Greater Discriminability Research Articles

Is threat detection Black and White? Race effects in threat-related perceptual decision-making.

There is a vast literature base indicating that people respond differently to Black and White individuals based on differential perceptions of threat. As facial affect is a fundamental way that individuals communicate their emotional state, studies have examined differences in how Black and White threatening facial expressions are perceived. However, perceptual decisions regarding threatening and neutral stimuli often occur in familiar contexts or in environments where explicit cues indicate the presence or absence of threat. Furthermore, these decisions often occur in "noisy" (i.e., ambiguous) environments where the quality of sensory evidence is poor, requiring us to rely on perceptual "sets" or expectations to interpret such evidence. Therefore, in the present study we used a two-alternative perceptual decision-making task in which participants used threatening and neutral cue-elicited perceptual sets to discriminate between subsequently presented threatening and neutral Black and White faces. Threatening cues led to a greater tendency to decide that both Black and White faces were threatening, as well as faster and greater discriminability between threatening and neutral Black and White faces. However, race-related differences revealed that, following both cue types, discriminability between threatening and neutral Black faces was worse compared to White faces. Therefore, using a paradigm that is ecologically valid, our findings highlight the importance of examining basic aspects of visual perception to understand race-related differences in threat-related perceptual decision-making. Furthermore, these findings emphasize the importance of anticipatory top-down factors when making perceptual decisions about the presence or absence of threat in faces of different races. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Judged Beauty of Fractal Symmetries

Fractals are patterns that show self-similarity at different levels of scale. Typically they appear in nature and this degree of similarity is approximate or statistical. However, artificial or exact fractals have also been studied and the advantage of these stimuli is the ability to more carefully control the relationships that occur across various hierarchies. In two experiments we studied the perceived beauty of a novel class of exact visual fractal in which we introduced reflection, rotation, translation, and random symmetries that repeated at a local and global levels. Rotation and reflection were consistently preferred to translation and randomness. Only reflected patterns were preferred at a vertical orientation. For all other symmetries there was no difference in preference between vertical and horizontal. In a second experiment we progressively eliminated the salience of local symmetry through opaque shading . Perceived beauty decreased with an increase in shading . For these patterns greater discriminability of their fractal quality makes them more aesthetically appealing.

Improving performance in motor imagery BCI-based control applications via virtually embodied feedback

ObjectiveBrain-computer interfaces (BCIs) based on motor imagery (MI) are commonly used for control applications. However, these applications require strong and discriminant neural patterns for which extensive experience in MI may be necessary. Inspired by the field of rehabilitation where embodiment is a key element for improving cortical activity, our study proposes a novel control scheme in which virtually embodiable feedback is provided during control to enhance performance. MethodsSubjects underwent two immersive virtual reality control scenarios in which they controlled the two-dimensional movement of a device using electroencephalography (EEG). The two scenarios only differ on whether embodiable feedback, which mirrors the movement of the classified intention, is provided. After undergoing each scenario, subjects also answered a questionnaire in which they rated how immersive the scenario and embodiable the feedback were. ResultsSubjects exhibited higher control performance, greater discriminability in brain activity patterns, and enhanced cortical activation when using our control scheme compared to the standard control scheme in which embodiable feedback is absent. Moreover, the self-rated embodiment and presence scores showed significantly positive linear relationships with performance. SignificanceThe findings in our study provide evidence that providing embodiable feedback as guidance on how intention is classified may be effective for control applications by inducing enhanced neural activity and patterns with greater discriminability. By applying embodiable feedback to immersive virtual reality, our study also serves as another instance in which virtual reality is shown to be a promising tool for improving MI.

Psychometric characteristics of the postconcussion symptom inventory in children and adolescents.

Psychometric characteristics of the Postconcussion Symptom Inventory (PCSI) were examined in both concussed (n = 633) and uninjured (n = 1,273) 5 to 18 year olds. Parent- and self-report forms were created with developmentally appropriate wording and content. Factor analyses identified physical, cognitive, emotional, and sleep factors; that did not load strongly or discriminate between groups were eliminated. Internal consistency was strong for the total scales (α = 0.8-0.9). Test-retest reliability for the self-report forms was moderate to strong (intraclass coeffecients, ICCs = 0.65-0.89). Parent and self-report concordance was moderate (r = .44-.65), underscoring the importance of both perspectives. Convergent validity with another symptom measure was good (r = .8). Classification analyses indicated greater discriminability from parent report, but caveats to this are presented. With strong psychometric characteristics, the four versions of the PCSI capture important postconcussion symptoms and can be utilized to track recovery from pediatric concussion and guide treatment recommendations.

