Bruce Weaver

Comparative responsiveness of generic and specific quality-of-life instruments

We assessed the relative responsiveness of generic and specific quality of life instruments in 43 randomized controlled trials that compared head-to-head 31 generic and 84 specific instruments. Using weighted effect size as the metric of responsiveness, we assessed the impact of instrument type, disease category, and magnitude of underlying therapeutic effect on responsiveness, and assessed the responsiveness of specific instruments relative to the corresponding domains of generic measures. In studies with a nonzero therapeutic effect, specific instruments (mean = 0.57) were significantly more responsive than generic instruments (mean = 0.39, P =.01), and than the corresponding domains of generic instruments (mean = 0.40, P =.03). Studies with low, medium, and high therapeutic effects showed a corresponding gradation in responsiveness differences between specific and generic instruments. We conclude that, overall, specific instruments are more responsive than generic tools, and that investigators may come to misleading conclusions about relative instrument responsiveness if they include studies in which the magnitude of the underlying therapeutic effect is zero.

Object-based and environment-based inhibition of return of visual attention.

Efficient search for an object often requires that attention be prevented from returning to recently examined environmental loci. M. I. Posner and Y. A. Cohen (1984) proposed that inhibition of return (IOR) of visual attention is a search mechanism that prevents such attentional perservation. The internal representations upon which IOR functions were examined and the following conclusions were drawn: First, IOR mechanisms have access to both object- and environment-based representations. Second, environment-based inhibition can be associated with a featureless environmental location, whereas the object-based mechanism requires that attention be oriented to a visible object. These findings are discussed in terms of physiological pathways that may mediate location- and object-based effects.

On the strategic modulation of the time course of facilitation and inhibition of return.

In studies of exogenous attentional orienting, response times for targets at previously cued locations are often longer than those for targets at previously uncued locations. This effect is known widely as inhibition of return (IOR). There has been debate as to whether IOR can be observed in discrimination as well as detection tasks. The experiments reported here confirm that IOR can be observed when target discrimination is required and that the cue-target interval at which IOR is observed is often longer in discrimination than in detection tasks. The results also demonstrate that the later emergence of IOR is related to perceptual discrimination rather than to response selection differences between discrimination and detection tasks. More difficult discrimination tasks lengthen the SOA at which IOR emerges. In contrast, increasing task difficulty by adding a distractor to the location opposite the target shortens the SOA at which IOR emerges. Together, the results reveal an adaptive interaction between exogenous and endogenous attentional systems, in which the action of the orienting (exogenous) system is modulated endogenously in accord with task demands.

Inhibitory mechanisms of attention in identification and localization tasks : time course and disruption

It has been proposed that 1 component of the mechanism of visual selective attention is active inhibition of distracting information. A series of studies examines the time course of inhibition and the possible interfering effects of other task demands. Results demonstrate that inhibition can last at least 7 s after selection processes and that it is unaffected by predictable, unrelated intervening events. However, intervening events that are less predictable, or are the same as the inhibited stimulus, disrupt inhibition. Such results motivate a reconsideration of the previous view of distractor inhibition as a transient, fragile phenomenon.

Behavioural goals determine inhibitory mechanisms of selective attention

It has been argued that during selection of target objects, irrelevant distractor objects are inhibited (e.g. Tipper, 1985). This article examines whether distractor inhibition is an invariant process that occurs in the same way for each act of selection, or whether it is a flexible process that adjusts to particular behavioural goals. We review previous studies and report new experiments that demonstrate that inhibition is a flexible process. Those internal representations of the distractor that are most associated with the action to be directed toward the target are inhibited. Other properties of the ignored object can remain in an active state and can facilitate subsequent behaviour.

Inhibition and Interference in Selective Attention: Some Tests of a Neural Network Model

We describe a neural network system that models selective action—that is, how an organism selectively responds to an object when other objects evoke competing responses. Performance of the model during simulations of various selective action situations reveals a number of interesting patterns of data. Specifically, the model shows a complex relationship between how much a distractor interferes with response to a target and how much inhibition is associated with the distractor. Subsequent experiments with human subjects reveal that the paradoxical behaviour of the model is also observed in human behaviour. We conclude that the similar performance characteristics of the model and human subjects in a variety of situations suggest that the model has captured some of the essential properties of mammalian selective action mechanisms.

