Jef's web files - Perception

A Career Spent Learning How the Mind Emerges From the Brain

Tue, 10 May 2005 17:11:01 -0400

If you walk into the office of a scientist, chances are you'll see a white board hanging on the wall covered in scrawls. A molecular biologist's white board might be covered by hideous tangles of protein chains. A geophysicist might doodle India crashing into southern Asia.

The scribbles of Dr. Michael Gazzaniga, the director of the Center for Cognitive Neuroscience at Dartmouth, are more metaphysical. Arrows travel from a pair of eyes into a cartoon brain, finally ending at the word "Apple." Another picture bluntly sums up the modern debate over free will, with a stick figure's head labeled "Brain," and two bubbles point toward it - one labeled "Judge" and the other "Neu" - short for neuroscience. Floating uncertainly off to one side is a third bubble that asks, "Mind?"

Big questions are Dr. Gazzaniga's stock in trade. In the 1980's he helped found cognitive neuroscience, a discipline designed to find out how the mind emerges from the brain. Today, at age 65, he continues to oversee a busy lab where brain scans offer clues to how we unconsciously create theories to explain the outer world and our inner lives.

Project Implicit (Harvard)

Tue, 08 Mar 2005 14:34:28 -0500

Project Implicit represents a collaborative research effort between researchers at Harvard University, the University of Virginia, and University of Washington. While the particular purposes of each study vary considerably, most studies available at Project Implicit examine thoughts and feelings that exist either outside of conscious awareness or outside of conscious control. The range of studies should provide you with a great variety of experiences and an opportunity to think about topics that are very important to you, or unique issues that you have not had the occasion to think about before.

Researchers Find That Color Perception Is Not Innate, But Acquired After Birth

Mon, 02 Aug 2004 12:17:29 -0400

Rearing experimental animals under special illumination, researchers have found new evidence that early visual experience is indispensable for the development of normal color perception.

The wavelength composition of the light reflected from an object changes considerably in different conditions of illumination. Nevertheless, the color of the object remains the same. This property, so-called "color constancy," is the most important property of the color visual system. It has been unclear based on previous work whether the attribute of color constancy is innate or acquired after birth.

In work reported this week, researcher Yoichi Sugita of the Neuroscience Research Institute, Tsukuba, Japan, shows that visual experience in early infancy is indispensable for normal development of the color constancy. He raised baby monkeys for nearly a year in a separate room where the illumination came from only monochromatic lights. After extensive training afterwards, the monkeys were able to perform color matching tasks, but their judgment of color similarity was quite different from that of normal animals. Furthermore, they had severe deficits in color constancy; their color vision was very much wavelength-dominated, such that they were unable to compensate for the changes in wavelength composition. These results indicate that early visual experience is indispensable for normal color perception.

That's not my hand! How the brain can be fooled into feeling a fake limb

Sat, 03 Jul 2004 15:03:31 -0400

Scientists have made the first recordings of the human brain's awareness of its own body, using the illusion of a strategically-placed rubber hand to trick the brain. Their findings shed light on disorders of self-perception such as schizophrenia, stroke and phantom limb syndrome, where sufferers may no longer recognize their own limbs or may experience pain from missing ones.
In the study published today in Science Express online, University College London's (UCL) Dr Henrik Ehrsson, working with Oxford University psychologists, manipulated volunteers' perceptions of their own body via three different senses - vision, touch and proprioception (position sense).

Clock Watchers

Sat, 08 May 2004 02:20:32 -0400

No wonder physicists can't explain past, present and future. The passage of time is just an illusion that we can't live without, says Marcus Chown

DEEP in the Amazon rainforest, a tree frog sits on a log watching a fly. A genetic fluke has furnished the frog with a brain that perceives its surroundings as they were a second ago. When the fly comes within range, the frog lunges. But, with its out-of-date observation, it misses. Weakened by a rarely sated hunger, the frog falls off the log and dies.

It's a sad story. But if you think it is completely fanciful, think again. There is nothing in the laws of physics that says all creatures have to process data about their environment in the same way as we do. A "behind the times" perception like that of our deceased frog is only ruled out by the handicap it imposes. "Natural selection has equipped people and frogs to experience the world in the most effective way for their survival," says James Hartle of the University of California, Santa Barbara. "A frog that calculates the trajectory of a fly from the most recent data, eats; one that doesn't, starves."

