Stefano Baldassi

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It is well known that attention improves the visibility of a target. In this study, we examined the effect of attention on the selectivity profile for a target. We used a masking technique to measure the tuning function for detecting a target while cueing either its orientation or its location. In the presence of an orientation mask, uncued thresholds were(More)
We have measured orientation discrimination in the presence of a variable number of neutral distracters for two distinct tasks: identification of the orientation of a tilted target and location of its position. Both tasks were performed in the presence of visual noise of variable contrasts. Under a range of conditions, subjects could identify the direction(More)
Visual cognition of observers with autism spectrum disorder (ASD) seems to show an unbalance between the complementary functions of integration and segregation. This study uses visual search and crowding paradigms to probe the relative ability of children with autism, compared to normal developments children, to extract individual targets from cluttered(More)
Search performance for a target tilted in a known direction among vertical distractors is well explained by signal detection theory models. Typically these models use a maximum-of-outputs rule (Max rule) to predict search performance. The Max rule bases its decision on the largest response from a set of independent noisy detectors. When the target is tilted(More)
Human observers are exquisitely sensitive to tilt in the orientation of a line. We can detect rotations away from the vertical of 0.5 degrees. It has been suggested [1,2] that this accuracy is a result of the orientation-selectivity of simple cells in the primary visual cortex (V1), many of which have receptive fields with an elliptical shape [3]. However,(More)
Perceptual decisions are often made in cluttered environments, where a target may be confounded with competing "distractor" stimuli. Although many studies and theoretical treatments have highlighted the effect of distractors on performance, it remains unclear how they affect the quality of perceptual decisions. Here we show that perceptual clutter leads not(More)
Facial expressions play a key role in affective and social behavior. However, the temporal dynamics of the brain responses to emotional faces remain still unclear, in particular an open question is at what stage of face processing expressions might influence encoding and recognition memory. To try and answer this question we recorded the event-related(More)
In a series of experiments we compared orientation discrimination performance for Gabor stimuli in which the stimulus profile was either matched to the receptive field profile of single V1 simple cells ('simple'), or in which the carrier and envelope orientations were different ('tigertails'). In the first Experiment, using small, high spatial frequency,(More)
Targets defined by attributes such as colour or brightness are said to "pop-out" from a cluttered scene, with little or no dependency on the size of the set to be searched, while search for other attributes can depend strongly on set-size. We measured contrast thresholds for increments and decrements in luminance or colour and show that they increase(More)