the biological basis of language the vocal tract the brain

The Biological Basis of Language

•The Vocal Tract•The Brain

Question from the readings.

• Why didn’t the British experts understand that there was a difference?

Evolution

• Evolution does not have a direction or purpose.

• There is no reason that the evolution of the vocal tract and the brain took the forms that they did.

• Things could be otherwise.

Stephen Jay Gould

Wonderful life : the Burgess Shale and the nature of history. New York : W.W. Norton, c1989.

The mismeasure of man. NewYork : Norton, c1981.

The Vocal Tract

• The source-filter theory– What are formants– How is the vocal tract an illustration of the source-filter

theory (what is the source? What is the filter?• How are the vowels /a/, /i/, /u/ produced? • What about consonants?• The segmentation of speech• The organs of speech

The source-filter theory

• What are formants?• How is the vocal tract an illustration of the

source-filter theory (what is the source? What is the filter?

Spectogram

The Filter• The filter is a simple

question of fitting a wave in a tube.

• A formant is the frequency of wave that is reinforced by the filter.

• Length is the primary consideration

• Open and closed tubes function differently.

• The first formant of schwa is the waveform that fits in a 17 cm open tube.

Calculating Schwa

Calculating Schwa

• Frequency: number of cycles (highs and lows per second).

• How long is a given sound wave?– How fast can sound travel in a second– 33,500cm/sec

• How long is a 500 hertz sound?– 33,500 divided by 500 = 67 cm

• What is the open tube filter for a 67cm wave.– 67 divided by 4 = 17 cm.

• What’s so great about 17 cm? Length of human vocal tract.

Schematic of a i u

Formant 1 versus Formant 2

The Vocal Tract

Human versus Chimp Vocal Tract

Consonantscon + sonant

Conclusion

• The source-filter theory explains the operation of the vocal tract.

• The larynx serves as the source• The pharynx and oral cavity and nasal cavity serve

as the filters.• The articulation of the vowels i a u involve gross

movements.• Consonants hang on the vowels.

The Brain

• Brief history of the science and the brain• The modular principle What is it• What are the modular areas of the brain most

relevant to the brain?• Broca’s area• Wernicke’s area• The functioning of language• Implications for Evolution

Brief history of the science and the brain

• Done in the context of Eurocentrism• Presumption of Superiority

– larger brains = more intelligence– adjust for size: change to percentage of

body weight.• Women have a higher ration of brain to

body weight than men.• Hypothesized that women had a lot of air

between the brain and the skull.

The modular principle

• Understood in the 2nd half of the 19th century.• Forgotten in the 1st half of the 20th century.• rediscovered in the 2nd half of the 20th century.• Forgotten in the 1st half of the 21st century???• What is it?• Areas of the brain are specialized for different

functions.

Face Recognition

What are the areas of the brain most relevant to the brain?

Area Damage to Results in

Possible functions

Broca slow degraded speechcomprehension is normal

Syntactic ProductionFunction words, not lexical content

Wernicke’s remarkably fluent, but empty speechloss of understandinganomia and use of circumlocutions

ComprehensionSelection of lexical content

AngularGyrus

Loss of Recognization of Written Characters

Graphic Identification of Words

The Brain and Language

Conclusion

• Both the Brain and the Vocal Tract have evolved to facilitate adult human language.

• This raises many questions. When did it happen?

• Are their behavioral equivalents?– Next lecture.