We have a sophisticated set of sensors that we use
everyday and usually take for granted. But in interpreting the electrical
signals from the sensors our brain has to do a great deal of processing whilst
multitasking. Cross-talk occurs, of course, and this is often put to good use.
As we build up our databank through experience, we can cut the processing time
and jump to the final result, which may not always be correct. There are many
examples of optical illusions with which we’ve been entertained.
Our everyday world seems to be three-dimensional
and change with time, so our brains are geared to turn the signals from our
retinas into an understanding of the three-dimensional forms in front of us.
Light, shade and perspective is what we think of immediately as supplying those
clues, and artists have been working their magic with these since the
renaissance.
Apparently surface texture is also a major clue to
shape. Fleming et al in the
Proceedings of the National Academy of Science, (1), have shown 2-D shapes
patterned from random (“white”) noise and their subjects saw 3-D shapes. The
more intense the pattern, the more 3-D the shape appeared to be.
Sometimes the cross-talk can be interesting, though.
An extreme example is seen with people who are synesthetic and see sounds as
distinct colors. Some recent work by Ludwig et
al has shown that this interaction between sound and color is widespread
(2). Of course, you and I expected that already.
The sound/color experiment used thirty-three humans
and six chimpanzees. (Note; that there were no political implications in the
choice of participants.) The candidates had to classify black or white squares
while listening to background noise. The noise was irrelevant to the task in
hand and was either high pitch or low pitch.
Both humans and chimps found it easier to pick out
the white squares when the sounds were high pitched, and the black when it was
low pitched. So high noises are brighter (higher luminance) and low pitched are
darker. One has to think about film background music when the low notes
dominate and our spines shiver, and then it’s all over and the music gets
lighter and higher as we move into the sunshine, and all is well after all.
- http://www.pnas.org/content/early/2011/12/05/1114619109.full.pdf+html
- http://www.pnas.org/content/early/2011/11/29/1112605108.abstract
