THE USE OF VERB CONTROL INFORMATION IN SENTENCE PROCESSING IN SPANISH.

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1 THE USE OF VERB CONTROL INFORMATION IN SENTENCE PROCESSING IN SPANISH. Josep Demestre, Jose E. García-Albea Laboratori de Psicologia Universitat Rovira i Virgili INTRODUCTION An empty category (from now on, EC) is a phonologically null syntactic element that fills a node in a phrase-structure tree. ECs create different problems to the sentence processing system: - First, an EC is not physically present in the input string (it is inaudible in speech, and invisible in orthographic input), and therefore its existence has to be inferred indirectly. - Secondly, to interpret correctly an EC, the processor has to associate the EC with an antecedent phrase from which it inherits its features. PRO is one of the ECs postulated by GB Theory (see Chomsky, 98, 986). PRO is a non-overt NP that occurs as the subject of non-finite clauses. The module of the grammar that regulates the occurrence and interpretation of PRO is called control theory. Control theory specifies which element is the coindexed antecedent (or the controller) of PRO. PRO is controlled by (or coindexed with) an antecedent in the next higher clause. In this paper we will present the results of three experiments that investigated the reactivation by PRO of its antecedent in sentences with obligatory control. In these sentences, PRO functions as the subject of an infinitival subordinate clause, and depending on the main verb control properties, PRO is controlled either by the subject or by the object. Consider the sentences below:. Subject Control: Bill promised Helen PRO to buy a new car. i j i, j* 2. Object Control: Bill persuaded Helen PRO to buy a new car. i j j, i* Presented at the IX Conference of the European Society for Cognitive Psychology, Würzburg (Germany). Correspondence and requests for reprints should be adressed to Josep Demestre, Laboratori de Psicologia, Universitat Rovira i Virgili, Ctra. de Valls s/n, Tarragona, SPAIN. jdv@astor.urv.es This work was supported by a DGICYT (Ministry of Science and Education of Spain) grant (FP ) to the fisrt author, and a DGICYT project grant (PB ) to the second author.

2 In these examples we see that the controller must be the subject () or the object (2) of the main clause. Verbs like promise, which impose subject control are called verbs of subject control. Verbs like persuade are verbs of object control. It is commonly assumed that when a referentially-dependent element (such as PRO) is encountered in the input string, the syntactic processor will proceed to coindex that element with its antecedent. The syntactic processor must decide which NP is to be coindexed with PRO. This coindexing decision has to be made with reference to control information, so, at some stage of processing, the syntactic processor has to access verb specific information stored in the mental lexicon. EXPERIMENTAL STUDIES Recent experiments in EC processing have used two different tasks to reveal the predicted reactivation of antecedents. One is probe recognition task (see Bever & McElree, 988; Cloitre & Bever, 988; MacDonald, 989; McElree & Bever, 989) in which a visually presented sentence is followed by the presentation of a single word, and the subject's task is to decide whether or not that word occurred in the sentence. In all cases of interest, the probe is the antecedent of the postulated EC. The other experimental paradigm involves cross-modal priming (CMP) (see García-Albea & Meltzer, 996; Meltzer, 995; Nicol, 988; Nicol, 993). At some point during the presentation of a spoken sentence, a string of letters appears briefly on a screen and the subject's task is either to decide whether the letters constitute a word (lexical decision) or to read the word aloud (naming task). In either case, the target is the antecedent or a word related to the antecedent. Reactivation by an EC of its antecedent should show up as a decrease in reaction time for the antecedent (or for a word related to it). Apparently conflicting results have been obtained from the probe recognition task and the CMP tasks. Probe recognition studies have shown reactivation of antecedents for all GB ECs (WH-traces, NPtraces and PRO) though to somewhat different degrees; the effect for the two traces appears stronger than that for PRO. CMP experiments have shown immediate reactivation of the antecedent for WHtraces, and delayed reactivation (sometimes of a wrong antecedent) for NP-traces and PRO. Osterhout & Nicol (988) (reported in Nicol & Swinney, 989), using CMP, obtained a complex pattern of reactivation by PRO in object control sentences composed of a matrix clause containing two potential antecedents and an infinitival clause. There was no reactivation of either antecedent until 000 ms downstream from the infinitive. At 000 ms there was reactivation of only the most recent noun. It wasn't until 200 ms that there was activation of the appropriate antecedent. At a final probe position, at 500 ms, there was reactivation of only the distant noun. The CMP evidence for PRO is inconclusive. 2

