Pearson and Sahraie (2003) have demonstrated that gaze motion interferes with the retention of spatial information in Working Memory. Postle et al. (2006) showed, moreover, that gaze motion affects more the retention of spatial information than the retention of visual information. Although these authors have shown a cause and effect relationship between gaze displacement and the retention of spatial information, they did not made an experiment to verify how this retention is affected when the amplitude of the gaze displacement is doubled and tripled (ΔӨ, 2ΔӨ, 3ΔӨ). In addition, they did not investigate whether the interference caused by gaze motion on the retention of spatial information would also occur for those small gaze displacements produced by the saccades made when studying instructional materials. In fact, the saccades that Pearson and Sahraie (2003) and Postle et al. (2006) used had an amplitude several times larger than the amplitudes of saccades typically made when studying instructional materials. Just like in Sahraie and Pearson (2003), we also used in our experiment the performance in the Corsi Blocks Test as a measure of the retention in Spatial Working Memory. However, our experiment differed from the experiment of Sahraie and Pearson (2003) in two aspects. Firstly, in our experiment we used saccades with amplitudes within the range of the amplitudes utilized in the study of instructional materials. Secondly in our experiments the presentations of the blocks were intercalated with saccades, in order to simulate saccades that are intercalated between one source and another when one studies instructional materials, allowing thus the investigation of the impact of these saccades on the retention of spatial information. Our experiments confirmed our hypothesis that saccades with amplitudes similar, as those practiced in the study of instructional material are able to affect the retention of spatial information in working memory. There was also a partial confirmation of our second hypothesis that a gradual increase in the amplitude of a saccades would result in gradual decay on the retention of spatial information. As a result, we obtained a partial confirmation as the retention of Spatial Information only declined when the amplitude of the saccades increased from 0° to 36o and from 36 o to 54o. When the amplitude of the saccades increased from 36o to 54o, no decrease in the level of retention was observed. An important result was the finding that whenever saccades were intercalated in the blocks presentations in the tests, regardless the saccade amplitude was 18o, 36 o, or 54o, always the retention levels in tests with saccades was inferior to the retention level in tests without saccades. It is also discussed the new perspectives that the experimental confirmation of our hypotheses bring for the improvement of the Split Attention Principle and to the explanation of what causes the Split Attention Effect in instructional materials with spatial content. We predict that if the results we obtained in our experiments can be generalized to instructional materials with spatial content, this will allow the effect of gaze shift to be considered one of the causal factors of the Split Attention Effect for instructional materials with space content. Finally, we report that John Sweller, the discoverer of the Split Attention Effect, agreed to participate in a joint research in this new line of research.
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