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The history of apparent movement begins in the 1820's (Boring, 1942), but its full importance for psychology was not recognized until the publication of Wertheimer's paper, Experimentelle Studien über das Sehen von Bewegung, in 1912 (translated in greater part in Shipley, 1961). Wertheimer saw the significance of the tact that, under certain temporal conditions, the successive presentation of a pair of stationary visual abjects "at a considerable spatial distance from one another," evokes the perception of movement. He called this impression of motion in the spatial interval between the two abjects the phi-phenomenon. [...]

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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.

Since Miskin and Forgays, lateralized differences in visual information processing has largely been explained by models consistent with theories of hemispheric specialization. The present study offers an alternative explaination to account for visual half field asymmetries while elucidating past methological inadequacies characteristic of many visual half field studies.Response times and accuracy scores were examined as a function of visual half fields and visual encoding strategies. All subjects responded manually to unilateral tachistoscopic stimulus presentation. Subjects were tested under two strategy conditions: (1) subjects responded to verbal stimuli using a verbal (linguist) encoding strategy, and (2) subjects responded to verbal stimuli using a non-verbal (visio-spatial) encoding strategy.Results were consistent with earlier studies which report a right visual half field superiority to unilateral presentation of verbal stimuli. Significant differences were noted between visual half field presentation and strategy conditions. Results are discussed in terms of an alternative explaination to account for visual half field asymmetries, based heavily upon methodological considerations and visual stimulus information encoding strategy.

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