Abstract in English:The focus here is on the paradoxical finding that whereas visually perceived egocentric distance is proportional to physical distance out to at least 20 m under full-cue viewing, there are large distortions of shape within the same range, reflecting a large anisotropy of depth and frontal extents on the ground plane. Three theories of visual space perception are presented, theories that are relevant to understanding this paradoxical result. The theory by Foley, Ribeiro-Filho, and Da Silva is based on the idea that when the visual system computes the length of a visible extent, the effective visual angle is a non-linear increasing function of the actual visual angle. The theory of Durgin and Li is based on the idea that two angular measures, optical slant and angular declination, are over-perceived. The theory of Ooi and He is based on both a default perceptual representation of the ground surface in the absence of visual cues and the "sequential surface integration process" whereby an internal representation of the visible ground surface is constructed starting from beneath the observer's feet and extending outward.
Abstract in English:Perception is crucial for the control of action, but perception need not be scaled accurately to produce accurate actions. This paper reviews evidence for an elegant new theory of locomotor space perception that is based on the dense coding of angular declination so that action control may be guided by richer feedback. The theory accounts for why so much direct-estimation data suggests that egocentric distance is underestimated despite the fact that action measures have been interpreted as indicating accurate perception. Actions are calibrated to the perceived scale of space and thus action measures are typically unable to distinguish systematic (e.g., linearly scaled) misperception from accurate perception. Whereas subjective reports of the scaling of linear extent are difficult to evaluate in absolute terms, study of the scaling of perceived angles (which exist in a known scale, delimited by vertical and horizontal) provides new evidence regarding the perceptual scaling of locomotor space.
Abstract in English:Numerous research efforts have been directed toward determining the origin of anisotropies of visual space, in contrast to real space. Recent neurophysiological studies have placed the origin in the primary visual cortex (V1) or beyond. The present study sought to provide new psychophysical evidence of the origin of these anisotropies using auto-stereograms as visual stimuli in a relative depth judgment task. The observers were presented with a hidden three-dimensional shape that consisted of two pairs of parallel line segments that were located in different depth planes and oriented at 0º (horizontal line segments), 45º, and 90º (vertical line segments). The influence of orientation on the visual performance of five observers was evaluated. The encountered differences at 45º compared with cardinal orientations revealed a non-conclusive trend toward a negative impact of oblique orientation on the observers' performance. Significant differences were found in accuracy between the horizontal and vertical orientations, and the best scores corresponded to vertical line segments. This finding may be interpreted as the expression of vertical-horizontal anisotropy in depth. The perception of hidden three-dimensional shapes in auto-stereograms occurs beyond the primary visual cortex in the dorsal stream, and the present findings provide psychophysical evidence of the location of vertical-horizontal anisotropy in non-retinotopic areas beyond V1.
Abstract in English:Human veering while walking blindfolded or walking straight without any visual cues has been widely studied over the last 100 years, but the results are still controversial. The present study attempted to describe and understand the human ability to maintain the direction of a trajectory while walking without visual or audio cues with reference to a proposed mathematical model and using data collected by a global positioning system (GPS). Fifteen right-handed people of both genders, aged 18-30 years, walked without vision in an open field directly toward a target after seeing it for a brief period of time. Time and distance were directly measured by the GPS receiver. The mathematical analysis indicated that both linear and angular velocities determined the shape of the trajectory. Careful observation of the trajectories clearly showed a geometrical pattern, and the circular trajectory was the most frequent. Such behavior can be explained by the almost constant linear and angular velocity during the walk. From the perspective of the mathematical model, angular velocity is the observable physical quantity that most determines the trajectory pattern. One can notice that better performance (i.e., lower angular velocity) is related to longer distances when comparing an individual's circular trajectory walking performance as a function of different target distances (i.e., 30.00, 41.60, 57.69, and 80.00 m).
