Selective attention was studied in displays containing singletons popping out for their odd form or color. The target was defined as the form-singleton, the distractor as the color-singleton. The task was to discriminate the length of a longer line inside the target. Target-distractor similarity was controlled using a threshold measurement as dependent variable in experiments in which distractor presence vs absence, bottom-up vs top-down selection (through knowledge of target features), and target-distractor distance were manipulated. The results in the bottom-up condition showed that length threshold was elevated when a distractor was present and that this elevation progressively increased as the number of distractors was increased from one to two. This set-size effect was not accounted by the hypothesis that selective attention intervenes only at the stage of decision before response. Selective attention produced a suppressive surround in which discriminability of neighboring objects was strongly reduced, and a larger surround in which discriminability was reduced by an approximately constant amount. Different results were found in the top-down condition in which target discriminability was unaffected by distractor presence and no effect of target-distractor distance was found. On the other hand, response times in both bottom-up and top-down conditions were slower the shorter the target-distractor distance was. On the basis of the experimental results, selective attention is a parallel process of spatial filtering at an intermediate processing level operating after objects have been segmented. This filtering stage explores high level interactions between objects taking control on combinatorial explosion by operating over only a limited spatial extent: it picks out a selected object and inhibits the neighboring objects; then, non-selected objects are suppressed across the overall image. When no feature-based selection is available in the current behavior, this filtering influences perception in decreasing discriminability of non-selected objects. When feature-based selection is available, spatial interactions are set before stimulus arrival, hence only the unmatching objects have their discriminability diminished.

Human observers discriminated the global orientation of a texture-defined figure which segregated from a texture surround. Global figure discriminability was manipulated through within-figure collinearity, figure-surround interaction, and figure connectedness, while the local orientation contrast at edges between figure and surround was kept constant throughout all the experiments. Visual evoked potentials (VEPs) were recorded during onset-offset stimulation in which the figure cyclically appeared and disappeared from a uniform texture background. A difference component was obtained by subtraction of offset-from onset-VEP. Two negative peaks of the difference component are found with latencies around 140-160 and 200-260 ms, respectively. Enhanced discriminability of the global figure reduced (11-25 ms) the latency of the second peak, hence indicating that the 200-260 ms component was produced by global figure-ground segmentation.

I describe a visual illusion which occurs when an observer sees his/her image reflected in a mirror in a dimly lit room. This illusion can be easily experienced and replicated as the details of the setting (in particular the room illumination) are not critical. These observations were made in a quiet room dimly lit by a 25 W incandescent light. The lamp was placed on the floor behind the observer so that it was not visible either directly or in the mirror. A relatively large mirror (0.5 m60.5 m) was placed about 0.4 m in front of the observer. Luminance of the reflected face image within the mirror was about 0.2 cd m À2 and this level allowed detailed perception of fine face traits but attenuated colour perception. The illusion occurred even at higher levels of illumination of observer's face (from 0.2 to 1.6 cd m À2). The task of the observer was to gaze at his/her reflected face within the mirror. Usually, after less than a minute, the observer began to perceive the strange-face illusion. Phenomenological descriptions were made by fifty naive individuals (age range 21^29 years; mean 23 years; SD 2.1 years). At the end of a 10 min session of mirror gazing, the participant was asked to write what he or she saw in the mirror. The descriptions differed greatly across individuals and included: (a) huge deformations of one's own face (reported by 66% of the fifty participants); (b) a parent's face with traits changed (18%), of whom 8% were still alive and 10% were deceased; (c) an unknown person (28%); (d) an archetypal face, such as that of an old woman, a child, or a portrait of an ancestor (28%); (e) an animal face such as that of a cat, pig, or lion (18%); (f) fantastical and monstrous beings (48%). The disappearance or attenuation of face traits could be linked to the Troxler fading that occurs in the periphery while staring at a central fixation. However, this explanation would predict that face traits should fade away and eventually disappear (Wade 2000), whereas the apparitions in the mirror consist of new faces having new traits. A possibly related`multiple-faces' phenomenon (Simas 2000) has been reported for photos of faces placed in peripheral vision. In this case, the reported deformations of features include variations of the facial traits and expressions or appearance of new ones like teeth, or a beard, as well as completely new faces, 3-D distortions, rotations, upside-down faces, the subject's own face, sometimes younger or older. Clearly, there are similarities in effects for peripherally viewed photos and centrally viewed self-reflections in dim light. However, in central viewing, the perception of the face is more accurate, making the distortion more salient, and, because the distortions are of one's own face, the effects are amplified from merely intriguing to often unsettling. The two types of distortion (peripheral versus low-illumination central viewing) can be compared by viewing one's own face in ÅÙ AE profile in a mirror in peripheral vision. From a perceptual viewpoint, the strange-face ill...

Aquatic therapy improves motor skills of persons with Autism Spectrum Disorders (ASD), but its usefulness for treating functional difficulties needs to be verified yet. We tested effectiveness of a multisystem aquatic therapy on behavioural, emotional, social and swimming skills of children with ASD. Multisystem aquatic therapy was divided in three phases (emotional adaptation, swimming adaptation and social integration) implemented in a 10-months-programme. At post-treatment, the aquatic therapy group showed significant improvements relative to controls on functional adaptation (Vineland Adaptive Behavior Scales), emotional response, adaptation to change and on activity level (Childhood Autism Rating Scale). Swimming skills learning was also demonstrated. Multisystem aquatic therapy is useful for ameliorating functional impairments of children with ASD, going well beyond a swimming training.

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