Cognition, Consciousness, and Language
After Chapter 4.6, you will be able to:
· Recall the expected milestones of language development and the ages at which they should occur
· Identify the primary characteristics of the nativist, behaviorist, and social interactionist theories of language development
· Describe the symptoms and brain regions associated with Broca’s, Wernicke’s, and conduction aphasia:
Whether it is written, spoken, or signed, language is fundamental to the creation of communities. As humans began to live in groups, the ability to communicate became essential. Division of labor and a sense of shared history require that the meaning of the language be the same for all speakers of the language.
COMPONENTS OF LANGUAGE
There are five basic components of language: phonology, morphology, semantics, syntax, and pragmatics.
Phonology refers to the actual sound of language. There are about 40 speech sounds or phonemes in English, although many more exist in other languages, as shown in Figure 4.16. Children must learn to produce and recognize the sounds of language, separating them from environmental noises and other human-created sounds, like coughing. Additionally, when a language has subtle differences in speech sounds that represent a change in meaning, children learn to distinguish those phonemes; this ability is called categorical perception. The ability to recognize a word as being the same, even if the pronunciation of the word varies between people is an auditory example of constancy, which is described in Chapter 2 of MCAT Behavioral Sciences Review.
Figure 4.16. The International Phonetic AlphabetThe IPA is an unambiguous system of writing all of the known phonemes of all human languages.
Morphology refers to the structure of words. Many words are composed of multiple building blocks called morphemes, each of which connotes a particular meaning. Consider the word redesigned, which can be broken into three morphemes: re—, indicating to do again; —design—, the verb root; and —ed, indicating an action in the past.
Semantics refers to the association of meaning with a word. A child must learn that certain combinations of phonemes represent certain physical objects or events, and that words may refer to entire categories, such as women, while others refer to specific members of categories, such as mommy. One can see this skill developing in young children as they may refer to all women as mommy.
Syntax refers to how words are put together to form sentences. A child must notice the effects of word order on meaning: Nathan has only three pieces of candy has a very different meaning than Only Nathan has three pieces of candy.
Finally, pragmatics refers to the dependence of language on context and preexisting knowledge. In other words, the manner in which we speak may differ depending on the audience and our relationship to that audience. Imagine asking to share a seat on a bus. Depending on whom we ask, we may word this request in wildly different ways. To a stranger, we may be more formal: Pardon me, do you mind if I share this seat? To a close friend, we may be less so: Hey, move over! Pragmatics are also affected by prosody—the rhythm, cadence, and inflection of our voices.
To effectively interact with society, a child must learn to communicate through language, whether oral or signed. An important precursor to language is babbling. Almost without exception, children—including deaf children—spontaneously begin to babble during their first year. For hearing children, babbling reaches its highest frequency between nine and twelve months. For deaf children, verbal babbling ceases soon after it begins.
The timeline of language acquisition is fairly consistent among children. From 12 to 18 months, children add about one word per month. Starting around 18 months, an explosion of language begins. During this naming explosion, the child quickly learns dozens of words, and uses each word with varying inflection and gestures to convey a desired meaning. For example, a child may ask, Apple? while pointing at an apple in a bowl of fruit, in an effort to request the apple. During this naming explosion, children may also frequently fall into overextension, in which they inappropriately apply a term to an object that bears cursory similarities to the term. For example, in an attempt to request a kiwi from a fruit bowl, a child might point at the kiwi and ask, Apple? For children at this age, gestures, inflection, and context are essential for the parent or caregiver to identify the meaning.
Timeline of language acquisition:
· 9 to 12 months: babbling
· 12 to 18 months: about one word per month
· 18 to 20 months: “explosion of language” and combining words
· 2 to 3 years: longer sentences (3 words or more)
· 5 years: language rules largely mastered
Between 18 and 20 months of age, children begin to combine words. The child in the previous example may say, Eat apple to tell a caregiver that he would like to eat an apple. In the grocery store, the same child may ask, That apple? to distinguish between fruit. In this way, context and gesture becomes less important as the ability to assemble sentences develops.
By the age of two or three years, children can speak in longer sentences. Vocabulary grows exponentially. As a child creates longer sentences, grammatical errors increase as the child internalizes the complex rules of grammar. These include errors of growth in which a child applies a grammatical rule (often a morpheme) in a situation where it does not apply: runned instead of ran, or funner instead of more fun. Interestingly, parents are less likely to correct errors of grammar than errors of word choice.
Pediatricians often monitor language development to determine if there is a developmental delay. For example, a two-year-old child who uses fewer than 10 words has a significant developmental delay and should be referred for speech therapy. This would also prompt a search for other developmental issues.
For the most part, language is substantially mastered by the age of five. The acquisition of language appears easy for most children, which has led to significant speculation on exactly how this occurs.
Nativist (Biological) Theory
The nativist (biological) theory, largely credited to linguist Noam Chomsky, advocates for the existence of some innate capacity for language. Chomsky is known for his study of transformational grammar. He focused on syntactic transformations, or changes in word order that retain the same meaning; for example, I took the MCAT vs. The MCAT was taken by me. Chomsky noted that children learn to make such transformations effortlessly at an early age. He therefore concluded that this ability must be innate. In this theory, this innate ability is called the language acquisition device (LAD), a theoretical pathway in the brain that allows infants to process and absorb language rules.
