Rosemary J. Stevenson

Effects of Text Structure and Prior Knowledge of the Learner on Navigation in Hypertext

In this study we examined the effects of 3 hypertext topologies—hierarchical, nonlinear, and mixed (hierarchical structure with cross referential links)—on the navigation performance of participants with high and low prior knowledge of the text topic. After reading the text, participants used the document to find the answers to 10 questions. After a filled distraction period, participants returned to the document to answer 10 more questions. The results showed that participants in the mixed condition performed better than those in the other 2 conditions and that the performance of knowledgeable participants was superior to that of nonknowledgeable participants. These results are discussed in relation to the ways in which text structure interacts with background knowledge of the user in enhancing or impeding performance. Actual or potential applications of this research include the design and implementation of hypertext systems for users with different levels of familiarity with the subject matter of the text.

Navigation in hyperspace: An evaluation of the effects of navigational tools and subject matter expertise on browsing and information retrieval in hypertext

Abstract This study examined the effectiveness of a map and a textual contents list on the navigation performance of subjects with and without prior knowledge of the text topic. After reading the text, subjects used the document to answer ten questions. The results showed that performance in the map condition was superior to that of the contents list condition, which in turn was superior to that of the hypertext only condition (no navigational aid). In addition, knowledgeable subjects performed better than non-knowledgeable subjects, except in the map condition where their performance was equivalent. The results also show that non-knowledgeable users tend to rely more heavily on navigational aids than knowledgeable users, and that aids were used primarily during browsing. These results are discussed in relation to the ways in which navigational aids interact with the prior knowledge of the user to enhance or impede performance.

Thematic roles, focus and the representation of events

Abstract Two experiments investigated the focusing properties of thematic roles, while a third experiment investigated the view that thematic role preferences reflect a focusing on the consequences of the represented event. Sentence continuation tasks were used in which subjects wrote continuations to sentence fragments containing two antecedents, each occupying a different thematic role. The results of Experiments 1 and 2 showed a preference for referring to a particular thematic role regardless of the presence or absence of a pronoun at the start of the continuation and regardless of whether the continuation was part of a different sentence from the one containing the antecedents (Experiment 1) or part of the same sentence (Experiment 2). These preferences were interpreted as being due to a focus on the consequences of the represented event in a mental model of the sentence. Experiment 3 tested this interpretation by using sentence fragments that ended in so (a connective that reinforces the focus on co...

Centering: A Parametric Theory and Its Instantiations

Centering theory is the best-known framework for theorizing about local coherence and salience; however, its claims are articulated in terms of notions which are only partially specified, such as utterance, realization, or ranking. A great deal of research has attempted to arrive at more detailed specifications of these parameters of the theory; as a result, the claims of centering can be instantiated in many different ways. We investigated in a systematic fashion the effect on the theorys claims of these different ways of setting the parameters. Doing this required, first of all, clarifying what the theorys claims are (one of our conclusions being that what has become known as Constraint 1 is actually a central claim of the theory). Secondly, we had to clearly identify these parametric aspects: For example, we argue that the notion of pronoun used in Rule 1 should be considered a parameter. Thirdly, we had to find appropriate methods for evaluating these claims. We found that while the theorys main claim about salience and pronominalization, Rule 1a preference for pronominalizing the backward-looking center (CB)is verified with most instantiations, Constraint 1a claim about (entity) coherence and CB uniquenessis much more instantiation-dependent: It is not verified if the parameters are instantiated according to very mainstream views (vanilla instantiation), it holds only if indirect realization is allowed, and is violated by between 20 and 25 of utterances in our corpus even with the most favorable instantiations. We also found a trade-off between Rule 1, on the one hand, and Constraint 1 and Rule 2, on the other: Setting the parameters to minimize the violations of local coherence leads to increased violations of salience, and vice versa. Our results suggest that entity coherencecontinuous reference to the same entitiesmust be supplemented at least by an account of relational coherence.

Deduction from Uncertain Premises

We investigate how the perceived uncertainty of a conditional affects a persons choice of conclusion. We use a novel procedure to introduce uncertainty by manipulating the conditional probability of the consequent given the antecedent. In Experiment 1, we show first that subjects reduce their choice of valid conclusions when a conditional is followed by an additional premise that makes the major premise uncertain. In this we replicate Byrne (1989). These subjects choose, instead, a qualified conclusion expressing uncertainty. If subjects are given a third statement that qualifies the likelihood of the additional premise, then the uncertainty of the conclusions they choose is systematically related to the suggested uncertainty. Experiment 2 confirms these observations in problems that omit the additional premise and qualify the first premise directly. Experiment 3 shows that the qualifying statement also affects the perceived probability of the consequent given the antecedent of the conditional. Experiment 4 investigates the effect of suggested uncertainty on the fallacies and shows that increases in uncertainty reduce the number of certain conclusions that are chosen while affirming the consequent but have no effect on denying the antecedent. We discuss our results in terms of rule theories and mental models and conclude that the latter give the most natural account of our results.

