Blobs strengthen repetition but weaken symmetry

Item does not contain fulltextThe human visual system is more sensitive to symmetry than to repetition. According to the so-called holographic approach [J. Math. Psychol. 35 (1991) 151; Psychol. Rev. 103 (1996) 429; Psychol. Rev. 106 (1999) 622], however, this perceptual difference between symmetry and repetition depends strongly on spatial scaling. This was tested in three experiments, using symmetry and repetition stimuli that consisted of black and white patches, with patch size as the critical variable. In Experiment 1, patch size was increased in the entire pattern, yielding fewer but larger patches (or blobs). This is known to have hardly any effect on symmetry but, as found now, it does have a strengthening effect on repetition. In the second experiment, we increased patch size in subpatterns only, yielding salient blob areas. This again strengthens repetition but, as double-checked in experiment 3, it can weaken symmetry. These results agree with the holographic approach, and enable an integration of computational, algorithmic, and implementational aspects of vision

Consensus on validation of forensic voice comparison

Since the 1960s, there have been calls for forensic voice comparison to be empirically validated under casework conditions. Since around 2000, there have been an increasing number of researchers and practitioners who conduct forensic-voice-comparison research and casework within the likelihood-ratio framework. In recent years, this community of researchers and practitioners has made substantial progress toward validation under casework conditions becoming a standard part of practice: Procedures for conducting validation have been developed, along with graphics and metrics for representing the results, and an increasing number of papers are being published that include empirical validation of forensic-voice-comparison systems under conditions reflecting casework conditions. An outstanding question, however, is: In the context of a case, given the results of an empirical validation of a forensic-voice-comparison system, how can one decide whether the system is good enough for its output to be used in court? This paper provides a statement of consensus developed in response to this question. Contributors included individuals who had knowledge and experience of validating forensic-voice-comparison systems in research and/or casework contexts, and individuals who had actually presented validation results to courts. They also included individuals who could bring a legal perspective on these matters, and individuals with knowledge and experience of validation in forensic science more broadly. We provide recommendations on what practitioners should do when conducting evaluations and validations, and what they should present to the court. Although our focus is explicitly on forensic voice comparison, we hope that this contribution will be of interest to an audience concerned with validation in forensic science more broadly. Although not written specifically for a legal audience, we hope that this contribution will still be of interest to lawyers.This article is published as Morrison, Geoffrey Stewart, Ewald Enzinger, Vincent Hughes, Michael Jessen, Didier Meuwly, Cedric Neumann, Sigrid Planting et al. "Consensus on validation of forensic voice comparison." Science & Justice (2021). Posted with permission.</p

Interactions between constituent single symmetries in multiple symmetry

Item does not contain fulltextAs a rule, the discriminability of multiple symmetries from random patterns increases with the number of symmetry axes, but this number does not seem to be the only determinant. In particular, multiple symmetries with orthogonal axes seem better discriminable than multiple symmetries with nonorthogonal axes. In six experiments on imperfect two-fold symmetry, we investigated whether this is due to extra structure in the form of so-called correlation rectangles, which arise only in the case of orthogonal axes, or to the relative orientation of the axes as such. The results suggest that correlation rectangles are not perceptually relevant and that the percept of a multiple symmetry results from an orientation-dependent interaction between the constituent single symmetries. The results can be accounted for by a model involving the analysis of symmetry at all orientations, smoothing (averaging over neighboring orientations), and extraction of peaks

Effects of asynchrony on symmetry perception,Psychologische Forschung

Item does not contain fulltextThe effect of temporal image segmentation on symmetry perception was investigated by means of stimuli composed of one part surrounding another. The two parts could be presented synchronously or with a temporal offset (20-100 ms), and each part could be either symmetrical or random. The task was to discriminate completely symmetrical (S) stimuli (in Experiment 1) or completely random (R) stimuli (in Experiment 2) from partially symmetrical (PS) stimuli in which one part was symmetrical and the other random. The R stimuli showed an asynchrony effect but the S stimuli did not. Furthermore, in both experiments, the PS stimuli showed an asynchrony effect when the symmetrical part was presented last but not when the symmetrical part was presented first (independent of whether it was the surrounded part or the surrounding part). Both results suggest that symmetry is strong enough to override this kind of temporal image segmentation.8 p

Symmetry versus repetition in cyclopean vision: a microgenetic analysis

Contains fulltext : 56108.pdf (publisher's version ) (Closed access)In four experiments, participants had to detect symmetries or repetitions distributed over two depth planes, under presentation times of 200-1000 ms. Structurally corresponding elements were placed in different planes (Experiments la and 1b) or in the same plane (Experiments 2a and 2b). Results suggest (a) an ongoing interaction between regularity cues and depth cues, and (b) that efficient detection of symmetry but not of repetition depends on structural correspondences within depth planes. The latter confirms the idea that, to perceptual organization, symmetry is a cue for the presence of one object, whereas repetition is a cue for the presence of multiple objects.12 p