Cohort model
Encyclopedia
The cohort model in psycholinguistics
and neurolinguistics
is a model of lexical retrieval first proposed by William Marslen-Wilson in the late 1980s. It attempts to describe how visual or auditory input (i.e., hearing or reading a word) is mapped onto a word in a hearer's lexicon
. According to the model, when a person hears speech segments real-time, each speech segment "activates" every word in the lexicon that begins with that segment, and as more segments are added, more words are ruled out, until only one word is left that still matches the input.
s as it enters the brain, rather than at the end of a word. This fact was demonstrated in the 1980s through experiments with speech shadowing
, in which subjects listened to recordings and were instructed to repeat aloud exactly what they heard, as quickly as possible; Marslen-Wilson found that the subjects often started to repeat a word before it had actually finished playing, which suggested that the word in the hearer's lexicon was activated before the entire word had been heard. Findings such as these led Marslen-Wilson to propose the cohort model in 1987.
Under this model, auditory lexical retrieval begins with the first one or two speech segments, or phoneme
s, reach the hearer's ear, at which time the mental lexicon activates every possible word that begins with that speech segment. The words that are activated by the speech signal but are not the intended word are often called "competitors." As more speech segments enter the ear and stimulate more neurons, causing the competitors that no longer match the input to be "kicked out" or to decrease in activation. The processes by which words are activated and competitors rejected in the cohort model are frequently called "activation and selection" or "recognition and competition." These processes continue until an instant, called the recognition point, at which only one word remains activated and all competitors have been kicked out.
For example, in the auditory recognition of the word "candle," the following steps take place. When the hearer hears the first two phonemes /k/ and /æ/, he or she would activate the word "candle," along with competitors such as "candy," "can," "cattle," and numerous others. Once the phoneme /n/ is added, "cattle" would be kicked out; with /d/, "can" would be kicked out; and this process would continue until the recognition point, the final /l/ of "candle," were reached. The recognition point need not always be the final phoneme of the word; the recognition point of "slander," for example, occurs at the /d/ (since no other English words begin "sland-"); all competitors for "spaghetti" are ruled out as early as /spəɡ/; Jerome Packard
has demonstrated that the recognition point of the Chinese
word huŏchē ("train") occurs before huŏch-; and a landmark study by Pienie Zwitserlood demonstrated that the recognition point of the Dutch
word kapitein (captain) was at the vowel before the final /n/.
Since its original proposal, the model has been adjusted to allow for the role that context
plays in helping the hearer rule out competitors, and the fact that activation is "tolerant" to minor acoustic mismatches that arise because of coarticulation
(a property by which language sounds are slightly changed by the sounds preceding and following them).
, in which a "priming word" is presented to a subject and then closely followed by a "target word" and the subject asked to identify if the target word is a real word or not; the theory behind the priming paradigm is that if a word is activated in the subject's mental lexicon, the subject will be able to respond more quickly to the target word. If the subject does respond more quickly, the target word is said to be "primed" by the priming word. Several priming studies have found that when a stimulus that does not reach recognition point is presented, numerous words targets were all primed, whereas if a stimulus past recognition point is presented, only one word is primed. For example, in Pienie Zwitserlood's study of Dutch compared the words kapitein ("captain") and kapitaal ("capital" or "money"); in the study, the stem kapit- primed both boot ("boat," semantically related to kapitein) and geld ("gold," semantically related to kapitaal), suggesting that both lexical entries were activated; the full word kapitein, on the other hand, primed only boot and not geld.
Later experiments refined the model. For example, some studies showed that "shadowers" (subjects who listen to auditory stimuli and repeat it as quickly as possible) could not shadow as quickly when words were jumbled up so they didn't mean anything; those results suggested that sentence structure and speech context also contribute to the process of activation and selection.
Psycholinguistics
Psycholinguistics or psychology of language is the study of the psychological and neurobiological factors that enable humans to acquire, use, comprehend and produce language. Initial forays into psycholinguistics were largely philosophical ventures, due mainly to a lack of cohesive data on how the...
and neurolinguistics
Neurolinguistics
Neurolinguistics is the study of the neural mechanisms in the human brain that control the comprehension, production, and acquisition of language. As an interdisciplinary field, neurolinguistics draws methodology and theory from fields such as neuroscience, linguistics, cognitive science,...
is a model of lexical retrieval first proposed by William Marslen-Wilson in the late 1980s. It attempts to describe how visual or auditory input (i.e., hearing or reading a word) is mapped onto a word in a hearer's lexicon
Lexicon
In linguistics, the lexicon of a language is its vocabulary, including its words and expressions. A lexicon is also a synonym of the word thesaurus. More formally, it is a language's inventory of lexemes. Coined in English 1603, the word "lexicon" derives from the Greek "λεξικόν" , neut...
. According to the model, when a person hears speech segments real-time, each speech segment "activates" every word in the lexicon that begins with that segment, and as more segments are added, more words are ruled out, until only one word is left that still matches the input.
