Visual perceptual abilities of Chinese-speaking and English-speaking children

This paper reports an investigation of Chinese-speaking and English- speaking children's general visual perceptual abilities. The Developmental Test of Visual Perception was administered to 41 native Chinese-speaking children of mean age 5 yr. 4 mo. in Hong Kong and 35 English-speaking children of mean age 5 yr. 2 mo. in Melbourne. Of interest were the two interrelated components of visual perceptual abilities, namely, motor-reduced visual perceptual and visual-motor integration perceptual abilities, which require either verbal or motoric responses in completing visual tasks. Chinese-speaking children significantly outperformed the English-speaking children on general visual perceptual abilities. When comparing the results of each of the two different components, the Chinese-speaking students' performance on visual-motor integration was far better than that of their counterparts (ES = 2.70), while the two groups of students performed similarly on motor-reduced visual perceptual abilities. Cultural factors such as written language format may be contributing to the enhanced performance of Chinese-speaking children's visual-motor integration abilities, but there may be validity questions in the Chinese version. © Perceptual and Motor Skills 2012

Summation versus suppression in metacontrast masking: On the potential pitfalls of using metacontrast masking to assess perceptual-motor dissociation.

A briefly flashed target stimulus can become "invisible" when immediately followed by a mask-a phenomenon known as backward masking, which constitutes a major tool in the cognitive sciences. One form of backward masking is termed metacontrast masking. It is generally assumed that in metacontrast masking, the mask suppresses activity on which the conscious perception of the target relies. This assumption biases conclusions when masking is used as a tool-for example, to study the independence between perceptual detection and motor reaction. This is because other models can account for reduced perceptual performance without requiring suppression mechanisms. In this study, we used signal detection theory to test the suppression model against an alternative view of metacontrast masking, referred to as the summation model. This model claims that target- and mask-related activations fuse and that the difficulty in detecting the target results from the difficulty to discriminate this fused response from the response produced by the mask alone. Our data support this alternative view. This study is not a thorough investigation of metacontrast masking. Instead, we wanted to point out that when a different model is used to account for the reduced perceptual performance in metacontrast masking, there is no need to postulate a dissociation between perceptual and motor responses to account for the data. Metacontrast masking, as implemented in the Fehrer-Raab situation, therefore is not a valid method to assess perceptual-motor dissociations

Summation versus suppression in metacontrast masking: On the potential pitfalls of using metacontrast masking to assess perceptual-motor dissociation

A briefly flashed target stimulus can become "invisible” when immediately followed by a mask—a phenomenon known as backward masking, which constitutes a major tool in the cognitive sciences. One form of backward masking is termed metacontrast masking. It is generally assumed that in metacontrast masking, the mask suppresses activity on which the conscious perception of the target relies. This assumption biases conclusions when masking is used as a tool—for example, to study the independence between perceptual detection and motor reaction. This is because other models can account for reduced perceptual performance without requiring suppression mechanisms. In this study, we used signal detection theory to test the suppression model against an alternative view of metacontrast masking, referred to as the summation model. This model claims that target- and mask-related activations fuse and that the difficulty in detecting the target results from the difficulty to discriminate this fused response from the response produced by the mask alone. Our data support this alternative view. This study is not a thorough investigation of metacontrast masking. Instead, we wanted to point out that when a different model is used to account for the reduced perceptual performance in metacontrast masking, there is no need to postulate a dissociation between perceptual and motor responses to account for the data. Metacontrast masking, as implemented in the Fehrer-Raab situation, therefore is not a valid method to assess perceptual-motor dissociations

Visual motion distorts visual and motor space

Much evidence suggests that visual motion can cause severe distortions in the perception of spatial position. In this study, we show that visual motion also distorts saccadic eye movements. Landing positions of saccades performed to objects presented in the vicinity of visual motion were biased in the direction of motion. The targeting errors for both saccades and perceptual reports were maximum during motion onset and were of very similar magnitude under the two conditions. These results suggest that visual motion affects a representation of spatial position, or spatial map, in a similar fashion for visuomotor action as for perception

Tilted frames of reference have similar effects on perception of the gravitational vertical and the planning of vertical saccadic eye movements