Facial expression influences recognition memory for faces: Robust enhancement effect of fearful expression

Memory for faces is important for social interactions. However, it is unclear whether negative or positive expression affects recollection and familiarity for faces and whether the effect can be modulated by retention interval. Two experiments examined the effect of emotional expression on recognition for faces at two delay conditions. In Experiment 1 participants viewed neutral, positive, and negative (including fearful, sad, angry etc.) faces and made gender discrimination for each face. In Experiment 2 they viewed and made gender discrimination for neutral, positive, and fearful faces. Following the incidental learning they were randomly assigned into the immediate and 24-hour (24-h) delay conditions. Findings from the two experiments are as follows: (1) In the immediate and 24-h delay conditions overall recognition and recollection for negative faces (fearful faces in Experiment 2) were better than for neutral faces and positive faces. (2) In the immediate and 24-h delay conditions recollection and familiarity for positive faces was equivalent to recollection for neutral faces. (3) The enhancement effect of fearful expression on recognition and recollection was not due to greater discriminability between the old and new faces in the fearful category. The results indicate that recognition and recollection for faces and the enhancement effect of fearful expression is robust within 24 hours.

Postidentification feedback affects subsequent eyewitness identification performance.

Eyewitnesses sometimes view more than one lineup during an investigation. We investigated the effects of postidentification feedback following one lineup on responses to a second lineup. Witnesses (N=621) viewed a mock crime and, later, attempted to identify the culprit from an initial (target-absent) lineup and a second (target-present or target-absent) lineup. Prior to viewing the second lineup, some witnesses received accurate feedback stating that the initial lineup did not contain the culprit. A compound-decision, signal detection approach allowed the effects of feedback on identification responses to be described in terms of differences in discriminability and response bias. For witnesses who made an incorrect foil identification from the initial lineup, feedback (vs. no feedback) was associated with poorer discriminability on the second test. For witnesses who correctly rejected the initial lineup, feedback (vs. no feedback) was associated with greater discriminability on the second test. Only witnesses who received feedback after an initial correct rejection performed at a level comparable with a single-lineup control group, suggesting that an initial identification test can impair, but not enhance, performance on a second test involving the same culprit. From a theoretical perspective, the results are consistent with the idea that the way people use memorial information when making memory decisions is flexible. Analyses of preidentification confidence ratings, obtained in a follow-up study (N=133), suggested that the effects of feedback on identification performance may have operated via differences in witnesses' metacognitive beliefs.

Influence of separate and mixed experimental designs on reaction times to two simple visual stimuli

Testing contexts have been shown to critically influence experimental results in psychophysical studies. One of these contexts that show important modulation of the behavioral effects of different stimulatory conditions is the separate (blocked) or mixed presentation of these stimulatory conditions. The study presents evidence that the apparent discriminabilities of two target stimuli can change according to which of these two testing contexts is used. A cross inside a ring and a vertical line inside a ring were presented as go stimuli in a go/no-go reaction time task. In one experiment, each of these stimuli was presented to a different group of volunteers and in another experiment they were presented to the same group of volunteers, randomly mixed in the blocks of trials. Similar reaction times were obtained for the two stimuli in the first experiment, and different reaction times (faster for the cross) in the second experiment. The latter result indicates that the two stimuli have different discriminabilities from the no-go stimulus; the cross having greater discriminability. This difference is however masked, presumably by the adoption of specific compensatory attentional sets, in a separate testing context.

Influence of separate and mixed experimental designs on reaction times to two simple visual stimuli.

contexts have been shown to critically influence experimental results in psychophysical studies. One of these contexts that show important modulation of the behavioral effects of different stimulatory conditions is the separate (blocked) or mixed presentation of these stimulatory conditions. The study presents evidence that the apparent discriminabilities of two target stimuli can change according to which of these two testing contexts is used. A cross inside a ring and a vertical line inside a ring were presented as go stimuli in a go/no-go reaction time task. In one experiment, each of these stimuli was presented to a different group of volunteers and in another experiment they were presented to the same group of volunteers, randomly mixed in the blocks of trials. Similar reaction times were obtained for the two stimuli in the first experiment, and different reaction times (faster for the cross) in the second experiment. The latter result indicates that the two stimuli have different discriminabilities from the no-go stimulus; the cross having greater discriminability. This difference is however masked, presumably by the adoption of specific compensatory attentional sets, in a separate testing context. Keywords: context effects; reaction time; discriminability; attentional strategy.

Is there a special association between self judgements and conscious recollection?

