Task differences on conservation and transitivity problems

Task differences were assessed with 120 first graders in a 2 × 3 × 3 factorial design combining Socioeconomic level (middle vs lower), Concepts (conservation of length, transitivity of length, and conservation of continuous quantity), and Tasks (three tasks for each concept selected on the basis of frequency of usage). As predicted, task by concept interactions were found on all four task response measures. This finding is consistent with Piaget's concept of horizontal decalage and with Flavell and Wohlwill's competence-performance model, which proposes that intermediate phases of stage transition are characterized by considerable intertask differences and initial and final phases by intertask consistency in performance. The importance of investigating the effects of task variables on multiple dependent measures at various age levels and points in time was emphasized. Concept, task, and socioeconomic class differences were also found on some of the measures.     

On the determination of appropriate dimensionality in data with error

The study deals with the problem of determining true dimensionality of data-with-error scaled by Kruskal's multidimensional scaling technique. Artificial data was constructed for 6, 8, 12, 16, and 30 point configurations of 1, 2, or 3 true dimensions by adding varying amounts of error to the true distances. Results show how stress is affected by error, number of points, and number of dimensions, and indicate that stress and the elbow criterion are inadequate for purposes of identifying true dimensionality when there is error in the data. The Wagenaar-Padmos procedure for identifying true dimensionality and error level is discussed. A simplified technique, involving a measure calledConstraint, is suggested.The authors wish to thank Dr. J. B. Kruskal for his valuable help and suggestions.Computer time for this research was supplied by the Instruction and Research Computer Center, The Ohio State University.     

Conditions necessary for sand digging in laboratory rats

Continuous availability of a sand blocked tube elicited intense and persistent digging by laboratory rats. Neither training nor prior exposure to the apparatus were necessary for response initiation. Continuous presence of an open pile of sand would not elicit digging. No theoretical explanation is offered.