Did you see the gorilla?

Tue, 03 Aug 2004 20:47:16 -0400

Our Stone Age brains may simply be unable to cope with the pace of modern life, says Roger Highfield.

Look around, and you could be forgiven for believing that you can see a vivid and detailed picture of your surroundings. Indeed, you may even think that your eyes never deceive you. Unfortunately, the same cannot be said for your brain.

Scientists have gathered some remarkable evidence which shows that it is possible to see something without observing it, in research that sheds new light on traffic accidents that occur when a driver "looked but failed to see", and other examples of mayhem and mishap in everyday life.

The astonishing lack of attention we pay to our surroundings has been highlighted by research conducted by Dr Daniel Simons of the University of Illinois and Dr Daniel Levin of Vanderbilt University. At the end of this article, Dr Simons invites readers to explore the limitations of their own brains.

Brain areas that “decode” emotions of others

Sun, 18 Apr 2004 13:24:57 -0400

Queen’s psychologists have discovered that our ability to assess how other people are feeling relies on two specific areas of the brain.

The findings, published in the April issue of the Journal of Cognitive Neuroscience, are expected to have implications for the treatment of developmental disorders such as autism.

Led by Mark Sabbagh, the study is supported by a grant from the Natural Sciences and Engineering Research Council (NSERC). Also on the team, from the Queen’s Psychology Department, are Margaret Moulson and Kate Harkness.

The study helps us understand the neural bases of everyday “theory of mind”: our ability to explain behaviour in terms of mental states like intentions and desires. “What we’re showing is that an important first step in theory of mind is being able to decode other people’s mental states, and that this skill is carried out within a very specific neural pathway,”says Dr. Sabbagh.

Storage limits on our visual hard drive

Thu, 15 Apr 2004 21:32:15 -0400

Scientists have discovered the region of the brain responsible for the old adage, "out of sight, out of mind."

The amount of information we can remember from a visual scene is extremely limited and the source of that limit may lie in the posterior parietal cortex, a region of the brain involved in visual short-term memory, Vanderbilt psychologist René Marois and graduate student J. Jay Todd have found. Their results were published in the April 15 edition of Nature.

"Visual short-term memory is a key component of many perceptual and cognitive functions and is supported by a broad neural network, but it has a very limited storage capacity," Marois said. "Though we have the impression we are taking in a great deal of information from a visual scene, we are actually very poor at describing its contents in detail once it is gone from our sight."

Akiyoshi's illusion pages

Tue, 06 Apr 2004 11:10:27 -0400

Kitaoka Akiyoshi, Department of Psychology, Ritsumeikan University, Kyoto, Japan

The Peripheral Drift Illusion

Tue, 06 Apr 2004 10:52:54 -0400

The Peripheral Drift Illusion

Hering Illusion

Tue, 06 Apr 2004 10:53:17 -0400

Hering Illusion

Hermann Grid Illusion

Mon, 04 Jun 2007 19:59:16 -0400

Herman Grid Illusion

Duck-Bunny Illusion

Tue, 06 Apr 2004 10:53:57 -0400

Duck-Bunny Illusion

Muller-Lyer Illusion

Tue, 06 Apr 2004 10:54:19 -0400

Muller-Lyer Illusion

MIT team reports new insights in visual recognition

Sun, 04 Apr 2004 21:22:14 -0400

MIT scientists are reporting new insights into how the human brain recognizes objects, especially faces, in work that could lead to improved machine vision systems, diagnostics for certain neurological conditions and more.

Look at a photo of people running a marathon. The lead runners' faces are quite distinct, but we can also make out the faces of those farther in the distance.

Zoom in on that distant runner, however, "and you'll see that there's very little intrinsic face-related information, such as eyes and a nose. It's just a diffuse blob. Yet somehow we can classify that blob as a face," said Pawan Sinha, an assistant professor in the Department of Brain and Cognitive Sciences (BCS). In contrast, performing this task reliably is beyond even the most advanced computer-recognition systems.

In the April 2 issue of Science, Sinha and colleagues show that a specific brain region known to be activated by clear images of faces is also strongly activated by very blurred images, just so long as surrounding contextual cues (such as a body) are present. "In other words, the neural circuitry in the human brain can use context to compensate for extreme levels of image degradations," Sinha said.