Independence of egocentric and exocentric direction processing in visual space

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.(AU)

Affective spatial compatibility task(AFFSCT): theory and applications / Tarefa de compatibilidade espacial afetiva (TCEA): teoria e aplicações / Tarea de compatibilidad espacial afectiva (TCEA): teoría y aplicaciones

Emotional stimuli are processed very efficiently, influencing physiological and behavioral responses as well as attention, perceptual processes and sensory-motor integration. In a previous work, we introduced a new paradigm, the Affective Spatial Compatibility task (AffSCt), to study whether the affective valence of the stimulus influences spatial compatibility effects. By using figures of soccer players of Favorite and Rival Teams as positive and negative valence stimuli, we found a normal Spatial Compatibility effect for the Favorite team and a reversed one for the Rival team. Here, we analyzed the time course of inhibitory and facilitatory effects of emotional valence by the Vincentization method. We found that for Favorite team, the facilitatory effect for the compatible condition, as compared to the incompatible one, increases as a function of the reaction time. In contrast, for Rival team, an opposite trend was found, in which inhibitory effect beEmotional stimuli are processed verycomes stronger for slower responses. We suggest that AffSCt is a powerful technology for investigating approach/avoidance effects and that it may be useful for diagnosing and following up the treatment of affective and behavioral disorders, such as anxiety, panic and ADHD. Potential applications in social psychology and consumer studies are also considered.(AU).

Os estímulos emocionais são processados de forma muito eficiente, influenciando as respostas fisiológicas e comportamentais, bem como a atenção, a percepção e a integração sensório-motora. Em um trabalho anterior, propusemos um novo paradigma, a Tarefa Afetiva de Compatibilidade Espacial (AffSCt), para estudar se a valência afetiva do estímulo influenciaria os efeitos de compatibilidade espacial. Ao usarmos figuras de jogadores de futebol dos times Favorito e Rival como estímulos de valência positiva e negativa, respectivamente, encontramos um efeito de compatibilidade espacial normal para o time Favorito e um invertido para o time Rival. No presente trabalho, foi analisado o desenvolvimento temporal dos efeitos inibitórios e facilitatórios da valência emocional pelo método da Vincentização. Descobrimos que, para o time Favorito, o efeito facilitatório na condição compatível em relação à incompatível aumenta em função do tempo de reação. Em contraste, para o time Rival, uma tendência oposta foi encontrada, em que o efeito inibitório se torna mais forte para as respostas mais lentas. Sugere-se que a AffSCt é uma tecnologia poderosa para investigar comportamentos de aproximação/afastamento, podendo ser útil na avaliação diagnóstica e acompanhamento terapêutico de transtornos emocionais e comportamentais, como o de ansiedade generalizada, síndrome de pânico e transtorno do déficit de atenção/hiperatividade. Também são consideradas as aplicações potenciais em psicologia social e estudos de consumidor.(AU).

Los estímulos emocionales se procesan de manera muy eficiente e influyen en las respuestas fisiológicas y de comportamiento, así como en la atención, la percepción y la integración sensorio-motora. En un trabajo previo, que presentó un nuevo paradigma, la tarea afectiva de compatibilidad espacial (AffSCt), para estudiar si la valencia afectiva de los estímulos influyen en los efectos de la compatibilidad espacial. Mediante el uso de las figuras de los jugadores de fútbol de los equipos favorito e rival como estímulos positivo y negativo de valencia, respectivamente, se observó un efecto ordinario de compatibilidad espacial para el equipo favorito y un efecto invertido para el equipo rival. En este estudio, hemos examinado la evolución temporal de los efectos inhibitorios y facilitatorio de la valencia emocional por el uso de la Vincentización. Hemos encontrado que, para el equipo favorito, el efecto facilitatorio aumenta para la condición compatible, respecto la incompatible, con el tiempo de eacción. En contraste, para el equipo rival, una tendencia inversa se encontró, en el que el efecto inhibidor se vuelve más fuerte para las respuestas más lentas. Se sugiere que AffSCt es una poderosa tecnología para investigar los comportamientos de aproximación/retirada que puede ser útil para diagnosticar y seguir el tratamiento de trastornos afectivos y conductuales como ansiedad, pánico y déficit de atención/trastorno de hiperactividad. También son consideradas aplicaciones potenciales del método en la psicología social y en los estudios de consumo.(AU).

