Ken W.L. Chan, Alan H.S. Chan* Displays 26 (2005) 109–119 Spatial S–R compatibility of visual and auditory signals: implications for human–machine interface design 學生. 莊靖玟

Introduction Displays and controls are the fundamental means of communication for people interacting with the machines and equipmen.

Purpose Compatible settings lead to faster reaction times (RTs) and lower error rates than incompatible settings. Chan et al.,(2003).

Reference The reduction of visual RT in spatially compatible S–R pairing has been thought to arise from a ‘natural’ tendency to respond in the direction of stimulation. Umilta et al.,1990

Reference Responses were always found to be faster with the hands uncrossed than with the hands crossed. Lau et al., 1999.

Reference The overall slowing of RT with the hands crossed is believed to be due to the mismatch between the locational code and the anatomical code. Lau et al., 1999.

Reference Doyle and Snowden (1999) found that in a choice reaction task, the overall visual reaction was facilitated by the use of auditory warning signals.

Purpose The current study was designed to investigate the spatial compatibility effect of visual and auditory signals on longitudinally and transversely oriented axes.

Method - Subjects Twenty male students of City University of Hong Kong The ages of 25–36 Right-handed All of them had normal or corrected-to- normal vision No hearing loss

Method ＊ A personal computer ＊ A Philips stereo headphone (SBS HP140) ＊ A 15” color CRT Monitor 80mm 直徑 20mm 500mm Four response keys ‘FR’ (front-right) ‘FL’ (front-left) ‘RR’(rear-right) ‘RL’ (rear-left) a 790 Hz, 60 dBA attention tone selected from the Microsoft Window’s sound library was presented via a headphone to either ear. middle fingers index

Method BC TC LC BI

Method

The experiment took place in a quiet environment with ambient sound level of less than 55 dBA. There were eight practice trials and 20 trials in each mapping condition. The time elapsing from the onset of signal to successful detection of subject’s response by the computer was taken as the reaction time (RT).

Method The green warning circle was then automatically reset and displayed again after 1 s, indicating the start of next trial. 1~4s signal 900ms or until a response

Method The mean RT computed for ： different signal types and positions (right auditory signal, left auditory signal, right visual signal and left visual signal), response key positions (FR, FL, RR and RL), hand conditions (uncrossed and crossed)

Results A total of 3200 (20 subjects×8 conditions×20 trials) responses were collected in this experiment. 145 responses (4.5%) were incorrect. The mean and standard deviation of RTs were 796 and 255 ms, respectively. Altogether 106 outliers (3.3%) beyond the G3s control limits were discarded from analysis. After scrutiny of the data, a total of 2949 (92.2%) responses were left for analysis.

Results

Results - Response error The subjects made 145 (4.5%) incorrect responses. The most accurate subject made one error (0.63%) while the least accurate one made 21 errors (13.13%).

Results

Further examination of EPs was performed with the non-parametric Kruskal–Wallis test. The main factors considered were S–R mapping, signal position, hand condition and warning time.

Results S–R mapping (p<0.0001) and hand condition (p<0.05) were Significant Signal position and warning time were non-significant (p>0.05). The order of magnitude of the four overall average EPs was BC (1.88%), TC (4.13%), LC(5.38%), and BI (6.75%).

Results EP=5.44%EP=3.63%

Discussion Wickens (1992) ‘if visual stimuli are appearing at the same frequency and providing information of the same general type or importance as auditory or proprioceptive stimuli, biases toward the visual source at the expense of the other two will be expected’. This provides an explanation for the longer RTs required for responses to the auditory signal than for visual ones found in this study.

Discussion This probably accounts for the faster responses made for the auditory signals coming from the right side than those from the left by the right handed subjects here.

Discussion If the S–R compatibility condition is disregarded, subjects took longer to respond using the less natural crossed hand posture than using the uncrossed hand posture for all four S–R mapping conditions. This was possibly due to the mismatch of locational and anatomical codes.

Discussion This result suggested the need to provide an alerting signal somewhat greater than 1 s, and preferably at 3 or 4 s.

Conclusion The relative positions of signals should be compatible with both the response key positions and the hand positions of the operators. Configurations requiring users to cross their hands to respond should not be used. For faster responses and higher accuracy, a warning fore period of 2 s or longer should be given to alert operators prior to the presentation of the operation signal asking for action.

Conclusion For faster responses, a visual signal is preferable to an auditory signal for requesting operator response on a control console. For faster reactions, auditory signals should be positioned on the right hand side of right-handed operators.