# Swat a way to drive

by Peter W McOwan, Queen Mary University of London

(updated from the archive)

Flies are small, fast and rather cunning. Try to swat one and you will see just how efficient their brain is, even though it has so few brain cells that each one of them can be counted and given a number. A fly’s brain is a wonderful proof that, if you know what you’re doing, you can efficiently perform clever calculations with a minimum of hardware. The average household fly’s ability to detect movement in the surrounding environment, whether it’s a fly swat or your hand, is due to some cunning wiring in their brain.

## Speedy calculations

Movement is measured by detecting something changing position over time. The ratio distance/time gives us the speed, and flies have built in speed detectors. In the fly’s eye, a wonderful piece of optical engineering in itself with hundreds of lenses forming the mosaic of the compound eye, each lens looks at a different part of the surrounding world, and so each registers if something is at a particular position in space.

All the lenses are also linked by a series of nerve cells. These nerve cells each have a different delay. That means a signal takes longer to pass along one nerve than another. When a lens spots an object in its part of the world, say position A, this causes a signal to fire into the nerve cells, and these signals spread out with different delays to the other lenses’ positions.

The separation between the different areas that the lenses view (distance) and the delays in the connecting nerve cells (time) are such that a whole range of possible speeds are coded in the nerve cells. The fly’s brain just has to match the speed of the passing object with one of the speeds that are encoded in the nerve cells. When the object moves from A to B, the fly knows the correct speed if the first delayed signal from position A arrives at the same time as the new signal at position B. The arrival of the two signals is correlated. That means they are linked by a well-defined relation, in this case the speed they are representing.

## Do locusts like Star Wars?

Understanding the way that insects see gives us clever new ways to build things, and can also lead to some bizarre experiments. Researchers in Newcastle showed locusts edited highlights from the original movie Star Wars. Why you might ask? Do locusts enjoy a good Science Fiction movie? It turns out that the researchers were looking to see if locusts could detect collisions. There are plenty of those in the battles between X-wing fighters and Tie fighters. They also wanted to know if this collision detecting ability could be turned into a design for a computer chip. The work, part-funded by car-maker Volvo, used such a strange way to examine locust’s vision that it won an Ig Nobel award in 2005. Ig Noble awards are presented each year for weird and wonderful scientific experiments, and have the motto ‘Research that makes people laugh then think’. You can find out more at http://improbable.com

## Car crash: who is to blame?

So what happens if we start to use these insect ‘eye’ detectors in cars, building

We now have smart cars with the artificial intelligence (AI) taking over from the driver completely or just to avoid hitting other things. An interesting question arises. When an accident does happen, who is to blame? Is it the car driver: are they in charge of the vehicle? Is it the AI to blame? Who is responsible for that: the AI itself (if one day we give machines human-like rights), the car manufacturer? Is it the computer scientists who wrote the program? If we do build cars with fly or locust like intelligence, which avoid accidents like flies avoid swatting or can spot possible collisions like locusts, is it the insect whose brain was copied that is to blame!?!What will insurance companies decide? What about the courts?

As computer science makes new things possible, society quickly needs to decide how to deal with them. Unlike the smart cars, these decisions aren’t something we can avoid.

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EPSRC supports this blog through research grant EP/W033615/1.