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Getting the most out of a cat's paw: Wind detection among expert sailors

Wednesday, April 29, 2015   (0 Comments)
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Stephan Lewandowsky

Who is an expert? Someone once suggested it’s “anyone who is more than 50 miles from home and is carrying a briefcase” or “someone who continually learns more and more about less and less”. The more somber but widely agreed definition in the cognitive community invokes reproducible superior performance in a particular domain. That is, an expert is someone who is repeatedly performing (far) better than most other people in an agreed arena of tasks. By requiring reproducibility, the definition guards against flukes and by requiring performance measurement it excludes dubious domains such as astrology or homeopathy.

But if performance can be reliably measured by an agreed set of tasks, then almost anything can constitute a “domain”. Indeed, it is intriguing how many domains of expertise have been studied by cognitive scientists, from the linking of car crime series by expert investigators to the ability to predict the spread of Australian bush fires by expert fire fighters.

recent article in the Psychonomic Society’s journal Attention, Perception, and Psychophysics addressed another domain of expertise, namely the detection of wind speed and direction. Apparently the detection of wind speed and direction is non-trivial and can be important in a surprising variety of contexts—including deer hunting.

Researcher Joost Pluijms and colleagues from the Vrije Universiteit Amsterdam studied the ability of expert sailors to detect and interpret wind through their cutaneous senses. Given that sailing is all about wind, it is not surprising that wind perception is a crucial skill for a sailor.

Pluijms and colleagues compared the performance of three groups of participants: There were top level experts who competed in the highest Dutch squad (i.e., at a professional level) or were members of the national youth teams of The Netherlands. All top experts competed at an international level. The intermediate group also had some sailing expertise but did not compete at an international level. Finally, there were nonsailors without any expertise.

For the experiment, participants were seated inside a wind simulator. The figure below shows the apparatus, which consisted of an array of automotive fans surrounding the participant that were computer controlled to simulate winds of different directions and speeds.

Participants were wearing earphones throughout, and they closed their eyes at the beginning of each trial, thus eliminating any information other than that provided by the simulated wind. Each trial involved 10 seconds of wind from a random direction and at one of three speeds (also chosen at random). Participants recorded the perceived wind direction using a dial and indicated the strength using a numerical estimation task.

There were several intriguing outcomes.

The first notable finding concerned the way in which expertise revealed itself. When wind speeds were high (i.e., 4.8 knots or about 8 km/h), experts and novices were equally adept at detecting wind direction. It was only when wind speeds were lower (3 knots or about 5.5 km/h) that the experts’ superiority became apparent. The top-level sailors were more accurate than the less expert sailors and nonsailors when the task required greater sensitivity, but that advantage disappeared when winds were sufficiently strong even for the nonexperts to differentiate.

Another finding involved the fact that wind speeds were perceived more accurately when presented from the front than from the back. At the same time, the top experts and nonsailors perceived the direction of the wind with equal accuracy, irrespective of its direction—that is, winds from the back were assigned the correct direction with the same accuracy as winds from the front; it was only the speed estimates for which frontal stimuli showed an advantage.

Finally, for all three groups of participants, subjective estimate of wind speeds were related to actual speeds by the famous power law. That is, the detection of wind speed seems to obey the same “law” that governs the perception of other sensory quantities, from loudness and brightness to tactual hardness.

Overall, the study by Pluijms and colleagues extends our knowledge of perceptual expertise into an area about which we know relatively little: namely, our cutaneous senses that perceive external objects through contact with our bodies. It appears that we can become expert at interpreting even very light contact with our skin indeed—air traveling at 3 knots is a mere whisper and yet expert sailors can accurately assign its direction.

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