Methodological constraints for detecting the modality effect

Introduction: The aim of our research was to investigate the modality effect in more detail by measuring it in a direct way. Two studies were conducted using the same subject and mate-rial. Method: Computer-based learning material was presented on several screens, each containing a short text and a picture. Modality was varied by presenting written versus oral text. Presen-tation time was system-paced and matched the time for oral text presentation. Based on the dual-task approach cognitive load was measured directly in terms of response time towards a stimulus. In study 1, we used a between-subjects design. Participants got the learning material (all screens) either presented visually (picture + written text, N = 24) or audiovisually in a combination of picture and oral text (N = 24). In study 2, we used the same learning material and cognitive load measurements as in study 1. However, instead of a between-subjects de-sign, we varied text modality within participants (N = 34) in such as that each participant re-ceived screens with text presented alternately in written and oral form. Starting modality was counterbalanced. Results: In study 1, we found no modality effect with respect to response time and learning outcome whereas in study 2, we found a significant difference in response times between screens with visually and orally presented text in the direction of the modality effect. Conclusion: The results are discussed with regard to error variance in different experimental designs and effect size of the modality effect as well as with regard to capabilities of partici-pants to strategically adjust to disadvantageous instructional conditions.