Affective spatial compatibility task(AFFSCT): theory and applications / Tarefa de compatibilidade espacial afetiva (TCEA): teoria e aplicações / Tarea de compatibilidad espacial afectiva (TCEA): teoría y aplicaciones

Emotional stimuli are processed very efficiently, influencing physiological and behavioral responses as well as attention, perceptual processes and sensory-motor integration. In a previous work, we introduced a new paradigm, the Affective Spatial Compatibility task (AffSCt), to study whether the affective valence of the stimulus influences spatial compatibility effects. By using figures of soccer players of Favorite and Rival Teams as positive and negative valence stimuli, we found a normal Spatial Compatibility effect for the Favorite team and a reversed one for the Rival team. Here, we analyzed the time course of inhibitory and facilitatory effects of emotional valence by the Vincentization method. We found that for Favorite team, the facilitatory effect for the compatible condition, as compared to the incompatible one, increases as a function of the reaction time. In contrast, for Rival team, an opposite trend was found, in which inhibitory effect beEmotional stimuli are processed verycomes stronger for slower responses. We suggest that AffSCt is a powerful technology for investigating approach/avoidance effects and that it may be useful for diagnosing and following up the treatment of affective and behavioral disorders, such as anxiety, panic and ADHD. Potential applications in social psychology and consumer studies are also considered.

Os estímulos emocionais são processados de forma muito eficiente, influenciando as respostas fisiológicas e comportamentais, bem como a atenção, a percepção e a integração sensório-motora. Em um trabalho anterior, propusemos um novo paradigma, a Tarefa Afetiva de Compatibilidade Espacial (AffSCt), para estudar se a valência afetiva do estímulo influenciaria os efeitos de compatibilidade espacial. Ao usarmos figuras de jogadores de futebol dos times Favorito e Rival como estímulos de valência positiva e negativa, respectivamente, encontramos um efeito de compatibilidade espacial normal para o time Favorito e um invertido para o time Rival. No presente trabalho, foi analisado o desenvolvimento temporal dos efeitos inibitórios e facilitatórios da valência emocional pelo método da Vincentização. Descobrimos que, para o time Favorito, o efeito facilitatório na condição compatível em relação à incompatível aumenta em função do tempo de reação. Em contraste, para o time Rival, uma tendência oposta foi encontrada, em que o efeito inibitório se torna mais forte para as respostas mais lentas. Sugere-se que a AffSCt é uma tecnologia poderosa para investigar comportamentos de aproximação/afastamento, podendo ser útil na avaliação diagnóstica e acompanhamento terapêutico de transtornos emocionais e comportamentais, como o de ansiedade generalizada, síndrome de pânico e transtorno do déficit de atenção/hiperatividade. Também são consideradas as aplicações potenciais em psicologia social e estudos de consumidor.

Los estímulos emocionales se procesan de manera muy eficiente e influyen en las respuestas fisiológicas y de comportamiento, así como en la atención, la percepción y la integración sensorio-motora. En un trabajo previo, que presentó un nuevo paradigma, la tarea afectiva de compatibilidad espacial (AffSCt), para estudiar si la valencia afectiva de los estímulos influyen en los efectos de la compatibilidad espacial. Mediante el uso de las figuras de los jugadores de fútbol de los equipos favorito e rival como estímulos positivo y negativo de valencia, respectivamente, se observó un efecto ordinario de compatibilidad espacial para el equipo favorito y un efecto invertido para el equipo rival. En este estudio, hemos examinado la evolución temporal de los efectos inhibitorios y facilitatorio de la valencia emocional por el uso de la Vincentización. Hemos encontrado que, para el equipo favorito, el efecto facilitatorio aumenta para la condición compatible, respecto la incompatible, con el tiempo de eacción. En contraste, para el equipo rival, una tendencia inversa se encontró, en el que el efecto inhibidor se vuelve más fuerte para las respuestas más lentas. Se sugiere que AffSCt es una poderosa tecnología para investigar los comportamientos de aproximación/retirada que puede ser útil para diagnosticar y seguir el tratamiento de trastornos afectivos y conductuales como ansiedad, pánico y déficit de atención/trastorno de hiperactividad. También son consideradas aplicaciones potenciales del método en la psicología social y en los estudios de consumo.

