Archive for June 25th, 2009

I’m fascinated by the ways our mental models can influence how we interpret and behave in the world of traffic. A new study by Graham Davies, “Estimating the speed of vehicles: the influence of stereotypes,” in Psychology, Crime and the Law, looks at this is an interesting way.

As described by BPS, Davies “played ten-second video clips of a BMW and a (smaller, less powerful) Volkswagen Polo to 42 undergrads and asked them to estimate how fast the cars were going. Based on past research showing that participants expect BMWs to be driven faster than Volkswagen Polos, Davies thought that the students would overestimate the speed of the BMW. In fact, he found the opposite. Participants tended to overestimate the speed of the Polo, perhaps because it was a noisier car, and smaller vehicles are generally perceived as going faster than larger cars.”

There was a bias here, but it seemed to be a perceptual bias.

“A second experiment pulled out all the stops in an attempt to provoke participants to rely on their driver stereotypes. Participants were told that the BMW was driven by a young male, and the Polo by a 62-year-old; they were shown photos of the drivers; and they were asked to speculate about the drivers’ personalities. But even after all this, the participants’ judgments of the cars’ speeds were still accurate and there was no tendency to overestimate the speed of the BMW. This was true even though participants had earlier made the kind of assumptions about the two drivers that you might expect — for example, that the BMW driver was more aggressive and reckless.”

Interestingly, it wasn’t until the third experiment that any predicted stereotype that BMW drivers drive faster was activated. A day after they viewed the speed clips, subjects were asked unexpectedly to recall the speeds. “In this case, the BMW’s speed was estimated to be significantly faster (56 mph) than the Polo’s (50 mph), even though both cars were actually traveling at the same speed (60 mph).”

I was reminded of work I had somewhere about stereotypes and “priming” — in some cases invoking presumed stereotypes seemed to force subjects to work harder to reject them. But when asked “out of the blue,” with no stereotypical context in mind, and perhaps less time or reason to think about the answer, the subjects here seemed to lean on preconceived notions that BMWs are driven faster. Davies’ experiment was meant as yet another calling into question of the reliability of eyewitness testimony, but as in the first experiment, it also shows the variety of ways the world of traffic is not always as it seems.