3 The experiments reported in this paper aimed to study the changes in activation levels of potential antecedents for PRO. We wanted to examine the availability of verb control information in identifying and coindexing an EC with its antecedent. If a verb's control properties are available once the verb has been encountered, then we should hypothesize that the parser uses such information in coindexing the null subject of infinitival clauses with an antecedent in the next higher clause. The process of coindexation should be manifested as an increase in the activation level of the antecedent of the EC. Then, for subject control verbs, we should predict an increase in the activation level of the subject once PRO has been encountered; for object control verbs, the reactivated antecedent should be the object of the main clause. PROBE RECOGNITION EXPERIMENTS In the first two experiments a probe recognition task was used to measure the reactivation by PRO of its antecedent. Experiment differed from Experiment 2 in the probe point: while in Experiment the probe was presented after the infinitive+past participle verb, in Experiment 2, it was presented at the end of the sentence. Using different probe points will be useful for examining the time course of coreference processing. All experimental sentences contained a main clause followed by an infinitival complement. The main clause introduced two participants: the subject and the object of the matrix verb. Matrix verbs were either subject control verbs or object control verbs. We had subjects perform a probe recognition task and tested one of two probe words on each trial: the subject or the object of the main clause. EXPERIMENT This experiment measured priming for the antecedents in an early position. If the syntactic processor has early access to control information, and coindexing takes place as soon as the EC has been encountered, then we should obtain facilitation only for the antecedent of PRO. Subject probes should be recognized faster in subject control sentences than in object control sentences. In contrast, object probes should be recognized faster in object control sentences than in subject control sentences. Method Subjects. Subjects were 40 students enrolled in psychology classes at Universitat Rovira i Virgili. Materials and Design. Two independent variables were manipulated. The verb category variable was manipulated at two levels (subject control verb vs. object control verb) by changing the main verb of the sentence. The syntactic role variable had two levels: subject probe and object probe. Example stimuli are presented in Table. 3

4 Twenty-eight pairs of sentences were prepared. Each sentence began with a subject NP, a verb, an object NP, followed by an infinitival complement. In one version, the matrix verb was a subject control verb. In the other version, the verb was an object control verb. The two probe words for the experimental sentences were the subject and the object of the main clause. The number of words intervening between the object and the probe point varied from four to six. We included 84 filler sentences, containing a variety of syntactic constructions. For all experimental sentences, the probes appeared in the sentences. In 56 of the 84 filler sentences the probe did not occur in the sentence. Subject control verb: Object control verb: (Translation: Table : Example stimuli for experiments and 2. El actor le aseguró a la portera del edificio (PRO) haber comprado la comida para la cena del martes 2 El actor le agradeció a la portera del edificio (PRO) haber comprado la comida para la cena del martes 2 Subject probe: ACTOR Object probe: PORTERA The actor assured/thanked the housekeeper of the building to have bought the meal for the dinner) Note: superscripts indicate the probe points for Experiment and 2. Procedure. Each word of the sentence appeared in the center of a computer screen. The display time for each word was a function of its number of characters plus a constant. The constant was 300 ms and the function 6,667 ms per character. Probe words were presented 500 msec just after the offset of the past participle verb. The average length of past participle verbs was 7.5 (from 4 to 0) characters. Then, probes were presented approximately 925 msec ( ) after the offset of the infinitive. Probes appeared in capital letters at the center of the screen and remained on the screen until the subject responded or 4 s elapsed. Subjects responded by pressing one of two response keys. Once the subject had responded, the remaining words of the sentence continued to be presented. Results The means of the subject's average response times and error rates are shown in Table 2. A two-step trimming procedure was employed. First, all responses greater than 2500 ms or less than 50 ms were removed. Next, the mean and standard deviation for response times were calculated, and all responses that were more than 2 SD above or 2 SD below the mean were discarded. Two ANOVAs were performed: one treating subjects as a random factor (F ), and another treating items as a random factor (F ). Separate analyses were performed for mean reaction times and error rates. 2 Reaction time analysis. A 2 (subject control verb vs. object control verb) by 2 (subject probe vs. 4