Independence of egocentric and exocentric direction processing in visual space

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.

Effects of affective valence on a mixed Spatial Correspondence Task: a reply to Proctor (2013)

The present study investigated the influence of emotional valence on the spatial stimulus-key location correspondence effect in three experiments using the Affective Spatial Correspondence task (AffSCt). We initially reanalyzed the results of Conde et al. (2011) according to the model proposed by Proctor (2013). In that study, compatible and incompatible responses were chosen according to the participants' team preference. In one block, the volunteers had to press a key on the same side for the Favorite team and on the opposite side for the Rival team. In another block, a reverse code was used. We found that responses were faster for the Favorite-compatible/Rival-incompatible condition (614 ms) compared with the Favorite-incompatible/Rival-compatible condition (691 ms). The same experimental arrangement was replicated in another Brazilian city, and similar results were found. Additionally, we employed non-affective "fake" soccer teams as a control condition, and no mapping-rule effect was observed. Finally, a final experiment that used the same design but different non-affective stimuli (yellow and blue bars) was performed to provide further evidence that the valence effect in the present experimental paradigm only occurs with affective stimuli. As expected, non-affective stimuli did not produce an overall advantage for any mapping rules, corroborating earlier findings with similar mixed designs. The results confirmed the previous findings and validity of the AffSCt as a methodology to investigate the effects of emotional valence on stimulus-response correspondence. However, we are unable to provide a conclusive explanation to support the several hypotheses proposed previously in our paper and by Proctor (2013).(AU)

Effects of affective valence on a mixed Spatial Correspondence Task: a reply to Proctor (2013)

The present study investigated the influence of emotional valence on the spatial stimulus-key location correspondence effect in three experiments using the Affective Spatial Correspondence task (AffSCt). We initially reanalyzed the results of Conde et al. (2011) according to the model proposed by Proctor (2013). In that study, compatible and incompatible responses were chosen according to the participants' team preference. In one block, the volunteers had to press a key on the same side for the Favorite team and on the opposite side for the Rival team. In another block, a reverse code was used. We found that responses were faster for the Favorite-compatible/Rival-incompatible condition (614 ms) compared with the Favorite-incompatible/Rival-compatible condition (691 ms). The same experimental arrangement was replicated in another Brazilian city, and similar results were found. Additionally, we employed non-affective "fake" soccer teams as a control condition, and no mapping-rule effect was observed. Finally, a final experiment that used the same design but different non-affective stimuli (yellow and blue bars) was performed to provide further evidence that the valence effect in the present experimental paradigm only occurs with affective stimuli. As expected, non-affective stimuli did not produce an overall advantage for any mapping rules, corroborating earlier findings with similar mixed designs. The results confirmed the previous findings and validity of the AffSCt as a methodology to investigate the effects of emotional valence on stimulus-response correspondence. However, we are unable to provide a conclusive explanation to support the several hypotheses proposed previously in our paper and by Proctor (2013)...

One-dimensional and multi-dimensional studies of the exocentric distance estimates in frontoparallel plane, virtual space, and outdoor open field.

The aim of this study is twofold: on the one hand, to determine how visual space, as assessed by exocentric distance estimates, is related to physical space. On the other hand, to determine the structure of visual space as assessed by exocentric distance estimates. Visual space was measured in three environments: (a) points located in a 2-D frontoparallel plane, covering a range of distances of 20 cm; (b) stakes placed in a 3-D virtual space (range = 330 mm); and (c) stakes in a 3-D outdoors open field (range = 45 m). Observers made matching judgments of distances between all possible pairs of stimuli, obtained from 16 stimuli (in a regular squared 4 x 4 matrix). Two parameters from Stevens' power law informed us about the distortion of visual space: its exponent and its coefficient of determination (R2). The results showed a ranking of the magnitude of the distortions found in each experimental environment, and also provided information about the efficacy of available visual cues of spatial layout. Furthermore, our data are in agreement with previous findings showing systematic perceptual errors, such as the further the stimuli, the larger the distortion of the area subtended by perceived distances between stimuli. Additionally, we measured the magnitude of distortion of visual space relative to physical space by a parameter of multidimensional scaling analyses, the RMSE. From these results, the magnitude of such distortions can be ranked, and the utility or efficacy of the available visual cues informing about the space layout can also be inferred.

Distance perception in a natural outdoor setting: is there a developmental trend to overconstancy?

The main purpose of the present study was to investigate whether in natural environment, using very large physical distances, there is a trend to overconstancy for distance estimates during development. One hundred and twenty-nine children aged 5 to 13 years old and twenty-one adults (in a control group), participated as observers. The observer's task was to bisect egocentric distances, ranging from 1.0 to 296.0 m, presented in a large open field. The analyses focused on two parameters, constant errors and variable errors, such as measuring accuracy and precision, respectively. A third analysis focused on the developmental pattern of shifts in constancy as a function of age and range of distances. Constant error analysis showed that there are two relevant parameters for accuracy, age, and range of distances. For short distances, there are three developmental stages: 5-7 years, when children have unstable responses, 7-11, underconstancy, and 13 to adulthood, when accuracy is reached. For large distances, there is a two-stage development: 5-11 years, with severe underconstancy, and beyond this age, with mild underconstancy. Variable errors analyses indicate that precision is noted for 7 year-old children, independently of the range of distances. The constancy analyses indicated that there is a shift from constancy (or slightly overconstancy) to underconstancy as a function of physical distance for all age groups. The age difference is noted in the magnitude of underconstancy that occurs in larger distances, where adults presented lower levels of underconstancy than children. The present data were interpreted as due to a developmental change in cognitive processing rather than to changes in visual space perception.

One-dimensional and multi-dimensional studies of the exocentric distance estimates in frontoparallel plane, virtual space, and outdoor open field

The aim of this study is twofold: on the one hand, to determine how visual space, as assessed by exocentric distance estimates, is related to physical space. On the other hand, to determine the structure of visual space as assessed by exocentric distance estimates. Visual space was measured in three environments: (a) points located in a 2-D frontoparallel plane, covering a range of distances of 20 cm; (b) stakes placed in a 3-D virtual space (range ≈ 330 mm); and (c) stakes in a 3-D outdoors open field (range = 45 m). Observers made matching judgments of distances between all possible pairs of stimuli, obtained from 16 stimuli (in a regular squared 4 × 4 matrix). Two parameters from Stevens' power law informed us about the distortion of visual space: its exponent and its coefficient of determination (R2). The results showed a ranking of the magnitude of the distortions found in each experimental environment, and also provided information about the efficacy of available visual cues of spatial layout. Furthermore, our data are in agreement with previous findings showing systematic perceptual errors, such as the further the stimuli, the larger the distortion of the area subtended by perceived distances between stimuli. Additionally, we measured the magnitude of distortion of visual space relative to physical space by a parameter of multidimensional scaling analyses, the RMSE. From these results, the magnitude of such distortions can be ranked, and the utility or efficacy of the available visual cues informing about the space layout can also be inferred (AU)

En este estudio se pretendía cubrir un doble objetivo. Por un lado, determinar cómo el espacio visual, evaluado en términos de estimaciones de distancias exocéntricas, se corresponde con el espacio físico. Y, por otro lado, determinar la estructura del espacio visual a partir de las mismas estimaciones de distancias. Para ello, registramos la respuesta (métrica) de los observadores en tres entornos espaciales: (a) puntos localizados en un plano 2-D (frontoparalelo) en un rango de distancias de 20 cm; (b) estacas vistas esteroscopicamente y situadas en un espacio virtual 3-D (rango de 33 cm); y (c) estacas físicas dispuestas en un espacio abierto exterior (rango de 45 m). Los observadores hicieron juicios de emparejamiento de distancias entre todos los posibles pares que se podían formar con 16 estacas (dispuestas en una matriz cuadrada regular de 4 filas × 4 columnas). Utilizamos dos parámetros de la ley potencial de Stevens, que nos informaron de la distorsión percibida del espacio visual: el exponente y el coeficiente de determinación (R2). Los resultados permitieron ordenar la magnitud de la distorsión encontrada en cada entorno experimental, proporcionando información sobre la utilidad y eficacia de las claves de profundidad disponibles. Nuestros datos concuerdan con los obtenidos en estudios previos en mostrar una cierta anisotropía espacial que difiere en cada entorno. Adicionalmente, aplicamos el escalamiento multidimensional y medimos la distorsión a través del RECM, lo que también nos permitió ordenar la magnitud de las distorsiones en cada contexto, así como la eficacia de las claves visuales de distancia (AU)

Distance perception in a natural outdoor setting: is there a developmental trend to overconstancy?

The main purpose of the present study was to investigate whether in natural environment, using very large physical distances, there isa trend to over constancy for distance estimates during development. One hundred and twenty-nine children aged 5 to 13 years old and twenty-one adults (in a control group), participated as observers. The observer’s task was to bisect egocentric distances, ranging from 1.0 to 296.0 m, presented in a large open field. The analyses focused on two parameters, constant errors and variable errors, such as measuring accuracy and precision, respectively. A third analysis focused on the developmental pattern of shifts in constancy as a function of age and range of distances. Constant error analysis showed that there are two relevant parameters for accuracy, age, and range of distances. For short distances, there are three developmental stages: 5-7 years, when children have unstable responses, 7-11, under constancy, and 13 to adulthood, when accuracy is reached. For large distances, there is a two-stage development: 5-11 years, with severe under constancy, and beyond this age, with mild under constancy. Variable errors analyses indicate that precision is noted for 7 year-old children, independently of the range of distances. The constancy analyses indicated that there is a shift from constancy (or slightly over constancy) to under constancy as a function of physical distance for all age groups. The age difference is noted in the magnitude of under constancy that occurs in larger distances, where adults presented lower levels of under constancy than children. The present data were interpreted as due to a developmental change in cognitive processing rather than to changes in visual space perception (AU)

El principal objetivo de este estudio fue investigar si en un medio natural, empleando distancias físicas muy grandes, hay una tendencia a sobre-constancia para las estimaciones de distancias durante el desarrollo evolutivo. Participaron como observadores 129 niños de edades entre 5 y 13 años y 21 adultos (en un grupo control). La tarea de los observadores consistió en biseccionar unas distancias egocéntricas, que variaban entre 1,0 y 296,0 m, presentadas en un gran campo abierto. El análisis se centró en dos parámetros, error constante y error variable, de la exactitud y precisión de medida, respectivamente. Un tercer análisis se centró en el patrón evolutivo de cambios en la constancia en función de la edad y el rango de distancias. El análisis de los errores constantes mostró que hay dos parámetros relevantes para la precisión, edad y rango de distancias. Para distancias cortas, hay tres fases evolutivas: 5-7 años, cuando los niños dan respuestas inestables, 7-11, infra-constancia, y 13 años hasta la adultez, cuando alcanzan la exactitud (constancia). Para las distancias largas, hay un desarrollo de dos fases: 5-11 años, con infra-constancia severa, y más allá de esta edad, con ligera infraconstancia. El análisis del error variable indica que se alcanza precisión a partir de 7 años, con independencia del rango de distancias. En análisis de la constancia indica que existe un cambio desde la constancia (o una ligera sobre-constancia) a infra-constancia en función de la distancia física para todos los grupos de edad. La diferencia de edad se nota en la magnitud de la infra-constancia que ocurre en las distancias más largas, donde los adultos presentaban niveles menores de infra-constancia que los niños. Estos datos se interpretan como debidos a un cambio evolutivo en el procesamiento cognitivo más que a cambios en la percepción visual del espacio (AU)

