Language module
Encyclopedia
Language module refers to a hypothesized structure in the human brain
(anatomical module) or cognitive system (functional module) that some psycholinguists (e.g., Steven Pinker
) claim contains innate capacities for language
. According to Jerry Fodor
the sine qua non
of modularity is information encapsulation; that is, the module is immune from information from other sources not directly associated with language processing (Fodor, 2005) There is currently ongoing debate about this in the field of cognitive science
(psycholinguistics
) and neuroscience
(neurolinguistics
).
, where sodium amobarbital is used to anaesthetise one hemisphere, shows that the left-hemisphere appears to be crucial in language processing (Wada & Rasmussen, 1960). Yet, neuroimaging does not implicate any single area but rather identifies many different areas as being involved in different aspects of language processing (Martin, 2003; Binder & Price, 2001; Raichle, 1998) and not just in the left hemisphere (e.g. Robertson et al., 2000). Further, individual areas appear to subserve a number of different functions (Raichle, 1998; Grodinsky, 2006). Thus, the extent to which language processing occurs within an anatomical module is considered to be minimal. Nevertheless, as many have suggested (e.g. Pinker, 1997; von der Malsburg, 1995), modular processing can still exist even when implemented across the brain; that is, language processing could occur within a functional module.
; e.g. Goodglass & Kaplan, 1972), there is no known acquired case where language is completely intact in the face of severe non-linguistic deterioration (Levy, 1996). Thus, functional module status cannot be granted to language processing based on this evidence.
However, other evidence from developmental studies has been presented (most famously by Pinker, 1994, pp.37-43) as supporting a language module, namely the purported dissociation between Specific Language Impairment
(SLI), where language is disrupted whilst other mental abilities are not (van der Lely, 2005), and Williams Syndrome
(WS) where language is said to be spared despite severe mental deficits (Bellugi et al. 1988). More recent and empirically robust work has shown that these claims may be inaccurate, thus, considerably weakening support for dissociation. For example, work reviewed by Brock (2007) and Mervis and Beccera (2007) demonstrated that language abilities in WS are no more than would be predicted by non-linguistic abilities. Further, there is considerable debate concerning whether SLI is actually a language disorder or whether its aetiology is due to a more general cognitive (e.g. phonological) problem (e.g. Norbury, Bishop & Briscoe, 2001; Leonard, 1998; Bishop, 1994; Kail, 1994, cf. van der Lely, 2005). Thus, the evidence needed to complete the picture for modularity – intact language coupled with gross intellectual deterioration – is not forthcoming. Consequently, developmental data offers little support for the notion that language processing occurs within a module.
Thus, the evidence from double dissociations does not support modularity, although it should be noted that lack of dissociation is not evidence against a module; this inference cannot be logically made.
, watching lips say one phoneme whilst another is played creates the percept of a blended phoneme (McGurk & MacDonald, 1976; Carston. 1996). Further, Tanenhaus, Spivey-Knowlton, Eberhard and Sedivy (1995) demonstrated visual information mediating syntactic processing. In addition, the putative language module should process only that information relevant to language (i.e., be domain-specific). Yet evidence suggests that areas purported to subserve language also mediate motor control (Heiser, Iacoboni, Maeda, Marcus & Mazziotta, 2003) and non-linguistic sound comprehension (Saygin, Dick, Wilson, Dronkers & Bates., 2003). Although it is possible that separate processes could be occurring but below the resolution of current imaging techniques, when all this evidence is taken together the case for information encapsulation is weakened.
The debate is ongoing.
Human brain
The human brain has the same general structure as the brains of other mammals, but is over three times larger than the brain of a typical mammal with an equivalent body size. Estimates for the number of neurons in the human brain range from 80 to 120 billion...
(anatomical module) or cognitive system (functional module) that some psycholinguists (e.g., Steven Pinker
Steven Pinker
Steven Arthur Pinker is a Canadian-American experimental psychologist, cognitive scientist, linguist and popular science author...
) claim contains innate capacities for language
Language
Language may refer either to the specifically human capacity for acquiring and using complex systems of communication, or to a specific instance of such a system of complex communication...
. According to Jerry Fodor
Jerry Fodor
Jerry Alan Fodor is an American philosopher and cognitive scientist. He holds the position of State of New Jersey Professor of Philosophy at Rutgers University and is the author of many works in the fields of philosophy of mind and cognitive science, in which he has laid the groundwork for the...
the sine qua non
Sine qua non
Sine qua non or condicio sine qua non refers to an indispensable and essential action, condition, or ingredient...
of modularity is information encapsulation; that is, the module is immune from information from other sources not directly associated with language processing (Fodor, 2005) There is currently ongoing debate about this in the field of cognitive science
Cognitive science
Cognitive science is the interdisciplinary scientific study of mind and its processes. It examines what cognition is, what it does and how it works. It includes research on how information is processed , represented, and transformed in behaviour, nervous system or machine...
(psycholinguistics
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 neuroscience
Neuroscience
Neuroscience 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,...
(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,...
).
What is a module?
The debate on the issue of modularity in language is underpinned, in part, by different understandings of this concept (Coltheart, 1999). There is, however, some consensus in the literature that a module is considered committed to processing specialized representations (domain-specificity) (Bryson, 2002; Bryson and Stein, 2001; Fodor, 1983) in an informationally encapsulated way (Flombaum, Santos & Hauser, 2002; Fodor, 1983). A distinction should be drawn between anatomical modularity, which proposes there is one 'area' in the brain that deals with this processing, and functional modularity that obviates anatomical modularity whilst maintaining information encapsulation in distributed parts of the brain (Calabretta, Ferdinando, Wagner, & Parisi, 2003).No singular anatomical module
The available evidence points towards no one anatomical area solely devoted to processing language. The Wada testWada test
The Wada test, named after Canadian neurologist and epileptologist Juhn Atsushi Wada, also known as the "intracarotid sodium amobarbital procedure" , is used to establish cerebral language and memory representation of each hemisphere.-Method:...
