On the processing of arguments

This paper is concerned with the processing of informal arguments, that is, arguments involving probable truth. A model of informal argument processing is presented that is based upon Hample's (1977) expansion of Toulmin's (1958) model of argument structure. The model postulates that a claim activates an attitude, the two components forming a complex that in turn activates reasons. Furthermore, the model holds occurrence of the reason, or possibly the claim and the reason, activates values. Three experiments are described that provide support for the model.This research was supported by the Mellon Foundation and by the Office of Educational Research and Improvement of the Department of Education via an award for the Center for the Study of Learning to the Learning Research and Development Center. The contents of the paper are not necessarily the position of any of these organizations.     

Taking visual disability into account: Explaining failure to experts and non-experts

The present study was designed to investigate visually handicapped students' explanations for failure when the motive to maintain or enhance self-esteem was in conflict with the motive to present a favorable social image. Subjects experienced manipulated failure in a text comprehension task and were subsequently asked to give causal and responsibility attributions in the presence of either a visually handicapped or a non-handicapped experimenter. It was expected that visually disabled participants would claim a handicap-bonus from the non-handicapped experimenter by explicitly presenting non-defensive attributions and accounts as well as handicap-related responses, while defensive explanations should be more pronounced when faced with a blind experimenter. The data provide support for the existence of presumed social expectations as determinants of individuals' verbal self-presentations.     

EFFECTS OF MEMORY AIDS ON THE DYADIC CONVERSATIONS OF INDIVIDUALS WITH DEMENTIA

The effects of a prosthetic memory aid on the conversational content and social skills of dyads with dementia were evaluated. Six individuals with moderate to severe dementia served as either subject or partner in dyads during 5-min conversational probes conducted three times per week in daycare and nursing-home settings. During phases when a memory aid, consisting of personally relevant picture and sentence stimuli, was available, most subjects used their own aid to improve the quality of conversations by increasing the frequency of on-topic statements, diminishing nonproductive utterances, lengthening their conversational turn, and/or increasing the frequency of turns taken. Most partners demonstrated awareness of social discourse conventions by appropriately relinquishing conversational dominance, decreasing both content and nonproductive utterances, and increasing acknowledging or affirmative comments when subjects used memory aids. Naive judges' ratings of aided and unaided conversational samples on seven conversational dimensions reflected differences in perceptions of significant improvement as a function of the conversational discourse style of each dyad.     

Testing a stochastic foraging model in an operant simulation: Agreement with qualitative but not quantitative predictions

An operant simulation of foraging through baited and empty patches was studied with 4 pigeons. On a three-key panel, side keys were designated as patches, and successive opportunities to complete 16 fixed-ratio 10 schedules on side keys were defined as encounters with feeders. In a random half of the patches in any session, some of the fixed-ratio 10 schedules yielded reinforcement (baited feeders) and the other schedules yielded nonreinforcement (empty feeders). In the other half of the patches, all feeders were empty. Pigeons could travel between patches at any time by completing a fixed-ratio schedule on the center key. An optimal foraging model was tested in Experiments 1 and 2 by varying center-key travel time and number of baited feeders in baited patches. The ordinal predictions that number of feeders visited in empty patches would increase with travel time and decrease as number of baited feeders increased were supported, but pigeons visited far more feeders in empty patches than the optimal number predicted by the model to maximize energy/time. In Experiment 3, evidence was found to suggest that the number of empty feeders encountered before the first baited feeder in baited patches is an important factor controlling leaving empty patches.     

Swedish translations of the Suicide Probability Scale, Perceived Social Support from Friends and Family Scales, and the Scale for Interpersonal Behavior: A reliability analysis

The Suicide Probability Scale (SPS), the Perceived Social Support (PSS) from Friends (PSS-Fr) and Family (PSS-Fa) scales, and the Scale for Interpersonal Behavior (SIB) were translated into Swedish and their reliability was estimated in a university student sample. The reliability coefficients indicated that both subscales and the total scales of the SPS, PSS, and SIB possess highly adequate reliabilities. The intercorrelations among the subscales and between the subscales and the total scales were found to be highly significant. The results of the study supported the use of SPS, PSS-Fr and PSS-Fa, and the SIB as reliable methods for assessing suicide risk, perceived social support from friends and family, and assertive behavior.     

The many null distributions of person fit indices

This paper deals with the situation of an investigator who has collected the scores ofn persons to a set ofk dichotomous items, and wants to investigate whether the answers of all respondents are compatible with the one parameter logistic test model of Rasch. Contrary to the standard analysis of the Rasch model, where all persons are kept in the analysis and badly fittingitems may be removed, this paper studies the alternative model in which a small minority ofpersons has an answer strategy not described by the Rasch model. Such persons are called anomalous or aberrant. From the response vectors consisting ofk symbols each equal to 0 or 1, it is desired to classify each respondent as either anomalous or as conforming to the model. As this model is probabilistic, such a classification will possibly involve false positives and false negatives. Both for the Rasch model and for other item response models, the literature contains several proposals for a person fit index, which expresses for each individual the plausibility that his/her behavior follows the model. The present paper argues that such indices can only provide a satisfactory solution to the classification problem if their statistical distribution is known under the null hypothesis that all persons answer according to the model. This distribution, however, turns out to be rather different for different values of the person's latent trait value. This value will be called ability parameter, although our results are equally valid for Rasch scales measuring other attributes.As the true ability parameter is unknown, one can only use its estimate in order to obtain an estimated person fit value and an estimated null hypothesis distribution. The paper describes three specifications for the latter: assuming that the true ability equals its estimate, integrating across the ability distribution assumed for the population, and conditioning on the total score, which is in the Rasch model the sufficient statistic for the ability parameter.Classification rules for aberrance will be worked out for each of the three specifications. Depending on test length, item parameters and desired accuracy, they are based on the exact distribution, its Monte Carlo estimate and a new and promising approximation based on the moments of the person fit statistic. Results for the likelihood person fit statistic are given in detail, the methods could also be applied to other fit statistics. A comparison of the three specifications results in the recommendation to condition on the total score, as this avoids some problems of interpretation that affect the other two specifications.The authors express their gratitude to the reviewers and to many colleagues for comments on an earlier version.     

Modeling item responses when different subjects employ different solution strategies

A model is presented for item responses when different subjects employ different strategies, but only responses, not choice of strategy, can be observed. Using substantive theory to differentiate the likelihoods of response vectors under a fixed set of strategies, we model response probabilities in terms of item parameters for each strategy, proportions of subjects employing each strategy, and distributions of subject proficiency within strategies. The probabilities that an individual subject employed the various strategies can then be obtained, along with a conditional estimate of proficiency under each. A conceptual example discusses response strategies for spatial rotation tasks, and a numerican example resolves a population of subjects into subpopulations of valid responders and random guessers.The first author's work was supported by Contract No. N00014-85-K-0683, project designation NR 150-539, from the Cognitive Science Program, Cognitive and Neural Sciences Division, Office of Naval Research. We are grateful to Murray Aitkin, Isaac Bejar, Neil Dorans, Frederiksen, and Marklyn Wingersky for their comments and suggestions, and to Alison Gooding, Maxine Kingston, Donna Lembeck, Joling Liang, and Kentaro Yamamoto for their assistance with Example 2.