This process is called biological motion perception, and humans are so good at it that even a few dots on a screen representing the major joints of a body are enough to retrieve all the information we need—as long as they move.
But what role does motion play in that process? Does the visual system use it only to connect the dots to create a coherent, or "global," structure? Troje and his colleagues—Masahiro Hirai and Daniel R. Saunders at Queen's, and Dorita H. F. Chang, now at the University of Birmingham, UK—investigated this question in a new study, to be published in an upcoming issue of Psychological Science, a journal of the Association for Psychological Science.
They presented their participants with computer-generated stimuli showing 11 light points representing the shoulder, hip, elbows, wrists, knees, and ankles of a person walking, as on a treadmill. After a two-second display, the observers had to indicate which direction they believed the walker was facing.
This is an easy task, and the participants performed it almost without fail—even though the point-light walker was masked with 100 randomly placed additional dots. But they were also able to do it if the global structure of the body was entirely disrupted by randomly scrambling the 11 dots. "The local motion of individual dots contained enough information about the walker's facing direction," says Troje.
But when the whole thing was turned upside-down, the participants could no longer discern which way the figure was walking. Why? Says Troje: "The visual system uses the information contained in these local dot movements—mainly the ones of the feet—only when it is validated by additional properties that do not in themselves carry any information about facing direction"—in this case the proper vertical orientation, feet on the bottom, head on top.
An observer can't tell the facing direction of a stationary upright figure. But put the local motion together with an upright position, even mix up and mask all the light points. And "direction discrimination of these 'scrambled' walkers is almost as good as with structurally coherent walkers," Troje says.
Why is the visual system so acute even when the shape of a figure is totally broken down? To survive, we have to be able "to detect the presence of a living being in the visual environment—regardless of whether it is a fellow human, a potentially dangerous predator, or even a prey animal," says Troje. "For that purpose, we need a detection mechanism that is independent of the particular shape of an animal."
Parsing these effects can help us understand—and appreciate—our extraordinary perceptual assets. "It tells us how sophisticated our visual system is in using information about the structure, the physics, and the regularities of the visual world," he says.
For more information about this study, please contact: Nikolaus F. Troje at email@example.com.
The APS journal Psychological Science is the highest ranked empirical journal in psychology. For a copy of the article "Body configuration modulates the usage of local cues to direction in biological motion perception" and access to other Psychological Science research findings, please contact Divya Menon at 202-293-9300 or firstname.lastname@example.org.
Divya Menon | EurekAlert!
Innovative genetic tests for children with developmental disorders and epilepsy
11.07.2018 | Christian-Albrechts-Universität zu Kiel
Oxygen loss in the coastal Baltic Sea is “unprecedentedly severe”
05.07.2018 | European Geosciences Union
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Life Sciences
18.07.2018 | Materials Sciences
18.07.2018 | Health and Medicine