Complexity of postural sway affects affordance perception of reachability in virtual reality

Visual perception of whether an object is within reach while standing in different postures was investigated. Participants viewed a three-dimensional (3D) virtual reality (VR) environment with a stimulus object (red ball) placed at different egocentric distances. Participants reported whether the object was reachable while in a standard pose as well as in two separate active balance poses (yoga tree pose and toe-to-heel pose). Feedback on accuracy was not provided, and participants were not allowed to attempt to reach. Response time, affordance judgements (reachable and not reachable), and head movements were recorded on each trial. Consistent with recent research on perception of reaching ability, the perceived boundary occurred at approximately 120% of arm length, indicating overestimation of perceived reaching ability. Response times increased with distance, and were shortest for the most difficult pose—the yoga tree pose. Head movement amplitude increased with increases in balance demands. Unexpectedly, the coefficient of variation was comparable in the two active balance poses, and was more extreme in the standard control pose for the shortest and longest distances. More complex descriptors of postural sway (i.e., effort-to-compress) were predictive of perception while in the tree pose and the toe-to-heel pose, as compared with control stance. This demonstrates that standard measures of central tendency are not sufficient for describing multiscale interactions of postural dynamics in functional tasks.

Haptic Distance Ratio Estimation: The Geometry of Space Within the Hands

In the current study of haptic distance perception, 20 younger (median age: 22 years) and 20 older adults (median age: 72 years) used active touch to estimate distance ratios(one length relative to another). Nine tactile stimuli were created from wooden dowels; each consisted of two perpendicular dowels. The stimulus distance ratios ranged from 1.0 to 5.0. Each participant used both hands (without vision) to actively explore (30 s) a single stimulus object on every trial. The task was to numerically estimate the distance ratio. Overall, the participants’ judgments were precise; the overall magnitude of the Pearson r correlation coefficient was 0.943 and did not differ for younger and older adults. While the participants’ judgments were precise, they were not completely accurate: The average slope (of the relationship between actual and judged distance ratios) for all participants was significantly greater than 1.0 (1.15). Surprisingly, differences in manual dexterity had no apparent effect on distance ratio estimates. Older adults apparently retain an excellent ability to perceive distances using their sense of touch. Our results also demonstrate that the geometry of haptic space (at the scale of the hand) is approximately Euclidean in nature (and certainly not merely topological, projective, or affine).

Temporal and spatial localization of prediction-error signals in the visual brain

It has been suggested that the brain pre-empts changes in the visual environment through generating predictions, although real-time eletrophysiological evidence of prediction violations remains elusive. In a series of experiments we showed participants sequences of images that followed a predictable implied sequence or whose final image violated the implied sequence. Through careful design we were able to use the same final image transitions across predictable and unpredictable conditions, ensuring that any differences in neural responses were due only to preceding context and not to the images themselves. EEG and MEG recordings showed that early/mid-latency visual evoked potentials were robustly modulated by images that violated the implied sequence across a range of types of image change (expression deformations, rigid-rotations and visual field location). This modulation occurred irrespective of stimulus object category. Although the stimuli were static images, MEG source reconstruction of the early latency signal (N/M170) localised expectancy violation signals to brain areas associated with motion perception. Our findings suggest that the N/M170 can index mismatches between predicted and actual visual inputs in a system that predicts trajectories based on ongoing context. This has important implications for understanding the N/M170 and investigating how the brain represents context to generate perceptual predictions.

ekphrasis

Ekphrasis refers to the literary and rhetorical trope of summoning up—through words—an impression of a visual stimulus, object, or scene. As critical trope, the word ekphrasis (ἔκφρασις) is attested from the first century ce onwards: it is discussed in the Imperial Greek Progymnasmata, where it is defined as a “descriptive speech which brings the subject shown before the eyes with visual vividness.”

Object Exploration in 3- to 7-Year-Old Children

The aim of the present study was to analyze free exploration of an unfamiliar, novel object in a semi-natural environment in 189 preschool children aged 3 to 7 years. The study used a purpose-built, novel, and complex stimulus object. Each child was shown the complex object lying on the floor and asked to explore it for 15 minutes. The child's behavior was video recorded. Age-dependent differences were found in the children's exploratory activity. No sex differences were found. Cluster analysis showed four main behavioral patterns that differed in their qualitative and quantitative parameters. Cluster membership was mainly age-dependent and not sex-specific. The results showed individual and developmental differences among the preschoolers with respect to their exploratory activity. This should be taken into account by school psychologists and teachers when designing the educational tasks and play situations.

