Perceptual narrowing
Encyclopedia
Perceptual narrowing is a developmental process in which the brain learns to experience the environment through a “fine-tuning” of the senses. The process of perceptual narrowing improves the perception of things that people experience often and causes them to lose the ability to perceive some things to which they are not exposed . This phenomenon is a result of neuroplasticity
, including Hebbian learning and synaptic pruning
. Through these mechanisms, neural pathways that are more consistently used are strengthened, making them more efficient. Those pathways that are unused are removed. This process is most evident during sensitive periods
of development. The prevailing theory is that human infants are born with the ability to sense a wide variety of stimuli. As they age, they begin to selectively narrow these perceptions, categorizing them in a more socio-cultural relevant way. Most of the research in this area focuses on facial discrimination and phoneme
distinction in human infants. Perceptual narrowing has also been implicated in synaesthesia.
procedure in cross racial studies, Caucasian infants were rated on their ability to recognize faces from their own race, as well as three other races, specifically - African, Asian, and Middle Eastern. At 3 months of age, infants were able to show recognition for familiar faces from all racial groups, but by 6 months, a pattern was beginning to emerge where the infants could only recognize faces from the Caucasian or Chinese groups. At 9 months, recognition took place only in the own-race group. These cross race studies provide strong evidence that children do start out with cross racial recognition abilities but as they age, they quickly begin to organize the data and select that stimuli that is most familiar to them .
, during sensitive periods
of development . This is a function of synaptic pruning
, a mechanism of plasticity where the overall number of neurons and neural pathways are reduced, leaving only the most commonly used--and most efficient--neural pathways. These pathways are also more myelinated which increases the speeds at which processing occurs.
Neuroplasticity
Neuroplasticity is a non-specific neuroscience term referring to the ability of the brain and nervous system in all species to change structurally and functionally as a result of input from the environment. Plasticity occurs on a variety of levels, ranging from cellular changes involved in...
, including Hebbian learning and synaptic pruning
Synaptic pruning
In neuroscience, synaptic pruning, neuronal pruning or axon pruning refer to neurological regulatory processes, which facilitate a change in neural structure by reducing the overall number of neurons or connections, leaving more efficient synaptic configurations. Pruning is a neurological...
. Through these mechanisms, neural pathways that are more consistently used are strengthened, making them more efficient. Those pathways that are unused are removed. This process is most evident during sensitive periods
Sensitive periods
Sensitive periods is a term coined by the Dutch geneticist Hugo de Vries and adopted by the Italian educator Maria Montessori to refer to important periods of childhood development....
of development. The prevailing theory is that human infants are born with the ability to sense a wide variety of stimuli. As they age, they begin to selectively narrow these perceptions, categorizing them in a more socio-cultural relevant way. Most of the research in this area focuses on facial discrimination and phoneme
Phoneme
In a language or dialect, a phoneme is the smallest segmental unit of sound employed to form meaningful contrasts between utterances....
distinction in human infants. Perceptual narrowing has also been implicated in synaesthesia.
Cross Racial
Most of the research done to date in the area of perceptual narrowing involves facial processing studies conducted on infants. Using a preferential lookingPreferential looking
Preferential looking is an experimental method in developmental psychology used to gain insight into the young mind/brain. The method as used today was developed by the developmental psychologist Robert L. Frantz in the 1960s.-General account:...
procedure in cross racial studies, Caucasian infants were rated on their ability to recognize faces from their own race, as well as three other races, specifically - African, Asian, and Middle Eastern. At 3 months of age, infants were able to show recognition for familiar faces from all racial groups, but by 6 months, a pattern was beginning to emerge where the infants could only recognize faces from the Caucasian or Chinese groups. At 9 months, recognition took place only in the own-race group. These cross race studies provide strong evidence that children do start out with cross racial recognition abilities but as they age, they quickly begin to organize the data and select that stimuli that is most familiar to them .
