We describe an experiment to test the view that structural focusing and thematic role focusing are distinct. Subjects were presented >Mth 2-clause sentences containing because or so The first clause introduced two individuals occupying the thematic roles Goal and Source, while the subject of the second was either a pronoun or repeated name. Results showed that reading times for the second clause were facilitated when the pronomis referred to the Goal rather than Source, particularly when the clauses were connected b> so. This facilitation occurred regardless of the surface position of the Goal and regardless of tlie type of anaphor, pronoun or repeated name. With pronouns, facilitation also occurred when the antecedent was in the first position in its clause, but onh when the antecedent was the Source. With Repeated Names, reading times were slowed when the antecedent was in the first position, regardless of its thematic role. These findings suggest that there are two foci in an utterance, one containing the first noun phrase in the utterance and the other containing the preferred thematic role. W e suggest that the focus based on initial mention corresponds to the forward lookmg center described by Grosz et al. (1963) and that the focus based on thematic roles is part of the global focus (Grosz and Sidner, 1986). W e also discuss the implications of our results for Sanford and Garrod's (1981) scenario mapping model.

We distinguish between instance learning and rule learning (e.g. Shanks & St. John, 1994). Instance learning involves memorizing learning mstances while rule learning involves the abstraction of an underlying rule. Instance learning and rule learning can be explained by a dual space model of leammg (Klahr & Dunbar, 1988; Simon & Lea, 1974). In relation to Simon and Lea's model, instance learning can be said to occur in instance space while rule learning makes use of both instance space and hypothesis space. We describe an experiment to test the view that whether instance learning or rule learning occurs depends on the learning goal and on whether or not the subjects explain what they are doing. Subjects were asked to learn a dynamic computer control task guided by either a specific or a non-specific goal. During learning, subjects also carried out a secondary task. They either described what they were doing during learning or explained what they were doing. We predicted that giving descriptions would favour instance learning and prevent rule learning irrespective of the learning goal, since giving descriptions forces subjects to focus on the task itself. Giving explanations should favour rule learning when subjects are given a non-specific goal, since both the non-specific goal and giving explanations focus on the reasons for the computer's behaviour. Giving explanations should not lead to rule learning when subjects have a specific goal since the specific goal forces subjects to focus on a search of instance space and to neglect the hypothesis space. The results confirmed these predictions. They support the view that goal specificity guides learning by directing attention to either instance space or both instance space and rule space, and that giving explanations encourages the revision of hypotheses in the light of the evidence.

The aim of this study was to distinguish between two heuristic strategies proposed to account for the assignment of ambiguous pronouns: a subject assignment strategy and a parallel function strategy. According to the subject assignment strategy a pronoun is assigned to a preceding subject noun phrase, whereas according to the parallel function strategy a pronoun is assigned to a previous noun phrase with the same grammatical function. These two strategies were tested by examining the interpretation of ambiguous subject and non-subject pronouns. There was a strong preference for assigning both types of pronouns to preceding subject noun phrases which supported the subject assignment strategy. However the preference was reduced for non-subject pronouns compared to subject pronouns which we interpreted as evidence for grammatical parallelism. A subsidiary aim of the study was to investigate text-level effects of order-of-mention where a pronoun is assigned to a noun phrase which has been mentioned in the szmne sequential position. We did not observe any strong effects although we did observe a possible topic assignment strategy where topic-hood depended on order-ofmention. A post hoc inspection of the materials revealed possible effects of intra-sentential order-of-mention parallelism. We conclude that a subject assignment strategy, a parallel grammatical function strategy, a topic assignment strategy and a parallel order-of-mention strategy m a y all constrain the interpretation of ambiguous subject and non-subject pronouns.

The aim of this study was to distinguish bet- ween three heuristic strategies proposed to ac- count for the assignment of ambiguous prono- uns: a subject assignment strategy, a paral- lel function strategy and a pwallel order-of- mention strategy. According to the subject assignment strategy a pronoun is assigned to a preceding subject noun phrase. A parallel function strategy predicts that a pronoun will be assigned to a noun phrase with a peirallel grzunmatical function whereas a parallel order strategy predicts that a pronoun will be a as- signed to a noun phrase in a parallel position in a previous clause. These strategies were te- sted by examining the interpretation of ambi- guous subject and non-subject pronouns. T h e results showed a bias to assign a pronoun to a preceding subject, suggesting the operation of a subject assignment strategy. However, this bias was reversed for non-subject pronouns. These pronouns showed a bias to preceding non-subjects with parallel grammatical roles, thus supporting a parallel function hypothe- sis. Finally, the subject assignment bias was reduced w h e n a non-subject pronoun had a dif- ferent grammaticaJ role from the non-subject antecedent, thus supporting a parallel order-of- mention strategy. W e conclude that all three strategies m a y constrain the assignment of am- biguous pronouns.

Two experiments tested the view that thematic roie information triggers the rapid retrieval of general knowledge in pronoun comprehension. Pairs of thematic roles were contrasted as antecedents of a subsequent pronoun. The results showed that intepretation of the pronoun depended on the thematic role of the antecedent. Experiment one measured reading rates for the clause which contained the pronoun. Rates were faster when the antecedent was an Agent subject, a Patient object, a Goal, or an Experiencer. Rates were slower when the antecedent was an Agent object, a Patient subject, a Source, or a Stimulus. Experiment two required subjects to write completions to sentence fragments such as Jill like Sue and she and the number of references to each antecedent was recorded. The results confirmed the findings from Experiment one, although there was also an antecedent position effect (first vs. second mention) in some of the sentences. We suggest that these results are consistent with the view that thematic role information triggers the retrieval of canonical events in the real world, and may thus be responsible for the rapid retrieval of general knowledge in language comprehension.

We describe an experiment that examines observational learning of either rules or instances. Subjects were asked to learn a dynamic computer control task and were given either a specific goal, to make the computer produce a specific response, or a nonspecific goal, to find the pattern underlying the computer's behavour. Subjects either interacted directly with the computer (the 'models') or observed a model's learning trials (the 'observers'). Both the goal of the models and the goal of the observers were varied so that specific goal and non-specific goal models were crossed with specific goal and non-specific goal observers. We predicted that the goal of the observer and not the goal of the model would determine whether observers learned rates or instances and that learning through observation would hinder instance learning. These predictions were confirmed. Non-specific goal models learned rules whereas specific goal models learned instances. Non-specific goal observers also learned rules, irrespective of the goal of the model, but specific goal observers failed to learn at all. A subsequent test confirmed that the failure of the specific goal observers to learn was due to the lack of feedback about correct responses. When such feedback was provided, specific goal observers learned instances. However, the presence of feedback was detrimental to rule learning. When non-specific goal observers received feedback, they learned only instances. These results support the view that both goal specificity and the presence or absence of feedback guide learning by directing attention to either instance space or both instance space and rule space.