The Biological Basis of Language (Acquisition)

LIGN 171

Wednesday, January 17, 2001

Andy Hickl

Where we’re headed…

• Today: – Why humans (think we) are so special…

• Friday: – Why we can’t talk to (or with) the animals…

• Monday:– The neurocognitive basis of language, or

“BRAINS, master, MORE BRAINS”!

• Wednesday:– Summary of Section 2

What do you believe?

Language Acquisition• Linguistic• Domain-Specificity• Structure• Genes/Instinct• Modularity• Specific Capacity

Child Language• Psychological• Domain-Generality• Function• Learning• Experience• Generalized

Intelligence

There’s still something about Human Language

1. All humans seem to acquire language following the roughly the same developmental path.

2. At birth, infants seem to have an infinite capacity to learn any language.

3. Humans can create new languages to communicate with other humans.

4. Language learning seems to be subject to specific critical period effects.

Pidgins and CreolesPidgin: a structurally-simple language that arises when

people who share no common language come into contact.

• Vocabulary is old, but (limited) grammar is new.• Often limited to specific situations, communicative functions, etc.

Examples:• Hawaiian Fish Market Pidgin• Chinese-English Pidgin• Russenorsk

Pidgins and Creoles

Creole:a language that develops when children acquire a pidgin as their native language. (e.g. Swahili, Tok Pisin, Nicaraguan Sign Language…)

• Big boost in grammatical complexity as time goes by, more speakers acquire it…– Grammatical properties of the creole don’t have to

look like either of the “parent” languages.

Language Creation• All creoles share some universal

grammatical properties, regardless of how/when/where they were created.

Where does this come from?1. Something in the human mind/brain/genetic

makeup?

2. Something about the way the new (creole) languages are used communicatively?

3. Something particular about the languages that have often been involved in forming creoles?

Nicaraguan Sign Language

• 1978: First deaf schools in Nicaragua.

• More complexity found with who learned the language at an early age.

Idiosyncratic Signing Systems

Pidgin NSL Fully-formed NSL

How does this happen?(Two familiar views, no?)

Nativist• All humans have an

innate “linguistic bioprogram” or a “core grammar” which allows them to learn or (in some cases) create languages based on the input they receive.

Empiricist• Creoles get to be more

complex grammatically because they are used in a wider variety of communicative situations – these new uses require the language to encode more differences.

Critical Period Effects

Critical Period: the biologically-determined period in which acquisition of a behavior or property must occur to be successful.

• Some environmental input is necessary for development to occur “normally”:– Imprinting in ducks, geese– Photoreceptors in humans

Kids gone WILD!(The cases of feral children…)

• Limited number of children have been found who have developed without exposure to language.

• Victor of Aveyron (19th century France, ???)• Isabelle (1930’s France, 6 years old)

– Normal IQ– Normal (?) use of language as an adult

• Genie (1970’s California, 13 years old)– Abusive situation, likely brain damage– Learned vocabulary, limited (if any) syntax.– Language processed on the right hemisphere, not the left.

No pressure, dudes…(More evidence for the Critical Period Hypothesis)

• Second Language Acquisition:– Younger learners native fluency.– Older learners (>17) never quite make it.

• ASL Acquisition:– Children of Deaf Adults (CODAs) have an

advantage over later-learners of ASL

• Aphasia:– Less chance of recovery of linguistic function after

age 5.

How does this happen?

Nativist• Language modules

are only fully-operational during a specific period of time. After that, a child’s conception of grammar (and language) is relatively fixed.

Empiricist• The CP for learning

language is the time when the child’s cognitive capacity is best attuned to learning the complex systems of grammar.

The tough questions…(Reprised from before…)

1. Why does language acquisition always follow the same developmental path?

2. How can infants learn any natural language?

3. How do humans create new languages in order to communicate?

4. Why should language learning be subject to specific critical period effects?

Why can’t it be both?