Nativists believe in a critical period for language acquisition between two years and puberty. If no language exposure occurs during this time, later training is largely ineffective. This idea came to light through an unfortunate test case: a victim of child abuse. This child had been isolated from all human contact from age two to thirteen, when she was discovered by authorities. Even with later language exposure, she was unable to master many rules of language, although she was able to learn some aspects of syntax. The fact that this child was able to learn some rules may indicate that there is a sensitive period for language development, rather than a critical period. A sensitive period is a time when environmental input has maximal effect on the development of an ability. Most psychologists consider the sensitive period for language development to be before the onset of puberty.
Learning (Behaviorist) Theory
The learning (behaviorist) theory, proposed by B. F. Skinner, explained language acquisition by operant conditioning. Very young babies are capable of distinguishing between phonemes of all human languages, but by six months of age show a strong preference for phonemes in the language spoken by their parents. Skinner explained language acquisition by reinforcement. That is, parents and caregivers repeat and reinforce sounds that sound most like the language spoken by the parents. Thus, over time, the infant perceives that certain sounds have little value and are not reinforced, while other sounds have value and are reliably reinforced by parents and caregivers. While this may account for the development of words and speech, many psycholinguists point out that this theory cannot fully explain the explosion in vocabulary that occurs during early childhood.
Social Interactionist Theory
The social interactionist theory of language development focuses on the interplay between biological and social processes. That is, language acquisition is driven by the child’s desire to communicate and behave in a social manner, such as interacting with caretakers and other children. Interactionist theory allows for the role of brain development in the acquisition of language. As the biological foundation for language develops and children are exposed to language, the brain groups sounds and meanings together. Then, as the child interacts with others, certain brain circuits are reinforced, while others are de-emphasized, resulting in atrophy of those circuits.
INFLUENCE OF LANGUAGE ON COGNITION
Psycholinguistics has long focused on the relationship between language and thinking. Linguist Benjamin Whorf proposed the Whorfian hypothesis, also called the linguistic relativity hypothesis, which suggests that our perception of reality—the way we think about the world—is determined by the content of language. In essence, language affects the way we think rather than the other way around. For instance, the Inuit language has a wide variety of names for different types of snow, whereas the English language has very few. Therefore, according to the Whorfian hypothesis, Inuits are better at discriminating subtleties between different types of snow than English speakers are. This is a somewhat controversial notion that depends on the definition of "a word," but most linguists agree that language can influence how we think to some degree. Word choice, inflection, context, and speaker all play a role in our perception of a message. In addition, language often provides an original framework for understanding information. A more expansive framework with more specific vocabulary allows for more sophisticated processing of that information and enhanced communication of that information to others.
BRAIN AREAS AND LANGUAGE
Two different areas of the brain are responsible for speech production and language comprehension, as shown in Figure 4.17. Both, however, are located in the dominant hemisphere, which is usually the left hemisphere. Broca’s area, located in the inferior frontal gyrus of the frontal lobe, controls the motor function of speech via connections with the motor cortex. Wernicke’s area, located in the superior temporal gyrus of the temporal lobe, is responsible for language comprehension. Broca’s area and Wernicke’s area are connected by the arcuate fasciculus, a bundle of axons that allows appropriate association between language comprehension and speech production.
Figure 4.17. Brain Areas Associated with LanguageBlue = Broca’s area; Green = Wernicke’s area. Other colored regions are associated with other aspects of language beyond the scope of the MCAT (yellow = supramarginal gyrus; orange = angular gyrus; light pink = primary auditory cortex).
Aphasia is a deficit of language production or comprehension. Much of what we know regarding language and aphasia is through observations of people with damage to speech-related areas. When damage occurs to Broca’s area, speech comprehension is intact but the patient will have a reduced or absent ability to produce spoken language. This is known as Broca’s (expressive) aphasia. These patients are often very frustrated because they are stuck with the sensation of having every word on the tip of their tongue.
On the other hand, when Wernicke’s area is damaged, motor production and fluency of speech is retained but comprehension of speech is lost. This is known as Wernicke’s (receptive) aphasia. Because speech comprehension is lost, these patients speak nonsensical sounds and inappropriate word combinations devoid of meaning. Patients with Wernicke’s aphasia often believe that they are speaking and understanding perfectly well, even though the people around them have no comprehension of what is being said. This can also be very frustrating to patients.
Finally, if the arcuate fasciculus is affected, the resulting aphasia is known as conduction aphasia. Because Broca’s and Wernicke’s areas are unaffected, speech production and comprehension are intact. However, the patient is unable to repeat something that has been said because the connection between these two regions has been lost. This is a very rare form of aphasia.
MCAT Concept Check 4.6:
Before you move on, assess your understanding of the material with these questions.
1. For each of the ages below, list the expected milestone(s) of language development:
9 to 12 months
12 to 18 months
18 to 20 months
2 to 3 years
2. For each of the theories of language acquisition below, what is the primary motivation or trigger for language development?
o Nativist (Biological):
o Learning (Behaviorist):
o Social interactionist:
3. Briefly describe the clinical features of each type of aphasia listed below:
o Broca’s aphasia:
o Wernicke’s aphasia
o Conduction aphasia: