Rik Crutzen*, Maastricht University/CAPHRI, Maastricht, Netherlands Track: Research Presentation Topic: Public (e-)health, population health technologies, surveillance Presentation Type: Oral presentation Submission Type: Single Presentation Building: MECC Room: 0.9 Athens Date: 2010-11-30 03:30 PM – 05:00 PM Last modified: 2010-09-21

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Background: High rates of attrition (i.e., drop-out) are characteristic of the Internet, especially in Internet-delivered interventions targeting health risk behaviours related to chronic diseases (e.g., a sedentary lifestyle, high fat intake and cigarette smoking). This touches upon the critical issue in Internet-delivered interventions: how can behaviour change ever be achieved if people do not or hardly use the actual intervention?

Objective: To assess the effects of visual complexity and cognitive load on user experience and intention to use Internet-delivered interventions, thereby aiming to better understand compatibility between design and user needs and to prevent high rates of attrition.

Methods: Visual complexity and cognitive load were manipulated within-subjects in thirteen experimental trials. The visual complexity stimulus was one out of thirteen screenshots from homepages of Internet-delivered interventions regarding alcohol consumption. The screenshots of these homepages differed on their degree of visual complexity according to the JPEG file sizes (N = 13, M = 432 kB, SD = 96 kB, range 279 – 575 kB). After each experimental trial, participants’intention to use the intervention and user experience were assessed.

Results: 1097 trials from 93 participants were included in the final analyses. Visual complexity had a negative effect on intention to use Internet-delivered interventions, but this effect was fully mediated through user experience. Hedonic value had the largest effect on intention to use the intervention regardless of the cognitive load. If the cognitive load was high, then the effect of utilitarian value disappeared.

Conclusions: Visual complexity of the homepage should be limited in future Internet-delivered interventions, regardless of the cognitive load, to optimize the user experience and therewith the use of the intervention.