Learning When (and When Not) to Omit Objects in English: The Role of Verb Semantic Selectivity Tamara Nicol Medina IRCS, University of Pennsylvania Collaborators: Barbara Landau, Johns Hopkins University Philip Resnik, University of Maryland

The (Indefinite) Implicit Object Construction (in English) John is eating John is reading Verb selects for an object, but none is overtly specified. Interpretation is of an indefinite and non- specific object. (something / some food). (something / written material). * John is reading (War and Peace). Grammaticality varies across verbs. * John is pushing. * John is opening. Verb Semantic Selectivity

Overview 1. Measures of Verb Semantic Selectivity Selectional Preference Strength (Resnik, 1996) Object Similarity 2. Children’s knowledge of Verb Semantic Selectivity 3. Implicit objects in spontaneous speech Young child Mother

Verb Semantic Selectivity The omitted object tends to be recoverable from the verb. John is eating (some food) / drinking (a beverage) / singing (a song). Verbs that select for a wide variety of semantic complements, and therefore there is no one recoverable interpretation, tend to resist implicit objects. John is bringing *(something) / making *(something) / hanging *(something). Indefinite implicit objects are allowed to the extent that they are recoverable.

Selectional Preference Strength (SPS) (Resnik, 1996) Don’t push your brother. Move that chair. Do you want an apple? “like” Tony likes that girl. I don’t like this couch. I really like bananas. “eat” Eat your lunch. He’s eating cereal. She always eats avocados. An information-theoretic model of verbs’ strength of semantic preferences. Calculates the strength of a verb’s selection for the semantic argument classes from which its complements (or objects) are drawn. For all argument classes (c), PRIOR, Pr(c) – the overall distribution of argument classes POSTERIOR, Pr(c|v i ) – the distribution of argument classes, given a particular verb The greater the difference between Pr(c) and Pr(c|v i ), the higher SPS will be. (Argument classes were those listed in WordNet.)

SPS and Implicit Objects Relative SPS is correlated with the relative frequency of an implicit object. Brown corpus of American English ( Francis and Kučera, 1982 ) SPS % Implicit Objects SPS r = 0.48, p < 0.05

Object Similarity A psychological measure of the semantic selectivity of a verb for its objects. Calculated as the average of similarity judgments given for pairs of objects that occur with a verb. “cereal”“bacon”4 “clothes”“shirt”5 “juice”“ladybug”1 “a pencil”“a summer toy”1 EAT PACK BRING WANT Similarity judgments made over the actual complements, not the argument classes.

Children’s Knowledge of Verbs’ Semantic Selectivity Does children’s knowledge of verbs’ semantic selectional preferences correspond to their mothers’? Comprehension: Accurate interpretation of omitted object Production: Appropriate restriction of omitted objects

Children’s Knowledge of Verbs’ Semantic Selectivity Subjects Children 2;6-3;0 yrs, n=20 3;6-4;0 yrs, n=20 Mothers earlier period, n=10 later period, n=10 Stimuli 30 verbs from Resnik (1996)

Children’s Knowledge of Verbs’ Semantic Selectivity Procedure Children Question and answer game with puppet: “What are some things you (could)… eat / bring / catch / etc. ?” 15 verbs per child 3 responses per verb Stickers as reward Mothers Take home questionnaire Instructed to “use the kind of words you would use in conversation with your child”.

SPS and OS: Comparable Measures Mothers of Older Children r = 0.72, p < 0.05  Correlated.  Some high, some low, some in-between.

SPS and OS: Comparable Measures Mothers of Younger Children r = 0.60, p < 0.05  Correlated.  Some high, some low, some in-between.

Older Children and Mothers SPS r = 0.79, p < 0.05 t(1,29) = -2.39, p < 0.05 OS r = 0.67, p < 0.05 t(1,29) = -2.38, p < 0.05 Correlated, but older children’s SPS and OS are lower (broader semantic selectivity).

Younger Children and Mothers SPS r = 0.75, p < 0.05 t(1,29) = -3.69, p < 0.05 OS r = 0.67, p < 0.05 t(1,29) = -2.33, p < 0.05 Correlated, but younger children’s SPS and OS are lower (broader semantic selectivity).

Younger and Older Children SPS r = 0.85, p < 0.05 t(1,29) = 1.27, p > 0.05 OS r = 0.74, p < 0.05 t(1,29) = -0.41, p > 0.05 Correlated. Younger children’s SPS and OS are NOT lower than older children’s (equivalent semantic selectivity).

Summary and Discussion Correlations between children’s and mothers’ SPS/OS: Verbs that are higher in SPS/OS for mothers are also higher in SPS/OS for children. - Could recover meaning of implicit objects - Could notice that only the high SPS/OS verbs occur with implicit objects At both age periods, children’s SPS/OS is lower overall than their mothers’. Does this really mean that children’s selection of semantic arguments is broader than their mothers’? - Maybe - Could be children’s approach to the task

Implicit Objects in Spontaneous Speech Does the use of indefinite implicit objects correspond to Verb Semantic Selectivity… In child-directed speech? In the child’s own productions?

