Language comprehension

Language comprehension

understanding speech

1. differentiating speech sounds from other noises

2. recognizing words3. activating their syntactic and semantic

properties4. building a grammatical structure5. interpreting this structure

building a grammatical structure?

Do we need to do that?

Well, consider this:

Man bites dog. vs. Dog bites man.

… and how about this?

Police kill man with TV tuner.Life means caring for hospital director.Retired priest may marry Springsteen.Kicking baby considered to be healthy.

Brand door kaars geblust.Slingerend in een jeep heeft de politie vrijdagnacht een 45-

jarige Zeisterse staande gehouden.De burgemeester ging na het telefoongesprek met de

officier van dienst naar bed.

upshot

• the intended meaning and the funny meaning do not result from different word meanings or sth.

• rather, they derive from different arrangements of words into word groups (phrases)

• so, structure determines meaning• so, yes, structure building (parsing) is a

necessary component of language comprehension

ambiguity

S

NP

hit

V

He

VP

NP PP

the man with the binoculars

ambiguity

S

NP

hit

V

He

VP

NP

PP

the man with the binoculars

NP

parsing algorithms

• wait-and-see• parallelism• conservative guessing

wait-and-see

• take in words up to a natural boundary (e.g. sentence ending), and then try to arrange them into a structure, following the grammatical rules

• comprehension will arise after a sentence has ended• but: we feel we often know how somebody else’s

sentence will end• and, if a sentence is interrupted, we nonetheless

understand what was said

parallelism

• at any bit of input, create all structures that are compatible with it

• prediction: the competing structural representations for an ambiguous piece of input will all be kept in memory until disambiguating information comes in

• problem: ambiguity is ubiquitous in natural language, and memory is limited

(conservative) guessing

• at any bit of input, attempt to build as much structure as possible

• prediction: mistakes will be made, and retracing (repairing) will occur

incremental parsing

Sentence

subject

He

incremental parsing

Sentence

subject verb phrase

V

He

incremental parsing

Sentence

subject verb phrase

V

He gave

incremental parsing

Sentence

subject verb phrase

V ind.obj. dir.obj.

He gave her

incremental parsing

Sentence

subject verb phrase

V ind.obj. dir.obj

He gave her flowers

incremental parsing

Sentence

subject verb phrase

??? ??? ???

V ind.obj. dir.obj

He gave her flowers to his mother

incremental parsing: repair

Sentence

subject verb phrase

ind.obj.

V dir.obj

He gave her flowers to his mother

herperspro herposspro

1

3

2

initial attachment decisions

• Garden Path Theory:attach incoming words to the evolving structure in the most economic way, I.e., without involving building blocks the necessity of which is unclear.

for example

He hit the man with the binoculars.

The structure in which “the binoculars” is the instrument of “hitting” has one node less than the structure in which it is an attribute of “the man”.

economic

S

NP

hit

V

He

VP

NP PP

the man with the binoculars

less economic

S

NP

hit

V

He

VP

NP

PP

the man with the binoculars

NP

parsing strategies

• minimal attachment• late closure• active filler strategy

ECONOMIZE

the most famous garden path

The horse raced past the barn fell.

Tom Bever, 19..

(The horse that was raced past the barn fell.)

the parser wants to do this:

The horse raced past the barn

S

PPV

VPNP

minimal attachment

…but it has to do this:

The horse raced past the barn

S

PPV

VPNP

fell.

NP S V

non-minimal attachment

how about this?

John said the man will die yesterday.

late closure

another nice one

While she was mending the sockfell off her lap.

what the parser likes: late closure

another nice one

While she was mending the sockfell off her lap.

what the parser has to do: early closure

note: since ‘while’ introduces a subordinate S, the main S is expected anyway: minimal attachment is irrelevant

Keep in mind that …

…the garden path model assumes that structural (syntactic) analysis is prior to, and independent of, semantic and pragmatic interpretation!

Is this correct?

• priority?• autonomy (modularity)?

a note on measurement

• Sometimes a garden path (i.e. parsing difficulty) is consciously noticeable, like in the horse raced example.

• However, language is full of ambiguities, and the majority go by unnoticed.