Dual-process models of recognition memory posit a rapid retrieval process that produces a general sense of familiarity and a slower retrieval process that produces conscious recollections of prior experience. The Remember–Know paradigm has been used to study the subjective correlates of these two processes with Remember judgements assumed to index conscious recollection and Know judgements assumed to index familiarity. In this paper we examine Conway and Dewhurst's recent finding that judgements of self during encoding produce more Remember responses than alternative semantic judgements. While one might interpret this result to suggest a special association between self judgement and conscious recollection, we consider the possibility that it occurs because of greater discriminability in this condition. The results of four experiments demonstrate that a self judgement condition produces more, fewer, or an equal number of Remember responses relative to a control condition depending on whether overall discriminability in the self judgement condition is greater than, less than, or equal to that in the control condition. The implications of these results for conceptions of self judgement and the use of the Remember–Know paradigm are detailed. Copyright © 1999 John Wiley & Sons, Ltd.

The opponent colour functions and their relations with the colour discriminability

The paper deals with the problem of a construction of opponent functions, which stem from the linear summation of three receptor (R, G, B) signals. It is considered two stages model: stage of the receptors and stage of the opponent cells. Each stage has the own intrinsic independent generators of noise. The colour is determined by the point in three-dimensional space with coordinates {xi}, (i=l, 2, 3), where xi is value of the output signals of the opponent cells. Let V be the volume of “colour body” and be the volume of sphere, where an end of a colour vector is located with a given probability P0. Then a ratio V/s characterizes a colour discriminability: the greater ratio V/s the greater discriminability of the system. It is looking for such transformation of receptor signals into opponent those (i.e. searching a linear operator A), that the ratio V/s would be maximal. The properties of the proposed model were investigated. They fit well to the properties obtained in traditional psychophysical experiments: opponent colour functions, hue coefficients, wavelength and saturation discrimination, achromatic channel sensitivity, non-additivity of brightness. This led to conclusion that the possible role of the colour opponency is ensuring optimal colour discriminability in human vision.

Learning spatial dimensions with a visual sensory aid: Molyneux revisited.

The relationship between sensory aid research and several areas of perceptual learning has been explored with five experiments on learning the use of the Binaural Sensory Aid, an electronic sensor in which pitch specifies distance and interaural amplitude difference (IAD) specifies direction. The training task required reaching to objects in near space, with tactile error feedback. Perceptual learning for both dimensions was demonstrated within 72 trials, giving a level of performance comparable to the use of a natural sound source, although performance with the direction cue did not reach asymptote until a second training session. Training was unaffected by various kinds of regularity in the spatial target sequences, or by a reduction in the number of spatial target locations until only two locations were used; at this point directional accuracy declines. Training only one dimension at a time did not produce additional improvement of performance on that dimension, but did impair generalization of the direction cue. Learning of the pitch-distance dimension was generally better than that of the IAD dimension, possibly because of its greater discriminability with this device. Generally, the pattern of results indicates that in learning to use such devices subjects readily determine the sensory dimensions of the codes and have considerable ability to generalize to new locations.

Comparison of Multivariate Techniques in the Prediction of Juvenile Postparole Outcome

Several strategies for the prediction of institutional outcome have been attempted by researchers in juvenile and parole prediction. The majority of researchers have utilized a variation of multiple regression, while a few have made use of discriminant functions and factor analysis. The present study contrasted the three approaches in terms of predictive efficiency for juvenile recidivism. A total of 579 juvenile cases were selected from the Washington state juvenile archives during the calendar year of 1971. Forty predictive variables from personal histories and behavioral records of the Office of Juvenile Rehabilitation were collated and quantified for the study. The total sample was divided randomly into two groups for purposes of double cross-validation. On each of the two sample halves, a set of predictors of juvenile outcome were generated by each of three methods, factor analysis, stepwise regression, and stepwise discriminant functions. Validation of the three methods was assessed by (1) D2 or discriminability of each predictive variable on the cross-validation sample, and (2) the accuracy of classifying each juvenile based on discriminant analyses. The results showed clearly that stepwise discriminant functions provided the more consistent selection of variables with seven of 10 variables the same for all samples. Also, discriminant functions was shown to manifest the most predictive efficiency with significantly fewer misclassifications and greater discriminability. By contrast, stepwise regression and factor analysis as strategies manifested more misclassifications and less discriminability. In addition, the two methods were found to be unreliable in the selection of predictive variables for the two validation samples. Results were discussed in terms of the shrinkage problems of regression analyses and the homogeneity of variance associated with factor analysis.