5 object probe) ANOVA revealed no reliable main effect of verb category, of syntactic role, and no interaction between the two variables. Error analysis. The results revealed a reliable main effect of syntactic role (F (, 39)=2.5, p<0.0; F (, 27)=7.40, p<0.0). Neither the verb category manipulation nor the interaction were 2 significant. Discussion Reaction time analysis shows no clear effect of reactivation for the appropriate antecedent of PRO. Recognition times for the subject probe in subject control sentences (853) are not significantly faster than those in object control sentences (863). The object probe is recognized faster in object control sentences than in subject control sentences, but the difference (5) is not reliable. Reaction times showed a trend for responses to object probes to be faster than responses to subject probes. Participants were more accurate responding to the object probe (97.7 %) than to the subject probe (92.8 %). This result is probably due to the fact that the object was presented more recently than the subject. This advantage for the object, although only reliable in error rates, is in accordance with the results of Osterhout & Nicol (988), who found priming for the most recent noun at 000 msec after the presentation of the infinitive. Remember that in our experiment, although approximately, the probes were presented at the same point. EXPERIMENT 2 The results of Experiment showed no early effect of selective reactivation for the antecedent of PRO. In this second experiment we used the same set of materials, design and procedure as in Experiment, with the only difference that the probes were tested at the end of the sentence. If the system does not have access to verb specific control information until a second stage of processing, then we should expect to find an effect of antecedent reactivation in a latter point of processing. The interval between the presentation of the infinitive and the presentation of the probe was about 920 msec (ranging from 33 msec to 306 msec). Table 2: Mean reaction times and error rates (in %). EXPERIMENT EXPERIMENT 2 SUBJECT OBJECT DIFF SUBJECT OBJECT DIFF SC-VERB 853 (5.7) 849 (2.5) 4 (3.2) 940 (8.9) 956 (5) -6 (3.9) OC-VERB 863 (8.6) 834 (2.) 29 (6.5) 926 (.4) 945 (5.4) -9 (6) DIFF -0 (-2.9) 5 (0.4) 4 (-2.5) (-0.4) 5

6 Method Results Subjects. Subjects were 40 students enrolled in psychology classes at Universitat Rovira i Virgili. The means of the subject's average response times and error rates are shown in Table 2. Reaction time analysis. The analysis revealed the main effect of verb category, the main effect of syntactic role and the interaction were nonsignificant. Error analysis. The results revealed a reliable main effect of syntactic role (F (, 39)=7.8, p=0.0; F (, 27)=5.32, p=0.029). The effect of verb category and the interaction were not reliable. 2 Discussion Analysis of the probe recognition times at the end of the sentence showed that the verb category x syntactic role interaction was not significant. The lack of this interaction shows that no effect of reactivation for the appropriate antecedent is obtained. There was a trend for overall responses to subject probe (933) to be faster than responses to object probes (950.5). This result could be explained by the first-mentioned participant advantage reported by Gernsbacher & Hargreaves (988). Participants were more accurate responding to the object probe (94.8 %) than to the subject probe (89.8 %). Recognition times and error rates are somewhat contradictory. Whereas recognition times analysis showed a trend for responses to subject probes to be faster than to object probes, error analysis revealed more accuracy in responding to object probes. Although the advantage for subjects probes over object probes is not reliable, recognition times pattern alike the data obtained by Osterhout & Nicol (988), which showed priming for the most distant noun at the probe position 500 msec downstream the infinitive. EXPERIMENT 3: CROSS MODAL PRIMING EXPERIMENT In this experiment we used a CMP naming task to assess the salience of antecedents at the point just after the past participle verb. CMP has proven as a useful on-line methodology for studying coreference processing (García-Albea & Meltzer, 996; Meltzer, 995; Nicol, 988; Nicol & Swinney, 989). Method Subjects. Subjects were 56 students enrolled in psychology classes at Universitat Rovira i Virgili. Materials and Design. This experiment manipulated three independent variables: verb category (subject control verb vs. object control verb), syntactic role (subject vs. object), and probe type (identity probe vs. control probe). For each sentence, four corresponding probe words were selected: two 6

