| Summary: | The Ericsson R380 is a so-called smartphone, combining an advanced mobile phone with a Personal Digital Assistant (PDA). To evaluate the usability of the Ericsson R380 and benchmark it against the Nokia 9110 Communicator and the Motorola A6188 Accompli, a repeated measurements experiment was performed. 18 subjects (10 men and 8 women) with no previous experience of any of the interfaces participated. Half of the subjects had extensive experience from using Ericsson mobile phones and half of the subjects had extensive experience from using Nokia mobile phones. A set of 9 tasks to be solved on each interface was presented to the subjects. The order in which the subjects used the interfaces was balanced with a Latin square design while the tasks were presented in consecutive order and were identical for all interfaces. Level of completeness, completion time and number of actions were assessed for each task and interface. Subjects also rated the perceived usability and aesthetics of the interfaces. Overall, subjects were most successful using the Motorola A6188 Accompli, using fewer keystrokes and less time as well as needing fewer hints compared to the Ericsson R380 and Nokia 9110 Communicator. However, the Ericsson R380 was rated significantly higher than the other interfaces on perceived usability. Previous experience with Ericsson or Nokia mobile phones did not have a major impact on how well subjects succeeded with using the interfaces in the test. Certain mistakes made by each group of subjects could be explained in terms of mental models, Einstellung effects and the use of so- called Function-Object interaction style where Object-Function interaction was appropriate. Contrary to earlier findings, aesthetics and perceived usability did not correspond to a great extent. Finally, the results are discussed and some suggestions for improvements are put forward.
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