Traffic (47 page)

locked on the video screen: One of Simon’s key findings is that subjects were less likely to see the gorilla when they were asked to count the number of passes made by the team wearing white T-shirts. This meant, according to Simons, that people did not see the gorilla because it did not look like what they were looking for—or because it
did
look like what they were ignoring (the team wearing black shirts). As Simons put it, “The more you’re focused on what you expect to see, the less likely you are to see unexpected stuff.”

“failure to see”: The role that a car driver’s vision (or lack thereof) plays in car-motorcycle crashes is huge: For nine of the ten types of leading car-motorcycle crashes, the motorcycle is proceeding in a straight line (with the most common being the car turning left across the path of an approaching motorcycle). See P. A. Hancock, G. Wulf, D. R. Thom, and P. Fassnacht, “Contrasting Driver Behavior During Turns and Straight Driving,” paper presented at the 33rd Annual Meeting of the Human Factors Society, Denver, Colorado, October 1989.

on the road: Another response, of course, is the “loud pipes save lives” approach, by which motorcyclists insist that an ear-shattering exhaust system will surely alert drivers of their presence. The problem is that drivers are often unaware of the
direction
of such sounds. Another problem is that for the people who have to listen to the loud pipes, the issue of saving motorcyclists’ lives might not exactly be a pressing agenda.

change lanes or slow down:
USA Today,
July 4, 2007.

moths to a flame: At a meeting I attended in Los Angeles, for example, the California Highway patrol was concerned with a recent spate of these crashes, which had claimed the lives of six officers over just a few months. “For whatever reason they tend to find us on the side of the road,” a CHP officer said at a traffic reporters’ meeting one morning. “It’s just a dangerous place to be.”

we see something interesting: Driving simulator studies have suggested that drivers have a tendency to at least momentarily steer in the direction of their gaze, “in many cases without the conscious awareness of doing so at all.” W. O. Readinger, A. Chatziastros, D. W. Cunningham, H. H. Bülthoff, and J. E. Cutting, “Gaze-Eccentricity Effects on Road Position and Steering,”
Journal of Experimental Psychology: Applied,
vol. 8, no. 4 (Dec. 2002), pp. 247–58. In an e-mail correspondence, James Cutting made the further point that he thought the reason drivers were not constantly driving off the road when they looked at something had to do with balance: “The ‘looking where you are going’ phenomenon is, I think, strongly related to balance. This is why it is a problem with novice motorcycle drivers, and can have a small effect in walking. Balance is not much an issue in driving (although people do tilt their heads when going into a turn, and they obviously don’t need to). Usually, when driving, one maintains direction while shifting gaze simply because the arm motions to make a turn are not reflexively relative to gaze direction. Balance is.”

their position in the lane: For a concise roundup of moth effect research, see Marc Green, “Is the Moth Effect Real?” Accessed from
http://www.visualexpert.com/Resources/motheffect.htm
.

while we are moving: See Mark Nawrot, Benita Nordenstrom, and Amy Olson, “Disruption of Eye Movements by Ethanol Intoxication Affects Perception of Depth from Motion Parallax,”
Psychological Science,
vol. 15, no. 12 (2004), pp. 858–65.

for both cars: Martin Langham, Graham Hole, Jacqueline Edwards, and Colin O’Neil, “An Analysis of ‘Looked but Failed to See’ Accidents Involving Parked Police Vehicles,”
Ergonomics,
vol. 45, no. 3 (2002), pp. 167–85. Another study found that police cars equipped with the more visible roof-top bar lights were struck just as often as cars with the less visible rear-deck lights, also suggesting that visibility per se may not be the most important factor in these crashes. See Lieutenant James D. Wells Jr., “Patrol-Car Crashes: Rear-End Collision Study—1999,” Florida Highway Patrol, 1999.

typically takes longer: Interestingly, a French study had subjects first take a Stroop test and then participate in a driving test on a closed course that required an unexpected evasive maneuver. Subjects who did poorly on the Stroop test tended to also do less well during the driving exercise. Christian Collet, Claire Petit, Alain Priez, and Andre Dittmar, “Stroop Color-Word Test, Arousal, Electrodermal Activity and Performance in a Critical Driving Situation,”
Biological Psychology,
vol. 69 (2005), pp. 195–203.

in the way of the less automatic: See Colin M. McLeod, “Half a Century of Research on the Stroop Effect: An Integrative Review,”
Psychological Bulletin,
vol. 109, no. 2 (1991), pp. 163–201.

