Attention to Monocular Images Bias Binocular Rivalry.

When monocular images cannot be fused, perception alternates between the two (or more) possible images. This phenomenon, binocular rivalry (BR), is driven by the physical properties of the stimuli (size, contrast, spatial frequency, etc.) but it can also be modulated by attention to features of one of the rival stimuli (Chong et al.

Generalisation decrement and not overshadowing by associative competition among pairs of landmarks in a navigation task with humans.

In three experiments, a virtual preparation for humans of the Morris water task (VMWT) was used. Experiment 1 established that four landmarks were of similar salience. Then, in Experiments 2 and 3, participants were trained to locate a hidden platform in the presence or either two or four of the previous landmarks.

Visual fatigue while watching 3D stimuli from different positions.

Purpose: When observers focus their stereoscopic visual system for a long time (e.g., watching a 3D movie) they may experience visual discomfort or asthenopia.

Attentional blink in children with attention deficit hyperactivity disorder.

Objective: To explore the temporal mechanism of attention in children with attention deficit hyperactivity disorder (ADHD) and controls using a rapid serial visual presentation (RSVP) task in which two letters (T1 and T2) were presented in close temporal proximity among distractors (attentional blink [AB]).

Method: Thirty children aged between 9 and 13 years (12 with ADHD combined type and 18 controls) took part in the study. Both groups performed two kinds of RSVP task.

Difference in visual processing assessed by eye vergence movements.

Orienting visual attention is closely linked to the oculomotor system. For example, a shift of attention is usually followed by a saccadic eye movement and can be revealed by micro saccades. Recently we reported a novel role of another type of eye movement, namely eye vergence, in orienting visual attention.

Psychometric properties of a test for ADHD based on binocular rivalry.

The psychometric properties of a Binocular Rivalry (BR)-based test on a group of 159 participants (57 with attention deficit hyperactivity disorder, ADHD) aged between 6 and 15 years are presented. Two factors, which explained 56.82% of the variance, were obtained by exploratory factor analysis: (a) Alternations and Duration of exclusive dominances, and (b) Decision time.

Onset time of binocular rivalry and duration of inter-dominance periods as psychophysical markers of ADHD.

Attention deficit hyperactivity disorder (ADHD) is one of the main neurobiological disorders in young children. Despite its prevalence, current diagnosis is debated. In this study we tested whether measures of binocular rivalry (BR) can contribute to the diagnosis of ADHD.

Assessing Attention Deficit by Binocular Rivalry.

Objective: To determine whether the frequency and duration of the periods of suppression of a percept in a binocular rivalry (BR) task can be used to distinguish between participants with ADHD and controls.

Method: A total of 122 participants (6-15 years) were assigned to three groups: ADHD-Combined (ADHD-C), ADHD-Predominantly Inattentive (ADHD-I), and controls. They each performed a BR task and two measures were recorded: alternation rate and duration of exclusive dominance periods.

A role of eye vergence in covert attention.

Covert spatial attention produces biases in perceptual and neural responses in the absence of overt orienting movements. The neural mechanism that gives rise to these effects is poorly understood. Here we report the relation between fixational eye movements, namely eye vergence, and covert attention.

Influence of background on precision of 3D depth judgment tasks in a real environment.

Presently, little is known about the effect of curved backgrounds against which the target stimulus is presented on precision in stereoacuity. The experiment analyzed the influence of stimulus orientation and 3D background configuration on stereoscopic vision. Participants were instructed to perform 3D visual alignment tasks on a modified version of the Howard-Dolman apparatus, whereupon precision in depth perception for different curved backgrounds (flat, black, concave, and convex) was evaluated.

Visual mechanisms governing the perception of auto-stereograms.

Background: Single image random dot stereograms (SIRDS) have been used to study diverse visual parameters and skills. The aim of the present study was to identify the main optometric factors involved in the perception of SIRDS and to obtain a discriminant model to categorise our participants in terms of their skill in perceiving SIRDS.

Methods: Response time was determined to assess the ability of 69 participants to perceive the hidden three-dimensional shape in an auto-stereogram presented under controlled conditions, whereupon three skill level groups were defined.

Differential intrinsic bias of the 3-D perceptual environment and its role in shape constancy.

In a three-dimensional (3-D) environment, sensory information is projected on a 2-D retina with the consequence that the visual system needs space information for accurately reconstructing the visual world. However, the 3-D environment is not accurately represented in the brain; in particular, the perception of distances in depth is imprecise. It has been argued that the visual system has an intrinsic bias of visual space where targets located on the ground floor are perceived on an implicit elevated surface.

Mental rotation of mirrored letters: evidence from event-related brain potentials.

Event-related brain potentials (ERPs) were recorded while participants (n=13) were presented with mirrored and normal letters at different orientations and were asked to make mirror-normal letter discriminations. As it has been suggested that a mental rotation out of the plane might be necessary to decide on mirrored letters, we wanted to determine whether this rotation occurs after the plane rotation in mirror rotated letters. The results showed that mirrored letters in the upright position elicited a negative-going waveform over the right hemisphere in the 400-500 ms window.

[Familiarity and recollection in fictitious face recognition: implications for recognition models].

Using the <> paradigm, participants were engaged in a fictitious face recognition experiment in which three between-subject conditions were manipulated by either adding or not adding wrinkles on the faces between the study and the recognition tasks (no change, single change, double change). Our hypothesis was that this procedure would maximize judgments based on familiarity, thus determining whether data provided better fit to the models based on the signal detection theory or to predictions of dual models. In global terms, our results support the signal detection model predictions, although we discuss whether these models better fit tasks based on familiarity or tasks based on recollection.

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.

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).