Exp 2

Language understanding & common sense reasoningJoshua K Hartshorne • Tobias Gerstenberg • Timothy J. O’Donnell • Joshua B. Tenenbaum

Massachusetts Institute of Technology

MotivationLanguage is massively ambiguous. Interpretation often requires world knowledge & common sense reasoning.

How and why is common sense recruited?

••

Simulate: A beat B and A was strong. If A had not!been strong, would A have beaten B? If not, A’s !strength caused A to beat B.

Details & Intuitions

Framework

message

world speaker’s!experience

speaker’s!knowledge

speaker’s!intentions

utterance

linguistic!knowledge

Goal is to recover information about world. Literal meaning is an intermediate stage. Prior beliefs about world plays key role.

listener

Winograd Schema

(Winograd, 1973)

The city council denied the protesters a !permit because they feared violence.The city council denied the protesters a !permit because they advocated violence.

• Require common sense • Easy to generate • Easy to score

Properties:

(cf Levesque, 2011)

message P(utterance|message)…because the city council feared violence

P(message)

…because the protesters feared violence…because the Red Sox feared violence…because the Dutch feared violence

…

likelylikely

unlikelyunlikely

…

likelyunlikely

very unlikelyvery unlikely

…Note: Current focus is on messages achieved from different interpretations of pronoun.

Conclusions & Future Directions

P(message|utterance) α P(utterance|message) * P(message)Factorization:

Find most likely message!given utterance

need model of world!(& speaker)

Exp 1

P(message) estimated by TurkersExp 1a

A scared B because he jumped out from behind something.

utterance (80 total):

Turkers asked:How likely is it that {A/B} jumping out from behind something would cause A to scare B?

-2 -1 0 1 2model

-5

-4

-3

-2

-1

0

1

2

3

4

5

Hum

an J

udgm

ents

log-odds he = A

model

hum

ans

r=.88

Utterance:The city council denied the protesters a permit because they feared violence.

Rarely use pronouns!to refer to new entities

Exp 1b

Because A scared B, he screamed.

utterance (80 total):

Turkers asked:How likely is it that A scaring B would cause {A/B] to scream?

-2 -1 0 1 2model

-5

-4

-3

-2

-1

0

1

2

3

4

5

Hum

an J

udgm

ents

log-odds he = A

model

hum

ans

r=.73

averageweak strong

strength

BA

B’B’B’

B’

B’

P(message) calculated via simulation over intuitive theoryA B

16 sentences!A {almost/-} {beat/lost to} B in tug-of-war {because/although}!he is {strong/weak}.

A beat B in tug-of-war because he is strong.

Note: Assume counterfactual semantics for “because”. p because q = p and q and (without q, no p). Determine probability by simulation over an intuitive model of tug-of-war (top-right).

Possible messages:! … because A is strong.! … because B is strong.! etc.

averageweak strong

strength

A

B A’A’A’

A’

A’

Simplifying Assumption:

-3 -2 -1 0 1 2 3

-2-1

01

23

log-odds he = A

model-3 -2 -1 0 +1 +2 +3

-2-1

0+1

+2+3

hum

ans

••

• ••••••••••••• r=.92

3 4 5 6 7

3040

5060

7080

B’s strength

model

hum

ans

r=.96•••••••• ••

••••••3 4 5 6 7

2030

4050

6070

80

A’s strength

model

hum

ans

r=.98•••••••• ••••••

••

Simplifications:! Stronger person always wins.! Prototype / soft threshold ! semantics for scalar adjectives.

••

Language comprehension as inference over intuitive model of the speaker explains how common sense affects language processing.

•

Limited need for theory of pronouns per se.•• Can derive pronoun biases (ask me).Productive paradigm for test theories of knowledge (e.g. reasoning about tug-of-war) and semantics (e.g., because=counterfactual).

•

Note: No notion of informativity (yet).

pdf: joshuakhartshorne.org/publications.html