Contingent feature analysis in speech perception

A contingent adaptation effect is reported for speech perception. Experiments were conducted to test the effects of an alternating sequence of two adapting syllables, [da] and [t^hi], on the perception of two series of synthetic speech syllables, [ba]-[p^ha] and [bi]-[p^hi]. Each of the test series consisted of 11 stimuli varying in voice onset time, a cue which distinguishes voiced from voiceless stop consonants in word-initial position. The [da]-[t^hi] adapting sequence produced opposite shifts in the loci of the phonetic boundaries for the two test series. For the [ba]-[p^ha] series, listeners made fewer identification responses to the [b] category after adaptation, while for the [bi]-[p^hi] series, listeners made more responses to the [b] category. The opposing shifts indicate that the perceptual analysis of voicing in stop consonants is carried out with respect to vowel environment.     

Acoustic feature analysis in the perception of voicing contrasts

Various types of acoustic cues have been shown to signal voicing contrasts in initial prestressed stop consonants. Two of the most important of these cues are the time interval between the release burst and the onset of voicing (voice onset time) and the duration of voiced transitions. In the present experiment, a selective adaptation procedure was used to investigate possible feature extraction mechanisms which underlie the perception of voicing. Subjects first identified either of two series of test stimuli, [ba-p^ha) or [ga-k^ha]. Next they listened to repeated presentations of an adapting stimulus and then again identified the original test series. Adapting stimuli having the same value of voice onset time but different voiced transition durations produced differential (and sometimes opposite) effects on the identification of the test stimuli. In every case, the adapting stimulus with the greater duration of voiced transitions led to larger reduction in voiced responses or to a smaller increase in voiceless responses. These results are incompatible with models of voicing perception based strictly on detectors for voice onset time. The results also suggest that the adaptation effect occurs at a point in the system prior to the actual phonetic decision.     

The role of structure in infant visual pattern perception

The research of the authors and others on the role of structure in infant visual pattern perception is reviewed. Two new experiments are reported on preference for symmetry in infants. It is shown that infants reliably prefer patterns with multiple axes of bilateral symmetry relative to asymmetrical patterns. Also, the results demonstrate that vertically oriented single axis bilateral symmetry is more salient than horizontally oriented symmetry in infants as it is in adults. It is argued that sensitivity to various kinds of pattern structure reflects fundamental operations of the visual system.     

Focal attention and the perception of pattern structure in extrafoveal vision

Several studies have shown that visual attention enhances the encoding of the positional relationships between pattern elements, i.e., the perception of pattern structure. This theoretical note discusses the possibility that the inferiority of extrafoveal vision in the perception of pattern structure results, at least partially, from less effective focal attention in the periphery. Hence, there may exist higher level differences between foveal and extrafoveal vision in information processing which cannot be explained by the spatial inhomogeneity of the retino-striate system.     

A computational feature binding model of human texture perception

We present a computational model for human texture perception which assigns functional principles to the Gestalt laws of similarity and proximity. Motivated by early vision mechanisms, in the first stage, local texture features are extracted by utilizing multi-scale filtering and nonlinear spatial pooling. In the second stage, features are grouped according to the spatial feature binding model of the competitive layer model (CLM; Wersing et al. 2001). The CLM uses cooperative and competitive interactions in a recurrent network, where binding is expressed by the layer-wise coactivation of feature-representing neurons. The Gestalt law of similarity is expressed by a non-Euclidean distance measure in the abstract feature space with proximity being taken into account by a spatial component. To choose the stimulus dimensions which allow the most salient similarity-based texture segmentation, the feature similarity metrics is reduced to the directions of maximum variance. We show that our combined texture feature extraction and binding model performs segmentation in strong conformity with human perception. The examples range from classical microtextures and Brodatz textures to other classical Gestalt stimuli, which offer a new perspective on the role of texture for more abstract similarity grouping.     

Syntactic structure and acoustic pattern in speech perception Arthur Wingfield

The interaction of syntactic structure and acoustic pattern in perceptual segmentation of heard speech was investigated using sentences recorded with intonation patterns appropriate to their underlying structure and sentences where intonation was placed in direct conflict with the underlying structure. Speech samples were monitored through dichotic earphones with messages switched from one ear to the other either between or within major linguistic constituents. Analysis of errors in source localization and in sentence reproduction suggested a primary role of acoustic pattern in segmentation is to cue underlying syntactic structure. Two subsidiary experiments provided evidence that observed effects were related to active perceptual processing of the speech signal.     

Visual and auditory processing of common pattern class structure

Visual and auditory classification of equivalent class structured patterns were examined. Underlying patterns from two classes were translated into auditory tone sequences and visual polygons. All Ss classified 50 visual patterns and their direct auditory analogs. Visual classification accuracy exceeded auditory accuracy (p < .01); however, auditory accuracy improved when auditory classification was preceded by the visual task (p < .01). Based on group data, classification strategies appeared similar across modalities, with accuracy of classification of individual patterns predicted to the same degree by common measures of physical class structure across modalities. Ss’ drawings of the prototypes also suggested a common strategy across modalities. While group data suggest some consistency of classification strategy across modalities, individual Ss were not at all consistent in their visual and auditory classifications.     

Principles of feature integration in visual perception

Several recent theories of visual information processing have postulated that errors in recognition may result not only from a failure in feature extraction, but also from a failure to correctly join features after they have been correctly extracted. Errors that result from incorrectly integrating features are called conjunction errors. The present study uses conjunction errors to investigate the principles used by the visual system to integrate features. The research tests whether the visual system is more likely to integrate features located close together in visual space (the location principle) or whether the visual system is more likely to integrate features from stimulus items that come from the same perceptual group or object (the perceptual group principle). In four target-detection experiments, stimuli were created so that feature integration by the location principle and feature integration by the perceptual group principle made different predictions for performance. In all of the experiments, the perceptual group principle predicted feature integration even though the distance between stimulus items and retinal eccentricity were strictly controlled.     

