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.     

Reliability and Validity of the Dyadic Observed Communication Scale (DOCS)

We evaluated the reliability and validity of the Dyadic Observed Communication Scale (DOCS) coding scheme, which was developed to capture a range of communication components between parents and adolescents. Adolescents and their caregivers were recruited from mental health facilities for participation in a large, multi-site family-based HIV prevention intervention study. Seventy-one dyads were randomly selected from the larger study sample and coded using the DOCS at baseline. Preliminary validity and reliability of the DOCS was examined using various methods, such as comparing results to self-report measures and examining interrater reliability. Results suggest that the DOCS is a reliable and valid measure of observed communication among parent-adolescent dyads that captures both verbal and nonverbal communication behaviors that are typical intervention targets. The DOCS is a viable coding scheme for use by researchers and clinicians examining parent-adolescent communication. Coders can be trained to reliably capture individual and dyadic components of communication for parents and adolescents and this complex information can be obtained relatively quickly.     

Adults' memories of childhood: Affect,knowing, and remembering

Adult questionnaire respondents reported, for each of a number of events, if they had experienced that event during childhood and, if so, if they remembered the experience or merely knew it had happened. Respondents also rated the emotion of each event and judged whether they would remember more about each reportedly experienced event if they spent more time trying to do so. Study 1 respondents were 96 undergraduates, whereas Study 2 tested 93 community members ranging widely in age. Respondents often reported no recollections of reportedly experienced events. Reportedly experienced events rated as emotional were more often recollected than those rated as neutral, and those rated as positive were more often recollected than those rated as negative. Predicted ability to remember more was related to current memory. Claims of remembering reportedly experienced events increased with age, but predicted ability to remember more about them declined with age.     

Self-Reported Cognitive Inconsistency in Older Adults

ABSTRACT

Insight into one's own cognitive abilities, or metacognition, has been widely studied in developmental psychology. Relevance to the clinician is high, as memory complaints in older adults show an association with impending dementia, even after controlling for likely confounds. Another candidate marker of impending dementia under study is inconsistency in cognitive performance over short time intervals. Although there has been a recent proliferation of studies of cognitive inconsistency in older adults, to date, no one has examined adults' self-perceptions of cognitive inconsistency. Ninety-four community-dwelling older adults (aged 70–91) were randomly selected from a parent longitudinal study of short-term inconsistency and long-term cognitive change in aging. Participants completed a novel 40-item self-report measure of everyday cognitive inconsistency, including parallel scales indexing perceived inconsistency 5 years ago and at present, yielding measures of past, present, and 5-year change in inconsistency. The questionnaire showed acceptable psychometric characteristics. The sample reported an increase in perceived inconsistency over time. Higher reported present inconsistency and greater 5-year increase in inconsistency were associated with noncognitive (e.g., older age, poorer ADLs, poorer health, higher depression), metacognitive (e.g., poorer self-rated memory) and neuropsychological (e.g., poorer performance and greater 5-year decline in global cognitive status, vocabulary, and memory) measures. Correlations between self-reported inconsistency and neuropsychological performance were attenuated, but largely persisted when self-rated memory and age were controlled. Observed relationships between self-reported inconsistency and measures of neuropsychological (including memory) status and decline suggest that self-perceived inconsistency may be an area of relevance in evaluating older adults for memory disorders.     

Anchoring and Adjusting in Questionnaire Responses

Do survey designers bias respondents' answers on attitude/opinion questionnaires through the organization of their survey items? We hypothesize that respondents often employ an anchoring and adjusting strategy in which their response to an initial survey item provides a cognitive anchor from which they insufficiently adjust in answering the subsequent item. Three experiments indicate that respondents often anchor and insufficiently adjust in certain situations. Ultimately, this tendency can affect reliability estimates of scales and the resultant correlations with other measures. In organizing their surveys, researchers may wish to combat this bias by intermixing items designed for different but related constructs.     

Determination of a behavioral transfer function: White-noise analysis of session-to-session response-ratio dynamics on concurrent VI VI schedules

Six pigeons were exposed to concurrent variable-interval schedules in which the programmed reinforcer ratios changed from session to session according to a pseudorandom binary sequence. This procedure corresponded to the stochastic identification paradigm (“white-noise experiment”) of systems theory and enabled the relation between log response ratios in the current session and log reinforcer ratios in all previous sessions to be determined. Such dynamic relations are called linear transfer functions. Both nonparametric and parametric representations of these, in the form of “impulse-response functions,” were determined for each bird. The session-to-session response ratios resulting from the session-to-session pseudorandom binary variations in reinforcer ratios were well predicted by the impulse-response functions identified for each pigeon. The impulse-response functions were well fitted by a second-order dynamic model involving only two parameters: a time constant and a gain. The mean time constant was 0.67 sessions, implying that the effects of abrupt changes in log reinforcer ratios should be 96% complete within about five sessions. The mean gain was 0.53, which was surprisingly low inasmuch as it should equal the sensitivity to reinforcement ratio observed under steady-state conditions. The same six pigeons were subjected to a similar experiment 10 months following the first. Despite individual differences in impulse-response functions between birds within each experiment, the impulse-response functions determined from the two experiments were essentially the same.     

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.     

Negative affect varying in motivational intensity influences scope of memory

Emotions influence cognitive processes involved in memory. While some research has suggested that cognitive scope is determined by affective valence, recent models of emotion–cognition interactions suggest that motivational intensity, rather than valence, influences these processes. The present research was designed to clarify how negative affects differing in motivational intensity impact memory for centrally or peripherally presented information. Experiments 1 & 2 found that, relative to a neutral condition, high intensity negative affect (anger) enhances memory for centrally presented information. Experiment 3 replicated this effect using another high intensity negative affect (threat). Experiment 4 extended this by finding that, relative to a neutral condition, low intensity negative affect (sadness) enhanced memory for peripherally presented information. Finally, in Experiment 5, the effects of sadness and threat on scope of memory were directly compared, finding that threat narrowed scope of memory, while sadness broadened scope of memory. Together, these results provide additional support for the motivational dimensional model of cognitive scope, in that high intensity emotions narrow cognitive scope, while low intensity emotions broaden cognitive scope.