McGurk incongruent syllables( auditory "ga" + visual "ba" producing auditory perception of "ga"). The researchers found that there was a positive correlation between the amplitude of response in the left STS and the probability of perceiving the McGurk effect. In other words, the subject with the weakest STS activation to incongruent speech had the smallest probability of experiencing a McGurk percept; whereas the subject with the strongest STS response had the highest probability.
Beauchamp et al. (2010) highlight the critical role of the left STS in audiovisual integration. They applied single pulses of transcranial magnetic stimulation (TMS) to the STS of McGurk perceivers during presentation of McGurk stimuli. The perception of the McGurk effect decreased from 94% to 43% and the subjects reported perceiving only the auditory syllable. Following from that, Beauchamp et al. conclude that the left STS is crucial for the audiovisual integration and thus for the perception of the McGurk effect.
Moreover, another study suggests that the basis of the interindividual differences in the perception of McGurk effect lies in the eye movements of the subject when viewing the talker's face. The experimenters carried out an eye tracking study and measured the eye movements of the participants while viewing audiovisual speech. They found that people who spent more time fixating the mouth of the talker were the more likely to perceive the McGurk effect than those who rarely fixated on the mouth of the speaker.
Hub AI
Interindividual differences in perception AI simulator
(@Interindividual differences in perception_simulator)
Interindividual differences in perception
Interindividual differences in perception describes the effect that differences in brain structure or factors such as culture, upbringing and environment have on the perception of humans. Interindividual (differing from person to person) variability is usually regarded as a source of noise for research. However, in recent years, it has become an interesting source to study sensory mechanisms and understand human behavior. With the help of modern neuroimaging methods such as fMRI and EEG, individual differences in perception could be related to the underlying brain mechanisms. This has helped to explain differences in behavior and cognition across the population. The present study using MRS provides direct evidence showing that the excitatory process in the suprasensory areas is linked to the individual differences in visual motion perception. The neurotransmitter concentration in the higher areas that execute cognitive functions is related to the interindividual variability in the perception of visual motion. Common methods include studying the perception of illusions, as they can effectively demonstrate how different aspects such as culture, genetics and the environment can influence human behavior.
A motion quartet is a bistable stimulus - it consists of two dots that change their position from frame to frame. This position change can either be interpreted as horizontal or vertical movement by viewers, and this experience can switch during viewing between interpretations. Depending on the aspect ratio of the two dots' positions, one or the other state is perceived longer or more often. At an aspect ratio of one, the illusion is biased towards the vertical perception. The reason for this might be the way the human brain processes the signals from both eyes in the visual system. The right half of an eye's field of view is processed by the left hemisphere, and the left half by the right hemisphere. A stimulus moving vertically only involves one field of view and so one hemisphere, while a stimulus moving vertically from one field of view to the other involves both hemispheres, and requires communication between them. The delay caused by this additional signalling might be the cause for the bias. There are also individual differences in the way the motion quartet is perceived: Some people require a different aspect ratio to perceive both axes of movement than others. A study using diffusion tensor imaging further showed differences in the structure of the corpus callosum, the primary connection between the two hemispheres, might be the origin of these differences.
There exist a variety of illusions that make objects appear bigger or smaller compared to their real size. Two such illusions are the Ebbinghaus and the Ponzo illusions. The Ebbinghaus illusion makes a dot seem bigger because it is surrounded by smaller dots, while the Ponzo illusion exploits human perspective processing by making a dot appear bigger because it seems farther away. Schwarzkopf et al. found that the size of the primary visual cortex (V1) has an effect on the magnitude of these illusions. The larger the subject's V1 surface area was, the less the subjects fell for the illusion. This is hypothesized to be due to the fact that a larger V1 dedicated to the same portion of the visual field means a lesser effect of later, fixed-size visual areas (which are the ones that are responsible for the illusion effect).
The McGurk effect is an auditory illusion in which people perceive a different syllable when incongruent audiovisual speech is presented: an auditory syllable "ba" is presented while the mouth movement is "ga". As a result, the listener perceives the syllable "da". However, according to Gentilucci and Cattaneo (2005), not everyone perceives this illusion; only about 26% to 98% of the population are susceptible to this illusion. One of the psychological models that explains the interindividual differences in speech perception is the fuzzy logic model of speech perception According to this model, a categorization process is carried out when processing speech sounds. When listening to a stimulus, the features of the acoustic signal are analyzed. Subsequently, this signal is compared with the features that are stored in the memory; finally the sound is classified into the category that best fits. However, this classification may have a blurred boundary respectively to the category which the sound belongs to. As a result, the final decision may depend on integration of multiple sources of information. When the McGurk effect is presented the auditory and visual components of the speech are separately evaluated before being integrated. In those who perceive the McGurk effect, the visual information has a higher influence on the perception of the ambiguous audiovisual information and thus the sound is classified as "da".
Many studies have concluded that the area responsible for the perception of this phenomenon is the left superior temporal sulcus(STS). This area is critical for the multisensory integration of visual and auditory information during speech perception. Moreover, there is a correlation between the activation of the STS and the perception of the McGurk effect. In that sense, if the left STS correctly integrates the mismatched audiovisual information, a McGurk effect is perceived; if the left STS is not active, the visual and auditory information are not integrated and thus a McGurk effect is not perceived.
In one study blood-oxygen-level dependent functional magnetic resonance imaging (BOLD fMRI) was used to measure the brain activity in perceivers and non-perceivers of the McGurk effect while presented with congruent audiovisual syllables, McGurk audiovisual syllables (auditory "ba" + visual "ga" producing perception of "da"), and non-McGurk incongruent syllables( auditory "ga" + visual "ba" producing auditory perception of "ga"). The researchers found that there was a positive correlation between the amplitude of response in the left STS and the probability of perceiving the McGurk effect. In other words, the subject with the weakest STS activation to incongruent speech had the smallest probability of experiencing a McGurk percept; whereas the subject with the strongest STS response had the highest probability.
Beauchamp et al. (2010) highlight the critical role of the left STS in audiovisual integration. They applied single pulses of transcranial magnetic stimulation (TMS) to the STS of McGurk perceivers during presentation of McGurk stimuli. The perception of the McGurk effect decreased from 94% to 43% and the subjects reported perceiving only the auditory syllable. Following from that, Beauchamp et al. conclude that the left STS is crucial for the audiovisual integration and thus for the perception of the McGurk effect.
Moreover, another study suggests that the basis of the interindividual differences in the perception of McGurk effect lies in the eye movements of the subject when viewing the talker's face. The experimenters carried out an eye tracking study and measured the eye movements of the participants while viewing audiovisual speech. They found that people who spent more time fixating the mouth of the talker were the more likely to perceive the McGurk effect than those who rarely fixated on the mouth of the speaker.