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Ignorance & Inference

by Hochstein, Bale, Fox, and Barner
by

Giselle Guillot Reyes

on 11 December 2014

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Transcript of Ignorance & Inference

Method

Participants:
22 monolingual English 4 year olds
21 monolingual English 5 year olds
recruited by phone or through daycares in San Diego
Procedure and Stimuli:
children sitting in a small table across the experimenter
were given 2 tasks: ignorance implicature task and scalar implicature task
for each they were shown an action figure scene, and a sentence
asked which of the two characters uttered the sentence given
the order was counterbalanced across subjects
Ignorance implicature task:
children were shown two figures: Farmer Brown and Captain Blue
Captain Blue was blindfolded (so he might say funny things or things that are not true)
received 4 warm-up trials and then 10 test trials
On the warm-up trials:
confirm that subjects understood the difference with Captain Blue and Farmer Brown
familiarize them with who uttered the sentence
On the test trials:
placed 2 small objects on the table while a stuffed animal introduced himself, named both items and announced his intention to take something
then took 1 or both objects (e.g. “It’s me, bear! Look, a cup and a plate! Look what I’m taking!”)
subjects were asked who uttered ‘the bear took the plate’ between Captain Blue or Farmer Brown
asked to justify their answer at the end of each trial

Table 1. Ignorance implicature task
Table 2. Scalar implicature task
Scalar implicature task:
resembled ignorance task
subjects attributed the speakers to be smart vs silly instead of knowledgeable vs ignorant
at the beginning of the task the subjects were introduced to two stuffed animals a bear and a cow, and a smart puppet (who always says things that are right) and a silly puppet (who always things that are weird or silly)
4 warm up trials and 8 test trials
a stuffed bear and cow were placed on a table with objects in front of them
facing the subjects, the smart and silly puppets
the subjects were presented with a sentence that described the scene and were asked whether it was the smart or the silly puppet who uttered it

On the warm-up trials:
confirm that they understood the difference between Smart and Silly puppet
familiarize them to who uttered the sentence
if they could interpret the “each” quantifier in the sentences

On the test trials:
items were placed in front of the bear and cow
subjects were presented with a sentence and asked to determine who uttered the sentence (e.g ‘Each animal has an apple or a strawberry.’ Who said that?)
asked to justify their response at the end of each trial

Introduction
"Unlike adults, children as old as 9 years of age fail to infer that a sentence like "
Some of the children slept
" implies the falsity of a stronger utterance like "
All of the children slept
"-an inference known as
scalar implicature
".
Ignorance & inference
Explanations proposed to account for children's failures with scalar implicatures:
domain-general processing limitations
pragmatic deficits
inability to access the relevant alternatives in a lexical scale
This study tests the different explanations by assessing children's ability to compute ignorance implicatures.
*Ignorance implicatures= inferences that require the same processing and pragmatic skills as scalar implicatures but that do not require accessing lexical alternatives.
Scalar Implicature
Communicaton involves making inferences beyond the literal meanings of utterances.
"Mary did some of her homework"
Hearer concludes:
speaker did not know whether true or false
speaker believes the 2nd one is false
Neo-Gricean accounts
Neo-gricean accounts
Scalar Implicature
"Mary did all of her homework"
Listener assumes:
Maxim of Quantity
Maxim of Quality
If speaker believed Mary did all of her homework, if would have uttered:
For example:
"Some of the horses jumped over the log"
Rejected by adults
Accepted by 5-year-old children
Results and Discussion

prefer to ascribe disjunctive statements to the blindfolded puppet when an animal took either one item (Ignorance-1 trials) or two items (Ignorance-2 trials)
were significantly more likely to correctly attribute disjunctive statements involving ignorance implicature to the blindfolded puppet than they were to correctly attribute disjunctive statements involving scalar implicature to the silly puppet

They asked the children to justify their answers following each trial. When asked why they chose the blindfolded doll on Ignorance-1 and Ignorance-2 trials, 5 year olds generally said that it was because:
Captain Blue (the blindfolded doll) could not see
When asked why they chose the smart puppet on the Scalar trials (i.e., the non-adult-like response), the 5 year olds said it was because:
he was smart (54%),
the statement was right (32%),
both animals had both objects (14% – e.g., “because they both do”)

The few who correctly attributed Scalar trials to the silly puppet justified their responses by saying it was because:
he was silly (21.4%),
both animals had both objects (14.3%),
“because he doesn’t know” (14.3%),
the statement was not true (7.1%),
the speaker used the word “or” (14.3%)

The answer to the main question is then yes. Children do acquire the ability to compute ignorance implicatures before scalar implicatures by the age of 5
Their next question was how early children are able to compute ignorance implicature. To answer this, they tested 4 year olds
When asked why they chose the seeing doll on Ignorance-1 and Ignorance-2 trials (i.e., the non-adult-like response), they said it was because:
he could see what was happening (73.9% on Ignorance-1 trials and 76.9% on Ignorance-2 trials),
“because he knew” (4.3% on Ignorance-1 trials),
the blindfolded doll couldn’t see (4.3% on Ignorance-1 trials)

