The impossible staircase in our heads: how we visualise the world around us

The impossible staircase in our heads: how we visualise the world around us
A ‘Penrose stairs’ optical illusion, or impossible staircase. Credit: Sakurambo on  Wikipedia.

(Medical Xpress) -- Our interpretation of the world around us may have more in common with the impossible staircase illusion than it does the real world, according to research published today in the open access journal PLoS ONE. The study, which was funded by the Wellcome Trust, suggests that we do not hold a three-dimensional representation of our surroundings in our heads as was previously thought.

Artists, such as Escher, have often exploited the paradoxes that emerge when a 3D scene is depicted by means of a flat, two-dimensional picture. In Escher's famous picture 'Waterfall', for example, it is impossible to tell whether the start of the waterfall is above or below its base.

Paradoxes like this can be generated in a drawing, but it is not possible to create such a 3D structure. The is possible because drawings of 3D scenes are inherently ambiguous, so there is no one-to-one relationship between the picture and 3D locations in space.

Most theories of 3D vision and how we represent space in our visual system assume that we generate a one-to-one 3D model of space in our brains, where each point in real space maps to a unique point in our model. However, there is an ongoing debate about whether this is really the case.

To test this idea, researchers at the University of Reading placed participants wearing a in a in which they had to judge which of two objects was the nearest. On some occasions, the size of the room was increased four-fold - previous research by the team showed that participants fail to notice this expansion.

In this new study, the researchers found that people's of the relative depth of objects depended on the order in which the objects were compared. Although the results are readily explained in relation to the expansion of the room, the participants had no idea that the room changed at any stage during the experiment. It is the properties of this that the experiment tested.

Dr. Andrew Glennerster from the University of Reading, who led the study, explains: "In the impossible staircase illusion, you cannot tell whether the back corner is higher or lower than the front one as it depends which route you take to get there. The same is true, we find, in our task. This means that our own internal representations of space must be rather like Escher's paradoxes, with no one-to-one relationship to real space."

"Even when the size of the room increases four-fold, people think they are in a stable room throughout the experiment. Their interpretation of the room does not update itself when the room itself changes.

"Does it make sense for their representation of the room to have 3D coordinates, as a proper staircase would? No - there is no way to write down the coordinates of the objects that could explain the judgements people made. Visual space - the internal representation - is much more like the paradoxical staircase than a physically realisable model."

More information: Svarverud E et al. A demonstration of ‘broken’ visual space. PLoS ONE 2012 (epub ahead of print).

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Isaacsname
5 / 5 (1) Mar 23, 2012
Dang, all this time I thought it was assembled in the brain and projected on the back of the lenses in my eyes through my hyaloid.

..too many Tom and Jerry cartoons as a kid I guess.
hyongx
5 / 5 (1) Mar 23, 2012
researchers at the University of Reading placed participants wearing a virtual reality headset in a virtual room...

the participants had no idea that the room changed at any stage during the experiment...

Did anyone think to question validity of the virtual reality system? I.E., would the same results be found if the experiment were performed in a real physical room? Somehow I doubt it.
DavidW
1 / 5 (1) Mar 23, 2012
While their research reveals interesting observations, the conclusion of "...This means that our own internal representations of space must be rather like Escher's paradoxes, with no one-to-one relationship to real space", silly. It seems to me that people use Truth as the third point of perspective over z-axis, and that they use life to get Truth.
Eikka
not rated yet Mar 23, 2012
I just see the picture as if the stairs were angled like overlapping roof tiles. That's the only way it makes intuitive sense to me in an isometric projection like that.
RitchieGuy
2.5 / 5 (2) Mar 23, 2012
I have part of a wall in my den full of M.C.Escher poster size photographs, such as concave and convex; ascending and descending; Belvedere and others.

I think that the brain perceives changes and adapts to it in a split second even before the person is conscious of the change in the virtual reality experiment which could be a bit dangerous in real situations. This could be caused by the concentration on which of the 2 objects are closer, to the exclusion of the room size change stimulus. Multi-tasking ability might eliminate that problem. IMO

I'd like the researchers to do an experiment in virtual reality with a tesseract.
Tausch
not rated yet Mar 25, 2012
The mind 'insists' on convergence.

The 'expression' for this 'insistence' is labeled or called mathematics - one of many parts of the human language.

What other parts of human languages is capable of more paradoxes or illusions?

Nature 'insists'...

(apologies to all those wanting to cleanse the human languages of all anthropogenic/anthropocentric 'contamination')

...on as few illusions as possible.

Why?
This gives 'evolution' a 'chance' to evolve to what we label 'life' (or what some label the image of God! - us!).