Perceptual Dependence Research Articles

Manipulating the Fourier spectra of stimuli comprising a two-frame kinematogram to study early visual motion-detecting mechanisms: Perception versus short latency ocular-following responses.

Two-frame kinematograms have been extensively used to study motion perception in human vision. Measurements of the direction-discrimination performance limits (Dmax) have been the primary subject of such studies, whereas surprisingly little research has asked how the variability in the spatial frequency content of individual frames affects motion processing. Here, we used two-frame one-dimensional vertical pink noise kinematograms, in which images in both frames were bandpass filtered, with the central spatial frequency of the filter manipulated independently for each image. To avoid spatial aliasing, there was no actual leftward-rightward shift of the image: instead, the phases of all Fourier components of the second image were shifted by ±¼ wavelength with respect to those of the first. We recorded ocular-following responses (OFRs) and perceptual direction discrimination in human subjects. OFRs were in the direction of the Fourier components' shift and showed a smooth decline in amplitude, well fit by Gaussian functions, as the difference between the central spatial frequencies of the first and second images increased. In sharp contrast, 100% correct perceptual direction-discrimination performance was observed when the difference between the central spatial frequencies of the first and second images was small, deteriorating rapidly to chance when increased further. Perceptual dependencies moved closer to the OFR ones when subjects were allowed to grade the strength of perceived motion. Response asymmetries common for perceptual judgments and the OFRs suggest that they rely on the same early visual processing mechanisms. The OFR data were quantitatively well described by a model which combined two factors: (1) an excitatory drive determined by a power law sum of stimulus Fourier components' contributions, scaled by (2) a contrast normalization mechanism. Thus, in addition to traditional studies relying on perceptual reports, the OFRs represent a valuable behavioral tool for studying early motion processing on a fine scale.

Perception and Quantization Model for Periodic Contour Modifications.

Periodic, wave-like modifications of 2D shape contours are often applied to convey quantitative data via images. However, to the best of our knowledge, there has been no in-depth investigation of the perceptual uniformity and legibility of these kind of approaches. In this paper, we design and perform a user study to evaluate the perception of periodic contour modifications related to their geometry and colour. Based on the study results, we statistically derive a perceptual model, which demonstrates a mainly linear stimulus-to-perception relationship for geometric and colour amplitude and a close-to-quadratic relationship for the respective frequencies, with a rather negligible dependency on the waveform. Furthermore, analyzing the distribution of perceived magnitudes and the overlapping of the respective 50% confidence intervals, we extract distinguishable, visually equidistant quantization levels for each contour-related visual variable. Moreover, we give first insights into the perceptual dependency between amplitude and frequency, and propose a scheme for transferring our model to glyphs with different size, which preserves the distinguishability and the visual equidistance. This work is seen as a first step towards a comprehensive understanding of the perception of periodic contour modifications in image-based visualizations.

Losing Touch: An Embodiment Perspective on Coordination in Robotic Surgery

Because new technologies allow new performances, mediations, representations, and information flows, they are often associated with changes in how coordination is achieved. Current coordination research emphasizes its situated and emergent nature, but seldom accounts for the role of embodied action. Building on a 25-month field study of the da Vinci robot, an endoscopic system for minimally invasive surgery, we bring to the fore the role of the body in how coordination was reconfigured in response to a change in technological mediation. Using the robot, surgeons experienced both an augmentation and a reduction of what they can do with their bodies in terms of haptic, visual, and auditory perception and manipulative dexterity. These bodily augmentations and reductions affected joint task performance and led to coordinative adaptations (e.g., spatial relocating, redistributing tasks, accommodating novel perceptual dependencies, and mounting novel responses) that, over time, resulted in reconfiguration of roles, including expanded occupational knowledge, emergence of new specializations, and shifts in status and boundaries. By emphasizing the importance of the body in coordination, this paper suggests that an embodiment perspective is important for explaining how and why coordination evolves following the introduction of a new technology.

