last updated:

May 02, 2021

[Brain Image]    

PSY 340 Brain and Behavior

Class 35: Evolution and Physiology of Language


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.

Internet Abbreviations  emojis

B.  Nonhuman Precursors to Language

[Chimpanzee]1.  Common chimpanzees can not learn to talk, but can learn some language skills using American Sign Language or other visual systems. Their use of language-related symbols differ from human language in many ways:

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.

[Bonobo]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) 

Trained by Dr. Irene Pepperberg (originally U Arizona, now affiliated with Brandeis U-Harvard-visiting @ MIT Media Lab) from age 1. Alex died unexpectedly Sept 6, 2007 of heart disease.
Alex had relatively extensive language ability with specific objects & concepts:[Alex the Parrot &
                Irene Pepperberg]
  • Alex "could identify fifty different objects and recognize quantities up to six; that he could distinguish seven colors and five shapes, and understand the concepts of "bigger", "smaller", "same", and "different," and that he was learning "over" and "under".
  • Alex had a vocabulary of about 150 words, but was exceptional in that he appeared to have understanding of what he said. For example, when Alex was shown an object and was asked about its shape, color, or material, he could label it correctly. If asked the difference between two objects, he also answered that, but if there was no difference between the objects, he said “none.”" (Wikipedia, retrieved April 21, 2008)
Pepperberg offers an evolutionary explanation for intelligence (which, presumably, is the basis of language) by citing the examples of both apes and parrots who live to become 30 to 60 years old:

"Nick Humphrey suggested these ideas almost 30 years ago:... given a long-lived creature that exists in a complex socio-ecological system, that creature has likely been selected for high-level intelligence and cognition. I think those same evolutionary pressures work on parrots." ("That damned bird," 2003)

C.  How Did Humans Evolve Language?

  1.  Is Language Just a Product of Overall Intelligence or a Specialized Adaptation? Answer: Probably a Specialized Adaptation

a. The relationship between brain and brain-to-body ratio is unclear (see chart below or click here for larger image). Human beings do not have the largest brain-to-body mass ratio: dolphins, elephants, and blue whales do. Yet these animals do no use language in ways that are parallel to human beings.

Brain Body Ratio

b. The evolution of language seems to require a brain mechanism called the 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).

Language also seems to depend upon gestures, particularly those gestures involving the face and mouth. When we listen to others in noisy settings, we pay particular attention to the face and mouth of the other speaker in order to understand what they are saying.

[KE Family
            Tree]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)

Presumably because of an altered dominant gene (FOXP2 ["“forkhead box P2”"] segment on chromosome 7), 16 of 30 people of normal intelligence within one family (& "CS") have severe difficulty with pronunciation, and all other aspects of language. Cases such as this suggest that genetic conditions which affect brain development can impair language without impacting other aspects of intelligence. (Itzhaki, 2003; Liegeois et al., 2003; MacAndrew, 2003).

==> 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).

Williams Person   Williams Syndrome FFA 

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. 

Pascual-Castroviejo et al. (2004) summarized other characteristic symptoms:

New/Not in book:

          FedorenkoEvelina 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
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?

Noam Chomsky @
              2017 APA Washington DCa.  First proposed by MIT linguistics scholar, Noam Chomsky and more recently championed by Steven Pinker at Harvard, an alternate view of the evolution of language is that language evolved as an extra brain module, called a language acquisition device (LAD).  This idea is supported by the fact that children learn language with amazing ease and that children learn language despite the fact they do not hear enough examples to learn the grammatical structure of language (this is called the poverty of the stimulus argument).

b. A Sensitive Period for Language Learning

Argument: Language has a critical period, because if you don't learn language when you are young, you will forever be language disadvantaged.

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. [Robin
              Dunbar]Without rejecting the LAD theory above, we should note that language always arises within a social context and depends upon social interaction for its development (a corollary of the "critical period" observation). A purely biological explanation for the emergence of language is unlikely. Vasanta (2005) states this caution by claiming:

"...syntax-centered definitions of language knowledge [such as the LAD theory] completely ignore certain crucial aspects of language learning and use, namely, that language is embedded in a social context; that the role of environmental triggering as a learning mechanism is grossly underestimated; that a considerable extent of visuo-spatial information accompanies speech in day-to-day communication; that the developmental process itself lies at the heart of knowledge acquisition; and that there is a tremendous variation in the orthographic systems associated with different languages." (Abstract)

b. Contrary to the theory of the evolution of general intelligence, 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: Small part of the frontal lobe of the left cerebral cortex that when damaged leads to impairments in language production.

  2b. Wernicke's Area

Binder 2017      Aphasias

  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.

a. Patients suffering from Broca's aphasia often speak meaningfully, but omit pronouns, prepositions, conjunctions, and qualifiers from their own speech; they also have trouble understanding these same kinds of words. Other more seriously impaired individuals have significant difficulty forming the words themselves and will slur or otherwise produce difficult to understand language.

YouTube:   Broca's aphasia - Sarah Scott - teenage stroke

  4. Wernicke's aphasia or fluent aphasia involves a 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). Note above the damage causing this may have nothing to do with "Wernicke's Area"

YouTube:Wernicke's aphasia - Retired dentist

  5. Language requires the activation of many different areas other than the frontal cortex (Broca's area and surrounding regions) and the temporal cortex.

     E. Dyslexia

1. Dyslexia: Inability to read or significant difficulty with reading despite adequate vision and intelligence.  Many kinds of dyslexia exist with different underlying causes. This is also a topic which has caused a great deal of argumentation and struggle among researchers, teachers, parents, and students for many decades.

              brain2. D'Mello & Gabrieli (2018) summarize the key findings from fMRI and other studies. These suggest that individuals with dyslexia show....

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 individuals with 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)

Fixation Dyslexia Readingc. Poor auditory memory: difficulty in remembering the sequence of sounds. Suggests that there may be a problem involving the connection between the visual and auditory processing areas of the brain.

c. 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.


Binder, J. R. (2017). Current controversies on Wernicke’s Area and its role in language. Current Neurology and Neuroscience Reports, 17, 58. https://doi.org/10.1007/s11910-017-0764-8

DeWitt, I., & Rauschecker, J. P. (2012) Phoneme and word recognition in the auditory ventral stream. PNAS. https://doi.org/10.1073/pnas.1113427109

D'Mello, A. M., & Gabrieli, J. D. E. (2019). Cognitive neuroscience of dyslexia. Language, Speech, and Hearing Services in Schools, 49, 798-809. doi: 10.1044/2018_LSHSS-DYSLC-18-0020

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Dunbar, R. I. M. (1998). The social brain hypothesis. Evolutionary Anthropology, 6, 178-190. [pdf version]

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NINDS Dyslexia Information Page (2005, February). Bethesda, MD: National Institute of Neurological Disorders and Stroke (NINDS). Downloaded from the NINDS Web site: http://www.ninds.nih.gov/disorders/dyslexia/dyslexia.htm

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Temple, E., Deutsch, G. K., Poldrack, R. A., Miller, S. L., Tallal, P., Merzenich, M. M., Gabrieli, J. D. E. (2003). Neural deficits in children with dyslexia ameliorated by behavioral remediation: Evidence from functional MRI. Proceedings of the National Academy of Sciences of the United States of America, 100(5), 2860-2865. [PubMed Abstract] [Full-text]

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This page was first posted April 24, 2005