Memória P&D Design

3º Congresso Brasileiro de Pesquisa e Desenvolvimento em Design

PUC-RJ — Rio de Janeiro (RJ)

Novembro/1998

Conferências

The Touchpad- Experiences with a Study on User Comfort and Performance

Ahmet E. Çakir
Gisela Çakir

Resumo

The user study on the touchpad,. a novel tablet technology input device, was designed to investigate the impact ofthe use of the device on the biomechanicalload and postural comfort of the users. The study has demonstrated bright future prospects for this technology which go well beyond the fields of application for which the device was originally designed.

In a one day test, the subjects, experienced Macintosh users, performed tests and worked on tasks, using a portable computer, that were organized to resemble normal office tasks and measure performance. The tasks included intensive use ofthe keyboard. The reason for this was to investigate the intermittent use ofboth devices.

The performance was measured by text editing tasks and eight Fitts's Tests with two leveis of difficulty. The biomechanicalload was measured and evaluated by means ofEMG and postural (motion) analyses. General comfort and postural comfort was evaluated with questionruiires.

The analyses of the EMG-measurements yielded no indication of progressive fatigue or increased muscular load from one session to the next. On the contrary, the recorded EMG-levels showed a decrease in muscular activity. The postural analyses indicated that undue deviation, extension, or flexion ofthe hands, which may cause discomfort, generally did not occur. The average values were within the limits given by the physiology ofthe human arm. However, personal preferences for the arm posture were highly different.

When performing the text editing task with the touchpad during the training session, the subjects had already achieved a performance equivalent to 65% of mouse performance. A performance of more than 9()0/o was achieved ~r two hours and 100% in the fi:fth hour session. This means that the learning period for such tasks will in practice be accomplished within one working day. The average performance achieved with the touchpad for the eight tasks with Fitts' s Test, during the last session, was lower than that with the mouse, but the difference was not statistically significant.

The results ofthis study indicated that the touchpad can be used for everyday tasks without causing postural discomfort or fatigue. In some respects, this device may even be preferable to the mouse, ifthe users can achieve the same levei ofperformance.

The precision with which the market success ofthe device was forecasted is a convincing prooffor the value of ergonomic studies in general.

Referências bibliográficas

  • Greenstein, J.S.: Pointing Devices, in: Helander, M.; Landauer, T.K.; Prabhu, P.: Handbook of Human Computer Interaction, North-Holland, 1997

  • Karlqvist. L.: Variation in upper limb posture and movement during word processing with and without mouse use, ERGONOMICS, 1994, Vol. 37, No. 7, 1261-1267

  • Karwowski, W.; Ray, E.; Salvendy, G.; Noland, S.: The effects of computer interface design on human postUral dynamics, ERGONOMICS, 1994, Vol. 37, No. 4, 703-724