Elsevier

Acta Psychologica

Volume 127, Issue 1, January 2008, Pages 1-11
Acta Psychologica

What does the nature of the stimuli tell us about the Global Precedence Effect?

https://doi.org/10.1016/j.actpsy.2006.12.001Get rights and content

Abstract

The “Global Precedence Effect” (GPE) is a well-established phenomenon characterised by a global advantage (global response times that are faster than local response times) and an interference effect from global distractors during identification of local targets but not vice versa. In the present study, two experiments were carried out to examine how the GPE is affected by the meaningfulness of the stimuli. Using global/local compound stimuli based on either meaningful or meaningless stimuli, we found, on the one hand, that the global level was always processed faster than the local level, irrespective of the meaningfulness of the material. On the other hand, results show that the interference effect occurred only with meaningful stimuli. We propose that automatic identification of meaningful stimuli plays a role in the interference effect. These results suggest that the GPE involves both “sensory mechanisms” (responsible for the global advantage) and “cognitive mechanisms” (responsible for the interference effect).

Introduction

A visual scene has different hierarchical levels of structure, from the most local elements to the largest global level of organization. For example, the perception of a forest is based upon a global analysis, whereas a local analysis is necessary to note the individual objects in the scene, such as the trees themselves or the individual features of each tree, their leaves and their branches. To study the mechanisms that underlie global and local perception, Navon used compound stimuli, consisting of large letters (the global level) composed of a suitable arrangement of small letters (the local level) (Navon, 1977). In the paradigms that used compound stimuli, the participants had to attend to one of the levels (i.e., the “target” level: global or local) and decide on each trial whether a target letter was present in that pre-specified level (e.g., global), while ignoring the other “irrelevant” unattended level (e.g., local). First, measuring participants’ response times (RTs) allows for determining whether the global or local level is processed faster. Second, this type of paradigm is suitable for the assessment of potential interference from the irrelevant unattended level on the target level. Two very reproducible effects have been found: a global advantage (global processing is faster than local processing) and a global interference (global processing interferes with the processing of local features) (reviewed by Kimchi, 1992). These effects have been called the “Global Precedence Effect” (GPE). Further investigation has shown, however, that the GPE can be reduced or even reversed by factors such as visual angle, eccentricity, and exposure duration (see Navon, 2003 for a recent revisitation of the paradigm based on compound stimuli).

To date, most global/local recognition studies on both healthy participants and patients have used compound letter forms (e.g. Goodarzi et al., 2000, Hübner, 2000, Robertson and Lamb, 1991, Weissman et al., 2005). However, few studies have examined whether the nature of the stimuli could affect the GPE, and in particular how the meaningful properties of a stimulus may be implicated during a global/local detection task. Peressotti, Rumiati, Nicoletti, and Job (1991) used global pseudoletters (meaningless patterns derived from large letters) in their study based on a letter detection task. During a local condition, the participants were presented with compound stimuli in which the global level could be consistent with the local level (i.e., global letters and local letters were the same), inconsistent with the local level (i.e., global letters and local letters were different) or neutral (i.e., global pseudoletters and local letters were used). The results showed that inconsistent stimuli were responded to more slowly than both consistent and neutral (meaningless) stimuli, which did not differ from each other. This study reiterated one aspect of GPE (i.e. the “global interference”) but the “global advantage” was not investigated. As a matter of fact, the participants had to perform a local letter detection task only, while pseudoletters only appeared at the global irrelevant level. Thus, this paradigm provided only a partial examination of meaningfulness on the GPE because neither a local pseudoletter detection condition nor a global detection condition with letters and pseudoletters was investigated.

We have recently conducted a “same/not the same” attention task, in which participants had to attend simultaneously to both global and local levels of compound stimuli (Poirel, Pineau, & Mellet, 2006). We provided further evidence that automatic identification of objects could affect the global precedence principle. In this paradigm, global and local forms represented either objects or non-objects. During a “same/not the same” categorization task, the participants were presented with pairs of compound stimuli and were instructed to report whether the two compound stimuli composing a pair were “identical” or “different”. In a “different” pair, items differed at one level (i.e., the target level); the other level, composed of similar forms on both sides, was irrelevant to task performance (i.e., the irrelevant level). We found that when the irrelevant level was composed of objects, the global precedence effect was reversed: local differences with an object at the irrelevant global level were processed faster than global differences with an object at the irrelevant local level. These results highlighted the effect of the nature of the irrelevant level on global/local processing during a comparison task. However, due to the type of task used (a categorization task), it remains difficult to compare these results with the “interference effect” of the GPE as it is generally presented in the literature (i.e., tasks in which a pre-defined target is not present at the pre-defined target level but is present at the unattended irrelevant level; see Navon, 1977).

The present study aimed at investigating the effect of the meaningfulness of stimuli on global/local processing during a target detection paradigm. The question raised here is how the meaningfulness of the stimuli affects the GPE and, in particular, whether both the global advantage and global interference are affected. Two experiments were carried out to answer this question. In Experiment 1, three types of stimuli were included (letters, objects and non-objects) and the participants had to perform a classic target detection task. Although object and non-object compound stimuli serve to highlight the role of meaningfulness in the GPE, we nevertheless included letter compound stimuli. First, it ensures that both the design and the materials used in this paradigm can produce a classical GPE with letter compound stimuli. Second, compared to non-objects, letters and objects shared a common meaningful attribute. If meaningfulness affects the GPE, we should observe comparable results for the letter and object compound stimuli. In Experiment 2, the participants were presented with a target detection task with object/non-object cross-set compound stimuli. We varied the object/non-object nature of the unattended irrelevant level to ascertain that the effects found in Experiment 1 were related to the meaningfulness of the stimuli.

Section snippets

Experiment 1

The purpose of Experiment 1 was to examine the effect of the nature of stimuli on global/local processing. In this experiment, the participants were presented with compound stimuli based on either letters, objects or non-objects and had to perform a focused global/local target detection task. We predict that the meaning of the stimuli and, in particular, identification processes have a role in the GPE. The present study examines the relative contribution of identification processes during a

Experiment 2

We employed a cross-set compound stimuli based on objects and non-objects, in order to examine further the implication of automatic identification processes for interference effects. Three objects and three non-objects were selected from the 10 objects and 10 non-objects of Experiment 1 and served as targets. Compound stimuli were based on either objects or non-objects at the global level with objects or non-objects at the local level. The targets were never presented at the unattended

General discussion

Experiments on global and local processing have traditionally used focused attention tasks with letters as compound stimuli. A classical Global Precedence Effect (GPE) is typically reported as being characterized by (1) faster response times to the global level than to the local level (i.e., global advantage) and (2) an interference effect from the global level. Based upon the seminal work of Navon, it has been suggested that the GPE could be affected by different factors such as complexity,

Acknowledgements

We are indebted to Nathalie Tzourio-Mazoyer, Marie-Renée Turbelin, Gael Jobard and Pierre Gagnepain for their helpful comments. This research was supported by a grant from CEA and Région Basse Normandie, France.

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