Visual angle as determinant factor for relative distance perception

Visual angles are defined as the angle between line of sight up to the meanpoint of a relative distance and the relative distance itself. In one experiment,we examined the functional aspect of visual angle in relative distanceperception using two different layouts composed by 14 stakes, one of themwith its center 23 m away from the observation point, and the other 36 maway from the observation point. Verbal reports of relative distance weregrouped in 10 categories of visual angles. Results indicated visual angle as adeterminant factor for perceived relative distance as observed in the absenceof perceptual errors to distances with visual angle equal or larger than 70degrees that could be attributed to a combination of sources of visualinformation. Another finding showed a possible intrusion of non-perceptualfactors (observer’s tendencies), leading to compressed estimates to relativedistances with visual angles smaller than 70 degrees

Perceptual constancy in judgments of egocentric distance: prevailing binocular information

Binocular cues were considered the prevailing on specifying depth since the beginning of vision research. In the present study, two perceptual responses, the classical verbal report and a more recent method, open-loop walking, were used to assess the role of binocular information for egocentric distance perception. In two cue conditions environments, full- and reduced-cue, observers judge and walked egocentric distances of stimuli presented at eye-level, under binocular or monocular viewing. Results indicated perceptual constancy for open-loop walking and binocular responses, as well as poor performances under strong degradation on visual information (reduced-cue under strong monocular viewing), thus presenting evidence to support the fundamental role of binocular information on perception of egocentric distances. Besides that, visually directed actions could be adequate measures of perceived distance, with a better reliability than verbal report, since they were quite free of intrusion of inferential processes and perceptual tendencies. In addition, reduced head movements, side-to-side as well as back and forth deflexion movements, could have contributed to a near perfect coupling between binocular disparity information and open-loop walking responses.

Interações entre sistemas de referência alocêntricos e egocêntricos: evidências dos estudos com direção percebida / Interactions between allocentric and egocentric frames of reference: evidences from studies on perceived direction

Sistemas de referência (frames of reference) são definidos como um locus ou conjunto de loci em relação ao qual as localizações espaciais são determinadas. Os sistemas de referência egocêntricos definem as localizações espaciais em relação ao observador, enquanto que nos sistemas de referência alocêntricos, as localizações são determinadas em relação a loci externos ao observador. Analisamsediversas evidências da utilização destes sistemas de referência pelo sistema visual humano, tanto para tarefas de percepção visual quanto para tarefas de navegação. Hipóteses da dissociação dosistema visual em função destes sistemas de referência são evidenciadas por resultados de estudos neuropsicológicos. O conjunto das evidências experimentais indica uma efetiva interação entre codificações em sistemas de referência egocêntricos e alocêntricos, de modo que os sistemas visual e visomotor introduzem transformações nas coordenadas de um sistema em função de outro, adequando a informação às características das diferentes tarefas. (AU)

Frame of reference is a locus or a set of loci in relation to which spatial locations are determined. Egocentrical frames of reference define spatial locations in relation to observer; in allocentricalframes of reference, spatial locations are determined in relation to external loci. Several evidences of usefulness of frames of references to human visual system are analysed, to perceptual tasks as well as navigational tasks. Neuropsychological studies provided empirical support to hypothesis ondissociation of visual system as a function of frames of reference. The whole of experimental evidenceindicates an effective interaction between codings in egocentrical and allocentrical frames of reference,thus visual and visuomotor systems introduce transformations on coordinates of a frame on another,adjusting information to different tasks requirements. (AU)

Interações entre sistemas de referência alocêntricos e egocêntricos: evidências dos estudos com direção percebida / Interactions between allocentric and egocentric frames of reference: evidences from studies on perceived direction

