A
key ability for survival is the recognition of the motion of objects. If you’re an
animal that may become lunch you certainly want to take good care that nothing
is sneaking up on you. Lying about in the sunshine watching gives you plenty of
warning as any movement out there will attract your attention.
This
is where Zabala et al start off in
their recent paper in Current Biology (1). Needless to say that’s not where
they finish as they pondered over the problem of detecting something moving
when you are in motion as static objects come into view, pass by and disappear
as you march onwards.
Specifically,
they pondered on flies. It is notoriously difficult to sneak up on a fly and
they asked the question would it be easier if the fly was also moving. To put
this too the test, they built a fly-sized robot that could move around with a
fly without dominating the visual space, so it would resemble a predator as
opposed to you or I with a copy of the Sunday newspaper in a tight roll.
They
tried this out with female flies walking around, no flying by in this case as
they wanted the robot to be more interesting than a passing tourist and more
like a predator or a promising version of a fly-lothario.
If
the robot was static, the female flies ignored it as though it were part of the
furniture. The habit of predators is to sneak up from behind and when the robot
played that role, the females froze until they knew if they were going to be
eaten or ravaged. Of course, with the robot, ravaging wasn’t on the menu, and
none of the flies were de-briefed during or after the experiment.
It
is interesting that we tend to react the same way. As I was walking this
morning my senses went onto high alert when I heard or spotted anyone out of
the corner of my eye beginning to catch up. Having been fine-tuned by this
report, I became keenly aware that a couple of different females paused as I
caught them up and waited for me to pass.
