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How Perceptual and Cognitive Factors
are Involved in a Car Accident:
A Case Study

By: Vanessa Dominguez & Marc Gentzler | Mentor: Dr. Andrew P. Daire

Expectancy Effects on Perception

Olson and Farber (2003) define expectancy as the predisposition of people to believe that things will happen or be arranged in a certain way. Experiences resulting in particular outcomes in life that remain constant (e.g., flipping a switch to turn on a light) cause a person to develop an expectation that every other similar experience will end similarly. Once formed, this convention creates difficulty for a person to break the habit or not have the expectation. Adding to this challenge, modern design usually follows what intuitively makes sense. These expectations arise in driving as well. Drivers develop expectations for their cars, other drivers, road signs, traffic signals, etc. However, there are positive and negative aspects to developing driver expectations. Some positives include highways and road design. For instance, to improve driver information processing speed, highways and the presentation of information are simplified and consistent. Negatives include decreased attention to environmental stimuli, such as road signs and traffic changes. Research indicates that expertise develops through increasing content-specific learning (Groeger & Chapman, 1996). Therefore, an important aspect of driving accuracy relies on the experiences to remain very similar. Drivers follow schemata that underlie anticipatory behavior while driving; such as following the brake lights on the back of cars signaling to slow down and stop. Improving the conditions for drivers, such as with braking, enhances their ability to react to unexpected situations, which reduces car accidents. Also, minimizing traffic makes the driving task easier. For instance, we are not expecting a stopped car in the middle of the road due to traffic. Violating these expectations decreases the driver's ability to detect hazardous situations.

According to Olson and Farber (2003), "the effective movement of traffic relies to a great extent, on an assumption that other roadway users will behave rationally" (p. 20). Expectations might have influenced the car accident previously described. The driver of Vehicle A followed the schemata of driving. According to conventions established in the US, cars travel on the right side of the road. His expectations were not met when he perceived Vehicle B's lights facing eastward, towards him, on the same side of the road. Although Vehicle B was really on the road's shoulder, from a distance Vehicle B looked like it was on the wrong side of the road. It appears that this very unusual situation made the driver of Vehicle A question whether he or Vehicle B was in the wrong lane, with neither situation meeting his expectations. If Vehicle B were on the actual road, one would expect it to be moving. It was impossible to tell whether Vehicle B was stationary or moving until closer up. Perception of distance involves image size. When a driver is able to perceive an oncoming object's size change it usually leads to a cue that distance also changes. Similar to distance perception, drivers determine speed based on image size (West, C. G., Gildengorin, G., Haegerstrom-Portnoy, G., Lott, L. A., Schneck, M. E., & Brabyn, J. A., 2003). The rate at which the space between the driver's car and an oncoming car closes or opens up allows the driver to determine the speed of an oncoming car. Although the judgment of speed and distance use similar cues, speed perception tends to be less reliable and thus prone to errors of estimation (Olson & Farber, 2003). These violations of expectancies must have created substantial confusion. Moreover, the expectancies of what the driver of Vehicle B would do next were also in question. The driver of Vehicle A may have never been entirely sure whether he or Vehicle B was in the wrong lane. The entire situation violated the driver of Vehicle A's expectations and experience, which lowered his reaction time (reaction time will be discussed later).

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