Within this study, the effects of implementing motivational design of instruction within hypermedia were tested. Motivational design of instruction was based on the ARCS-model and resulted in strategies for increasing attention and relevance in respect to learning content. In addition, an aptitude-treatment-interaction (ATI)-approach was developed which related motivational design of instruction to mental resources management, motivational processing, pre-motivation, motivation to learn, and knowledge acquisition. There were four types of hypermedia teaching software (no ARCS, with attention-, with relevance-, and with both attention- and relevance-strategies) which were presented to elementary school students (n = 68). As dependent variables, the motivation to learn and knowledge acquisition after learning were measured. Pre-motivation (outcome-valence), pre-knowledge, and cognitive load represented covariables. Results indicated that a combination of both ARCS-strategies improved motivation to learn, especially for those students with low levels of pre-motivation. Pre-knowledge increased and cognitive load decreased knowledge acquisition. Finally, open research questions and methodological aspects are outlined. Also, suggestions for the design of instructional hypermedia are given.

Within Instructional Psychology, there is a common goal to find instructional (training) procedures that result in overall improvement on learning and in the reduction of individual differences in abilities. The combinations of these approaches, first proposed by Cronbach (1957) as the study of aptitude-treatment-interactions (ATIs), represent the search for treatments that are adapted to individual differences in aptitudes, that is, treatments that are optimally effective for students of different aptitude levels (see Caspi & Bell, 2004, for a recent integration of the ATI method). In the field of research on instructional hypermedia programs, ATI plays a major role within delivering the basics for the development of "adaptive instructional systems" (Park & Lee, 2003; Shute & Towle, 2003). Related combined ATI- and instructional hypermedia-research was published mainly for cognitive aspects of learning, neglecting to a large degree motivational processes and influences on learning. Most of ATI- and instructional hypermedia-research which was focused on motivation, did not relate to a sophisticated model of motivational design of instruction which can build the bases for "motivationally adaptive hypermedia-based instruction" (e.g., Astleitner, 1997; Astleitner & Keller, 1995; Martens, Gulikers, & Bastiaens, 2004; Zumbach & Reimann, 2001).

The ARCS-model from Keller (1997) represents an instructional model, which can influence motivational processes during hypermedia-based instruction in a comprehensive and effective way (see ARCS-strategies for instructional hypermedia in Keller & Suzuki, 1988). From ARCS-research, there are some indications that ARCS-strategies varied in their effects for different types of learners or aptitude-variables. However, those indications are highly general, theoretically unspecified, not replicated by experimental studies, and must be anchored within a theoretical approach of hypermedia learning and motivation. Astleitner and Wiesner (2004) presented such a theory of hypermedia learning and motivation, which is related to the prominent cognitive approach from Mayer (2001). The two theories of cognitive and motivational multimedia learning by Mayer (2001) and by Astleitner and Wiesner (2004) can be integrated into an approach of hypermedia learning, motivation, and ATIs. The approach represents a framework for analyzing and testing specific hypotheses which are integrated within an ATI-related research for finding guidelines in order to realize effective adaptive hypermedia-based instruction.

Based on this approach, it is assumed that ARCS-strategies have different effects on learning and motivation to learn when different aptitudes (pre-motivation and pre-knowledge) are considered. These effects are for the decrease of prior given deficits (compensation) or for the increase of prior given deficits (polarisation):

a) Compensation: Learners with low pre-motivation should - in comparison to learners with high pre-motivation - profit the most from ARCS-strategies in respect to the motivation to learn. Also, learners with low pre-knowledge should profit more from ARCS-strategies for learning than learners with high pre-knowledge.

b) Polarisation: Learners with high pre-knowledge or pre-motivation profit the most from ARCS-strategies, because these strategies deliver additional information about the learning process that can better be processed by advanced learners. Other learners might not have enough pre-motivation or pre-knowledge to work with the ARCS-strategies, which might increase cognitive load of the learners, effectively.

Within this study, based on the presented model and on related evidence, the effects of ARCS-strategies (treatment) on motivation to learn and knowledge acquisition (dependent variables) were tested. As aptitude-variables, pre-motivation and pre-knowledge were considered. Also, extraneous cognitive load was measured as indicator of working memory activities. Cognitive load was seen as process-variable which can be treated as a covariable. The ARCS-strategies were implemented within an instructional hypermedia program dealing with physics and chemistry.  There were four different versions of the instructional hypermedia program. A first version contained no ARCS-strategies, a second version had attention-related strategies and a third version included relevance-related strategies. A fourth version had both attention- and relevance-strategies.

Forty-six male and twenty-two female 8th grade students with an average age of 14 years participated in this experiment. All students attended an elementary school and were assigned to the experimental conditions randomly. The experiment was based on a one-factorial-covariance-analytic design. As experimental condition, the motivational design of the instructional hypermedia program was manipulated. One fourth of the students (control group, n = 17) was presented an instructional hypermedia program without ARCS-strategies. A second group of the students (experimental group 1, n = 17) got the same instructional hypermedia program with attention strategies; a third group (experimental group 2, n = 17) with relevance strategies; and a fourth group (experimental group 3, n = 17) with attention and relevance strategies. Pre-knowledge, pre-motivation, and extraneous cognitive load served as covariables. As dependent variables, knowledge acquisition and motivation to learn were measured. The instructional hypermedia program was programmed by using Dreamweaver- and Visual C-software on a standard PC.

Results showed that, as expected, the implementation of both, attention- and relevance-strategies increased motivation to learn. In addition, there was an ATI-effect, which indicated that especially those students profited from ARCS-strategies, which had low levels of pre-motivation. Therefore, ARCS-strategies had - as assumed within hypotheses - a compensation effect. Relevance-strategies did not have stronger effects on motivation to learn than attention-strategies. Knowledge acquisition was strongly affected by pre-knowledge and cognitive load, but not significantly from ARCS-strategies. There were no ATI-effects, both with pre-knowledge and with cognitive load on knowledge acquisition.

The design guidelines derived from this research have to be formulated in a rather preliminary way. The results of this study suggest for instructional hypermedia designers to use combined attention- and relevance-strategies, especially for students with low level of pre-motivation. In addition, instructional elements for acquiring pre-knowledge before learning starts should be implemented and low extraneous cognitive load seemed to be positive for knowledge acquisition. Low extraneous cognitive load can be realized when, for example, presenting relatively few and stable instructional elements in hypermedia programs.