No description available.

No description available.

No description available.

No description available.

Eight experiments were performed to investigate factors affecting the discrimination of two characteristics of very brief tones. The subjects (adults with normal hearing) were asked to rate targets that differed either by amplitude envelope or by a change in frequency. For the majority of the trials, a target was followed (after a brief silent interval) by a pure tone referred to as a "mask". Two factors affecting discrimination within this simple paradigm were examined in detail; the frequency separation and the duration of the silent interval between the target and the mask. For most of the other conditions, a target and mask were embedded in a series of sounds that were presented with an isochronous rhythm. Several features of these "background" sounds were varied across the experiments, including their timbre, presentation rate and frequency relationships with the target and mask. / Superior discrimination was obtained when targets were able to perceptually "emerge" from a background of tones or noises. Specifically, performance was strongest when a target was easily segregated from the other sounds in the series by timing factors or through having a unique frequency. Discrimination was also enhanced when the interfering effects of the mask were removed through association with other tones in the sequence. The data suggest that a simple "interruption" model of processing, in which the presence of a mask disrupts subjects' ability to process individual characteristics of a target, does not adequately explain the differences in discrimination observed across the conditions. A more comprehensive explanation could consider attentional factors that may influence subjects' ability to accurately identify which tone in a sequence is to be rated. However, a perspective based on auditory segregation seems to most consistently explain the data; individual characteristics of a target were most easily discriminated when the target was perceived as belonging outside of an auditory group formed by the background sounds. This was especially true when the mask was likely to have been perceived as belonging within the group due to frequency proximity and/or rhythmic regularity.

A set of empirical studies is presented that examines the relationship between face perception, the modular hypothesis of cognitive function proposed by Fodor (1983), and attention. In the first study, two different manipulations were used to examine whether faces automatically trigger holistic processing operations as measured by the composite effect. The results support a modular account of face perception. / The second study introduces a novel rivalry phenomenon produced by overlapped upright tilted faces. The results indicate that this effect is dependent upon orientation with overlapped inverted faces being perceived as ambiguous in a majority of trials. The third study further examined the factors underlying this rivalry effect. It was found that contrast reversal did not influence the rivalry effect produced by overlapped upright faces and that overlapped houses did not produce rivalry. Results from both studies were taken as evidence that faces are more readily processed as Gestalts compared to other complex objects and therefore engage domain specific operations. The results also suggest that fast operations underlie perception of a face as a Gestalt. Finally, it was suggested that the rivalry effect produced by overlapped faces may illustrate informational encapsulation in face perception. / In the fourth study, faces were used to investigate the relationship between attention and modular functions. Three separate experiments showed that faces and houses compete for attention. This finding suggests that the face perception module does not have its own dedicated attentional resources but rather shares a common pool with other visual processes. Results from one experiment also suggested an advantage for faces in the allocation of attention at very short presentation times. This advantage was postulated to arise from two interacting mechanisms that is, faces capture attention over other objects and faces are more automatically encoded than other objects. Together, these studies indicate that a modular conceptualization of face processing is both appropriate and useful. They also demonstrate the utility of faces for investigating cognitive mechanisms that mediate modular functions.

No description available.

A forced-choice reaction time (RT) task was used to examine the development of visual filtering. Specifically, this study examined whether visual filtering is more efficient in smaller spatial ranges, and the extent to which age-related changes in filtering efficiency could be attributed to improvements in the ability to expand and contract an attentional focus. Participants included 20 children in each of four age groups (4, 5, 7, and 9 years), as well as 20 adults aged between 20 and 29 years. Conditions varied with regard to the location or presence of distracters, and the presence of a window within which target stimuli were presented. RT's were slower in the presence of distracters located within one 1 degree of visual angle from target stimuli than when distracters were presented 5.7 degree of visual angle away. In addition, young children were less capable than either older children or adults to filter task-irrelevant stimuli. With regard to the window, RT's were faster in the presence of a window than in its absence. Finally, the window was most effective in improving the filtering efficiency of 4 year old children. These results are discussed in terms of the zoom-lens metaphor of visual attention, and the development of the ability to vary the size of an attentive zoom-lens in response to task requirements.

The change blindness phenomenon, which is described as changes in the environment that are missed under natural viewing conditions because they occur simultaneously with another visual disruption, was studied from a developmental perspective. Participants included a total of 65 children in 3 age groups, 6, 8, and 10 years, and 20 adults, who were administered a version of the flicker paradigm, a technique in which blank screen is inserted between presentations (Rensink, O'Regan, & Clark, 1997). Participants responded to multiple presentations of 2 objects, positioned side by side, displayed on a computer screen. In each presentation, a distracter object remained unchanged, whereas the target object changed in 1 of 3 ways, color switch, missing part, and rotation. Stimuli consisted of inanimate objects, photographs and drawings, and were displays in either 50 milliseconds or 250 milliseconds. Results revealed that 6 years old participants displayed the highest degrees of change blindness.

No description available.