Controlling the Ground Reaction Force During Lifting

The control of the ground reaction force vector relative to the center of gravity (CoG) was examined while subjects performed a back-lifting task. Six male subjects (aged 24.0 +/- 2.5 years) repeatedly lifted a barbell. A biomechanical analysis that used a linked segment model revealed that the summed rotations of body segments during lifting yielded a specific rate of change of the angular momentum of the entire body. This equaled the external moment provided by Fsubg; relative to CoG. This implies that multisegment movements involve control of the angular momentum of the entire body through an appropriately directed Fsubg;. Thus, in dynamic tasks Fsubg; is pointed away from rather than lined up with the CoG, as is the case in static tasks.     

Evaluating the Impact of a National AIDS Prevention Radio Campaign in St. Vincent and the Grenadines1

Based on extensive formative research in the three Eastern Caribbean countries of St. Lucia, St. Vincent and the Grenadines, and Grenada (Fishbein, Middlestadt, & Trafimow, 1993; Fishbein, Trafimow, et al., 1993), a three-nation, mass media, condom use campaign was developed. In order to assess the impact of the campaign, a follow-up survey was conducted in St. Vincent and the Grenadines. This paper examines the effectiveness of the campaign by comparing responses on this survey by respondents who were or were not exposed to the campaign. A statistically significant impact of exposure to the campaign was obtained, indicating that a well-designed, empirically based, mass media campaign can be an effective tool in the battle to prevent the spread of AIDS.     

Reviews

Editor's note: The original edition of the book is (nearly) sold out, but a shortened, updated version will probably be published by Sage Publications, Thousand Oaks CA. Information can be obtained from: T.U.P., P.O. Box 90153, 5000 LE Tilburg, The Netherlands.     

The generation effect and the modeling of associations in memory

The search of associative memory (SAM) model of Gillund and Shiffrin (1984) was applied to data of two experiments that examined the generation effect (Slamecka & Graf, 1978). Subjects studied a list of related word pairs, in which they either read both words in the pair or generated the righthand response term using the left-hand stimulus term plus the response word fragment as generation cues. Experiment 1 manipulated encoding condition within subjects and used an incidental learning procedure. Experiment 2 manipulated encoding condition between subjects and used an intentional learning procedure. Memory was tested with recognition, cued recall, and free recall. A higher order association model gave a better and more parsimonious fit to the results than did an item-level association model. The relationship between various versions of SAM and current accounts of the generation effect are discussed, particularly the two-factor theory of Hirshman and Bjork (1988).     

Gender,politics, and the theoretical virtues

Traits like simplicity and explanatory power have traditionally been treated as values internal to the sciences, constitutive rather than contextual. As such they are cognitive virtues. This essay contrasts a traditional set of such virtues with a set of alternative virtues drawn from feminist writings about the sciences. In certain theoretical contexts, the only reasons for preferring a traditional or an alternative virtue are socio-political. This undermines the notion that the traditional virtues can be considered purely cognitive.I am grateful to participants in the Indiana University Workshop on Social Values in the Context of Justification for their comments on an earlier, spoken, version of this paper.     

The psychology of christian prayer: a review ofempirical research

This paper presents, discusses and evaluates empirical studies concerned with Christian prayer. These studies are classified within four main areas. The first area concerns what is known about the practice of prayer from empirical surveys and demonstrates that a much higher proportion of people pray privately than attend public places of worship. The second area concerns what is known about changing patterns of prayer during childhood and adolescence and argues that these changes need to be interpreted within the context of both developmental and social psychology. The third area concerns the subjective effects of prayer, beginning with Galton's early observations concerning the comparative longevity of the clergy (who are regarded as praying people) and including more recent studies of the psychological correlates of self-reported prayer, like personal well-being and purpose in life. It is concluded that, while such studies may demonstrate the beneficial nature of prayer, they cannot demonstrate the causal efficacy of prayer. The fourth area concerns the objective effects of prayer, beginning with Galton's early observations concerning the absence of comparative longevity among royalty (who are regarded as prayed for people) and including more recent studies of the growth correlates of prayer for pot plants. It is concluded that such studies currently provide contradictory evidence. It is recommended that further research in the field needs both to observe the strict criteria of objective empirical research and to be alert to theological nuances regarding the actual claims made for the efficacy of prayer within the community of believers.     

Division of labor in conversations: Are Fishman's results replicable and generalizable?

Fishman's (1978a) conclusion that women do the bulk of the support work in their conversations with male partners has had widespread appeal. In this article, we present the results of two studies designed to assess the generalizability and replicability of her findings. In Study 1. the get-acquainted conversations of 20 mixed-sex, 10 male same-sex, and 10 female same-sex dyads were analyzed for the support strategies identified by Fishman. No support for a sexual division of labor was found. In Study 2, we analyzed the casual, at-home conversations of 17 intimate male-female couples. Again, we found no evidence that the women used more of the support strategies than their male partners. Rather, our findings suggest that the women may have helped to sustain the conversations with their male partners simply by talking more. The appeal of Fishman's conclusions in the absence of empirical evidence suggests that she has touched on a mythic truth.This article is based on a Master's thesis by the second author (Study 1) and an Honour's thesis by the third author (Study 2) under the supervision of the first author.     

Uncertainty in estimating distances from memory

Magnitude estimations involving spatial characteristics, such as distance, typically show a compressive function when estimates are made from memory. In particular, as the magnitude of a property grows larger and larger, estimates become more and more inaccurate, with increasing underestimates of the actual magnitude. Previous theories have attempted to explain this difference by supposing that magnitude estimation was accomplished through a reperceptual process, in which the errors of perception are magnified, or a transformation process, in which the memory trace undergoes a consistent alteration toward a more schematic form. The present experiments present evidence in support of an uncertainty hypothesis. When subjects are uncertain of the actual value of a distance, they are forced to guess on the basis of the mean distance they encountered, because they are unable to retrieve the information accurately. When they can retrieve the information, they are more certain and their estimates are more accurate. This hypothesis was also extended to integrative conditions in which the subjects were presented with the stimulus display in a piecemeal fashion. In these cases, distance estimates were derived by combining spatial representations. This method of presentation caused distance estimates to become less accurate.     

The role of attention in the shift from orientation-dependent to orientation-invariant identification of disoriented objects

In two experiments, the naming of rotated line drawings of natural objects was examined after a training phase in which the objects were either attended or ignored. In the training phase of Experiment 1, subjects were presented with objects in a number of orientations over five repeated blocks of trials. In the center of each object, seven letters (Xs and Ts, colored red or blue) were presented in rapid succession. Half the subjects named aloud the rotated object and ignored the changing letter display (object-attend). The other half ignored the object and counted the number of red Ts, and then used this number to perform a simple multiplication (object-ignore). In the test phase, all subjects named the rotated objects. The results showed that in the first block of trials in the training phase, mean naming time in the object-attend condition increased the further an object was rotated from the upright. This effect of orientation for attended objects was much reduced in the later presentations of the test phase. In contrast, there was no such benefit of prior presentation observed for the naming of objects that had previously been ignored. Instead, a substantial orientation effect was shown for the naming of previously ignored objects, which was similar to the orientation effect observed for attended objects named in the first block. Similar results were found in Experiment 2, in which object-attend subjects in training covertly named the objects and then performed a letter count and multiplication task. In both experiments, performance on the letter count and multiplication task varied with the angle of the ignored object. The results suggest that full attentional resources must be allocated in order for orientation-invariant representations to be formed and used in the identification of rotated objects.