Short answer: It probably is.

Longer answer: • The development of language isn’t directly

observable – so we can’t reliably determine what is innate and what is ultimately learned.

• Approaches like nativism and empiricism give us logical extremes to start with…

• But we can do better, can’t we?

Consider this…(New insights that might prove useful…)

• Human infants pay attention to faces and people who are talking.

• Human infants like listening to human speech – and especially speech from their own language.

• Human infants constantly seek new sources of stimulation.• Human infants attach to nurturing figures and environments.• Human infants babble long before they are able to produce

words.

WHY?

What’s my motivation?• Any time we ask why a behavior evolved in the

way that it did, we have to consider 4 different factors:

1. Evolutionary Component• How did the behavior develop?

2. Developmental Component• How does the behavior develop in infants?

3. Mechanistic Component• How does the body perform such a behavior?

4. Functional Component• Why does the individual engage in the behavior?

The Teleological Trap(For catching Teleogies, right?)

• Insects developed wings in order to fly.• Birds fly south in winter because it’s too cold

for them in the north.• Kids babble at 9 months because they’re

getting ready to start speaking.

Teleology:• The notion that a process (like development)

proceeds to achieve a single logical goal.

Teleological Explanations

What’s wrong here?• We can’t say that kids start babbling in order

to get to language any more than we can say that insects decided that wings would be a good idea!

• Kids (like insects) have no idea where the course of development will take them!

So, what can we say?

• Instead of adopting a teleological approach, let’s try a teleonomic one.

Teleonomic: • The notion that a process (like development)

proceeds in a sequence of stages, each of which facilitates or reinforces the next step in the sequence.

• Okay, this is more than a little fuzzy…

A Teleonomic Explanation

BehaviorKid learns mother’s

voice.

Kid recognizes

mother.

Kid figures mother is a

good person to attach to.

Kid is taken care of by mother.

KID LIVES!

Kid isn’t so scared of the

world.

Kid is comfortable

in a nurturing

environment

Kid undergoes fruitful social-

cognitive development.

Kid exposed to plenty of language

stimuli from mother.

KID ACQUIRES

LANGUAGE!

•We can build similar chains of events for most behaviors…

Making Sense…

A teleonomic approach should make some intuitive sense…

• Complex behaviors like language can now be seen as a series of complementary developmental advances.

• Unfortunately, this doesn’t get rid of the nativist/empiricist distinction entirely: we still need to figure out where each individual advance, skill, or module “comes from”…

Hopeful Monsters…

BehaviorKid learns mother’s

voice.

Kid recognizes

mother.

Kid figures mother is a

good person to attach to.

Kid is taken care of by mother.

KID LIVES!

Kid isn’t so scared of the

world.

Kid is comfortable

in a nurturing

environment

Kid undergoes fruitful social-

cognitive development.

Kid exposed to plenty of language

stimuli from mother.

KID ACQUIRES

LANGUAGE!

•Mutation causes a leap “across” the teleonomic chain.

…and Missing Links.

BehaviorKid learns mother’s

voice.

Kid recognizes

mother.

Kid figures mother is a

good person to attach to.

Kid is taken care of by mother.

KID LIVES!

Kid isn’t so scared of the

world.

Kid is comfortable

in a nurturing

environment

Kid undergoes fruitful social-

cognitive development.

Kid exposed to plenty of language

stimuli from mother.

KID ACQUIRES

LANGUAGE!

•Without the acquisition of certain stages no language.

Hopeful Monsters: A big assumption

The hypothesis that a mutation could be the single factor that allows humans (and only humans) to have language is a powerful one…

It presumes that human language may be fundamentally different than any other form of animal communication.

The flip side: Missing Links

Conversely, the hypothesis that animals lack certain cognitive aspects needed to process language forces us into an opposite position:

Human language may not be fundamentally different than the forms of communication employed by animals.

The Answer?

See you Friday!