Implicit Objects in Spontaneous Speech Corpus Sarah corpus (Brown, 1973), set of 29 verbs Sarah 2;6-3;0 yrs, 455 utterances 3;6-4;0 yrs, 559 utterances Sarah’s Mother earlier period, 836 utterances later period, 706 utterances

Children’s Knowledge of Verbs’ Semantic Selectivity Coding Presence or absence of complement Definite Implicit Object = referrent available in previous 4-5 utterances and/or physically present Indefinite Implicit Object = referrent NOT available in previous 4-5 utterances and/or physically present Grammaticality Presence of absence of subject Measures SPS / OS from Elicited Objects Task

Rate of Indefinite Implicit Objects 7.5% (n = 34) 11 verbs 71% grammatical 4.5% (n = 38) 7 verbs 100% grammatical * 4.8% (n = 27) 9 verbs 81% grammatical 3.4% (n = 24) 6 verbs 100% grammatical

Possible Reasons for Object Omission Verb Semantic Selectivity “Matching” the input Memory overload

Indefinite Implicit Objects and Verb Semantic Selectivity Does the rate of indefinite implicit objects increase as a function of SPS/OS? Linear Regression – Does one continuous variable (SPS/OS) predict another (rate of implicit objects)? F(1,23) = 0.33, p > 0.05 F(1,23) = 0.88, p > 0.05 Sarah’s Mother: Older Age Period

Indefinite Implicit Objects and Verb Semantic Selectivity Does the rate of indefinite implicit objects increase as a function of SPS/OS? Linear Regression – Does one continuous variable (SPS/OS) predict another (rate of implicit objects)? F(1,23) = 3.04, p > 0.05 F(1,23) = 3.62, p > 0.05 Sarah’s Mother: Younger Age Period

Indefinite Implicit Objects and Verb Semantic Selectivity Does the rate of indefinite implicit objects increase as a function of SPS/OS? Linear Regression – Does one continuous variable (SPS/OS) predict another (rate of implicit objects)? F(1,23) = 3.06, p > 0.05 F(1,23) = 3.62, p > 0.05 Sarah: Older Age Period

Indefinite Implicit Objects and Verb Semantic Selectivity Does the rate of indefinite implicit objects increase as a function of SPS/OS? Linear Regression – Does one continuous variable (SPS/OS) predict another (rate of implicit objects)? F(1,23) = 3.49, p > 0.05 F(1,23) = 8.23, p < 0.05 Sarah: Younger Age Period

Indefinite Implicit Objects and Verb Semantic Selectivity Does the rate of indefinite implicit objects increase as a function of SPS/OS? No. (Except for Sarah with regard to OS during the younger age period.)

Indefinite Implicit Objects and Verb Semantic Selectivity Is a verb more likely to occur with an implicit object given higher SPS/OS? Logistic Regression – Does one continuous variable (SPS/OS) predict a binary variable (whether a verb ever occurred with an implicit object)?  2 = 2.24, p < 0.05 Sarah’s Mother: Older Age Period  2 = 4.38, p < 0.05

Indefinite Implicit Objects and Verb Semantic Selectivity Is a verb more likely to occur with an implicit object given higher SPS/OS? Logistic Regression – Does one continuous variable (SPS/OS) predict a binary variable (whether a verb ever occurred with an implicit object)?  2 = 7.19, p < 0.05 Sarah’s Mother: Younger Age Period  2 = 8.10, p < 0.05

Indefinite Implicit Objects and Verb Semantic Selectivity Is a verb more likely to occur with an implicit object given higher SPS/OS? Logistic Regression – Does one continuous variable (SPS/OS) predict a binary variable (whether a verb ever occurred with an implicit object)?  2 = 3.14, p = 0.07 Sarah: Older Age Period  2 = 2.51, p = 0.11

Indefinite Implicit Objects and Verb Semantic Selectivity Is a verb more likely to occur with an implicit object given higher SPS/OS? Logistic Regression – Does one continuous variable (SPS/OS) predict a binary variable (whether a verb ever occurred with an implicit object)?  2 = 0.39, p > 0.05 Sarah: Younger Age Period  2 = 0.06, p > 0.05

Indefinite Implicit Objects and Verb Semantic Selectivity Is a verb more likely to occur with an implicit object given higher SPS/OS? Yes, for Sarah’s mother. No, for Sarah. But there appears to be improvement by the older age period.

Verbs Used with Implicit Objects Does Sarah use implicit objects with the same verbs as her mother? 6 verbs % 5 verbs % 5 verbs 11.1 – 50.% 4 verbs 6.3 – 33% 37%3.4%34%9.8%

A Performance Explanation? Could memory overload be contributing to Sarah’s higher rate of indefinite implicit objects at the younger age period? 23 implicit objects (7.1%)11 implicit objects (8.4%)  2 = 0.23, p > 0.05

Review of Findings: Verb Semantic Selectivity At both age periods, children’s verb semantic selectivity appeared somewhat broader than their mothers’. –May be due to the nature of the task. Even so, verbs that are high/low in SPS/OS for mothers were similarly high/low for children. –Comprehend indefinite implicit objects in the child-directed input. –Recognize the systematicity with which implicit objects occur in the child-directed input.

Review of Findings: Indefinite Implicit Objects Sarah’s Mother Higher SPS/OS predicted which verbs she used indefinite implicit objects with. –Did not use a higher rate of implicit objects as a function of increasing SPS/OS. Sarah Higher SPS/OS did not predict which verbs she used implicit objects with. –However, she appears to be getting closer by the older age period. Used implicit objects with some verbs that her mother did not. –However, at both age periods, the majority of her implicit objects are with the same verbs her mother used with implicit objects. Not due to memory overload.

Discussion Not a conservative start. –Child doesn’t wait to hear which verbs occur with implicit objects, and then start dropping with these verbs herself. How will she arrive at the adult target grammar? –By paying attention to the relationship between a verb’s SPS/OS and whether it occurs with an overt or implicit indefinite object.  Younger age period: Mother used 18 overt indefinite objects with 5 low SPS/OS verbs.  Older age period: Mother used 7 overt indefinite objects with 7 low SPS/OS verbs. –Adjust parameters of grammar to result in overt objects for low SPS/OS verbs.

Selectional Preference Strength (SPS) (Resnik, 1996)