Tag Archives: Mark Changizi

Spacebook: a facebook for space

I follow the work of Mark Changizi on vision. Previously I mentioned one of his early papers on this subject, “Harnessing vision for computation” .

One of the applications of computing with space  could be to SHARE THE SPATIAL EXPERIENCE ON THE WEB.

Background. When I was writing the paper on the problem of computing with space, I stumbled upon this article by Mark in Psychology Today

The Problem With the Web and E-Books Is That There’s No Space for Them

The title says a lot. I was intrigued by the following passage

“My personal library serves as extension of my brain. I may have read all my books, but I don’t remember most of the information. What I remember is where in my library my knowledge sits, and I can look it up when I need it. But I can only look it up because my books are geographically arranged in a fixed spatial organization, with visual landmarks. I need to take the integral of an arctangent? Then I need my Table of Integrals book, and that’s in the left bookshelf, upper middle, adjacent to the large, colorful Intro Calculus book.”

So I posted the following comment:  Is your library my library?

“Good point, but you have converted a lot of time into understanding, exploring and using the space of your library. To me the brain-spatial interface of your library is largely incomprehensible. I have to spend time in order to reconstruct it in my head.

Then, your excellent suggestion may give somebody the idea to do a “facebook” for our personal libraries. How to share spatial competences, that is a question!”

In the section 2.7 (“Spacebook”) of the paper on computing with space I mention this as an intriguing application of this type of computing (the name itself was suggested by Mark Changizi after I sent him a first version of the paper).

What more?Again from browsing Mark Changizi site, I learned that in fact this problem of non-spatiality (say) of e-books has measurable effects. Indeed, see this article by Maia Szalavitz

Do E-Books Make It Harder to Remember What You Just Read?

Nice! But in order to do a spacebook we need first to understand the primitives of space (as represented in the human brain) and then how to “port” them by using the web.

The structure of visual space

Mark Changizi has an interesting post “The Visual Nerd in You Undestands Curved Space” where he explains that spherical geometry is relevant for the visual perception.

At some point he writes a paragraph which triggered my post:

Your visual field conforms to an elliptical geometry!

(The perception I am referring to is your perception of the projection, not your perception of the objective properties. That is, you will also perceive the ceiling to objectively, or distally, be a rectangle, each angle having 90 degrees. Your perception of the objective properties of the ceiling is Euclidean.)

Is it true that our visual perception senses the Euclidean space?

Look at this very interesting project

The structure of optical space under free viewing conditions

and especially at this paper:

The structure of visual spaces by J.J. Koenderink, A.J. van Doorn, Journal of mathematical imaging and vision, Volume: 31, Issue: 2-3 (2008), pp. 171-187

In particular, one of the very nice things this group is doing is to experimentally verify the perception of true facts in projective geometry (like this Pappus theorem).

From the abstract of the paper: (boldfaced by me)

The “visual space” of an optical observer situated at a single, fixed viewpoint is necessarily very ambiguous. Although the structure of the “visual field” (the lateral dimensions, i.e., the “image”) is well defined, the “depth” dimension has to be inferred from the image on the basis of “monocular depth cues” such as occlusion, shading, etc. Such cues are in no way “given”, but are guesses on the basis of prior knowledge about the generic structure of the world and the laws of optics. Thus such a guess is like a hallucination that is used to tentatively interpret image structures as depth cues. The guesses are successful if they lead to a coherent interpretation. Such “controlled hallucination” (in psychological terminology) is similar to the “analysis by synthesis” of computer vision.

So, the space is perceived to be euclidean based on prior knowledge, that is because prior controlled hallucinations led consistently to coherent interpretations.