Cross Species
Cross species studies have been conducted where human infants at 3 months of age were familiarized with individual monkeys. When the monkey faces were associated with name labels, the infants maintained their ability to discriminate between them when retested at 6 and 9 months of age. If the exposure was just to monkey faces in general, without name labels, the infants gradually lost the ability to discriminate between them when retested at the 6 and 9 months marks. These studies provide evidence that this individuation process is important for recognition of familiar faces later in life.Phoneme Distinction
At birth infants are born with the broad abilities to detect similarities and differences among languages. The phonemes of different languages sound distinct to infants less than 6 months of age, but as the infant grows and its brain develops, it becomes less able to distinguish phonemes of nonnative languages and more responsive to its native language. Research suggests that this perceptual narrowing phenomenon occurs within the first year of life. Infants aged 6-8 months have a greater ability to distinguish between nonnative sounds in comparison to infants who are 8-10 months of age. Near the end of 12 months, infants are beginning to understand and produce speech in their native language, and by the end of the first year of life infants detect these phonemic distinctions at low levels that are similar to that of adults.Intersensory Perception
A study was done involving 4-6 month old babies and 12-18 month babies. The two groups were show looped clips of two monkey calls on two screens, a coo and a grunt. The two calls were made by the same monkey. The calls were presented 666ms earlier than the videos. The infants did not show preference for the video matching audio calls. While a previous experiment with the audio and video synchronized showed that younger infants can distinguish between the two calls. Thus, synchrony is important in cross-species intersensory matching, not duration. 12-18 month old babies could not distinguish between the two calls even when the video and audio were synchronized. However 7 month old babies could perceive the relationship between asynchronized sound and image, but only if they are native faces.This suggests that older infants look for higher-level features in intersensory perception, but they do not detect cross-species features because they do not have experience with nonnative faces and vocalizations.Neural Mechanisms
brain plasticity is responsible for this “tuning” of infants’ perceptual ability. While plasticity is evident throughout the human lifespan, it occurs most often at younger agesDevelopmental psychology
Developmental psychology, also known as human development, is the scientific study of systematic psychological changes, emotional changes, and perception changes that occur in human beings over the course of their life span. Originally concerned with infants and children, the field has expanded to...
, during sensitive periods
Sensitive periods
Sensitive periods is a term coined by the Dutch geneticist Hugo de Vries and adopted by the Italian educator Maria Montessori to refer to important periods of childhood development....
of development . This is a function of synaptic pruning
Synaptic pruning
In neuroscience, synaptic pruning, neuronal pruning or axon pruning refer to neurological regulatory processes, which facilitate a change in neural structure by reducing the overall number of neurons or connections, leaving more efficient synaptic configurations. Pruning is a neurological...
, a mechanism of plasticity where the overall number of neurons and neural pathways are reduced, leaving only the most commonly used--and most efficient--neural pathways. These pathways are also more myelinated which increases the speeds at which processing occurs.
Synaesthesia and Perceptual Narrowing
Synaesthesia is a condition in which the stimulation of one sense evokes an additional stimulation in another sense, such as a tone (auditory stimulation) evoking the experience of color or shapes (visual stimulation). Some research suggests that infants universally have this experience due to the greater number of functional synaptic connections across sensory domains compared to adults, and that over the course of normal development this experience dissipates through the process of perceptual narrowing. There is evidence that a failure in the perceptual narrowing process can, in rare cases, lead to adult synaethesia.See also
- neuroscienceNeuroscienceNeuroscience is the scientific study of the nervous system. Traditionally, neuroscience has been seen as a branch of biology. However, it is currently an interdisciplinary science that collaborates with other fields such as chemistry, computer science, engineering, linguistics, mathematics,...
- synaptic pruningSynaptic pruningIn neuroscience, synaptic pruning, neuronal pruning or axon pruning refer to neurological regulatory processes, which facilitate a change in neural structure by reducing the overall number of neurons or connections, leaving more efficient synaptic configurations. Pruning is a neurological...
- neuroplasticityNeuroplasticityNeuroplasticity is a non-specific neuroscience term referring to the ability of the brain and nervous system in all species to change structurally and functionally as a result of input from the environment. Plasticity occurs on a variety of levels, ranging from cellular changes involved in...
- developmental plasticityDevelopmental plasticityDevelopmental plasticity is a general term referring to changes in neural connections during development as a result of environmental interactions as well as neural changes induced by learning...
- phonemePhonemeIn a language or dialect, a phoneme is the smallest segmental unit of sound employed to form meaningful contrasts between utterances....
- synaesthesia
- Hebbian learning
- sensitive periodsSensitive periodsSensitive periods is a term coined by the Dutch geneticist Hugo de Vries and adopted by the Italian educator Maria Montessori to refer to important periods of childhood development....
- preferential lookingPreferential lookingPreferential looking is an experimental method in developmental psychology used to gain insight into the young mind/brain. The method as used today was developed by the developmental psychologist Robert L. Frantz in the 1960s.-General account:...
- myelinMyelinMyelin is a dielectric material that forms a layer, the myelin sheath, usually around only the axon of a neuron. It is essential for the proper functioning of the nervous system. Myelin is an outgrowth of a type of glial cell. The production of the myelin sheath is called myelination...