tesis doctoral - e-Spacio - Uned

Organización perceptiva y procesamiento visual preatencional
6) random numbers between 0 and 9, each lasted 200 ms Participants had to press a key
(space bar) as fast as possible each time digit zero was displayed on the screen. There was an
enough number of digits zero to ensure a high involvement of attentional resources.
Performance in the digit task was registered in order to filter non-valid trials that did not reach a
determinated hit rate. During the digit task, visual patterns, grouped by luminance similarity,
could be displayed on the background at different locations, and with several SOAs (stimulus
onset asynchrony) between grouped stimulus and attentional task onsets. The grouped patterns
consisted of twelve white circles inside a matrix of dark circles on a grey background (Fig. 1).
a b c d
e
Figure 1. (a) Ungrouped matrix consist of 16 dark circles and (b, c, d, e) grouped patterns consist of 12
white circles used in Experiments 1 to 5.
In the present work, the second stage included one of two different attentional tasks:
either (1) a grouped pattern identification task (Experiments 1-4), or (2) a grouped pattern visual
search task (Experiments 4 and 5). Both tasks are typical examples of experimental procedures
involving selective attentional mechanisms.
Basically, the experimental design of preattention paradigm included two main
conditions (Fig. 2):
1. Preexposure condition, including presentation of grouped patterns during the digit task
at differents SOAs from 29 ms to 1113 ms.
2. Non-preexposure or control condition, not including presentation of grouped patterns
during the digit task. Grouped stimuli only were displayed at the beggining of the
attentional task phase, when the digit task had already finished.
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