Spatio-temporal multidimensionality of the Ukrainian organ symphonies: from sound to genre

The relevance of the study is because the organ symphonies of Ukrainian composers created at the end of the 20th and the beginning of the 21st centuries have not yet become the subject of a special study. The principal dissimilarity between works with a similar genre name, as well as the growing interest of researchers in the ontological parameters of the symphony genre, makes it possible to endow with the genre-defining functions the ratio of the spatial and temporal characteristics of each symphony for an organ.Main objective of the study is determination of the spatial-temporal parameters of organ symphonies written by Ukrainian composers in the late twentieth and early twenty-first centuries using the example of three works for organ solos united by the symphony's genre name – the Organ Symphony by Y. Lyonko, the “White Symphony” by V. Nazarov and “Symphony of Creation” by S. Ostrova.Methodology of the research: system analysis and comparison of three different organ symphonies, the principles of the asymmetry overcoming by the composers are modeled.The main results and conclusions of the study are that there are three types of concepts of organ symphonies – temporal, spatial and modulating. The time and space of the Ukrainian organ symphonies turns out to be heterogeneous and reflects the views of modern scientific thought about the instability of temporal and spatial parameters of reality, their perceptual dependence. Without breaking with the traditional symphonic concepts, the organ symphonies of Y. Lyonko, V. Nazarov, and S. Ostrova are built on the new principles of interpreting the concept of a symphony as co-sounds. In all analyzed works, symphony as a stable artistic concept ensures the continuity of musical development showing various aspects of life (not just human’s one). The deepening of spatial characteristics occurs primarily with techniques of sonoristics and minimal art. Because of attempts by composers to reveal the metaphysical basis of the name “symphony”, the genre is ontologized, pushing the traditional concept of Man into the background. The basic principles of development are the processes of self-movement of the sound mass, subject to the laws of continuity. The significance of the research is in the perspective of its results to clarify the genre invariant of the organ symphony as a whole, as well as its national identification within the framework of Ukrainian organ music

Experienced listeners’ differential perception of enhancing and non-enhancing cue pairs

The perception of a pair of enhancing cues, pitch and breathiness, and non-enhancing cues, pitch and vowel duration, were compared in a cue-shifting experiment with Hani listeners who have experience with both cue pairs in the same tense-lax contrast. Results show that, when the correlation between the non-enhancing cues was the reverse of their experience, it was equally difficult for Hani listeners to shift attention from pitch to vowel duration as from vowel duration to pitch. For the enhancing cues, difficulty with cue-shifting was asymmetric; shifting from pitch to breathiness was easy, but shifting from breathiness to pitch was difficult. This asymmetry may occur because the perceptual dependence between pitch and breathiness is unidirectional: breathiness is associated with pitch but not vice versa. Thus, listeners experience interference only when shifting attention from breathiness to pitch. The difference between two cue pairs and the direction of asymmetry found for the enhancing cue pair is consistent with earlier results from English listeners who do not have phonemic experience with either pair. Collectively, these results indicate that enhancing cues are perceived differently from non-enhancing cues, even when listeners’ language experience with cue pairs is equated.

Divisively Normalized Sparse Coding: Toward Perceptual Visual Signal Representation.

Sparse representation has been shown to be highly correlated with the visual perception of natural images, which can be characterized by a linear combination of neuronal responses in the visual cortex. Divisive normalization transform (DNT) has been proven to be an effective method in reducing statistical and perceptual dependencies for nonlinear properties in primary visual cortex. In this paper, we develop a divisively normalized sparse coding scheme, aiming to further bridge the gap between sparse representation and human visual perception. We show that such a scheme is perceptually meaningful for representing visual signals, with which the pixel-domain image representation and processing tasks can be feasibly and efficiently achieved in the divisively normalized sparse-domain. Specifically, we develop a sparse-domain similarity (SDS) index for perceptual quality evaluation, where the DNT is employed for transforming image signals into a perceptually uniform space. Furthermore, the proposed SDS index is employed to optimize the sparse coding process when representing natural images. The experimental results indicate that the SDS can provide accurate and consistent predictions of perceived image quality, and the performance of sparse coding can be significantly improved in terms of both objective and subjective quality evaluations.

Enhanced Speechreading Performance in Young Hearing Aid Users in China.

