I found this study interesting: Do flies have fear (or something like it)? — ScienceDaily.
A fruit fly starts buzzing around food at a picnic, so you wave your hand over the insect and shoo it away. But when the insect flees the scene, is it doing so because it is actually afraid? Using fruit flies to study the basic components of emotion, a new Caltech study reports that a fly’s response to a shadowy overhead stimulus might be analogous to a negative emotional state such as fear — a finding that could one day help us understand the neural circuitry involved in human emotion.
It might seem obvious that, since a fly avoids the fly swatter, it must have some kind of fear. However:
“There are two difficulties with taking your own experiences and then saying that maybe these are happening in a fly. First, a fly’s brain is very different from yours, and second, a fly’s evolutionary history is so different from yours that even if you could prove beyond any doubt that flies have emotions, those emotions probably wouldn’t be the same ones that you have,” he says. “For these reasons, in our study, we wanted to take an objective approach.”
It’s a fair point. Fly fear is probably very different from human fear. Still, it’s hard not to conclude that flies have some type of fear. The only way to conclude otherwise would be to narrow the definition of fear so that it only applies to mammalian brains, but that seems excessively speciesist, and anyway, this study did find what appears to be evidence for fly emotions.
“These experiments provide objective evidence that visual stimuli designed to mimic an overhead predator can induce a persistent and scalable internal state of defensive arousal in flies, which can influence their subsequent behavior for minutes after the threat has passed,” Anderson says. “For us, that’s a big step beyond just casually intuiting that a fly fleeing a visual threat must be ‘afraid,’ based on our anthropomorphic assumptions. It suggests that the flies’ response to the threat is richer and more complicated than a robotic-like avoidance reflex.”
What’s interesting about this evidence is that it seems to mean that, to at least some extent, flys are sentient beings. What makes that interesting is that their brains are relatively simple systems, with about 100,000 neurons and 10 million synapses (compared to the 100 billion neurons and 100 trillion synapses in humans).
Mapping brains to computing capacity is fraught with problems, but unless you assume the resolution of mental processing is smaller than neurons and synapses, the device you’re using to read this post has far more storage and processing complexity than a fruit fly’s brain. Yet I doubt you see your device as a sentient being. (You may not see a fly as a sentient being either, but you have to admit it seems more sentient than a smartphone.)
All of which brings me back to the realization that sentience is a matter of having the right software, the right data processing architecture. We don’t understand that architecture yet. As simple as a fly brain is, we have little understanding of how it generates the fly’s emotions, although the researchers do hope to change that.
In the future, the researchers say that they plan to combine the new technique with genetically based techniques and imaging of brain activity to identify the neural circuitry that underlies these defensive behaviors. Their end goal is to identify specific populations of neurons in the fruit fly brain that are necessary for emotion primitives — and whether these functions are conserved in higher organisms, such as mice or even humans.
I have to wonder how they plan to do brain imaging on flies.
Anyway, one of the things that is becoming sharper in my mind is the distinction between intelligence and sentience. Fly sentience is almost certainly not as rich as mouse sentience, much less human sentience. But while we have computing systems that are intelligent enough to beat humans in narrow domains like chess or Jeopardy, we don’t yet have a system with even the limited sentience of a fly. (At least none that I know of. I’m sure the fly biologists and neuroscientists of all types would like to know if we did.)
A lot of sci-fi scenarios have sentience creeping in by accident as machines progressively become more intelligent. Personally, I doubt we’re going to get it by accident. We’re probably going to have to understand how it arises in creatures such as flies well before we have much of a chance of generating it in machines. Fortunately, sentience won’t be required for most of what we want from artificial intelligence.