Posts tagged face perception
Articles and news from the latest research reports.
Electrical stimulation of brain area causes strange visual illusions
A new study shows that electrical stimulation of a small patch of the brain causes illusions that only affect the perception of faces. (Matt Cardy/Getty Images)
Ron Blackwell didn’t enter the hospital expecting to see his doctor’s face melt before his eyes. But that’s exactly what happened when researchers electrically stimulated a small part of his brain, according to a study published Tuesday in the Journal of Neuroscience.
The doctor’s face did not actually melt, of course. Instead, the researchers argue, the stimulation short-circuited a brain area called the fusiform gyrus. Previous studies have linked a part of that area to face processing by showing that it becomes active when people perceive faces. But it’s hard to know just how important the area is for facial processing unless you can actually change its activity level while someone views faces.
Blackwell, an epileptic, turned out to be the perfect test case. He was in Stanford’s hospital so that doctors — including the study author, Dr. Josef Parvizi — could study his epilepsy and decide whether they could perform surgery to remove the part of the brain responsible for his seizures. As part of that procedure, Parvizi laid down a strip of electrodes on the surface of the brain. That gave him the capacity to painlessly and harmlessly stimulate the part of the brain they covered, and one of those electrodes was right over the fusiform gyrus.
Along with collaborators led by Stanford psychologist Kalanit Grill-Spector, Parvizi stimulated the area to see whether it would affect Blackwell’s perception of the doctor’s face. When he performed a sham stimulation — counting down from three and pressing a button that did nothing — Blackwell reported no change.
But when Parvizi applied voltage, strange things suddenly began to happen to Blackwell’s face perception. “You just turned into somebody else,” Blackwell said in a video that was recorded as part of the experiment. “Your face metamorphosed. Your nose got saggy, went to the left. You almost looked like somebody I’d seen before, but somebody different. That was a trip.” As soon as the electricity was turned off, Blackwell’s visualization of Parvizi’s face returned to normal.
Later, Blackwell confirmed that it was only the doctor’s face that changed — his body and hands remained the same.
Though only a single case, the experiment provides strong confirmatory evidence that the fusiform gyrus is indeed directly involved in processing face perception, and that the area is specialized for doing so.
(Source: Los Angeles Times)
Cross-Category Adaptation: Objects Produce Gender Adaptation in the Perception of Faces
Adaptation aftereffects have been found for low-level visual features such as colour, motion and shape perception, as well as higher-level features such as gender, race and identity in domains such as faces and biological motion. It is not yet clear if adaptation effects in humans extend beyond this set of higher order features. The aim of this study was to investigate whether objects highly associated with one gender, e.g. high heels for females or electric shavers for males can modulate gender perception of a face. In two separate experiments, we adapted subjects to a series of objects highly associated with one gender and subsequently asked participants to judge the gender of an ambiguous face. Results showed that participants are more likely to perceive an ambiguous face as male after being exposed to objects highly associated to females and vice versa. A gender adaptation aftereffect was obtained despite the adaptor and test stimuli being from different global categories (objects and faces respectively). These findings show that our perception of gender from faces is highly affected by our environment and recent experience. This suggests two possible mechanisms: (a) that perception of the gender associated with an object shares at least some brain areas with those responsible for gender perception of faces and (b) adaptation to gender, which is a high-level concept, can modulate brain areas that are involved in facial gender perception through top-down processes.
Caltech study shows that the distance at which facial photos are taken influences perception
Previous studies have examined how our social judgments of pictures of people are influenced by factors such as whether the person is smiling or frowning, but until now one factor has never been investigated: the distance between the photographer and the subject. According to a new study by researchers at the California Institute of Technology (Caltech), this turns out to make a difference—close-up photo subjects, the study found, are judged to look less trustworthy, less competent, and less attractive.
The new finding is described in this week’s issue of the open-access journal PLoS One.
Humans aren’t the only animals who possess special skills with mugs
Paper wasps aren’t mammals, or even vertebrates. Before this study, the notion that a creature so distant from humankind in the tree of life could possess face expertise was weirder than an upside-down Darwin. Now the wasp development has added some sizzle to the endeavor of establishing what face-perception abilities other creatures may actually have. Emerging patterns in the animal world may reveal what drives the evolution of remarkable face prowess.
“The search is on,” says neuroscientist Winrich Freiwald of Rockefeller University in New York City.
While some researchers continue to invent tests (and debate how to interpret test results) for probing facial aptitudes among humankind’s primate cousins, other efforts have pushed beyond primates. Sheep, as well as those paper wasps, appear to have some special face skills. And faces may be important among rodents in ways that demand a more ticklish view of what face perception means. When it comes to face smarts, researchers are finding that the size of an animal’s brain may not matter as much as the company it keeps.
Roger Alsing coded a program to give a slight mutation to a random string of DNA which was used to render polygons on a canvas.