(i.e., the word itself): This idea comes from Jennifer J. Freyd, Susan R. Martorello, Jessica S. Alvardo, Amy E. Hayes, and Jill C. Christman, “Cognitive Environments and Dissociative Tendencies: Performance on the Standard Stroop Task for High Versus Low Dissociators,”
Applied Cognitive Psychology,
vol. 12 (1998), pp. 91–103.

than the arrow: S. B Most and R. S. Astur, “Feature-Based Attentional Set as a Cause of Traffic Accidents,”
Visual Cognition,
vol. 15 (2007), pp. 125–32.

consultant in California: P. L. Jacobsen, “Safety in Numbers: More Walkers and Bicyclists, Safer Walking and Bicycling,”
Injury Prevention,
vol. 9 (2003), pp. 205–09. The “safety in numbers” effect has been found in many other studies as well. For example, Noah Radford and David Ragland of the University of California at Berkeley looked at the city of Oakland, California. They found that nearly all of the city’s most dangerous intersections were on the city’s east side, an area with low pedestrian volumes. Only one of the most dangerous intersections for pedestrians was downtown. Noah Radford and David R. Ragland, “Space Syntax: An Innovative Pedestrian Volume Modeling Tool for Pedestrian Safety,” U.C. Berkeley Traffic Safety Center, Paper UCB-TSC-RR-2003-11, December 11, 2003. Available at
http://www.repositories.cdlib.org/its/tsc/UCB-TSC-RR-2003-11
.

the slower they drive: See Kenneth Todd, “Pedestrian Regulations in the United States: A Critical Review,”
Transportation Quarterly,
vol. 46, no. 4 (October 1992), pp. 541–59.

for a longer period: The Danish transportation planner Jan Gehl makes this point in his seminal book
Life Between Buildings
(New York: Van Nostrand Reinhold, 1986), p. 79.

safest place to be a cyclist: Conversation with Dan Burden.

asked to remember something: A. M. Glenberg, J. L. Schroeder, and D. A. Robertson, “Averting the Gaze Disengages the Environment and Facilitates Remembering,”
Memory & Cognition,
vol. 26 (July 1998), pp. 651–58.

thought to aid memory: See A. Parker and N. Dagnall, “Effects of Bilateral Eye movements on Gist Based False Recognition in the DRM Paradigm,”
Brain and Cognition,
vol. 63, no. 3 (April 2007), pp. 221–25.

other things, like driving: M. A. Recarte and L. M. Nunes, “Effects of Verbal and Spatial-Imagery Tasks on Eye Fixations While Driving,”
Journal of Experimental Psychology: Applied,
vol. 6, no. 1 (2000), pp. 31–43.

on our mental workload: See, for example, M. C. Lien, E. Ruthruff, and D. Kuhns, “On the Difficulty of Task Switching: Assessing the Role of Task-Set Inhibition,”
Psychonomic Bulletin & Review,
vol. 13 (2006), pp. 530–35.

for us to process things: C. Spence and L. Read, “Speech Shadowing While Driving: On the Difficulty of Splitting Attention Between Eye and Ear,”
Psychological Science,
vol. 14 (2003), pp. 251–56.

consumes even more effort: Curiously, this has not been studied extensively per se in driving simulator studies, but the work of Nilli Lavie, at the Institute of Cognitive Neuroscience at University College London, and her colleagues hints at the problem. In a study, subjects were asked to perform a “linguistic task” that was either “high load” or “low load” when the task was low load, they were more likely to notice an irrelevant display of motion than when it was high load. Her finding—that people are unable to ignore
irrelevant
stimuli when their “perceptual load” is not fully taxed, carries, as she mentioned to me in a conversation, the reverse implication that relevant stimuli will be less likely to be noticed under high-load conditions. See G. Rees, C. D. Frith, and N. Lavie, “Modulating Irrelevant Motion Perception by Varying Attentional Load in an Unrelated Task,”
Science,
vol. 278 (1997), pp. 1616–19. In more recent research, Lavie found that people engaged in intensive visual tasks were less likely to notice sounds at a low volume. It is not difficult to extrapolate from this that an intensive auditory task—for example, straining to hear a voice at low volume on a cell phone—will exact more pressure on the “perceptual load” and thus reduce performance in performing visual tasks.

they still remembered fewer: David L. Strayer and Frank A. Drews, “Multitasking in the Automobile,” in
Attention: From Theory to Practice,
ed. A. Kramer, D. Wiegmann, and A. Kirlik (New York: Oxford University Press, 2006).

When first asked this question: This is drawn from a conversation with Benjamin Coifman.