7 identity probes, and two control probes. A control probe was selected for each identity probe. Control probes were selected to be like the identity probes in the following respects: number of characters, grammatical gender, frequency of occurrence and the same letter at the onset. 56 sets of eight sentences each were constructed. In addition, we included 64 filler items with different syntactic constructions. Example stimuli are presented in Table 3. Eight experimental lists were formed. Procedure. Sentences were recorded by an adult female native Spanish speaker reading at a normal rate of speech. Subjects were seated before a computer screen which they monitored while listening to a recording through a headset. The subjects were told that their main task was to listen attentively to a series of sentences, and to watch the screen in front of them. At some point during each sentence, a word would flash briefly in the center of the screen; they were to say the word aloud as quickly as they could, while continuing to listen the sentence. After ten practice items, the experiment ran for approximately 30 minutes. Subject control verb: Object control verb: Table 3: Example stimuli for Experiment 3. 3 El actor le aseguró a la portera del edificio haber comprado la comida para la cena del martes 3 El actor le agradeció a la portera del edificio haber comprado la comida para la cena del martes Identity Subject probe: ACTOR Control Subject probe: ARBOL Note: superscripts indicate the probe point for Experiment 3. Identity Object probe: PORTERA Control Object probe: PEINETA Results The means of the subject's average naming times are shown in Table 4. Before analysis, a two-step trimming procedure was employed. First, all responses greater than 2000 ms or less than 50 ms were removed. Next, the mean and standard deviation for response times were calculated, and all responses that were more than 2 SD above or 2 SD below the mean were discarded. The average naming times were submitted to a 2 (verb category) x 2 (syntactic role) x 2 (probe type) repeated measures ANOVA. Subjects (F ) and items (F ) were treated as random factors. The results showed no reliable main effect of verb category. The main effect of syntactic role was only reliable in the item analysis (F (, 55)=.9, p>0.5; F (, 55)=5.29, p=0.025), showing an advantage for the object. The main effect of probe type was reliable (F (, 55)=5.79, p<0.0; F (, 55)=60.53, p<0.0), clearly showing faster naming times for those (identity) probes that appeared in the sentence. The 7