Interpreting pronouns and connectives: Interactions among focusing, thematic roles and coherence relations

This paper investigates the relationship between focusing and coherence relations in pronoun comprehension. In their focusing model of pronoun comprehension, Stevenson, Crawley and Kleinman (1994) proposed a default focus on the thematic role associated with the consequences of a described event, a focus that may be modified by the attention-directing properties of a subsequent connective. In this paper we examine a second function of connectives: that of signalling the coherence relations between two clauses (e.g., a NARRATIVE relation or a RESULT relation). In three studies, we identified the coherence relations between sentence fragments ending in pronouns and participants’ continuations to the fragments. We then examined the relationship between the coherence relation, the preferred referent of the pronoun and the referent’s thematic role. The results of studies 1 and 2 showed that people aim to keep the focused entity, the coherence relation and the referent of the pronoun in alignment. Study 3 included the connective next, which enabled us to generate different predictions for the roles of focusing and coherence relations in pronoun resolution. The results favoured the focusing view. The preferred referent of the pronoun was the focused, first mentioned, individual, whereas the coherence relation was consistent with the thematic role of the pronominal referent. If the pronoun referred to an Agent, a NARRATIVE relation was preferred, if the pronoun referred to a Patient, a RESULT relation was preferred. Discussion of these and other results led to the following conclusions. First, pronoun resolution is primarily determined by focusing, either semantic or structural, although a range of other features, including coherence relations and verb semantics, may also act as pressures on pronoun resolution. Second, the consistent link we observed between thematic roles and coherence relations may provide a mapping between a represented entity and a represented event. Third, the connectives we used have three distinct functions: an attention directing function, a function for constraining the possible coherence relation between two events, and a function for interpreting a clause as having either a causal or a temporal structure.

Pre-school children's use of the articles in definite and indefinite referring expressions.

Three experiments investigated the ability of children aged 2; 2–4; 10 to use identifying expressions to introduce new referents and the definite article to refer to already introduced referents. The results suggest that young children initially master the nominative use of a , but that from the age of 3 they have mastered the non-egocentric use of the definite article. On first mention their referring expressions are predominantly indefinite, and on second mention definite. The results are discussed in relation to previous studies, and the questions of suitable adult controls and ‘appropriateness’ of article usage are also considered.

Reasoning from uncertain premises: Effects of expertise and conversational context

Four experiments investigated uncertainty about a premise in a deductive argument as a function of the expertise of the speaker and of the conversational context. The procedure mimicked everyday reasoning in that participants were not told that the premises were to be treated as certain. The results showed that the perceived likelihood of a conclusion was greater when the major or the minor premise was uttered by an expert rather than a novice (Experiment 1). The results also showed that uncertainty about the conclusion was higher when the major premise was uttered by a novice and an alternative premise by an expert, compared to when the major premise was uttered by an expert and the alternative by a novice (Experiment 2). Similarly, the believability of a conclusion was considerably lower when the minor premise was uttered by a novice and denied by an expert, as opposed to when an expert uttered the minor premise and a novice denied it (Experiment 3). Experiment 4 showed that the nature of the uncertainty induced by a denial of the minor premise depended on whether or not the context was a conversation. These results pose difficult problems for current theories of reasoning, as current theories are based on the results of experiments in which the premises are treated as certain. Our discussion of the results emphasises the importance of pragmatics in reasoning, namely, the role of general knowledge about the world in assessing the probability of a premise uttered by an expert or a novice and the role of interpretations of the premise based on pragmatic inferences in revising these initial probabilities.

Explicit Learning of a Dynamic System with a Non-salient Pattern:

We examine the hypothesis that a specific goal leads to implicit learning, whereas a nonspecific goal leads to explicit learning, even though the pattern to be learnt is non-salient. Subjects learned a dynamic control task (Berry & Broadbent, 1984). One group of subjects had a specific control goal, the second group had a non-specific pattern-search goal, and the third group had both goals. On measures of learning (control performance, prediction, and general questions), the non-specific group learnt explicitly, outperforming the other two groups on all learning measures. The specific group performed next best on control performance and prediction questions but performed very poorly on general questions. The dual-goal group performed poorly on all measures. Non-specific subjects predicted well on both familiar and unfamiliar situations. Specific-goal subjects predicted well on familiar situations, regardless of whether their previous response had been correct or incorrect. Dual-goal subjects predicted well only on familiar correct situations. We conclude that the non-specific group learned through explicit hypothesis testing, the specific group learned through a mixture of explicit problem solving and implicit instance learning, and the dual-goal group learned instances. Results are discussed in terms of dual-space models of problem solving and hypothesis testing and in terms of implicit instance learning. We consider how the choice of learning goal affects the cognitive processes used during learning and suggest that having subjects learn the same information implicitly or explicitly is potentially useful for drawing clearer distinctions between implicit and explicit modes of learning.

The Role of Parallelism in Strategies of Pronoun Comprehension

Two experiments investigated the role of parallelism in strategies of pronoun assignment and tested the proposition that a parallel function strategy and the subject assignment strategy jointly contribute to the interpretation of pronouns. The parallel function strategy interprets a pronoun as coreferential with a preceding noun phrase in the same grammatical role, while the subject assignment strategy interprets a pronoun as coreferential with a preceding subject noun phrase. The results of Experiment I showed that the subject assignment and parallel function strategies jointly constrained assignment. When both strategies yielded the same interpretation, as was the case for subject assignments with subject pronouns, subject assignment preferences were greater than when only the subject assignment strategy was available, as was the case with nonsubject pronouns in partially parallel sentences (i.e., sentences in which the pronoun and antecedent differed grammatically). When the two strategies yielded conflicting assignments, as was the case with nonsubject pronouns in fully parallel sentences, subject assignments were reduced even further and nonsubject assignments were preferred. Experiment 2 replicated the results of Experiment 1 in isolated sentences rather than in short texts and ruled out the idea that a third “parallel order” strategy might be used in partially parallel sentences. We suggest that the subject assignment strategy reflects the topic status of the subject noun phrase, while parallel function reflects the use of correspondences between sentence structures in comprehension. We also suggest that the joint operation of heuristic strategies implies a model of discourse processing in which a number of constraints compete in the interpretation of noun phrases.