Multidimensional scaling of nominal data: The recovery of metric information with alscal

Multidimensional scaling has recently been enhanced so that data defined at only the nominal level of measurement can be analyzed. The efficacy of ALSCAL, an individual differences multidimensional scaling program which can analyze data defined at the nominal, ordinal, interval and ratio levels of measurement, is the subject of this paper. A Monte Carlo study is presented which indicates that (a) if we know the correct level of measurement then ALSCAL can be used to recover the metric information presumed to underlie the data; and that (b) if we do not know the correct level of measurement then ALSCAL can be used to determine the correct level and to recover the underlying metric structure. This study also indicates, however, that with nominal data ALSCAL is quite likely to obtain solutions which are not globally optimal, and that in these cases the recovery of metric structure is quite poor. A second study is presented which isolates the potential cause of these problems and forms the basis for a suggested modification of the ALSCAL algorithm which should reduce the frequency of locally optimal solutions.     

Interactive similarity ordering

The interactive similarity ordering (ISO) system gathers similarity data that can be symmetric, asymmetric, or rectangular in form. Because the subject makes a very simple judgment and the number of judgments is interactively minimized, this procedure can be used for a relatively large number of stimuli. This system has been programmed on a PDP-11/45 and on a Motorola 6800-based microprocessor. An empirical investigation indicates that the ISO system compares favorably with other large stimulus set procedures.     

On the precision of a euclidean structure

This paper is concerned with the development of a measure of the precision of a multidimensional euclidean structure. The measure is a precision index for each point in the structure, assuming that all the other points are precisely located. The measure is defined and two numerical methods are presented for its calculation. A small Monte Carlo study of the measure's behavior is performed and findings discussed.The authors are indebted to Bert F. Green, Jr., Ronald Helms, Andrea Sedlak, and three anonymous reviewers for their valuable comments on earlier drafts of this paper.     

BEHAVIORAL RESEARCH IN PREVENTIVE DENTISTRY: EDUCATIONAL AND CONTINGENCY MANAGEMENT APPROACHES TO THE PROBLEM OF PATIENT COMPLIANCE

This study examined the effects of reinforcement on compliance with an oral hygiene education program. Patients 18 years of age or older who enrolled in an ongoing program at a periodontal practice received 3–5 sessions of instruction in preventive dental care. Using a between-subjects design, patients who entered the program during alternating months also had a portion of their fees refunded contingent upon improvements in their dental plaque scores. Pre- and posttreatment data showed that all subjects exhibited lower plaque levels following the program, but that greater improvements were seen in patients who were exposed to the fee reduction contingency. Plaque scores taken at a 6-month follow-up revealed some relapse for the Fee Reduction subjects. However, their scores were still substantially better than pretreatment, and better than those of the Education only subjects, whose data differed little from untreated Controls. Methodological and practical issues related to behavioral research in preventive dentistry are discussed.     

Young children's storage behavior in a memory-for-location task

Two experiments concerned with children's intentional preparation for future retrieval in a memory-for-location task are presented. In the first experiment, 3-, 5-, 7-, and 9-year-olds were instructed to store and subsequently retrieve an object on a large spatial display. All age groups, except the 3-year-olds, tended to store the object at distinctive locations and their retrieval performance was facilitated accordingly. The four age groups did not differ in the types of selections made in a nonmemory control task. The second experiment dealt with the effects of feedback and informational factors on strategy acquisition. Preschoolers were given experience at retrieving the object from distinctive and nondistinctive positions on the stimulus display. Later, when instructed to store the object by themselves, older preschoolers produced the distinctive-position storage strategy following a feedback procedure in which they directly observed the consequences of their retrieval selections. The strategy was adopted by younger preschoolers, but only when additional strategy and task information accompanied visual feedback. The use of external memory tasks with young children and factors affecting strategy acquisition and utilization are discussed.     

When is a question not answered? The understanding of young children of utterances violating or conforming to the rules of conversational sequencing

Knowledge of the conventional rules of conversational sequencing enables a speaker or listener to evaluate the pragmatic use of an utterance. This study explored young children's ability to discriminate among utterances that violated or conformed to these rules (Experiment 1), and ability to explain rule violations (Experiment 2). In both experiments children were read short episodes containing utterances that conformed to the rules in that the utterances were used appropriately in the episodic context of utterance, or utterances that violated the conversational rules of contingency, relevance, or informativeness. In Experiment 1, kindergarten, and first- and second-grade children (5, 6, and 7 years of age) were asked to discriminate among the conforming and rule violating utterances by assigning each utterance to one of two female conventional and unconventional speakers. The results showed that the first and second graders, but not the kindergarten children, generally discriminated among the utterances. In Experiment 2, first and third graders (6 and 8 years of age) were asked to explain the rule violations. The results showed that only the third graders consistently generated correct explanations. These results suggest that children can use the rules of conversational sequencing to evaluate the need for an inference to the speaker's intent in deliberately violating a rule by 6 or 7 years of age, but do not correctly infer that intent until they are 8 or 9 years old.     

Environmental and cognitive factors in social play

The impact of differing play environments, as well as cognitive and social egocentrism factors, on the social play of preschoolers was examined. Fifteen boys and thirteen girls (55 months of age) were allowed free access to two distinctly different environments containing play materials which were aimed at exercising either big or fine muscle coordination. The children's cognitive abilities and social egocentrism were also measured. The results indicate that the play environment strongly influenced the type of social play as well as the size of the play groups. Differences in cognitive level and social egocentrism influenced the children's choice of play environment, suggesting an organism-environment interaction in the children's social play. The results indicate that today's generation of children may not be less social in their play, as Barnes has suggested, but that differences between studies may be a consequence of differing play environments and not generational differences.     

Encoding specificity in the recall of pictures and words in children and adults

In this study, the modality of the retrieval cues (pictures or words) was varied in a cued recall task to determine how second and fourth grade children and college adults encode words (Experiment 1) and pictures (Experiment 2). According to the assumptions of the encoding specificity principle, cue modality should affect recall only to the degree to which subjects focus on modality specific (sensory) rather than nonmodality specific (semantic) information in stimuli. In both experiments, the results showed progressively smaller encoding specificity effects with increasing age. To ensure that differences in encoding activity were responsible for these effects, comparisons were made of recall patterns under intentional learn conditions, and under incidental conceptual and sensory orienting conditions. The recall patterns of the children in the conceptual orienting condition were similar to the adult patterns in the learn condition, and the adult recall patterns in the sensory orienting conditions were similar to those of the children in the learn conditions. These results suggest that there are developmental differences in encoding the sensory and semantic information in stimuli that may result from differences in the efficiency with which the semantic information in stimuli is processed. The results suggest that young children typically encode stimuli in a fashion that stresses the sensory aspects of the stimuli, and that recall suffers as a result.     

The understanding of young children and adults of the deictic adequacy of communications

When a communication is used in a discourse context, the deictic information in the communication may be important in achieving a successful speech act. This information includes the temporal and spatial coordinates of the speech act that locate the communication in a context. In the present study, first- and fourth-grade children (6 and 9 years of age) and college adults were read short stories and asked to evaluate the adequacy of deictically ambiguous or informative communications (Experiment 1) or situations (Experiment 2). The results showed that subjects in all the grades discriminated among the deictically adequate and inadequate communications and situations, though the first graders made fewer correct judgments than did the other subjects of the adequacy of the informative communications and situations.