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.     

Fixed Effects vs. Random Effects Meta-Analysis Models: Implications for Cumulative Research Knowledge

Research conclusions in the social sciences are increasingly based on meta-analysis, making questions of the accuracy of meta-analysis critical to the integrity of the base of cumulative knowledge. Both fixed effects (FE) and random effects (RE) meta-analysis models have been used widely in published meta-analyses. This article shows that FE models typically manifest a substantial Type I bias in significance tests for mean effect sizes and for moderator variables (interactions), while RE models do not. Likewise, FE models, but not RE models, yield confidence intervals for mean effect sizes that are narrower than their nominal width, thereby overstating the degree of precision in meta-analysis findings. This article demonstrates analytically that these biases in FE procedures are large enough to create serious distortions in conclusions about cumulative knowledge in the research literature. We therefore recommend that RE methods routinely be employed in meta-analysis in preference to FE methods.     

Multimedia mug books: how multi should the media be?

The impact of allowing witnesses to choose the type of cues presented in multimedia mug books was explored in two experiments. In Experiment 1, participants viewed a videotaped crime and attempted to identify the perpetrator from one of three types of mug books: (a) dynamic‐combined—participants could choose to follow static mug shots with a computerized video clip combining three types of dynamic cues: the person walking, talking, and rotating; (b) dynamic‐separable—participants could limit the types of dynamic cues presented; and (c) static—just the static mug shot was presented. The dynamic‐separable condition produced significantly fewer false positive foil identifications than the static condition. Within the dynamic‐separable condition, voice was the most preferred cue. Experiment 2 explored the contribution of the individual cues. Participants attempted identifications from single dynamic cue mug books where only one type of cue was presented if a participant chose additional information. It was found that providing individual cues did not improve performance over the static mug book control. Based on the potential danger of witnesses choosing to rely on single dynamic cues, it was suggested that multimedia mug books should present dynamic cues in combination. Copyright © 2000 John Wiley & Sons, Ltd.     

The power of one reinforcer: The effect of a single reinforcer in the context of shaping

During shaping, if the organism is engaged in behaviors other than the current approximation, the amount of time between reinforcers increases. In these situations, the shaper may resort to what is referred to as a “desperation‐driven click.” That is, after a period of no reinforcement, the shaper delivers one reinforcer for a nontarget approximation. Reports from professional animal trainers suggest that the animal may continue performing this new behavior, even if it is reinforced only once. This study attempted to model this phenomenon with college students. Results from the study demonstrated that a desperation‐driven click situation can be reliably produced in a controlled setting. When participants received one reinforcer for interacting with a new object following a period of no reinforcement, they interacted with the new object for a longer or equal amount of time as compared to an object that had a longer history of reinforcement. The results of this study have implications for the understanding of how reinforcement controls behavior.