Abstract in English:One major issue concerning investigations of visual perception is determination of the geometrical properties of visual space. To address this issue, one must determine the relationships between geometrical features of visual space, distance, direction, angle, and size. Consistent evidence indicates that visual angle is a determinant of perceived exocentric distance. Previous evidence suggests that exocentric distance and direction are hierarchically processed, with distance preceding direction. The present study investigated the relationship between the perceptual processing of egocentric direction and exocentric direction using a task that independently provides both perceptual variables in a single judgment. The results indicated that egocentric directions were systematically overestimated, and this was not caused by either the global shape of the layout or leg length effects. Exocentric directions presented a discontinuous pattern of overestimation of smaller angles that were subtended by radial orientations and accuracy of right angles that were subtended by horizontal orientations. This could be explained by the anisotropy of visual space, a well-established phenomenon from visual space studies. The analysis of the association between the processing of these two variables revealed independence between them in which exocentric direction processing did not depend on the processing of egocentric direction processing, and vice versa. The present results and prior evidence converge on the notion of hierarchical processing in which the visual system processes the egocentric distance of objects followed by exocentric distance processing and subsequent processing. The precise positions of egocentric and exocentric directions in this chain of processing remain to be determined.
Abstract in English:The present study investigated the mechanisms involved in processing orientation on the frontal and ground planes. The stimuli comprised two yellow circles conceived as the endpoints of a segment and depicted on a black background. In Experiment 1, the observers performed two tasks on both planes (frontal and ground). In Task 1 they were asked to indicate the absolute location of the two endpoints, presented one at a time (successive task). In Task 2 they had to locate the relative position of the endpoints presented simultaneously (simultaneous task). Relative and absolute errors were analyzed according to a cyclopean coordinate system derived from the geometry of the visual scene. These two kinds of errors were studied within the framework of the hypothesis that each kind of task would minimize the error related to its codification. The results showed greater absolute errors in the simultaneous task than in the successive task and greater relative errors in which the successive task seemingly activated a more accurate way of codification of the orientation. In Experiment 2 we controlled the availability of visual depth cues by changing the presentation time (50 and 3000 ms) and viewing conditions (monocular and binocular) in the simultaneous task. The results showed that the precision of orientation judgments was poorer on the ground plane than on the frontal plane, except when the observers used binocular vision. These results suggest that the orientation of a segment, at least on the ground plane, can be conceptualized as a gradient of disparities.
Abstract in English:Several studies have emphasized the contribution of haptic input that results from the use of rigid and non-rigid tools to the postural control system. Experimental protocols such as the light touch and the anchor system are based on individuals' haptic exploration of the environment through direct tactile-kinesthetic contact, or indirectly through rigid or flexible tools that are attached to the body. In this article, we introduce the main findings of humans' haptic use of non-rigid tools during postural control tasks. We illustrate the effects of an anchor system paradigm on the maintenance of stability via haptic information. Haptic anchoring includes the handling of flexible cables that are attached to loads that are in contact with a surface. We include results of studies about haptic information gathered during the holding of a walking dog's leash. Studies that used the anchor system demonstrated its effectiveness in reducing body sway in several groups, including young adults, children, older individuals, and intellectually disabled individuals. We discuss several experimental designs and intervention protocols in order to illustrate how haptic anchoring could prompt functional plasticity.
Abstract in English:The selection of alternate foot placement is based on visual inputs and the prediction of future foot placement combined with a set of internal rules that are guided by three determinants: minimum foot displacement, stability, and maintenance of forward progression. These three determinants are weighted differently, depending on different constraints. The first purpose of this review is to define and provide evidence to support this model. Alternate foot placement response latency appears to vary according to methodological and/or task constraints. The paradigms and latency measurement methods that are used to investigate alternate foot placement may have important implications for alternate foot placement control. Very short latencies to initiate alternate foot placement can be observed when walking on a treadmill, and longer latencies can be observed when walking on the ground. The second purpose of this review is to discuss differences in the latency to initiate alternate foot placement. The data reviewed herein indicate that looking at multiple parameters is important when studying movement selection and planning during human locomotion. Different latencies to select and implement alternate foot placement are part of a continuum that ranges from the most to the least automatic response.
Abstract in English:The aim of the present study was to determine the effects of motor practice on visual judgments of apertures for wheelchair locomotion and the visual control of wheelchair locomotion in wheelchair users who had no prior experience. Sixteen young adults, divided into motor practice and control groups, visually judged varying apertures as passable or impassable under walking, pre-practice, and post-practice conditions. The motor practice group underwent additional motor practice in 10 blocks of five trials each, moving the wheelchair through different apertures. The relative perceptual boundary was determined based on judgment data and kinematic variables that were calculated from videos of the motor practice trials. The participants overestimated the space needed under the walking condition and underestimated it under the wheelchair conditions, independent of group. The accuracy of judgments improved from the pre-practice to post-practice condition in both groups. During motor practice, the participants adaptively modulated wheelchair locomotion, adjusting it to the apertures available. The present findings from a priori visual judgments of space and the continuous judgments that are necessary for wheelchair approach and passage through apertures appear to support the dissociation between processes of perception and action.
