Implementing context information management in forensic casework: Minimizing contextual bias in firearms examination.

Managing context information in forensic casework aims to minimize task-irrelevant information while maximizing the task-relevant information that reaches the examiner. A design and implementation of context information management (CIM) is described for forensic firearms examination. Guided by a taxonomy of different sources of context information, a flow-chart was constructed that specifies the process of casework examination and context information management. Due to the risk of bias, another examiner may need to be involved when context information management is unsuccessful. Application of context information management does not make a subjective examination objective, but can limit the risks of bias with a minimal investment of time and resources.

The role of meaning and familiarity in mental transformations.

Eighty-four participants mentally rotated meaningful and meaningless objects. Within each type of object, half were simple and half were complex; the complexity was the same across the meaningful and meaningless objects. The patterns of errors were examined as a function of the type of stimuli (meaningful vs. meaningless), complexity, and angle of rotation. The data for the meaningful objects showed steeper slopes of rotation for complex objects than that for simple objects. In contrast, the simple and complex meaningless objects showed comparable increases in error rates as a function of angle of rotation. Furthermore, the slopes remained comparable after pretraining that increased familiarity with the objects. The results are discussed in terms of underlying representations of meaningful and meaningless objects and their implications to mental transformations. The data are consistent with a piecemeal rotation of the meaningful stimuli and a holistic rotation of the meaningless stimuli.

Object identification as a function of discriminability and learning presentations: the effect of stimulus similarity and canonical frame alignment on aircraft identification.

Aircraft that were relatively similar (homogeneous) and relatively dissimilar (heterogeneous) in appearance were studied at orientations either consistent (canonical) or inconsistent (noncanonical) with the environmental frame of reference. At test, participants' identification performance was measured with stimuli rotated to novel orientations within the picture plane. During learning and testing, identification of heterogeneous aircraft was better than that of homogeneous aircraft. At test, only identification of homogeneous aircraft revealed a strong linear degradation of performance as angular disparity between the novel test orientations and the original learning orientations increased. During learning and testing, identification was better for aircraft studied at canonical orientations than for those studied at noncanonical orientations. The results are discussed in terms of object identification, aircraft recognition training, categorization, mental representations, and visual mental rotation.

Decision making under time pressure: an independent test of sequential sampling models.

Choice probability and choice response time data from a risk-taking decision-making task were compared with predictions made by a sequential sampling model. The behavioral data, consistent with the model, showed that participants were less likely to take an action as risk levels increased, and that time pressure did not have a uniform effect on choice probability. Under time pressure, participants were more conservative at the lower risk levels but were more prone to take risks at the higher levels of risk. This crossover interaction reflected a reduction of the threshold within a single decision strategy rather than a switching of decision strategies. Response time data, as predicted by the model, showed that participants took more time to make decisions at the moderate risk levels and that time pressure reduced response time across all risk levels, but particularly at the those risk levels that took longer time with no pressure. Finally, response time data were used to rule out the hypothesis that time pressure effects could be explained by a fast-guess strategy.

Aging and the scope of visual attention.

OBJECTIVE: To discover whether some cognitive deficits associated with aging could be related to a restricted scope of visual attention. DESIGN: Cross-sectional study, with subjects in each age group receiving the same four conditions. SUBJECTS: 24 elderly (mean age 65.2 years, 12 men and 12 women) and 24 young (mean age 21.8 years, 12 men and 12 women) matched for handedness, gender, and education level. METHODS: SUBJECTS viewed a display that contained four light-gray squares arranged as if on the tips of a plus sign, then black X marks appeared and the subjects indicated whether one or two Xs appeared in the squares as quickly and accurately as possible. The time to respond and accuracy level were recorded. Two types of displays were used; one with squares spread out over a large area and one with squares condensed into a small area. In two thirds of the trials the size remained the same (with half being large, and half small), and in one third it changed (with half of these trials changing from large-to-small and half from small-to-large). RESULTS: In the trials that had a consistent display size, the elderly subjects performed the task better with the smaller display, whereas the young subjects performed equally well with both sized displays. In addition, the elderly found it easier to shift from large to small scope than to maintain attention at the large scope; in contrast, the younger subjects found it easiest to maintain attention on a static display size. CONCLUSIONS: The elderly prefer to focus attention on a smaller region of space than do younger people.

Computational analyses in cognitive neuroscience: in defense of biological implausibility.

Because cognitive neuroscience researchers attempt to understand the human mind by bridging behavior and brain, they expect computational analyses to be biologically plausible. In this paper, biologically implausible computational analyses are shown to have critical and essential roles in the various stages and domains of cognitive neuroscience research. Specifically, biologically implausible computational analyses can contribute to (1) understanding and characterizing the problem that is being studied, (2) examining the availability of information and its representation, and (3) evaluating and understanding the neuronal solution. In the context of the distinct types of contributions made by certain computational analyses, the biological plausibility of those analyses is altogether irrelevant. These biologically implausible models are nevertheless relevant and important for biologically driven research.

Age degradation in top-down processing: identifying objects from canonical and noncanonical viewpoints.