Cardiopulmonary resuscitation directives on admission to intensive-care unit: an international observational study

BACKGROUND Resuscitation directives should be a sign of patients preference. Our objective was to ascertain prevalence, predictors, and procurement pattern of cardiopulmonary resuscitation directives within 24 h of admission to the intensive-care unit (ICU). METHODS We enrolled 2916 patients aged 18 years and older from 15 ICUs in four countries, and recorded whether, when, and by whom their cardiopulmonary resuscitation directives were established. By polychotomous logistic regression we identified factors associated with a resuscitate or do-not-resuscitate directive. FINDINGS Of 2916 patients, 318 (11%; 95% CI 9.8-12.1) had an explicit resuscitation directive. In 159 (50%; 44.4-55.6) patients, the directive was do-not-resuscitate. Directives were established by residents for 145 (46%; 40.0-51.3) patients. Age strongly predicted do-not-resuscitate directives: for 50-64, 65-74, and 75 years and older, odds ratios were 3.4 (95% CI 1.6-7.3), 4.4 (2.2-9.2), and 8.8 (4.4-17.8), respectively. APACHE II scores greater than 20 predicted resuscitate and do-not-resuscitate directives in a similar way. An explicit directive was likely for patients admitted at night (odds ratio 1.4 [1.0-1.9] and 1.6 [1.2-2.3] for resuscitate and do-not-resuscitate, respectively) and during weekends (1.9 [1.3-2.7] and 2.2 [1.5-3.2], respectively). Inability to make a decision raised the likelihood of a do-not-resuscitate (3.7 [2.6-5.4]) than a resuscitate (1.7 [1.2-2.3]) directive (p=0.0005). Within Canada and the USA, cities differed strikingly, as did centres within cities. INTERPRETATION Cardiopulmonary resuscitation directives established within 24 h of admission to ICU are uncommon. As well as clinical factors, timing and location of admission might determine rate and nature of resuscitation directives.

Negative priming in a spatial localization task: feature mismatching and distractor inhibition

Negative priming has recently been demonstrated in tasks requiring spatial localization (S. P. Tipper, J. C. Brehaut, & J. Driver, 1990), supporting the notion that distractors are actively inhibited during selection. However, it has since been argued that this effect is caused by the appearance of mismatching identities at a single location (J. Park & N. Kanwisher, 1994). The present studies show that negative priming in a spatial localization task can occur when the ignored distractor and subsequent target are identical. However, feature mismatches can also lead to negative priming. The argument is made that distractor inhibition and implicit retrieval of previously presented items together provide a better account of efficient sequential selective behavior than does either process alone. Consider a bartender clearing glasses from a table. This apparently simple perceptual-motor interaction can be broken down into two complex stages of processing. The first stage encompasses the movement of the hand toward one glass among others in the same path of motion, and thus affords conflicting motor responses (see Tipper, Lortie, & Baylis, 1992). The second stage encompasses subsequent motor behavior after action toward the first glass has been completed. This second stage of processing is the focus of the present article. However, a complete understanding of how action is directed toward an object that was ignored in a recent perceptual-motor interaction begins with an understanding of the processing consequences of originally ignoring that object. Two mechanisms have been proposed to explain how action can be selectively directed toward one object when there are distracting objects in the scene. Most early models of selective attention proposed that internal representations of the attended object receive analysis beyond that of initial perceptual processing. This extra level of excitation was considered sufficient to separate the target from distractor (Broadbent, 1958, 1982; Van der Heijden, 1981). More recently, inhibitory mechanisms have been proposed to play a role complementary to that of excitation in separating

Virtual reality and brain anatomy: a randomised trial of e-learning instructional designs

Context  Computer‐aided instruction is used increasingly in medical education and anatomy instruction with limited research evidence to guide its design and deployment.

SPSS and SAS programs for comparing Pearson correlations and OLS regression coefficients.

Several procedures that use summary data to test hypotheses about Pearson correlations and ordinary least squares regression coefficients have been described in various books and articles. To our knowledge, however, no single resource describes all of the most common tests. Furthermore, many of these tests have not yet been implemented in popular statistical software packages such as SPSS and SAS. In this article, we describe all of the most common tests and provide SPSS and SAS programs to perform them. When they are applicable, our code also computes 100 × (1 − α)% confidence intervals corresponding to the tests. For testing hypotheses about independent regression coefficients, we demonstrate one method that uses summary data and another that uses raw data (i.e., Potthoff analysis). When the raw data are available, the latter method is preferred, because use of summary data entails some loss of precision due to rounding.