We investigated the effects of a tilted reference frame (i.e., allocentric visual context) on perception of the gravitational vertical and saccadic eye movements along a planned egocentric vertical path. Participants (n=5) in a darkened room fixated a point in the center of a circle on an LCD display, and decided which of two sequentially presented dots was closer to the unmarked ‘6 o’clock’ position on that circle (i.e., straight down towards their feet). The slope of their perceptual psychometric functions showed that participants were able to locate which dot was nearer the vertical with a precision of 1-2°. For three of the participants, a square frame centered at fixation and tilted (in the roll direction) 5.6° from the vertical caused a strong perceptual bias, manifest as a shift in the psychometric function, in the direction of the traditional ‘rod and frame’ effect, without affecting precision. The other two participants showed negligible or no equivalent biases. The same subjects participated in the saccade version of the task, in which they were instructed to shift their gaze to the 6 o’clock position as soon as the central fixation point disappeared. The participants who showed perceptual biases showed biases of similar magnitude in their saccadic end points, with a strong correlation between perceptual and saccadic biases across all subjects. Tilting of the head 5.6° reduced both perceptual and saccadic biases in all but one observer, who developed a strong saccadic bias. Otherwise, the overall pattern and significant correlations between results remained the same. We conclude that our observers' saccades-to-the-vertical were dominated by perceptual input, which outweighed any gravitational or head-centered input

Dissociation between the Perceptual and Saccadic Localization of Moving Objects

Visual processing in the human brain provides the data both for perception and for guiding motor actions. It seems natural that our actions would be directed toward perceived locations of their targets, but it has been proposed that action and perception rely on different visual information [1-4], and this provocative claim has triggered a long-lasting debate [5-7]. Here, in support of this claim, we report a large, robust dissociation between perception and action. We take advantage of a perceptual illusion in which visual motion signals presented within the boundaries of a peripheral moving object can make the object's apparent trajectory deviate by 45° or more from its physical trajectory [8-10], a shift several times larger than the typical discrimination threshold for motion direction [11]. Despite the large perceptual distortion, we found that saccadic eye movements directed to these moving objects clearly targeted locations along their physical rather than apparent trajectories. We show that the perceived trajectory is based on the accumulation of position error determined by prior sensory history-an accumulation of error that is not found for the action toward the same target. We suggest that visual processing for perception and action might diverge in how past information is combined with new visual input, with action relying only on immediate information to track a target, whereas perception builds on previous estimates to construct a conscious representation

Larger Stimuli Require Longer Processing Time for Perception

The time it takes for a stimulus to reach awareness is often assessed by measuring reaction times (RTs) or by a temporal order judgement (TOJ) task in which perceived timing is compared against a reference stimulus. Dissociations of RT and TOJ have been reported earlier in which increases in stimulus intensity such as luminance intensity results in a decrease of RT, whereas perceived perceptual latency in a TOJ task is affected to a lesser degree. Here, we report that a simple manipulation of stimulus size has stronger effects on perceptual latency measured by TOJ than on motor latency measured by RT tasks. When participants were asked to respond to the appearance of a simple stimulus such as a luminance blob, the perceptual latency measured against a standard reference stimulus was up to 40 ms longer for a larger stimulus. In other words, the smaller stimulus was perceived to occur earlier than the larger one. RT on the other hand was hardly affected by size. The TOJ results were further replicated in a simultaneity judgement task, suggesting that the effects of size are not due to TOJ-specific response biases but more likely reflect an effect on perceived timing

