Academic journal article Attention, Perception and Psychophysics

Investigating the Stability of and Relationships among Global/local Processing Measures

Academic journal article Attention, Perception and Psychophysics

Investigating the Stability of and Relationships among Global/local Processing Measures

Article excerpt

Published online: 26 January 2013

© Psychonomic Society, Inc. 2013

Abstract Global/local stimuli have been used to estimate global processing biases in individuals and groups, as well as in response to various manipulations. Throughout the literature, multiple different versions of global/local stimuli have been used, such as traditional hierarchical letters and numbers (i.e., Navon letters), abstract hierarchical shapes, and high- and low-spatial-frequency gratings and faces. However, currently it is unclear how reliable or stable performance is on these measures within individuals over time, and whether these seemingly different measures are tapping into the same underlying process. As such, the purpose of the present study was to examine the stability of individual performance on three distinct global/local measures over time and to examine the relationships among the measures. In two studies, we examined the reliability of the biases within, and the relationships among, standard Navon letters in a traditional interference task, hierarchical shapes in a forced choice task, and superimposed high- and low-pass spatial frequency faces in a forced choice task. In both studies, participants completed all three of the tasks, and then returned 7-10 days later to again complete the same tasks. The degree of global/local bias within an individual was found to be highly reliable in the hierarchical shape task and the spatial frequency face task, but less reliable in the traditional Navon letter task. Interestingly, in both studies we found that none of the three measures of global bias were related to each other. Therefore, while these measures do appear to be reliable over time, they may be tapping into distinct aspects of global/local processing.

Keywords Global/local bias · Global precedence · Individual differences · Reliability

Visual stimuli can often be viewed at either a broad, global level (e.g., the forest) or at a more detailed, local level (e.g., a free). Researchers often investigate a bias toward global or local information with hierarchical global/local stimuli known as "Navon stimuli" (Navon, 1977, 1981). Navon stimuli are typically large single letters that are composed of smaller letters (see Fig. lc below and Navon, 1977). Variations of such stimuli can also involve hierarchical shapes (Kimchi & Palmer, 1982) or objects (Fink et al., 1997).

For Navon stimuli, the large element represents the global perceptual level, whereas the smaller elements represent the local perceptual level. The elements at the two different levels can either be the same (congruent) or different (incongruent). Participants are usually directed to attend to either the global or the local level and to identify the stimulus at that level as quickly as possible. The results from using hierarchical stimuli typically show that more interference occurs from the global information when one is trying to focus on the local information than occurs in the reverse situation (i.e., a global advantage). This suggests that the processing ofthe broad aspects of a stimulus takes precedence over the processing of finer, more detailed aspects (Navon, 1981).

Individual differences

While a global advantage is generally observed with Navon stimuli, evidence suggests that the degree of individual bias toward global information can be altered by varying stimulus parameters, such as the aspect ratio of the local to the global items (Kimchi, 1992; Yovel, Yovel, & Levy, 2001), the overall visual angle (Kinchla & Wolfe, 1979), or the exposure duration (Paquet & Merikle, 1984). Kimchi and Palmer (1982), in particular, have shown that the relative number and size of the elements in a global/local hierarchical figure can greatly influence whether or not a global advantage emerges. Specifically, the use of relatively few, large-size local elements within the global pattern promotes a local processing advantage, while the use of many smaller local elements within the global pattem promotes a global processing advantage. …

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