Model
The cohort model is based on the concept that auditory or visual input to the brain stimulates neuronNeuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
s as it enters the brain, rather than at the end of a word. This fact was demonstrated in the 1980s through experiments with speech shadowing
Speech shadowing
Speech shadowing is an experimental technique in which subjects repeat speech immediately after hearing it . The reaction time between hearing a word and pronouncing it can be as short as 254 ms or even 150 ms. This is only the delay duration of a speech syllable...
, in which subjects listened to recordings and were instructed to repeat aloud exactly what they heard, as quickly as possible; Marslen-Wilson found that the subjects often started to repeat a word before it had actually finished playing, which suggested that the word in the hearer's lexicon was activated before the entire word had been heard. Findings such as these led Marslen-Wilson to propose the cohort model in 1987.
Under this model, auditory lexical retrieval begins with the first one or two speech segments, or phoneme
Phoneme
In a language or dialect, a phoneme is the smallest segmental unit of sound employed to form meaningful contrasts between utterances....
s, reach the hearer's ear, at which time the mental lexicon activates every possible word that begins with that speech segment. The words that are activated by the speech signal but are not the intended word are often called "competitors." As more speech segments enter the ear and stimulate more neurons, causing the competitors that no longer match the input to be "kicked out" or to decrease in activation. The processes by which words are activated and competitors rejected in the cohort model are frequently called "activation and selection" or "recognition and competition." These processes continue until an instant, called the recognition point, at which only one word remains activated and all competitors have been kicked out.
For example, in the auditory recognition of the word "candle," the following steps take place. When the hearer hears the first two phonemes /k/ and /æ/, he or she would activate the word "candle," along with competitors such as "candy," "can," "cattle," and numerous others. Once the phoneme /n/ is added, "cattle" would be kicked out; with /d/, "can" would be kicked out; and this process would continue until the recognition point, the final /l/ of "candle," were reached. The recognition point need not always be the final phoneme of the word; the recognition point of "slander," for example, occurs at the /d/ (since no other English words begin "sland-"); all competitors for "spaghetti" are ruled out as early as /spəɡ/; Jerome Packard
Jerome Packard
Jerome Packard is an American linguist specializing in Chinese linguistics and psycholinguistics. He is currently a professor of linguistics at the University of Illinois at Urbana-Champaign. His book The Morphology of Chinese is influential and widely cited in Chinese linguistics.-External...
has demonstrated that the recognition point of the Chinese
Standard Mandarin
Standard Chinese or Modern Standard Chinese, also known as Mandarin or Putonghua, is the official language of the People's Republic of China and Republic of China , and is one of the four official languages of Singapore....
word huŏchē ("train") occurs before huŏch-; and a landmark study by Pienie Zwitserlood demonstrated that the recognition point of the Dutch
Dutch language
Dutch is a West Germanic language and the native language of the majority of the population of the Netherlands, Belgium, and Suriname, the three member states of the Dutch Language Union. Most speakers live in the European Union, where it is a first language for about 23 million and a second...
word kapitein (captain) was at the vowel before the final /n/.
Since its original proposal, the model has been adjusted to allow for the role that context
Context (language use)
Context is a notion used in the language sciences in two different ways, namely as* verbal context* social context- Verbal context :...
plays in helping the hearer rule out competitors, and the fact that activation is "tolerant" to minor acoustic mismatches that arise because of coarticulation
Assimilation (linguistics)
Assimilation is a common phonological process by which the sound of the ending of one word blends into the sound of the beginning of the following word. This occurs when the parts of the mouth and vocal cords start to form the beginning sounds of the next word before the last sound has been...
(a property by which language sounds are slightly changed by the sounds preceding and following them).
Experimental evidence
Much evidence in favor of the cohort model has come from priming studiesPriming (psychology)
Priming is an implicit memory effect in which exposure to a stimulus influences a response to a later stimulus. It can occur following perceptual, semantic, or conceptual stimulus repetition...
, in which a "priming word" is presented to a subject and then closely followed by a "target word" and the subject asked to identify if the target word is a real word or not; the theory behind the priming paradigm is that if a word is activated in the subject's mental lexicon, the subject will be able to respond more quickly to the target word. If the subject does respond more quickly, the target word is said to be "primed" by the priming word. Several priming studies have found that when a stimulus that does not reach recognition point is presented, numerous words targets were all primed, whereas if a stimulus past recognition point is presented, only one word is primed. For example, in Pienie Zwitserlood's study of Dutch compared the words kapitein ("captain") and kapitaal ("capital" or "money"); in the study, the stem kapit- primed both boot ("boat," semantically related to kapitein) and geld ("gold," semantically related to kapitaal), suggesting that both lexical entries were activated; the full word kapitein, on the other hand, primed only boot and not geld.
Later experiments refined the model. For example, some studies showed that "shadowers" (subjects who listen to auditory stimuli and repeat it as quickly as possible) could not shadow as quickly when words were jumbled up so they didn't mean anything; those results suggested that sentence structure and speech context also contribute to the process of activation and selection.