• So how can we, in such cases, determine whether the sentence processor has a problem?

time

• The answer lies in the assumption that every bit of work the sentence processor does takes some time.

• If the processor is garden-pathed, it will have to retrace and correct its previous decisions, in order to accommodate the incoming words that don’t ‘fit in’.

• This we can measure by the time it takes to process the critical words.

self-paced reading

The ----- ----- --- ------ ---- --- ---- ---.--- quick brown --- ------ ---- --- ---- ---.--- ----- ----- fox ------ ---- --- ---- ---.--- ----- ----- --- jumped over --- ---- ---.--- ----- ----- --- ------ ---- the ---- ---.--- ----- ----- --- ------ ---- --- lazy dog.--- ----- ----- --- ------ ---- --- ---- ---.--- ----- ----- --- ------ ---- --- ---- ---.

self-paced reading

-80

-40

0

40

80

120

160

rel.

pro

Vf-

emb

pre

p

det

adj n

Vf-

mat X Y

Re

sid

ua

l Re

ad

ing

Tim

es

(m

s)

N1 N2

de moeder van de kleuters die zwaaide/en naar de vertrekkende bus vergat …

eye-movement recording

eye-movement recording

eye-movement recording

the priority issue

relative clauses are ambiguous

… in Dutch:Karel hielp de mijnwerker die de man vond.Karel helped the mineworker REL the man found

‘mijnwerker’ and ‘man’ can both be finder and ‘findee’

in other words:“die”, which refers back to “mijnwerker” can be both subject (subject-relative) and object (object-relative)

subject-relative is preferred

1. Karel hielp de mijnwerkers die de man vonden.Karel helped the mineworkers-PL REL the man-SG found-PLplural verb needs plural subject; “die” = subject

2. Karel hielp de mijnwerkers die de man vond.Karel helped the mineworkers-PL REL the man-SG found-SGsing. verb needs sing. subject; “die” = object

• Less errors, shorter reading times, for 1 than for 2

subject-relative is preferred

Explanation:readers want to analyse the relative pronoun (“die”) as the subject of the embedded clause, due to the Active Filler Strategy(I.e., this is the most economic option)if “die” turns out to be the object, the processor has to re-analyze

Frazier 1987

Mak 2001

1. … moeten de inbrekers, die de bewoner beroofd hebben, nog een tijdje op het …

2. … moet de bewoner, die de inbrekers beroofd hebben, nog een tijdje op het …

3. … moeten de inbrekers, die de computer gestolen hebben, nog een tijdje op het …

4. … moet de computer, die de inbrekers gestolen hebben, nog een tijdje op het …

Mak 2001

1. … inbrekers, die de bewoner … hebben …SR; animate - animate

2. … bewoner, die de inbrekers … hebben …OR; animate - animate

3. … inbrekers, die de computer … hebben …SR; animate - inanimate

4. … computer, die de inbrekers … hebben …OR inanimate - animate

350

386

347

336

ms. on aux + 1

summary

• when the two nouns are both animate, SR is faster than OR

• when there is a difference in animacy, the difference in reading time disappears

animacy helps deciding which of the two has to be the subject – immediately

NO REANALYSIS

upshot

• Mak has shown that semantics (the animacy factor) has a very early effect on parsing decisions.

• So it would seem unlikely that semantic interpretation really follows structural analysis.

• Rather, it looks like the two work in tandem.

… but one could argue that the measurements are not sufficiently sensitive…

does this mean that …

… syntactic and semantic analysis are basically the same process?

the independence issue

the brain …

… appears to provide an answer to this question

event-related potentials

N400

negative is up!

P600

positive is down!

upshot

• N400 is specifically sensitive to semantic information

• P600 is specifically sensitive to syntactic information

upshot

• These two components are different in various attributes:– polarity (N vs. P)– latency (400 vs. 600 ms)– distribution over the scalp

• So it would seem that different neural networks generate them

different centers for syntactic and semantic processing

wrap-up

• Classical models of sentence processing assumed that syntactic analysis is prior to and independent of semantic/pragmatic interpretation

• reading-time evidence casts doubt on the priority assumption

• electrophysiological evidence supports the independence (autonomy) assumption