PSY 340 Brain and Behavior
Class 35: Evolution and Physiology of Language [Outline]
The Evolution and Physiology of Language
A. Human language is unique because of it productivity, that is, its ability to produce new signals to represent new ideas.
Consider how the invention of the Internet has forced us to create a whole new set of symbols and ways of conveying meanings.
B. Nonhuman Precursors to Language
1. Common chimpanzees
a. The chimpanzees seldom used the symbols in new original combinations (they are not productive).
b. The chimpanzees used their symbols almost always to make a request, only rarely to describe.
c. The chimpanzees produced requests far better than they seem to understand anyone else's request.
d. They do show a moderate degree of understanding of what is communicated to them, e.g., "who?" questions answered by names; "what?" questions answered by things; and "where?" questions answered by places.
2. Bonobos (Pan paniscus) , a "cousin" of the common chimpanzee, when given language training uses symbols in several ways that more resemble humans than common chimpanzees:
a. They understood more information than they produce.
b. They use symbols to name and describe objects even when they are not requesting them.
c. They request items that they do not see.
d. They occasionally use the symbols to describe past events.
e. They frequently make original, creative requests.
3. The reason for the better language skills in the bonobos than in chimps is unknown.
4. Nonprimates: Alex, African gray parrot (1976-2007)
Alex had relatively extensive language ability with specific objects & concepts
C. How Did Humans Evolve Language?
1. Is Language Just a Product of Overall Intelligence or a Specialized Adaptation? Answer: Probably a Specialized Adaptation
b. Phonological loop, that is, the ability to hear and remember something (remember that this loop is one of the elements in Baddeley's model of working memory).
Gestures involving the face and mouth
c. People with Normal Intelligence but Impaired Language
"KE" Family (a British family of Pakistani origin) & "CS" (an unrelated English boy with same language problem)Conclusion 1: General intelligence is not sufficient for language.
d. People with Intellectual Disability (Low Intelligence) but Relatively Spared Language
Williams syndrome (also known as Williams-Beuren Syndrome) = people with intellectual disability but good language skills. Also musical rhythm ability. Fascination with faces (fusiform gyrus is 2X normal).
A rare disorder (~1 in 20,000 births according to Kalat; ~1 in 8000 live births according to Haas & Reiss, 2012) in which individuals with intellectual impairments have relatively skillful use of language, but limited abilities in other regards. This disorder is caused by a deletion of several genes from chromosome 7.New/Not in book:
Evelina Fedorenko (MGH/Harvard) & Rosemary Varley (UCL, UK; 2016) report that "language and thought are not the same thing" on the basis of multiple neuroimaging studies
- Patients with global aphasia (= have almost no ability to understand or produce language) can still "add/subtract, solve logic problems, thing about other person's thoughts, appreciate music, and successfully navigate their environments" (abstract)
Conclusion 2: Language does not appear to be a by-product of general intelligence or general intellectual activity
2. Is Language a Speciaiization of the Brain?
a. Noam Chomsky and more recently championed by Steven Pinker at Harvard
- language acquisition device (LAD).
- poverty of the stimulus argument
b. A Sensitive ("Critical") Period for Language Learning
- Late vs. Early Second Language Learning
- Deaf children: Early learning of sign language = better use of sign language
- NOT IN BOOK: See, also, the experience of what are called "feral children'
Conclusion 3: There is no language module which automatically causes a person to learn to speak. Rather the predisposing neural structures require social experience in the company of other people in order to develop most appropriately.
3. Language and the "Social Brain" Hypothesis (not in textbook)
a. All language develops within social contexts
b. Robin Dunbar (U Liverpool, UK) and others propose that language developed as a way of helping organize larger and larger social grouping. This "social brain" hypothesis rests upon a variety of observations including two advantages conveyed by language:
- the ability to categorize individuals into distinct types (e.g., doctor, sheriff, chief)
- the ability to instruct other individuals about how they should respond "toward specific types of individuals within society" (Dunban, 1993)
Essentially, language permits societies of much larger size than would be possible otherwise. Such groups, e.g., bands, tribes, etc., have an survival advantage vis-a-vis those who do not have language.
D. Brain Damage and Language
1. Aphasia = Severe language impairment
2a. Broca's Area
2b. Wernicke's Area
3. Broca's aphasia (or nonfluent aphasia): A language impairment whose most prominent symptom is a deficit in language production. Caused by damage to Broca' area and surrounding areas.
Broca's aphasia - Sarah Scott - teenage stroke
4. Wernicke's aphasia or fluent aphasia = difficulty in comprehending the verbal and written communications of others. Although patients can still speak smoothly, their speech content is often nonsensical. They also have anomia (difficulty recalling the names of objects).
Wernicke's aphasia - Retired dentist
1. Dyslexia: Inability to read or significant difficulty with reading despite adequate vision and intelligence.
- Roughly 10-20% of population has a form of dyslexia
- Equally found in males and females
- Strong genetic component (children of dyslexic readers are much more likely to be dyslexic themselves)
- While remediation can help dyslexic readers improve, one does not "outgrow" the condition in adulthood
2. Compared to normal readers, dyslexic readers (both children and adults) show a distinctive pattern of brain functioning in the cortex of the left hemisphere. These include
- Underactivation in Verbal Word Form Area (in the fusiform gyrus of the left occipital-temporal cortex)
- Underactivation in the left temporo-parietal cortex
- Increased activation of the left inferior frontal cortex (including Broca's area)
3. As a rule, a dyslexic person is more likely to have a bilaterally symmetrical cerebral cortex (i.e., the planum temporale and other structures are the same size on the left and right hemisphere).
4. Other problems observed in persons with dyslexia (note that not all dyslexia shows all these problems):
a. Dysphonic dyslexia (dys = poor; phonos = sound) = difficulty sounding out printed words
b. Dyseidetic dyslexia (dys = poor; eidos = image) = difficulty recognizing words as a whole (though can sound them out)
c. Poor auditory memory: difficulty in remembering the sequence of sounds.
d. Dyslexia is a function of attentional differences in which there are problems attending to information directly in front of the reader, that is, dyslexic readers have a fixation point 5 to 10 degrees to the right or left of the word in front of them. Check out the image on the right side.
Try to keep your eye fixated on the dot in the middle while you try to read the letters on either the right or the left of the dot. Individuals with dyslexia often find it easier to do so than those who do not have dyslexia.