Purpose The study was designed primarily to determine if the use of hearing aids (HAs) in individuals with hearing impairment in China would affect their speechreading performance. Method Sixty-seven young adults with hearing impairment with HAs and 78 young adults with hearing impairment without HAs completed newly developed Chinese speechreading tests targeting 3 linguistic levels (i.e., words, phrases, and sentences). Results Groups with HAs were more accurate at speechreading than groups without HA across the 3 linguistic levels. For both groups, speechreading accuracy was higher for phrases than words and sentences, and speechreading speed was slower for sentences than words and phrases. Furthermore, there was a positive correlation between years of HA use and the accuracy of speechreading performance; longer HA use was associated with more accurate speechreading. Conclusions Young HA users in China have enhanced speechreading performance over their peers with hearing impairment who are not HA users. This result argues against the perceptual dependence hypothesis that suggests greater dependence on visual information leads to improvement in visual speech perception.

Linear Summation of Repulsive and Attractive Serial Dependencies: Orientation and Motion Dependencies Sum in Motion Perception.

Recent work from several groups has shown that perception of various visual attributes in human observers at a given moment is biased toward what was recently seen. This positive serial dependency is a kind of temporal averaging that exploits short-term correlations in visual scenes to reduce noise and stabilize perception. To date, this stabilizing "continuity field" has been demonstrated on stable visual attributes such as orientation and face identity, yet it would be counterproductive to apply it to dynamic attributes in which change sensitivity is needed. Here, we tested this using motion direction discrimination and predict a negative perceptual dependency: a contrastive relationship that enhances sensitivity to change. Surprisingly, our data showed a cubic-like pattern of dependencies with positive and negative components. By interleaving various stimulus combinations, we separated the components and isolated a positive perceptual dependency for motion and a negative dependency for orientation. A weighted linear sum of the separate dependencies described the original cubic pattern well. The positive dependency for motion shows an integrative perceptual effect and was unexpected, although it is consistent with work on motion priming. These findings suggest that a perception-stabilizing continuity field occurs pervasively, occurring even when it obscures sensitivity to dynamic stimuli.SIGNIFICANCE STATEMENT Recent studies show that visual perception at a given moment is not entirely veridical, but rather biased toward recently seen stimuli: a positive serial dependency. This temporal smoothing process helps perceptual continuity by preserving stable aspects of the visual scene over time, yet, for dynamic stimuli, temporal smoothing would blur dynamics and reduce sensitivity to change. We tested whether this process is selective for stable attributes by examining dependencies in motion perception. We found a clear positive dependency for motion, suggesting that positive perceptual dependencies are pervasive. We also found a concurrent negative (contrastive) dependency for orientation. Both dependencies combined linearly to determine perception, showing that the brain can calculate contrastive and integrative dependencies simultaneously from recent stimulus history when making perceptual decisions.

Perceptual Dependencies in Fabric Appearance between Texture and Color

Perceptual Dependencies in Fabric Appearance between Texture and Color

Tests for Configural processing in the Thatcher Illusion

Thatcherisation of facial features is immediately apparent only in upright faces. Detection of Thatcherisation is therefore widely upheld as being dependent on configural processing. Configural processing has clear predictions of perceptual dependence between facial features and of supercapacity processing. Perceptual dependence: Configurality in General Recognition Theory (GRT, Ashby & Townsend, 1986) can be conceptualized in terms of violations of perceptual independence, in which the perceptions of the eyes and mouth of a single face are positively correlated; for example, the more inverted the eyes look, the more inverted the mouth will look. Participants were briefly presented with normal, partially Thatcherised and fully Thatcherised faces, and were asked to report whether the outline, eyes and mouth were upright or inverted. Consistent with the predictions, multi-dimensional probit models (DeCarlo, 2003) revealed that within-stimulus perceptual interactions occurred more frequently for upright than inverted faces. However, for the Thatcherised stimulus itself, there was no overall correlation between the eyes and the mouth, suggesting a lack of configural processing for this type of stimulus. Processing capacity: Supercapacity processing is predicted to accompany configural processing (O’Toole, Wenger & Townsend, 2001; Wenger & Townsend, 2001). Therefore, the detection of Thatcherised features in upright faces should be marked by supercapacity processing of inverted eyes and mouths relative to the inversion of only eyes or only mouths. Response times were used to compute measures of processing capacity (capacity coefficient, Townsend & Wenger, 2004; proportional hazards ratio, Wenger & Gibson, 2006) in Thatcherised upright faces. Results demonstrated limited evidence of supercapacity processing, and only in some individuals, implying that configural processing is not necessary for processing of upright Thatcherised faces. In summary, predictions from GRT and of processing capacity were tested across two separate studies, with little evidence found for perceptual independence or supercapacity processing for Thatcherised face stimuli.