Sistemas de referência (frames of reference) são definidos como um locus ou conjunto de loci em relação ao qual as localizações espaciais são determinadas. Os sistemas de referência egocêntricos definem as localizações espaciais em relação ao observador, enquanto que nos sistemas de referência alocêntricos, as localizações são determinadas em relação a loci externos ao observador. Analisamsediversas evidências da utilização destes sistemas de referência pelo sistema visual humano, tanto para tarefas de percepção visual quanto para tarefas de navegação. Hipóteses da dissociação dosistema visual em função destes sistemas de referência são evidenciadas por resultados de estudos neuropsicológicos. O conjunto das evidências experimentais indica uma efetiva interação entre codificações em sistemas de referência egocêntricos e alocêntricos, de modo que os sistemas visual e visomotor introduzem transformações nas coordenadas de um sistema em função de outro, adequando a informação às características das diferentes tarefas.

Frame of reference is a locus or a set of loci in relation to which spatial locations are determined. Egocentrical frames of reference define spatial locations in relation to observer; in allocentricalframes of reference, spatial locations are determined in relation to external loci. Several evidences of usefulness of frames of references to human visual system are analysed, to perceptual tasks as well as navigational tasks. Neuropsychological studies provided empirical support to hypothesis ondissociation of visual system as a function of frames of reference. The whole of experimental evidenceindicates an effective interaction between codings in egocentrical and allocentrical frames of reference,thus visual and visuomotor systems introduce transformations on coordinates of a frame on another,adjusting information to different tasks requirements.

Evidências da elevação angular como indício de distância absoluta em aléia visual / Evidences of angular elevation as an absolute distance cue in visual alley

Em duas condições de movimentos vergenciais, fusional e acomodativo, e condição de vergência reduzida, o efeito da elevação angular foi observado em duas condições relativas ao plano do olho, (1) plano do nível do olho na altura do objeto e (2) elevação de 48,8 cm acima do piso da aléia. A elevação angular em conjunção com os sinais vergenciais permitiu estimativas acuradas de distância absoluta maiores que um metro. Outros fatores, não-perceptuais e tendências perceptuais do observador, podem também ter combinado com a elevação angular (AU)

Análise dos desvios angulares da locomoçäo em uma tarefa para evitar colisäo contra objeto fixo em ambiente rígido: uma breve comunicaçäo / Angular deviation analysis of locomotion in a task to avoid colision against obstacles: a brief communication

Pessoas controlam através da informaçäo visual disponível suas açöes para realizar tarefas com metas específicas. Em uma tarefa do caminhar direto para pontos de evitaçäo visualizados previamente com objetivos de evitar colisäo contra um obstáculo fixo, foram analisados os erros de desvio ou o componentes de locomoçäo, a translaçäo e a rotaçäo. Os erros angulares de desvios foram observados dentro dos limites considerados para uma acurácia da orientaçäo espacial percebida, e produziram componentes da locomoçäo acurados para evitar colisäo. A acurácia foi explicada por dois fatores, a disponibilidade de fontes de informaçöes espaciais e a potência das propriedades da cena, que permitiram aos observadores a construçäo de uma representaçäo visual da cena física, e a manutençäo da orientaçäo espacial durante a locomoçäo para alvos predeterminados de modo seguro a fim de evitar possíveis acidentes de choque contra obstáculos

Analise dos desvios angulares da locomocao em uma tarefa para evitar colisao contra objeto fixo em ambiente rigido: uma breve comunicacao

Pessoas controlam atraves da informacao visual disponivel suas acoes para realizar tarefas com metas especificas. Em uma tarefa do caminhar direto para pontos de evitacao visualizadas previamente como objetivos d evitar colisao contra um obstaculo fixo, foram analisados os erros de desvio ou os componentes da locomocao, a translacao e a rotacao. Os erros angulares de desvio foram observados dentro dos limites considerados para uma acuracia da orientacao espacial percebida, e produziram componentes da locomocao acurados para evitar colisao. A acuracia foi explicada por dois fatores, a disponibilidade de fontes de informacoes espaciais e a potencia das propriedades da cena, que permitiram aos observadores a construcao de uma representacao visual da cena fisica, e a manutencao da orientacao espacial durante a locomocao para alvos predeterminados de modo seguro a fim de evitar possiveis acidentes de choque contra obstaculos.