Twenty-four young (mean age 21.8 years) and 24 old (mean age 65.2 years) participants were asked to determine whether spoken words correctly named pictures of objects. Half of the objects were portrayed from noncanonical (unusual) viewpoints, and half were portrayed from canonical viewpoints. The older participants required more time and made more errors when they evaluated the noncanonical pictures (relative to the canonical pictures) than the younger participants. This finding is consistent with previous evidence that frontal lobe function degrades with aging and with results from a positron emission tomography study (S. M. Kosslyn et al., 1994) that showed that the frontal lobes (among other areas) are activated more in the noncanonical condition than in the canonical condition.

Aging and scanning of imagined and perceived visual images.

The authors examined adult age differences in the proficiency of visually scanning across perceived and imagined displays. Participants were asked to indicate whether an arrow in the central region of a square grid ring pointed to a target square. The distance between arrow and target was varied, and all participants showed the expected increase in response times and error rates as scanning distance increased. The arrow and grid display either remained visible until the participant responded (perceptual condition) or disappeared after 50 ms (imagery condition). In both conditions, older participants required more time to scan and made more errors as distance increased than did younger participants. These findings conflict with previous studies showing that perceptual and imagery scanning are preserved with aging. Although methodological factors may have contributed to these differences, further research is needed to elucidate effects of aging on visual scanning.

Age differences in decision making: to take a risk or not?

A controlled laboratory experiment was used to assess the efficacy of the cognitive processes that underlie risk taking decision making in young and elderly people. Thirty-six participants took part in the study: half the subjects were elderly (mean age of 74) and the other half were young adults (mean age of 19). The elderly participants made equivalent decisions to those of the control young adults. Both age-groups of participants systematically and comparably changed their behavior as a function of risk levels. Furthermore, the elderly participants, relative to young adults, did not exhibit any slowing down in the speed of processing the information involved in making risk taking decisions, reflecting that healthy elderly people are cognitively apt to making risk taking decisions. Both age-groups took comparably less time on the easy trials (trials with either low or high levels of risk) and comparably more time on the difficult trials (trials with medium levels of risk).

Visual mental rotation of possible and impossible objects.

Participants were tested on two visual mental rotation tasks using three-dimensional "possible" and "impossible" shapes. Both types of stimuli can be easily encoded by their parts and how they are spatially organized. However, while possible shapes can also be easily encoded as a global image, it is more difficult to encode impossible shapes in such a way. Participants visually rotated both types of stimuli at comparable rates, reflecting that local representations were used in the process of visual mental rotation.

Using artificial bat sonar neural networks for complex pattern recognition: recognizing faces and the speed of a moving target.

Two sets of studies examined the viability of using bat-like sonar input for artificial neural networks in complex pattern recognition tasks. In the first set of studies, a sonar neural network was required to perform two face recognition tasks. In the first task, the network was trained to recognize different faces regardless of facial expressions. Following training, the network was tested on its ability to generalize and correctly recognize faces using echoes of novel facial expressions that were not included in the training set. The neural network was able to recognize novel echoes of faces almost perfectly (above 96% accuracy) when it was required to recognize up to five faces. In the second face recognition task, a sonar neural network was trained to recognize the sex of 16 faces (eight males and eight females). After training, the network was able to correctly recognize novel echoes of those faces as 'male' or as 'female' faces with accuracy levels of 88%. However, the network was not able to recognize novel faces as 'male' or 'female' faces. In the second set of studies, a sonar neural network was required to learn to recognize the speed of a target that was moving towards the viewer. During training, the target was presented in a variety of orientations, and the network's performance was evaluated when the target was presented in novel orientations that were not included in the training set. The different orientations dramatically affected the amplitude and the frequency composition of the echoes. The neural network was able to learn and recognize the speed of a moving target, and to generalize to new orientations of the target. However, the network was not able to generalize to new speeds that were not included in the training set. The potential and limitations of using bat-like sonar as input for artifical neural networks are discussed.

Mental imagery and aging.

Young adult and elderly Ss performed 4 visual mental imagery tasks, each of which tapped different processes. The elderly had relatively impaired image rotation and image activation (the process of accessing and activating stored visual memories), and there was a hint that aging may impair the ability to maintain images. In contrast, the elderly were able to compose (the process of generating the segments of the shape, 1 by 1) and scan visual mental images as well as young adults. However, when the authors correlated the mean performance of each age group across all the tasks, they found that the response times of the elderly were almost perfectly predicted by the performance of the young Ss but that the error rates were not correlated. These findings suggest that although there is slowing with age, individual imaging processes are affected selectively by aging.

The role of the corpus callosum in the representation of lateral orientation.

How do people recognize objects when they face in a novel lateral (left/right) orientation? The results of three experiments with a split-brain patient, who has a totally nonfunctional corpus callosum, demonstrate that the corpus callosum cannot play a critical role in allowing one to recognize mirror-reversed objects. First, both cerebral hemispheres could recognize mirror-reversed versions of pictures as accurately as the original renditions in an incidental memory task. Second, when asked to decide whether pictures faced the same way that they had originally, neither hemisphere performed better than chance in an incidental memory task--suggesting that the shape representations in the hemispheres do not specify lateral orientation. Third, neither hemisphere exhibited "priming" for lateral orientation, as assessed in an "object decision task", and only the left hemisphere exhibited priming for encoding the shape (independent of its lateral orientation).