Spatial stimulus-response (S-R) compatibility effects for visual signals with hand and foot controls

視覺訊號與手腳操縱器的運用在刺激與反應中的空間相容效應

Student thesis: Doctoral Thesis

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Author(s)

  • Wai Lun CHAN

Detail(s)

Awarding Institution
Supervisors/Advisors
Award date4 Oct 2010

Abstract

Most of the previous studies on spatial stimulus-response (S-R) compatibility have been limited to the use of hand controls, and so far there are no ergonomics guidelines on utilizing foot controls in the context of spatial compatibility. If some controls of a process can be given over to the feet, there would be an obvious advantage in having the hands free for other tasks which require higher level of precision and dexterity. In this study, four experiments were conducted to explore the spatial compatibility (SRC) effects and interactions for visual signals used with hand and foot controls. Response performance was measured in terms of speed and errors. The first experiment, in two parts (1a and 1b), examined spatial S-R compatibility effects for use of foot (part 1a) and hand (part 1b) controls individually in response to transverse and longitudinally oriented visual signals presented on a horizontal plane. Significant interactions between visual signal positions and response key positions revealed marked compatibility effects for the feet and for the hands. The magnitude of the compatibility effect for the operation of foot controls was more or less the same as for hand controls, which suggested the possibility that more extensive use of foot controls could be considered in industrial environments. There was also evidence that the spatial compatibility effect for the right-left dimension was stronger than for the front-rear dimension. The second experiment examined spatial compatibility effects with the combined use of hand and foot controls to respond to visual signals on a vertical plane. Strong spatial S-R compatibility effects were revealed by the significant interaction of visual signal positions and hand/foot response key positions, which suggested that the hands and feet could be used cooperatively in control tasks. The spatial compatibility effect for the top-bottom (vertical) dimension was stronger than for the right-left (horizontal) dimension. The subjects in this experiment responded slightly faster to the visual signals in the top-right position than to visual signals in top-left, bottom-right and bottom-left positions. The third experiment examined spatial compatibility effects with visual display and hand/foot controls in orthogonal orientations. The experiment was in two parts (3a and 3b). In part 3a, hand and foot controls were in a single plane orthogonal to the visual signals plane. Subjects responded to visual signals on a horizontal plane with desk level (top) hand controls and floor level (down) foot pedals directly under the hand controls. Part 3b replicated part 3a except that the foot pedals were moved forward and placed directly underneath the front row of signals so that the hand controls and foot controls were in different orthogonal planes relative to the visual signals. The effect was to create an additional pair of parallel stimulus (front and rear visual signals) and response (front foot pedals and rear hand controls) relationships in the horizontal dimension. The result for part 3a showed a strong orthogonal SRC effect as revealed by the significant interaction of visual signal position and response key position. There was an obvious advantage to mapping the front signals with hand controls and rear signals with foot pedals. A similar result was found in part 3b, but here there was the additional interpretation of an apparently direct front and rear location mapping for the visual signals and response keys. The results from this setup showed better compatibility effects in the front-hand/rear-foot than in the front-foot/rear-hand mapping condition. The findings demonstrated that the front-hand/rear-foot mapping relationship was very robust with regard to the relative locations of the response devices. It was also found that subjects responded slightly faster to visual signals in the front-right position than to visual signals in other positions. The final experiment examined the spatial compatibility effects with the combined use of four hand and four foot controls (of two pedals) to respond to the eight visual signals in a three-dimensional (3D) space. The visual signals were positioned at the corners of an imaginary cube, and responses were by hands and feet in different S-R compatibility conditions. There was a significant interaction of visual signal positions and response device positions which demonstrated the existence of a strong spatial S-R compatibility effect in a three-dimensional environment. Relatively faster reaction times (RTs) and lower error percentages (EPs) were obtained for the compatible S-R conditions. The findings suggested that the relative positions of the visual signals and response devices should be spatially compatible in three-dimensional space for the best human-machine system performance. There was also evidence that the spatial compatibility effect in the top-bottom dimension was the strongest, and the compatibility effect in the left-right dimension was stronger than in the front-rear dimension. Overall, the result of this study suggested that when both hand and foot controls were used concurrently in a reaction task, priority should be initially be given to the compatibility in the vertical dimension. The findings of this study can be translated into practical and useful ergonomics recommendations for designing visual displays and hand/foot control devices from a simple to complex spatial S-R relationships to improve efficiency and overall system performance in human-machine systems. Keywords: Spatial S-R compatibility; orthogonal S-R compatibility; hand and foot controls; three-dimensional arrangement

    Research areas

  • Visual evoked response, Stimulus generalization