The system relies on a recent technology called a streak camera, deployed in a totally unexpected way. The aperture of the streak camera is a narrow slit. Particles of light — photons — enter the camera through the slit and pass through an electric field that deflects them in a direction perpendicular to the slit. Because the electric field is changing very rapidly, it deflects late-arriving photons more than it does early-arriving ones.

The image produced by the camera is thus two-dimensional, but only one of the dimensions — the one corresponding to the direction of the slit — is spatial. The other dimension, corresponding to the degree of deflection, is time. The image thus represents the time of arrival of photons passing through a one-dimensional slice of space.

— MIT.edu | Read The Full Article

The original image of the illusion.
The squares marked A and B are the same shade of gray, yet they appear different.

The original image plus two stripes.
By joining the squares marked A and B with two vertical stripes of the same shade of gray, it becomes apparent that both squares are the same.

Why does the illusion work?

The visual system needs to determine the color of objects in the world. In this case the problem is to determine the gray shade of the checks on the floor. Just measuring the light coming from a surface (the luminance) is not enough: a cast shadow will dim a surface, so that a white surface in shadow may be reflecting less light than a black surface in full light. The visual system uses several tricks to determine where the shadows are and how to compensate for them, in order to determine the shade of gray “paint” that belongs to the surface.

The first trick is based on local contrast. In shadow or not, a check that is lighter than its neighboring checks is probably lighter than average, and vice versa. In the figure, the light check in shadow is surrounded by darker checks. Thus, even though the check is physically dark, it is light when compared to its neighbors. The dark checks outside the shadow, conversely, are surrounded by lighter checks, so they look dark by comparison.

A second trick is based on the fact that shadows often have soft edges, while paint boundaries (like the checks) often have sharp edges. The visual system tends to ignore gradual changes in light level, so that it can determine the color of the surfaces without being misled by shadows. In this figure, the shadow looks like a shadow, both because it is fuzzy and because the shadow casting object is visible.

The “paintness” of the checks is aided by the form of the “X-junctions” formed by 4 abutting checks. This type of junction is usually a signal that all the edges should be interpreted as changes in surface color rather than in terms of shadows or lighting.

As with many so-called illusions, this effect really demonstrates the success rather than the failure of the visual system. The visual system is not very good at being a physical light meter, but that is not its purpose. The important task is to break the image information down into meaningful components, and thereby perceive the nature of the objects in view.

This can be proven using the following methods:

• Open the illusion in a image editing program and use the eyedropper tool – both A and B will register an RGB value of 120-120-120.
• Cut out a paper mask –- by viewing the areas of the image in question without the surrounding context, the effect of the illusion is dispelled.
• Print the image and cut out the areas labelled A and B –- once again, viewing them out of context removes all doubt.
• Use a photometer.

The experiment itself was simple: Nicholas Christenfeld and Jonathan Leavitt of UC San Diego gave several dozen undergraduates 12 different short stories. The stories came in three different flavors: ironic twist stories (such as Chekhov’s “The Bet”), straight up mysteries (“A Chess Problem” by Agatha Christie) and so-called “literary stories” by writers like Updike and Carver. Some subjects read the story as is, without a spoiler. Some read the story with a spoiler carefully embedded in the actual text, as if Chekhov himself had given away the end. And some read the story with a spoiler disclaimer in the preface.

Wired | Read the Full Article

Link to Epagogix. The artificial intelligence company telling Hollywood what screenplays to green light.

Published in the Oxford University Press journal Social Cognitive and Affective Neuroscience, the functional MRI study suggests that what may be going on is due to a perceptual mismatch between appearance and motion…

According to their interpretation of the fMRI results, the researchers say they saw, in essence, evidence of mismatch. The brain “lit up” when the human-like appearance of the android and its robotic motion “didn’t compute.”

“The brain doesn’t seem tuned to care about either biological appearance or biological motion per se,” said Saygin, an assistant professor of cognitive science at UC San Diego and alumna of the same department. “What it seems to be doing is looking for its expectations to be met – for appearance and motion to be congruent.”

In other words, if it looks human and moves likes a human, we are OK with that. If it looks like a robot and acts like a robot, we are OK with that, too; our brains have no difficulty processing the information. The trouble arises when – contrary to a lifetime of expectations – appearance and motion are at odds.

US San Diego | Read More