YOUR SENSE OF THE WORLD AND MOVEMENT WITHIN ITexperience the effect for yourself. This film instructs viewers to count the
number of times a basketball is thrown between players dressed in white,
while ignoring passes made by players in black. Most people who watch
the clip are so engrossed by the task that they fail to notice a person in a
gorilla suit walk right across the screen!
So our experience of the world is heavily edited, partly because of the
attentional bottleneck. But another reason why our experience of the
world is incomplete is because we can only process the world via the
sensory tools at our disposal. Evolution has equipped us with a whole
range of sophisticated sensory equipment, from light-sensitive cells,
to temperature-sensitive touch receptors, but like a thermometer that
only measures from 100°C down to minus -5°C, these biological sensory
tools have their limits. It’s well known, for example, that dogs can hear
high-pitched sounds that we’re oblivious to. And of course, there is a lot
of information and material we simply don’t have the tools to detect and
experience directly, for example X-rays and infrared light.
So, rather than feeling that you have an unhindered, flawless view
of what’s out there in the world, it would be more accurate for you to
imagine your perception as a best guess – one that’s based on infer-
ential processes in your brain that are forever crunching away, mostly
beneath the level of conscious awareness. In the language of science,
these processes are considered by many to operate according to Bayesian
principles, after the English mathematician Reverend Thomas Bayes
(1702–61), in which fresh evidence from the senses is considered against
existing beliefs derived from past experience. According to the neuropsy-
chologist Chris Frith, this understanding of perception helps explain the
hallucinations experienced by people with schizophrenia. Such halluci-
nations are perceptual beliefs like any other, except for the fact they are
less constrained by past evidence and current sensory information.
Yet another impediment to the accuracy of our sensory experience is
delay. We feel as though we’re experiencing the world as it is right now.
But it takes time for incoming sensory signals to be conducted down
nerve pathways, to be processed, and to give rise to conscious experience.
The moment you experience a sensation it’s already out of date. The
brain knows this and to compensate it spends a lot of effort predicting
what the world is probably like now given how it was just a moment ago,
all the while taking into account complicating factors such as whether
you’ve moved. These predictive processes are extremely useful, but
they’re yet another reason why your experience of the world isn’t raw, real
or, as psychologists say, “veridical”. Often what you see or feel isn’t what’s
really there, but what your brain predicted would be there. A powerful