Abstract in English:Blind people can invent drawings for material objects like cups, and matters esthetic, like "glory" at the climax of a story. In sketches of cups, their drawings are realistic, using lines for surface edges of profiles, and borders of cross-sections. They are metaphoric if they show purely mental events. These points are illustrated by two drawings by EW, a blind woman with two notable uses of a "fountain" device. One shows "glory" in the opera "Aida" and one is for memories overflowing.
Abstract in English:The purpose of the present study was to evaluate pain in the aging process in long-term care institutions. The study included 46 elderly subjects of both genders and with chronic pain. Descriptors of chronic pain were analyzed using psychophysical category estimation methods, and the thematic content of semi-structured interviews was analyzed. Chronic pain was perceived in 33.33% of the elderly subjects. For the descriptors of pain, the results showed higher scores for "painful." In the interview, the thematic units were time, start of symptoms, coping, pain-related causes, current situation, and other perceptions about pain. Pain was related to physical, emotional, and cognitive factors. The present results shed light on "pain" and "aging" phenomena and may contribute to improving the management of pain symptoms in long-term institution residents.
Abstract in English:Pain assessment is very important in establishing the efficacy of analgesics and therapies, but because pain is a subjective experience, using methods that represent pain objectively is necessary. A number of biopotentials have been employed in studies of the objective assessment of pain. However, few investigations have considered the peripheral nervous system response to electrical stimulation. The present study evaluated a method for pain quantification based on the analysis of biopotentials. We assessed electromyographic activity that resulted from evoked movements from the nociceptive flexion reflex (NFR). We investigated correlations between stimulus intensity, features extracted from surface electromyography (EMG), and subjective pain reported by subjects using a Visual Analog Scale (VAS). A total of 10 healthy male subjects without any pain disorder, aged 20-27 years, participated in the study. A high correlation (r2 > .87) was found between stimulus intensity and the following features extracted from the EMG: area, root mean square (RMS), and entropy. A high correlation (r2 > .99) was also found between stimulus intensity and subjective pain reported on the VAS. We conclude that estimating features from electromyographic signals that are correlated with subjective pain sensations and the intensity of the electrical stimulus is possible. Entropy, RMS, and the area of the electromyographic signal appear to be relevant parameters in correlations with subjective pain.
Abstract in English:The objective measurement of subjective, multi-dimensionally experienced pain is a problem for which there has not been an adequate solution. Although verbal methods (e.g., pain scales and questionnaires) are commonly used to measure clinical pain, they tend to lack objectivity, reliability, or validity when applied to mentally impaired individuals. Biopotential and behavioral parameters may represent a solution. Such coding systems already exist, but they are either very costly or time-consuming or have not been sufficiently evaluated. In this context, we collected a database of biopotentials to advance an automated pain recognition system, determine its theoretical testing quality, and optimize its performance. For this purpose, participants were subjected to painful heat stimuli under controlled conditions. One hundred thirty-five features were extracted from the mathematical groupings of amplitude, frequency, stationarity, entropy, linearity, and variability. The following features were chosen as the most selective: (1) electromyography corrugator peak to peak, (2) corrugator shannon entropy, and (3) heart rate variability slope RR. Individual-specific calibration allows the adjustment of feature patterns, resulting in significantly more accurate pain detection rates. The objective measurement of pain in patients will provide valuable information for the clinical team, which may aid the objective assessment of treatment (e.g., effectiveness of drugs for pain reduction, information on surgical indication, and quality of care provided to patients).
Abstract in English:Time perception can be affected by real emotional pictures of people that evoke different levels of arousal. Figurative artwork images of body postures that imply movement with different intensities and evoke different levels of arousal can modulate the perception of time. The present study investigated whether abstract paintings that represent motion in different ways affect the perception of time when subjects are exposed to the paintings for different durations. Undergraduate students observed 20 abstract paintings from different artistic schools (i.e., cubism, constructivism, expressionism, and futurism). They observed for 3 s each painting and estimated the time of exposure (reproduction method). After the time estimations, the subjects completed different semantic Movement, Arousal, Complexity, and Recognition scales to obtain information about how the painting compositions were perceived. Time distortions were observed for only two cubist paintings that represented human forms, which were related to both evoked arousal and implied movement (Experiment 1). Experiment 2 further verified whether these time distortions were related to implied movement perception or arousal. Different groups of participants were exposed for 3 and 9 s to only four cubist paintings that represented human forms. These time exposures (3 and 9 s) were used because the arousal-evoking effects may be transient for exposure times that are longer than 2-3 s. The data analysis revealed overestimation of time for the cubist painting that had greater arousal and movement scores only when the subjects were exposed for 9 s, showing that implied movement in abstract human figures is more effective than images with emotional content. We discuss the effect of durations of exposure to pictorial characteristics of artwork on time perception, emphasizing aspects of the visual perception of human forms in cubist paintings and arousal effects in an aesthetic episode.