Transitivity of Spanish perception verbs: a gradual category?

<span style="font-size: 10.0pt; font-family: &quot;Times New Roman&quot;; mso-ansi-language: EN-GB;" lang="EN-GB">This article examines to what extent perception verbs occurring in a syntactically transitive scheme are also semantically transitive. Indeed, since the perception process represents a mental rather than a physical contact between the perceiver/subject and the stimulus/object, it should be distinguished from the prototypical transfer of energy. It is shown that the semantic and conceptual differences between the perception modalities influence on the linguistic behaviour of Spanish perception verbs. In this perspective, the verbs <em style="mso-bidi-font-style: normal;">ver</em> (<em style="mso-bidi-font-style: normal;">to see</em>), <em style="mso-bidi-font-style: normal;">o&iacute;r </em>(<em style="mso-bidi-font-style: normal;">to hear</em>), <em style="mso-bidi-font-style: normal;">mirar </em>(<em style="mso-bidi-font-style: normal;">to look at</em>) and <em style="mso-bidi-font-style: normal;">escuchar </em>(<em style="mso-bidi-font-style: normal;">to listen to</em>) are ranged on a scale of transitivity. The validity of the elaborated hierarchy of transitivity is verified by means of empirical data. Based on a large corpus of infinitive constructions, it will be examined to what extent the position of a perception verb on the scale of transitivity correlates with the preferred case markings of its stimulus/object. A specific morphosyntactic phenomenon is studied, namely the special marking of the DO by the prepositional accusative.</span> <!--[endif] -->

Syntactic prominence in Icelandic Experiencer arguments: quirky subjects vs. dative objects

As has often been demonstrated, Icelandic Quirky Subjects largely behave like canonical nominative subjects and unlike topicalized objects. Among verbs selecting for Quirky Subjects, experiential predicates with a dative Experiencer subject and a nominative Stimulus object are the most common type. Recently, several studies have proposed a sub-class within this group of dat-nom-verbs, characterized by an alternation in their argument mapping. Here, both the dative Experiencer and the nominative Stimulus can occur as either the syntactic subject or object.This paper empirically investigates this class as well as the extent to which its alternation is determined by semantic and pragmatic factors.

Mere Exposure: A Gateway to the Subliminal

In the mere-repeated-exposure paradigm, an individual is repeatedly exposed to a particular stimulus object, and the researcher records the individual's emerging preference for that object. Vast literature on the mere-repeated-exposure effect shows it to be a robust phenomenon that cannot be explained by an appeal to recognition memory or perceptual fluency. The effect has been demonstrated across cultures, species, and diverse stimulus domains. It has been obtained even when the stimuli exposed are not accessible to the participants’ awareness, and even prenatally. The repeated-exposure paradigm can be regarded as a form of classical conditioning if we assume that the absence of aversive events constitutes the unconditioned stimulus. Empirical research shows that a benign experience of repetition can in and of itself enhance positive affect, and that such affect can become attached not only to stimuli that have been exposed but also to similar stimuli that have not been previously exposed, and to totally distinct stimuli as well. Implications for affect as a fundamental and independent process are discussed in the light of neuroanatomical evidence.

A Quantitative Method to Explore the Assimilation Effects

The role of central processes in the assimilation effect can easily be shown qualitatively (de Weert and Spillmann, 1995 Vision Research35 1413 – 1419), but it is difficult to measure quantitatively because of the subtlety of the effect. In most experimental designs, the match stimulus differs greatly in appearance from the test stimulus, eg in size or configuration, and because these differences are far more striking than the assimilation effect, matching is difficult. Central processing, eg object segmentation, influences colour spreading. It is this property that we explored with a new approach: a matching task in which the match stimulus has the same properties (eg size and configuration) as the test stimulus. Object segmentation is forced by stereopsis-induced depth. The test stimulus consists of two depth planes, one with black dots and the other with white dots, on a homogeneous gray background. The match stimulus has the same configuration of black and white dots, but now squeezed into a single depth plane. The basic idea behind this stimulus is that assimilation mainly acts on the back plane of a scene (as can be shown experimentally). So, while keeping the appearance of the stimulus the same, subjects can focus on the assimilation effect itself. This new approach allows us to explore more aspects of the assimilation effect and gain insight into the processes involved.