Position effects in encoding briefly exposed item matrices: evidence for a reading bias or merely a matter of the selection criterion?

Uta Lass 0 1 Song Yan 0 1 Guopeng Chen 0 1 Dietrich Becker 0 1 Gerd Ler 0 1 0 G. Chen Department of Psychology, East China Normal University , Shanghai, People's Republic of China 1 U. Lass (&) S. Yan D. Becker G. Ler Georg-Elias-Mller-Institute for Psychology, University of Gttingen , Gosslerstrasse 14, 37073 Gttingen, Germany Position eVects are frequently reported in experiments that investigate the recognition of items from brieXy exposed stimulus matrices. A reliable Wnding is the ability to report items from the Wrst row of the matrix more accurately than from the second row. The present experiments explore whether this position eVect depends upon the selection criterion used to indicate the subgroup of items that has to be reported in a given trial. In Experiment 1, German and Chinese participants were presented with language-speciWc items which had to be selected by column. In Experiment 2, Germans were presented with Latin letters and the selection criterion was letter color. A strong row eVect was evident in both experiments although the selection criteria did not prompt a line-by-line grouping of the items. The row eVect is seen as a manifestation of top-down processing that is derived from reading habits. - In previous experiments that focused on the inXuence of native language on encoding brieXy exposed items, we observed a very reliable position eVect (Lass et al. 2003, 2006). In our experiments we made use of an experimental technique that was originally designed by Sperling (1960): A cue following the 50 ms-presentation of a two-row matrix at varying delays indicated whether all matrix items had to be reported (full report) or only a subset, namely those from either the Wrst row or the second row (partial report). With two-row matrices and linguistic items our German and Chinese participants reported more items correctly from the Wrst row than from the second row. This row eVect is consistent with results in the classic experiments by Sperling (1960, Exp. 7) and Averbach and Coriell (1961), who also utilized two-row matrices. In our opinion, the row eVect is caused by a scanning strategy by which attention is allocated on a Wrst row Wrst basis. There is substantial evidence that participants begin encoding as soon as possible even though they do not yet know which items will be cued (e.g., Averbach and Coriell 1961; Gegenfurtner and Sperling 1993; Loftus et al. 1985; Rumelhart 1970; Sperling 1960). This so-called nonselective readout from the visual buVer continues until the cue following the oVset of the matrix indicates which subset of matrix items has to be reported. Then the attention window might be shifted and selective readout begins. As the visual buVer is strictly time-limited the number of items identiWed by selective readout will decrease with increasing cue delay (for details of the interplay between nonselective and selective readout, see Gegenfurtner and Sperling 1993). According to the scanning strategy mentioned above, the participants, knowing about the format of the stimulus array in advance, approach the task with the most eYcient strategy available to them. In the case of a matrix containing linguistic items (single Latin letters, compounds of consonants and vowels (CVs), signs composed by elements from Chinese characters), it is plausible that spontaneous encoding was accomplished through an analogy with reading, which proceeds in German and Chinese language by line and begins with the upper row (for a related view, see Heron 1957). Experiments that made use of single sequences of letters that were to be reported presented evidence of sequential left-to-right processing thus supporting the reading hypothesis: accuracy of report decreased and reaction time increased from left to right within a sequence (e.g., Lefton et al. 1978; Merikle et al. 1971). As outlined above, we favor an explanation of the row eVect in terms of reading habits. That is, we see the row eVect as a manifestation of top down processing. But there is a reasonable alternative explanation for the row eVect as well. In the experiments under discussion, the selection criterion for partial report was the position of the row. The items from either the Wrst or the second row had to be reported. Subsets of items that share a spatial location provide an optimal situation for the focusing of attention (Kahneman 1973). Following Kahneman, attention can most eVectively be focused on subsets of items that form good perceptual groups, and the formation of perceptual groups depends to a large extent on Gestalt principles of organization. For example, the items in a subset speciWed by the criterion row are easily grouped together according to the principle of proximity. There is evidence that good groupings determined by spacial arrangement lead to high levels of report (Fryklund 1975; Kahneman and Henrik 1977). In keeping with these Wndings, Merikle (1980) observed that the spatial selection criteria in partial report were more eVective when their demand characteristics were compatible with the implied perceptual groups in the stimulus array. Thus, it is possible that the compatibility between the demand characteristics of the selection criterion in question, namely to select one row, and the goodness of the perceptual grouping is a precondition for the row eVect to appear. Since scanning the item matrix by line is highly compatible with a perceptual grouping by row, reading habits may be of secondary importance for the interpretation of the row eVect. The present experiments explored whether perceptual grouping provides an alternative explanation for the Wrst-row-Wrst strategy observed in our previous experiments (Lass et al. 2003, 2006). The purpose of the experiment was to investigate whether the row eVect that might be attributed to reading habits survived when the selection criterion did not prompt a line-byline grouping of the matrix items. Since the row eVect had been found with both Germans and Chinese (Lass et al. 2003, 2006), participants from both language groups took part in the experiment. The participants were asked to report as many items as possible from a brieXy presented item matrix, either from the whole matrix (full report) or from one column of the matrix (partial report). If the selection criterion can lead to a speciWc perceptual grouping of the matrix items, then columns of items should result from such processing. As a consequence, there should exist no compatibility between the perceptual grouping and the scanning of the items by line. The replication of a signiWcant row eVect under these conditions would provide implicit support for the reading hypothesis by proving that the row eVect found in the previous experiments was not prompted by the selection criterion. Language-speciWc items were used that had been controlled for visual complexity (Lass et al. 2006, Exp. 3). The Germans were presented with CV items and the Chinese with radical (...truncated)