The few who correctly attributed Ignorance-1 and Ignorance-2 trials to the blindfolded doll typically justified their responses by saying that:
“he couldn’t see” (80% on Ignorance-1 trials and 81.8% on Ignorance-1 trials),
that he couldn’t see and “thought that [the bunny] took the plate” (6.7% on Ignorance-1 trials)
that he couldn’t see, “so how would he know which?” (6.7% on Ignorance-1 trials)

When asked why they incorrectly chose the smart puppet on the Scalar trials, the 4 year olds said it was because:
both animals had both objects (42.9% – e.g., “because they both have an apple and a strawberry”),
he was smart (25%),
the utterance was right (7.1%),
he saw it (3.6%)

The few who correctly attributed Scalar trials to the silly puppet justified their responses by saying it was because:
both animals had both objects (50.0%),
he was silly (41.7%)
The results, for the second question, show that most children acquire the ability to compute ignorance implicatures sometime between the ages of 4 and 5


Compared the 4 and 5 year olds
Although 5 year olds clearly compute ignorance implicatures before scalar implicatures
Although only 4 year olds showed no difference between implicature types
The difference between the two age groups was relatively modest
Suggesting that the ability to compute ignorance implicatures emerges between 4 and 5 years of age
The 5 year olds:
The 4 year olds:
The justifications suggest that 5 year olds failed at Scalar trials not because they did not understand the distinction between the smart and silly puppets but because they considered sentences like, “Each animal has an apple or a strawberry” to be acceptable descriptions of scenes in which each animal had both objects
Why do children have difficulty with scalar implicature?
3 broad classes of explanation:
Pragmatic in nature
(children master the pragmatics of scalar terms "some/all" very late in development....they initially treat "some" as acceptable whenever "all" is true.
Not pragmatic in nature but instead :
*stem from difficulty accessing/manipulating linguistic knowledge

More on non-pragmatic:
Barner et al. supporting this idea:

children have difficulty activating "some" and "all" as scale mates even when the sentence does not involve pragmatic inference.

they have little difficulty with equivalent utterances that have contextually defined scales (they are readily accessible alternatives unlike Horn Scales)
Children were shown 3 animals sleeping.

Are only some of the animals sleeping?
YES
(literally false)
Are only the cat and the dog sleeping?
NO
*Based on this evidence, Barner et al. concluded that their failure with ONLY SOME = inability to access ALL as a scale mate of SOME.
Studies
The evidence so far is not conclusive
Problematic previous findings:
purely pragmatic limit
: problematic
--> children exhibit sensitivity to speaker knowledge much earlier in development.
-->children compute highly pragmatic inferences by 2 years old
focus on processing limits: problematic
-->don't actually test children's processing capacity

Evidence
5 year olds can reason about speaker knowledge/informativeness but difficult to explain deficit w/ scalar implicatures.
GENERAL DISCUSSION
Results are consistent with hypothesis
In this experiment, 5 year-olds successfully computed ignorance implicatures despite failing to compute scalar implicatures.
4 year-olds failed at both types of implicature
so children learn to compute ignorance implicatures between 4&5 years old
Katsos & Bishop argued that children fail at pragmatic tasks whenever they are binary
if this were true.. children would have failed the Ignorance Implicature task as well (since both were binary tasks)

Difficulties accessing alternatives
can lead to children's difficulties with scalar implicature. 2 possible ways:

1-lexical alternatives are generated differently for ignorance & scalar implicature

2-children have a general difficulty accessing Horn Scale alternatives but can successfully access these alternatives when they are made noticeable/important in context.
Children accepted underinformative statements when scalar implicature but not when involving ignorance implicature..difficult to explain on the pragmatic tolerance hypothesis.
Formal alternatives
"some", "all"=formal alternatives which belong to common substitution classes (Horn Scales)

Computing a scalar inference involves :
generating relevant alternative statements to an utterance via Horn Scales
negating the stronger alternatives
In this study...
investigated the nature of children's delay with scalar implicature by :
focus on children's ability to compute Gricean epistemic inferences

argument: the cause of children's delay with scalar implicature cannot be epistemic in nature
therefore, 2 possibilities:
-due to deficits in general capacity
-problems accessing the specific alternatives that are required to compute scalar implicature
caused by a difficulty accessing Horn Scales/failure to represent relevant alternatives as members of Horn Scales
*either lack of knowledge on which items constitute Horn Scales or knowledge of the r/ship b/w scalar items is weak in early development
In this study :
tested the nature of children's difficulty with scalar implicature by assessing their ability to compute both scalar implicatures and ignorance implicatures.
Results make it unlikely that children's difficulties stem from a deficit in Gricean epistemic reasoning.

...based on this, they discuss other possible accounts of children's difficulty with scalar implicature
.
Their main question was whether, at any point in development, children exhibit evidence of computing ignorance implicatures before scalar implicatures or vice versa
They initially only tested 5 year olds who are known to fail with scalar implicatures and have acquired relevant theory of mind capacities
They subsequently tested 4 year olds using the same methods, to determine the age at which ignorance implicatures are first computed for disjunction
They analyzed the 5 year olds first then the 4 year olds and compared the performance across these age groups

When 5 year olds incorrectly attributed Ignorance-1 and Ignorance-2 trials to the seeing doll they typically justified their responses by saying that:
“he could see”
Why did they choose the smart puppet?
Why did they choose the seeing doll?
Full transcript