Abstract in English:Research on false memories has extensively used the recognition and recollection of lists of semantically associated words, called the Deese-Roediger-McDermott (DRM) paradigm. In the DRM procedure, the measure of accuracy/errors is usually the main dependent variable. In this paper we review research that integrated reaction time measures into the DRM paradigm and discuss the future contributions of measures of reaction time to the understanding of false memories.
Abstract in English:The asymmetric pattern of binding of features in working memory is a controversial topic in the literature. The binding of visual- spatial and verbal-spatial information was studied in a serial recognition task to address the contribution of spatial location, visual appearance, and verbal identity to binding in working memory. The participants (n = 32) made a recognition judgment of two sequences of four stimuli each based on a relevant dimension while ignoring changes in an irrelevant dimension. In the visual and verbal tasks, the location was irrelevant. In the spatial tasks, the visual or verbal dimension was irrelevant. Our data showed that the visual or verbal characteristics of the object were incidentally encoded with the spatial location, but the spatial location of the items was not codified together with either the verbal features or visual characteristics when a verbal strategy was limited by articulatory suppression. This asymmetry in binding memory when the participants had to retain one of the features that was presented suggests a functional interaction between specific components of modalities of information and a system that maintains the multimodal representation.
Abstract in English:The present research examined the effect, on recall of a scene, of the distribution of viewpoints during the encoding of the scene. Participants completed a visual search task in a 3-D model of a room during which they were given the opportunity to view the room from viewpoints at opposing sides of the room. Subsequently, participants were tasked to recall the locations of the objects in the room. Participants who distributed their views of the room unequally acrossavailable viewpoints remembered the objects inthe room as being too close to their preferred side of the room. Participants who distributed their views of the room equally across available viewpoints remembered the objects in each half of the room as being too close to the corresponding side of the room. Mindful of previous research that has shown exocentric distances to be underestimated along the depth dimension (Loomis, DaSilva, Fujita, & Fukusima, 1992; Wu, He, & Ooi, 2008), we suggest that the present results reflect underestimation of the distance between the objects and the sides of the room. We suggest that participants used an accumulator-like process to integrate the inconsistent location informationthattheyacquiredconsequenttotheir underestimation of distances from opposing viewpoints (Heathcote & Love, 2012).
Abstract in English:A common feature of Alzheimer's disease (AD) is lack of awareness of neuropsychological deficit or illness, including poor appreciation of impaired task performance. Nevertheless, it has been shown in different clinical groups that levels of awareness may vary according to whether appraisal of symptoms is made in a first-or third-person perspective. This study explored this issue further in two experiments in which people with AD and control participants completed tests of memory and reaction time and had to judge both how difficult the tasks were for them and also for other people if they attempted the same tasks. Results showed that the AD group systematically indicated that others would do as well as they themselves had done. In comparison, control participants indicated other people would perform worse than they did themselves on the reaction time tasks, but similarly on the memory tasks. In addition, attribution of difficulty for self/other correlated with pre-morbid personality traits, such as neuroticism and agreeableness, in the AD group. The theoretical and clinical implications of these findings are discussed.
Abstract in English:Motion perception is essential to adapt behavior in a dynamic environment. Many studies have suggested that looming motion captures attention, whereas receding motion does not, highlighting the behavioral urgency of motion perception. The present study examined whether attentional resources can be attracted by a specific directed flow in the presence of multiple flows that are simultaneously displayed in the visual field. The results showed that when two flows of opposite direction (looming and receding) are displayed together, participants more efficiently discriminate the target inside the looming motion. When four flows are presented (one looming and three receding or three looming and one receding), the results showed that the target displayed inside the looming flow was more rapidly identified but also suggest that attention can be attracted by receding motion. This suggests that the process inside a looming flow is more efficient, but this effect could not be attributed to attentional focusing processes.