The spatial tuning of perceptual serial dependence

The spatial tuning of perceptual serial dependence

Perceptual Dependence of Size and Distance? A Within Subjects Variability Approach

Perceptual Dependence of Size and Distance? A Within Subjects Variability Approach

Automatic Aspects in Face Perception

We examined the perceptual dependency of local facial information on the whole facial context. In Experiment 1 participants matched a predetermined facial feature that appeared in two sequentially presented faces judging whether it is identical or not, while ignoring an irrelevant dimension in the faces. This irrelevant dimension was either (a) compatible or incompatible with the target's response and (b) same or different in either featural characteristics or metric distance between facial features in the two faces. A compatibility effect was observed for upright but not inverted faces, regardless of the type of change that differentiated between the faces in the irrelevant dimension. Even when the target was presented upright in the inverted faces, to attenuate perceptual load, no compatibility effect was found (Experiment 2). Finally, no compatibility effects were found for either upright or inverted houses (Experiment 3). These findings suggest that holistic face perception is mandatory.

Strain experienced by caregivers of stroke survivors in the Western Cape

Recovery after stroke is often incomplete and many stroke survivors depend on family caregivers. The demands of caring can negatively impact quality of life of these carers. This study explores levels of strain experienced by caregivers and the variables that impact on their strain. A concurrent, mixed method, descriptive design was utilized. Fifty-seven caregivers of stroke survivors who received rehabilitation at the Western Cape Rehabilitation Centre participated in the study. The Barthel Index and Caregiver Strain Index were utilised to collect quantitative data, which was statistically analysed (p <0.05). Qualitative data was collected through semi-structured interviews and thematically analysed.Fifty eight percent of caregivers were experiencing high levels of strain. The following variables significantly impacted on strain namely, caregiver loss of employment (0.04), emotional pressure (0.01), patient residual cognitive and perceptual impairments (0.01), personality changes (0.01) and physical dependency (0.0012). According to the qualitative data the burden was aggravated by financial problems, patient perceptual problems and patient personality changes. The findings indicate the need for support after discharge, ongoing community support and respite care to enable time off for caregivers.

Holistic processing, crowding, and perceptual and decisional dependencies

Holistic processing, crowding, and perceptual and decisional dependencies

Perceptual dependencies in information visualization assessed by complex visual search

A common approach for visualizing data sets is to map them to images in which distinct data dimensions are mapped to distinct visual features, such as color, size and orientation. Here, we consider visualizations in which different data dimensions should receive equal weight and attention. Many of the end-user tasks performed on these images involve a form of visual search. Often, it is simply assumed that features can be judged independently of each other in such tasks. However, there is evidence for perceptual dependencies when simultaneously presenting multiple features. Such dependencies could potentially affect information visualizations that contain combinations of features for encoding information and, thereby, bias subjects into unequally weighting the relevance of different data dimensions. We experimentally assess (1) the presence of judgment dependencies in a visualization task (searching for a target node in a node-link diagram) and (2) how feature contrast relates to salience. From a visualization point of view, our most relevant findings are that (a) to equalize saliency (and thus bottom-up weighting) of size and color, color contrasts have to become very low. Moreover, orientation is less suitable for representing information that consists of a large range of data values, because it does not show a clear relationship between contrast and salience; (b) color and size are features that can be used independently to represent information, at least as far as the range of colors that were used in our study are concerned; (c) the concept of (static) feature salience hierarchies is wrong; how salient a feature is compared to another is not fixed, but a function of feature contrasts; (d) final decisions appear to be as good an indicator of perceptual performance as indicators based on measures obtained from individual fixations. Eye tracking, therefore, does not necessarily present a benefit for user studies that aim at evaluating performance in search tasks.