A feature analysis of stuttered phonemes

Stuttered and nonstuttered phonemes of 20 adult males were analyzed for distinctive feature patterns using the Chomsky-Halle system. The features (+ consonantal), (- voice), (+ continuant), and (- strident) occured significantly more often in stuttering than in nonstuttering instances. Results suggest that adult stuttering is most likely to occur when the primary sites of tension and discoordination are lingual and laryngeal and when the speaker must shift from (- voice) to (+ voice).     

When complexity helps: an electrophysiological analysis of multiple feature benefits in object perception

Fournier, L. R., Eriksen, C. W. and Bowd, C. (1998. Multiple feature discrimination faster than single feature discrimination within the same object? Perception & Psychophysics 60, 1384-1405) found that judging the presence of multiple features within an object is faster than judging the presence of the least discriminable of these features alone (multiple feature benefits, MFBs). When an 'absent' response is required, responses are slower when some of the relevant (target) features are present (multiple feature costs, MFCs). The present study utilized psychophysiological measures (of the event-related brain potential and the electromyogram) to determine the contributions of response priming and stimulus evaluation processes (P300 latency) to these effects. P300 latency and reaction time (RT) both showed evidence of MFBs and MFCs. These findings suggest that MFBs and MFCs can be attributed to processing that occurs prior to response selection. No dissociations between P300 latency and RT measures were found for 'present' responses across the single and multiple feature judgements. However, for 'absent' responses, partial dissociations were found between these measures, and partial errors and longer response execution intervals were observed more often when an object contained some target features. These findings suggest that response priming contributes to MFCs, but may not contribute to MFBs.     

Visual pattern perception: a multidimensional analysis of development of children's reading skills

This study was designed to assess the extent to which there are visual pattern processing deficits which are related to differential reading skill of young children. Discrimination problems were constructed using visual patterns with features known to be processed differentially by the central nervous system based upon neurophysiological data. Analysis of variance and multidimensional scaling techniques were used to analyze the discrimination latencies of kindergarten through third grade children (12 per grade) who were classified either as good or poor readers. The results show that there are no pattern-specific effects which discriminate good from poor readers. Rather, good readers process all patterns more efficiently than do poor readers, and efficiency improves with age for all readers studied. This suggests that the locus of the reading deficit occurs at levels in the nervous system beyond where pattern-feature processing occurs.     

The role of auditory feature detectors in the perception of speech

Attention, Perception, & Psychophysics - Two adaptation experiments were conducted to determine some of the sufficient acoustic properties for excitation of the feature detectors underlying...     

The effect of feature displacement on the perception of well-known faces

The effect of feature displacement within two well-known faces (Terry Wogan and Cyril Smith) was examined. Image processing equipment was used to produce stimuli in which the features of an original facial image were displaced to form a number of modified images. This technique was first reported by Haig, in a recognition study in which the effect of feature displacement within unfamiliar faces was investigated. In the present experiment a perceptual judgement task was carried out in which subjects were presented with a number of modified faces and asked to judge how dissimilar these were with respect to an original image. A multi-dimensional scaling analysis of the comparative judgements of the subjects revealed a two-dimensional solution involving displacement of the eyes and mouth. A clear division between up/down and inward/outward displacement within these features (particularly the eyes) was observed. A similar pattern of results was found for both well-known faces. This result indicates that subjects were responding to changes in the facial configuration produced by the different types of feature displacement (horizontal or vertical), as opposed to movement of the features per se. Finally, the results also indicate that the displacement of inner features (mouth, eyes, nose) was more noticeable than displacement of the outer facial features (eg hairline).     

Investigating the anticipatory nature of pattern perception in sport

The aim of the present study was to examine the anticipatory nature of pattern perception in sport by using static and moving basketball patterns across three different display types. Participants of differing skill levels were included in order to determine whether the effects would be moderated by the knowledge and experience of the observer in the same manner reported previously for simple images. The results from a pattern recognition task showed that both expert and recreational participants were more likely to anticipate the next likely state of a pattern when it was presented as a moving video, but only the experts appeared to have the depth of understanding required to elicit the same anticipatory encoding for patterns presented as schematic images. The results extend those reported in previous research and provide further evidence of an anticipatory encoding in pattern perception for images containing complex, interrelated patterns.     

Roughness perception of unfamiliar dot pattern textures

Both vision and touch yield comparable results in terms of roughness estimation of familiar textures as was shown in earlier studies. To our knowledge, no research has been conducted on the effect of sensory familiarity with the stimulus material on roughness estimation of unfamiliar textures.The influence of sensory modality and familiarity on roughness perception of dot pattern textures was investigated in a series of five experiments. Participants estimated the roughness of textures varying in mean center-to-center dot spacing in experimental conditions providing visual, haptic and visual–haptic combined information.The findings indicate that roughness perception of unfamiliar dot pattern textures is well described by a bi-exponential function of inter-dot spacing, regardless of the sensory modality used. However, sensory modality appears to affect the maximum of the psychophysical roughness function, with visually perceived roughness peaking for a smaller inter-dot spacing than haptic roughness. We propose that this might be due to the better spatial acuity of the visual modality. Individuals appeared to use different visual roughness estimation strategies depending on their first sensory experience (visual vs. haptic) with the stimulus material, primarily in an experimental context which required the combination of visual and haptic information in a single bimodal roughness estimate. Furthermore, the similarity of findings in experimental settings using real and virtual visual textures indicates the suitability of the experimental setup for neuroimaging studies, creating a more direct link between behavioral and neuroimaging results.