Brain activity during selective and divided attention

This thesis investigated brain activity with functional magnetic resonance imaging (fMRI) during selective and divided attention. Selective attention refers to the ability to selectively attend and process certain stimuli while ignoring others. Divided attention is needed, when two or more tasks requiring selective attention are performed in parallel. However, attention is easily caught by sudden changes in the environment. Brain activity and task performance during distracted and undistracted attention was also compared. The results showed that selective attention to auditory or visual modality enhanced activity in the auditory and visual cortices, respectively. However, the results also implied that the effects of selective attention may be influenced by task-irrelevant variation of the stimuli. The present thesis also showed that during divided attention, when two cognitively demanding tasks are performed in parallel, brain activity is enhanced in cortical areas in relation to the two tasks performed one at a time. Such activity enhancements specifically associated with divided attention were found in left middle frontal cortex during several different divided attention tasks. This suggests that division of attention requires specific, higher-level cognitive processes not needed in other attention-engaging tasks. However, not all dual tasks were associated with frontal activity enhancements. Complex selective attention tasks performed in parallel with another selective attention task may influence the higher-level cognitive processes or integration of two tasks needed during dual tasking.Tämä väitöskirja tutki valikoivaan ja jaettuun tarkkaavaisuuteen liittyvää aivotoimintaa toiminnallisen magneettikuvauksen (fMRI) avulla. Valikoivalla tarkkaavaisuudella tarkoitetaan kykyä huomioida ja käsitellä tiettyjä ärsykkeitä samanaikaisesti, kun muut ympäristön ärsykkeet jätetään huomiotta. Jaetulla tarkkaavaisuudella viitataan tilanteeseen, jolloin kahta tai useampaa valikoivaa tarkkaavaisuutta vaativaa tehtävää suoritetaan samanaikaisesti. Yllättävät muutokset ympäristössä voivat kuitenkin johtaa tarkkaavaisuutta vaativan tehtävän häiriintymiseen. Lisäksi tutkittiin yllättävien häirintä-ärsykkeiden vaikutusta aivotoimintaan ja tehtäväsuoriutumiseen. Tulokset osoittavat, että valikoiva tarkkaavaisuus ääniin tai kuviin johti aivotoiminnan vilkastumiseen vastaavilla kuulo- ja näköaivokuoren alueilla. Tulokset kuitenkin antoivat viitteitä myös siitä, että tehtävän kannalta epäolennaiset muutokset ärsykeympäristössä vaikuttaisivat valikoivan tarkkaavaisuuden aikaiseen aivotoimintaan. Tulokset osoittivat myös, että jaettaessa tarkkaavaisuutta kahden samanaikaisen tehtävän välillä, aivotoiminta vilkastuu aivokuorella verrattuna tehtävien suoritukseen yksitellen. Tällaista aivotoiminnan vilkastumista havaittiin vasemman keskiotsalohkon alueilla useiden erilaisten kaksoistehtävien aikana. Nämä tulokset voisivat viitata siihen, että jaettu tarkkaavaisuus vaatii erityisiä kognitiivisia resursseja, joita muut tarkkaavaisuutta vaativat tehtävät eivät edellytä. Kaikkien jaettua tarkkaavaisuutta vaativien tehtävien aikana ei kuitenkaan havaittu aivotoiminnan vilkastumista otsalohkojen alueilla. Tämä taas voisi viitata siihen, että monimutkaiset osatehtävät jaetun tarkkaavaisuuden aikana saattavat vaikuttaa jaetun tarkkaavaisuuden vaatimiin kognitiivisiin prosesseihin tai kahden samanaikaisen tehtävän integraatioon, jota suoriutuminen kaksoistehtävässä vaatii

Категориальная модель различения линий, углов и крестообразных фигур

The geometrical model of recognizing stimuli represented by the images composed of lines has been considered in the article. We have constructed the three-dimensional space having made use of the multidimensional scaling technique for averaged superthreshold estimations of the subjective differences between lines, angles and cross-shaped images. By means of the terms of Sokolov and Izmailov’s theory this space was the recognition model of differentiating our selected stimuli. The main specific feature of the model was the differentiation of these images by use of visual categorization.В статье рассмотрена геометрическая модель различения стимулов, представляющих собой изображения из линий. С помощью многомерного шкалирования усредненных надпороговых оценок субъективных различий между линиями, углами и крестами было получено пространство, которое в рамках концепции Соколова—Измайлова является моделью различения этих стимулов. Особенностью полученной модели является различение изображений путем выявления зрительных категорий

Особенности различения цветных объектов в условиях изменения характеристик фона

Visual recognition features of images with different figure-ground segregation have been considered in the article. The research was carried out within the framework of Sokolov and Izmaylov’s spherical model and was based on the construction of color objects discrimination models depending on the changes of background characteristics. The research has revealed the specific influence of the background on figure discrimination. The derived models reflect the mechanisms of the all-in-one perception of the visual space.Настоящая работа посвящена изучению особенностей зрительного распознавания изображений с разными фигуро-фоновыми отношениями. Исследование проводилось в рамках сферической модели Соколова—Измайлова и основывалось на построении моделей различения цветных объектов в зависимости от изменений характеристик фона. В результате исследования выявлено взаимовлияние фигуры и фона. Полученные модели отражают механизмы целостного восприятия видимой сцены