Information conveyed by f0 for vowel identification

Our recent experiments with vocoded natural speech, wherein the spectral envelope and fundamental frequency are manipulated independently, have confirmed that some coordination of f0 and formant patterns are beneficial to vowel identification by humans. In an effort to model the perceptual dependency more precisely, we have investigated the performance of several alternative pattern recognition models on natural speech samples. This paper reports on several quite distinct methods of exploiting statistical relations between formant frequencies and f0 for recognition. Many of these methods yield quite similar results on the classic Peterson and Barney data and on larger, more recently collected data sets. Methods involving indirect normalization whereby the f0 of a single token is restricted to the role of estimating the formant frequency average of a speaker’s entire vowel system perform well. Indeed, they are often better than a method where the role of f0 is unconstrained, thus accommodating inherent pitch differences among vowels. The indirect use of f0 also allows for methods of combining f0 and formant range information in ways that preliminary results suggest to be more effective for modeling perceptual effects with modified stimuli. More formal evaluation against perceptual data will be presented.

Non‐algorithmic quantitative problem solving in university physical chemistry: a correlation study of the role of selective cognitive factors

This work provides a correlation study of the role of the following cognitive variables on problem solving in elementary physical chemistry: scientific reasoning (level of intellectual development/developmental level), working‐memory capacity, functional mental (M) capacity, and disembedding ability (i.e., degree of perceptual field dependence–independence). Nine individual studies, with seven problems and with various samples of first‐year undergraduate chemistry students at the University of Ioannina, were used. The problems were open‐book, while the students were as a rule not supplied with the necessary data (facts, figures, values of constants, etc.). The results were analysed by calculating Spearman’s ρ and Pearson r correlation coefficients. In addition, the seven individual studies were combined using a quasi meta‐analysis (n = 250). The main findings are: (1) scientific reasoning showed lack of correlation; (2) working‐memory capacity also showed weak correlation, but stronger than scientific reasoning; and (3) functional M‐capacity and disembedding ability played a very important role. The field may thus be of paramount importance in the novel (for the students) non‐algorithmic problems used in this study. Implications of the findings are discussed.

Perceptual interactions of facial dimensions in speeded classification and identification.

The representation underlying the identification and classification of semirealistic line drawings taken from a computer model of the face was investigated by using a speeded classification task and an identification task. These data were analyzed by using a multidimensional extension of signal detection theory, within which varieties of perceptual interactions between dimensions within and across stimuli can be characterized. The dimensions of interest here were eye separation, nose length, and mouth width. The response time and accuracy data from the speeded classification task suggest that processing of a given feature did depend on whether other features were present or absent, but given that other features were present, the results strongly support separability (a macrolevel, across-stimulus form of invariance) for all pairs of facial dimensions used. This separability was confirmed by the subsequent identification task. Owing to its greater resolution, the identification task can reveal interactions that might exist at more microlevels of processing. In fact, the identification data did indicate the presence of perceptual dependence between facial dimensions within a stimulus when the dimensions that were varied were close in spatial proximity (i.e., eye separation and nose length). Within the theoretical framework, perceptual dependence can be interpreted as correlated noise between otherwise separate channels (and hence, is logically distinct from separability). This dependence was greatly reduced for dimensions that were more distant (eyes and mouth). The relation between these results and the configural effects that have been observed with faces as stimuli in other studies is discussed.

The perceptual interaction between the pitch and timbre of musical sound

The perceptual dependency of the timbre of musical sounds on their fundamental frequency (F0) was examined through two timbral dissimilarity experiments. In Experiment 1, subjects judged timbral dissimilarity between pairs of stimuli produced by 12 musical instruments equal in F0, duration, and loudness. There were three sessions, each at a different F0 (B2, Db3, Bb3). In Experiment 2, the same stimuli were presented in pairs with a constant difference in F0. Two sessions corresponded to two different intervals (B2-Db3 and B2-Bb3). Subjects were instructed to ignore pitch difference. The results are interpreted in terms of an evolution of timbre space as a function of F0. Experiment 1 produced dissimilarity matrices that were similar at different F0s, suggesting that the relative positions of instruments within the timbre space varied little with F0. Experiment 2 produced dissimilarity matrices that were symmetrical, suggesting further that F0-dependent displacements within the timbre space are small. Patterns of dissimilarity were similar with or without an F0 difference, showing that subjects could ignore a constant difference in pitch when making timbral dissimilarity judgments. Results suggest that the perception of timbre is relatively independent of pitch and can be abstracted across differences in F0 under these conditions.