100 miles per hour: Robert Winkler, “The Need for Speed,”
New York Times,
November 13, 2005.

sequential “frames”: Tim Andrews and Dale Purves, “The Wagon Wheel Illusion in Continuous Light,
Trends in Cognitive Neuroscience,
vol. 9, no. 6 (2005), pp. 261–63.

demonstration of motion parallax): Mark Nawrot provided me with a simple exercise in “seeing” motion parallax at work: “For example, pick out two objects, near and far, on your desktop. Hold up your two index fingers, near to your face, one below the objects pointing up, one above pointing down. Hold your fingers stationary, fixate on the ‘near’ object, close one eye, and move your head side to side. Easy. Now do the same as you move your top finger along with your head movement so that it ‘matches’ the distant object. If you had to guess, you’d now say your top finger is farther away than your lower finger.” For further interesting research on the mechanics of motion parallax, see Mark Nawrot, “Eye Movements Provide the Extra-retinal Signal Required for the Perception of Depth from Motion Parallax,”
Vision Research,
vol. 43 (2003), pp. 1553–62.

more realistic: In the scene in
The Lord of the Rings
in which the “beacons” are being lit to sound the alarm for the impending danger to Rohan, the aerial camera sweeps across the landscape, but the beacon remains in the center of the shot as the background sweeps by. Nawrot suggests that the motion might trigger an involuntary “optokinetic response.” To prevent us from simply being visually swept up in that background movement, however, the eye responds with a “smooth pursuit” movement to effectively countermand the motion and maintain the fixation on the lit beacon. This, Nawrot posits, mimics the series of compensatory eye movements we are constantly making in real life. Mark Nawrot and Chad Stockert, “Motion Parallax in Motion Pictures: The Role of Background Motion and Eye Movements” (unpublished paper, Department of Psychology, North Dakota State University). For a further fascinating discussion on human vision and the movies, see James E. Cutting, “Perceiving Scenes in Film and in the World,” in
Moving Image Theory: Ecological considerations,
ed. J. D. Anderson and B. F. Anderson (Carbondale: Southern Illinois University Press, 2005), pp. 9–27.

“illusory pavement markings”: Actually,
any
pavement marking is rather illusory.

reduced their speed: “Evaluation of the Converging Chevron Pavement Marking Pattern,” AAA Foundation for Traffic Safety (Washington, D.C.), July 2003.

have been mixed: “A Review of Two Innovative Pavement Marking Patterns That Have Been Developed to Reduce Traffic Speeds and Crashes,” AAA Foundation for Traffic Safety (Washington, D.C.), August 1995.

at the higher speed: G. G. Denton, “The Influence of Adaptation on Subjective Velocity for an Observer in Simulated Rectilinear Motion,”
Ergonomics,
vol. 19 (1976), pp. 409–30.

sensation of moving backward: In a study by Stuart Anstis, subjects asked to jog on a treadmill for as little as a minute experienced this aftereffect. Once the treadmill was stopped, subjects asked to jog in place actually jogged, on average, 162 centimeters
forward.
Anstis notes, “The backward motion of the treadmill produces an artificial mismatch between motor output and normal postural feedback, for which the adaptation compensates or nulls out by adjusting internal gain parameters to bring output and feedback back into line. But once the runner steps on to solid ground these newly adjusted parameters are now inappropriate and manifest themselves as an aftereffect, which dissipates as the parameters automatically update to match the solid ground. So these new aftereffects reveal the continuous neural recalibration of the gait control system.” See Stuart Anstis, “Aftereffects from Jogging,”
Experimental Brain Research,
vol. 103 (1995), pp. 476–78.

when asked to speed up: For an excellent discussion of this issue see John Groeger,
Understanding Driving
(East Sussex, Psychology Press: 2001), p. 14.

largely, it is thought: This theory is credited to the pioneering work of J. J. Gibson, who wrote: “The aiming point of any locomotion is the center of the centrifugal flow of the ambient optic array.” Gibson,
The Ecological Approach to Visual Perception
(Boston: Houghton Mifflin, 1979), p. 182. The “steering” process is much more complicated than this, as we must somehow compensate, like Steadicams, for the fact that our eyes and heads are also moving as we move. For a good discussion of some of these complexities, see William H. Warren, “Perception of Heading Is a Brain in the Neck,”
Nature Neuroscience,
vol. 1, no. 8 (1998), pp. 647–49. Warren also provides the example of the
Millennium Falcon
in hyperspace to describe the radial pattern away from the focus of expansion.