, where sodium amobarbital is used to anaesthetise one hemisphere, shows that the left-hemisphere appears to be crucial in language processing (Wada & Rasmussen, 1960). Yet, neuroimaging does not implicate any single area but rather identifies many different areas as being involved in different aspects of language processing (Martin, 2003; Binder & Price, 2001; Raichle, 1998) and not just in the left hemisphere (e.g. Robertson et al., 2000). Further, individual areas appear to subserve a number of different functions (Raichle, 1998; Grodinsky, 2006). Thus, the extent to which language processing occurs within an anatomical module is considered to be minimal. Nevertheless, as many have suggested (e.g. Pinker, 1997; von der Malsburg, 1995), modular processing can still exist even when implemented across the brain; that is, language processing could occur within a functional module.
No double dissociation - acquired or developmental
A common way to demonstrate modularity is to find a double dissociation. That is two groups: First, people for whom language is severely damaged and yet have normal cognitive abilities and, second, persons for whom normal cognitive abilities are grossly impaired and yet language remains intact (Dunn & Kirsner, 2003; Coltheart & Davies, 2003; Moscovitch & Umiltà, 1990). Whilst extensive lesions in the left hemisphere perisylvian area can render persons unable to produce or perceive language, (global aphasiaAphasia
Aphasia is an impairment of language ability. This class of language disorder ranges from having difficulty remembering words to being completely unable to speak, read, or write....
; e.g. Goodglass & Kaplan, 1972), there is no known acquired case where language is completely intact in the face of severe non-linguistic deterioration (Levy, 1996). Thus, functional module status cannot be granted to language processing based on this evidence.
However, other evidence from developmental studies has been presented (most famously by Pinker, 1994, pp.37-43) as supporting a language module, namely the purported dissociation between Specific Language Impairment
Specific language impairment
Specific language impairment is diagnosed when a child's language does not develop normally and the difficulties cannot be accounted for by generally slow development , physical abnormality of the speech apparatus, autistic disorder, acquired brain damage or hearing loss.-Overview:Specific...
(SLI), where language is disrupted whilst other mental abilities are not (van der Lely, 2005), and Williams Syndrome
Williams syndrome
Williams syndrome is a rare neurodevelopmental disorder characterized by a distinctive, "elfin" facial appearance, along with a low nasal bridge; an unusually cheerful demeanor and ease with strangers; developmental delay coupled with strong language skills; and cardiovascular problems, such as...
(WS) where language is said to be spared despite severe mental deficits (Bellugi et al. 1988). More recent and empirically robust work has shown that these claims may be inaccurate, thus, considerably weakening support for dissociation. For example, work reviewed by Brock (2007) and Mervis and Beccera (2007) demonstrated that language abilities in WS are no more than would be predicted by non-linguistic abilities. Further, there is considerable debate concerning whether SLI is actually a language disorder or whether its aetiology is due to a more general cognitive (e.g. phonological) problem (e.g. Norbury, Bishop & Briscoe, 2001; Leonard, 1998; Bishop, 1994; Kail, 1994, cf. van der Lely, 2005). Thus, the evidence needed to complete the picture for modularity – intact language coupled with gross intellectual deterioration – is not forthcoming. Consequently, developmental data offers little support for the notion that language processing occurs within a module.
Thus, the evidence from double dissociations does not support modularity, although it should be noted that lack of dissociation is not evidence against a module; this inference cannot be logically made.
Lack of information encapsulation
Indeed, if language were a module it would be informationally encapsulated. Yet, there is evidence to suggest that this is not the case. For instance, in the McGurk effectMcGurk effect
The McGurk effect is a perceptual phenomenon which demonstrates an interaction between hearing and vision in speech perception. "It is a compelling illusion in which humans perceive mismatched audiovisual speech as a completely different syllable". The visual information a person gets from seeing a...
, watching lips say one phoneme whilst another is played creates the percept of a blended phoneme (McGurk & MacDonald, 1976; Carston. 1996). Further, Tanenhaus, Spivey-Knowlton, Eberhard and Sedivy (1995) demonstrated visual information mediating syntactic processing. In addition, the putative language module should process only that information relevant to language (i.e., be domain-specific). Yet evidence suggests that areas purported to subserve language also mediate motor control (Heiser, Iacoboni, Maeda, Marcus & Mazziotta, 2003) and non-linguistic sound comprehension (Saygin, Dick, Wilson, Dronkers & Bates., 2003). Although it is possible that separate processes could be occurring but below the resolution of current imaging techniques, when all this evidence is taken together the case for information encapsulation is weakened.
The alternative
The alternative, as it is framed, is that language occurs within a more general cognitive system (Rumelhart & McClelland, 1986). The counterargument is that there appears to be something ‘special’ (Pinker & Jackendoff, 2005) about human language. This is usually supported by evidence such as all attempts to teach animals human languages to any great success have failed (Hauser et al. 2003) and that language can be selectively damaged (a single dissociation) (Pulvermüller, 2003) suggesting proprietary computation may be required. Instead of postulating 'pure' modularity, theorists have opted for a weaker version, domain-specificity implemented in functionally specialised neural circuits and computation (e.g. Jackendoff and Pinker’s (2005) words, we must investigate language “not as a monolith but as a combination of components, some special to language, others rooted in more general capacities” (p.223).The debate is ongoing.