Searching for threat

In a series of experiments, a visual search task was used to test the idea that biologically relevant threatening stimuli might be recognized very quickly or capture visuo-spatial attention. In Experiment 1, there was evidence for both faster detection and faster search rates for threatening animals than for plants. However, examination of the basis of this effect in Experiment 2 showed that it was not due to threat per se, as detection and search rate advantages were found for pleasant rather than threatening animals compared to plants. In Experiment 3, participants searched for the plants and pleasant and threatening animals used in Experiments 1 and 2, among a fixed heterogeneous selection of non-target items. There was no search rate or detection advantage for threatening animals compared to pleasant animals or plants. The same targets and non-targets as those used in Experiment 3 were also used in Experiment 4. In Experiment 4, participants searched for targets that were presented either close to or distant from an initial fixation point. There was no evidence for a "threat" detection advantage either close to or distant from the cross. Finally, an experiment was conducted in which target categories (fruit, flowers, and animals) were not pre-specified prior to each trial block. There were no differences in reaction times to detect pleasant animals, threatening animals, or fruit. We conclude that the visual search paradigm does not readily reveal any biases that might exist for threatening stimuli in the general population.     

The effects of externalization on syllogistic reasoning

An experiment is reported that investigated the effects of externalization of mental models in syllogistic reasoning. Although there was no evidence that the requirement to “externalize” mental models of syllogisms improved reasoning, an unexpected recognition test demonstrated that subjects' memory for the meaning of the premises was improved by externalization. In particular, where the correct conclusion had been deduced using the externalization procedure, responses in the recognition test reflected an appreciation of the relations between the end terms of the premises.     

Emotion and prior knowledge in memory and judged comprehension of ambiguous stories

Abstract

Two experiments investigated the effects of experimentally induced mood states on memory and judged comprehension of stories. The experiments examined the issue of whether induction of a depressed mood would affect prose memory and comprehension and impair the ability of individuals to use prior knowledge, activated by way of a title, in remembering the passage. In Experiment 1, depressed subjects who were given a title for the passage recalled fewer idea units when compared with neutral control conditions, but no depressive deficit in recall occurred in the absence of a title. In Experiment 2 the same pattern of results occurred when subjects learned two successive passages. The depressive deficits obtained were interpreted in terms of a resource allocation model which proposes that emotional states increase the production of irrelevant, competing thoughts that interfere with processes important in remembering the criterion passage. Alternative explanations involving cognitive initiative and schema theory were discussed. Finally, judgments of comprehension predicted passage recall and were better predictors for neutral than depressed mood subjects. A depressed mood state did not affect average judgments of comprehension even when recall was correspondingly impaired.     

Effects of Expectancy and Attention in Vibrotactile Choice Reaction Time Tasks

The orienting of attention in space has not been considered in the tactile domain. This issue is examined using a modified version of a visual paradigm initially adopted by Posner, Snyder, and Davidson (1980), which manipulates the probability of a stimulus occurring at different spatial locations. Slower RTs at an unexpected stimulus location are thought to reflect the time required to shift attention from the expected to the unexpected location. In two experiments involving vibrotactile choice RT between left and right hands, the two hands were either crossed or uncrossed, and the hands were held both on the left side of the body, both on the right, or one on either side of the midline. There was no evidence to suggest that spatial location (left or right) affected the orienting of attention in the tactual modality. As predicted, RTs were slower when the arms were crossed compared with uncrossed, though this effect was smaller for the expected trials. A coding conflict hypothesis may explain both these findings, but the smaller effect in the expected trials may also reflect attentional factors. Both the relative and absolute location of the hands affected the magnitude of the crossed-arm effect and indicated that attention may play a role in the perceptual division of space into left and right sides. Possible reasons for hand or hemispace asymmetries in different simple and choice RT paradigms were discussed.     

The sources of visual recency: Movement and language in serial recall

Four experiments examine the importance of movement—the sequential ordering of stimulus features—in producing recency in the ordered serial recall of visual lists. The written recall of handsigns produced more recency when they were seen moving than still (Experiment I). Number lists presented as moving bar figures showed more recency than numbers which were displayed in the normal way with all features displayed simultaneously (Experiment II). The order in which features of abstract shapes are displayed can, itself, determine recency (Experiment III). However, a final experiment showed that still lip pictures of speech sounds generate more recency than letters representing those speech sounds. Therefore movement of stimulus features need not account for the extensive recency advantage in remembering lipread lists. The theoretical implications of these findings are discussed.     

Shoulder Muscle Activity Dampens Arm Swing Motion When Altering Upper Limb Mass Characteristics During Locomotion

Weighting the arms during locomotion results in decreased swing motion and increased shoulder muscle activity. To determine the functional relevance of this activity, participants walked on a treadmill with the arms unweighted, or weighted unilaterally or bilaterally. Similar to past work, the weighted arms decreased in swing amplitude and increased their shoulder muscle activity. A close examination of shoulder muscle activities in specific regions of the arm swing cycle suggested these muscles primarily acted eccentrically for all weighting conditions. These findings suggest that the increased shoulder muscle activities when weighting the arms act to dampen the arms when the inertial characteristics of the arms are altered, as opposed to assisting in driving swing of the heavier arms.