BY KAREN PATTERSON
Attention and perception are an important part of driving. A research experiment was conducted that measured the effects of various driving environments, sign stimuli, and individual characteristics on response time. The three driving environments- residential, business, and business plus- were progressively more complex. For sign stimuli, there were four categories of independent variables. These were negative/positive, sign type, stimulus direction, and sign location. Negative signs are inhibitory (DON'T WALK), and positive signs are permissive (YIELD). Sign type can either be written words or a figure drawing. Stimulus direction signs are those that indicate action that involve direction (e.g. RIGHT TURN ONLY). Finally, sign location refers to whether the sign is on the left or right side of the viewing field. Next, for individual characteristics, field-dependency and gender were considered. Field-dependent individuals are those who can extract specific information from a complex background. Individuals in the experiment were assessed for this ability by a pencil and paper comparison figure test. Those who scored below 60 were considered field-independent, and those who scored above were considered field-dependent.
The results of the experiment show that response times are quicker for simple backgrounds, word signs, negative signs, signs on the right side of the road, and for field dependent individuals. Also, response times were quicker when the sign was on the same side of the road as the directional stimulus of the sign. For example, responses to a "TURN LEFT" sign are quicker when the sign is on the left side of the road than when it is on the right side. No significant correlation was established between gender and response time, although there was a correlation between gender and field dependency. Females were more field-independent than males.
An important aspect of the experiment design was the measurement of verbal response time instead of motor response time. Previous research had established that field-dependent individuals have a slower response time for driving. But whether this was due to slower cognitive processing or slower motor responses was not determined. The results of the present experiment indicate that it is the rate of cognitive perception that accounts for the slower response time (since no motor response was required, and a slower response time was still observed).
The results of this experiment can be used for engineers and public planners as they attempt to make road signs as clear and effective as possible. Understanding the ways in which people perceive information in road signs can enable the development of signs that allow for minimal response time. For example, since people respond best in simple background environments, it would be beneficial to keep distracting and unpertinent signs further from the direct viewing field (for example, off to the side of the road). This would allow drivers to perceive more quickly the necessary signs from the background. Quicker response times will have an affect on accident rates. In this way, this experiment on perception has important 3real-world2 meaning.
REFERENCE
Carol F, & Whitaker, Leslie A. (1984). Verbal Response Times to Directional Traffic Signs Embedded in Photographic Street Scenes. Human Factors, 26 (2), 235-244.