8 interaction between verb category and syntactic role was marginally significant in the item analysis (F (, 55)=.9, p>0.5; F (, 55)=3.76, p=0.058). The interaction between verb category and probe type was marginally significant in both analyses (F (, 55)=3.8, p=0.08; F (, 55)=3., p=0.084). The interaction between syntactic role and probe type was not reliable. The three-way interaction was reliable (F (, 55)=7.6, p=0.008; F (, 55)=6.45, p=0.04). Table 4: Mean naming latencies in msec. SUBJECT OBJECT CONTROL IDENTITY DIFF. CONTROL IDENTITY DIFF. SC-VERB OC-VERB DIFF We performed two separate analyses, one for identity probes and another for control probes. In the analysis with identity probes, the main effect of syntactic role was only reliable in item analysis (F (, 55)=.9, p>0.; F (, 55)=4.4, p<0.05). The analysis performed with control probes revealed a clear 2 interaction between verb category and syntactic role (F (, 55)=7.3, p<0.0; F (, 55)=7.9, p<0.0). Discussion The main effect of syntactic role revealed an advantage for the most recent noun, the object. This result patterns alike the ones found by other researchers (Osterhout & Nicol, 988). The results of this experiment are somewhat surprising since the three-way interaction might arise more because of facilitation acting differentially on form-related control probes than because of facilitation acting differentially on identity probes. Control probes analysis revealed a clear interaction between verb category and syntactic role, arising because of faster response times to control probes that were formally similar to the antecedent of PRO. This pattern of facilitation was unexpected since recent experiments conducted in Spanish (García-Albea & Meltzer, 996; Meltzer, 995) showed inhibition acting on form-related control probes. As can be seen in table 4, the magnitude of priming (control probes - identity probes) was smaller for the subject in subject control verbs (38) and for the object in object control verbs (28), than for the subject in object control verbs (49) and for the object in subject control verbs (6). 8

9 GENERAL DISCUSSION The main goal of the research presented in this paper was to study the changes in activation level for potential antecedents of null subjects in infinitival constructions. The three experiments we have reported investigated the use of control information in coreference processing. Results are far less than clear, in accordance with the results obtained in other experiments studying the processing of PRO (see McElree & Bever, 989; Osterhout & Nicol, 988). The three experiments showed no clear effect of reactivation by PRO of its antecedent at the two probe positions we tested. Probe recognition experiments revealed a different pattern of data at the two probe points. While at the first point the object was more activated than the subject, at the end of the sentence the subject was recognized faster than the object. This pattern of results is somewhat similar to the one reported by Osterhout & Nicol (988). The inclusion of an intermediate probe point would be more informative, and would allow us to study in more detail the time course of coreference processing. A really surprising result was found in the CMP experiment. The magnitude of priming was smaller in the two conditions in which the control probes were form-related to the proper antecedent of PRO, and was due to facilitation to control probes rather than to facilitation to identity probes. These experiments are a first step toward a more detailed research program in empty categories processing. Further research has to be done in order to describe in more detail the complex pattern of reactivation that arises as the result of processing a referentially-dependent element such as PRO. 9

10 REFERENCES Bever, T. G. & McElree, B. (988). Empty categories access their antecedents during comprehension. Linguistic Inquiry, 9, Chomsky, N. (98). Lectures on Government and Binding. Dordrecht: Foris. Chomsky, N. (986). Barriers. Cambridge, MA: MIT Press. Cloitre, M. & Bever, T. G. (988). Linguistic anaphors, levels of representation, and discourse. Language and Cognitive Processes, 3, García-Albea, J. E. & Meltzer, S. G. (996). Processing empty categories in Spanish. In Carreiras, M., García-Albea, J. E., Sebastián, N. (Eds). Language Processing in Spanish. Hillsdale, N.J.:Lawrence Erlbaum Associates. Gernsbacher, M. A. & Hargreaves, D. J. (988). Accessing sentence participants: The advantage of fisrt mention. Journal of Memory and Language, 27, MacDonald, M. C. (989). Priming effects from gaps to antecedents. Language and Cognitive Processes, 4 (), McElree, B. & Bever, T. G. (989). The psychological reality of linguistically defined gaps. Journal of Psycholinguistic Research, 8 (), Meltzer, S. G. (995). Modularity: Evidence from coreference processing is Spanish. Doctoral dissertation. CUNY. Nicol, J. & Swinney, D. (989). The role of structure in coreference assignment during sentence comprehension. Journal of Psycholinguistic Research, 8 (), 5-9. Nicol, J. L. (993). Reconsidering reactivation. In G. T. Altmann & R. Shillcock (Eds). Cognitive models of speech processing: The second Sperlonga Meeting. Hillsdale, NJ: LEA. Nicol, J. L. (988). Coreference processing during sentence comprehension. Unpublished doctoral dissertation, MIT, Cambridge, MA. 0