Sphexishness

Dennett, in his book Elbow Room, describes a particular emotional reaction to determinism, a fear called ‘Sphexishness’¹. This is after the digger wasp (Sphex ichneumoneus). The digger wasp is a solitary wasp, which lives in a burrow, rather than communally in a hive. The digger wasp follows a particular behavioural pattern before it lays its young, which you can see here:

Or here:

It will capture a grasshopper, paralysing it, then drag it to the edge of its burrow. Next it goes into the burrow, presumably to check for blockages, returns and retrieves the grasshopper and then drags it into the burrow (it then lays its lavae inside the paralysed grasshopper, meaning they have fresh meat to eat when they hatch¹). This behaviour looks purposeful enough, until a curious ethologist intervenes. Tinbergen², waited until a wasp was halfway through its routine, down the burrow checking for blockages, and moved the grasshopper from the lip of the burrow, a few inches further away. The effect of this was that the wasp emerged, dragged the grasshopper back to the lip of the burrow and then left it, again to explore the burrow for blockages. Tinbergen moved the grasshopper again, and the wasp, again, emerged and dragged the grasshopper to the lip before - again - leaving it to check for blockages. The seemingly purposeful behaviour of the wasp had been hacked - there was no limit to the number of times the ethologist could move the grasshopper and evoke the ‘checking’ pattern from the wasp, revealing that it has no sophisticated goal planning, no memory of burrow being definitely unblocked. It has a behavioural routine which depends on the grasshopper being exactly at the lip of the burrow and outside intervention can force this routine to endlessly loop. The outside observer can see the ridiculousness of this, knowing the causal forces at work (i.e. the actions of the ethologist), but the wasp is trapped in a deterministic cycle.

This argues Dennett, is what people have in mind when they imagine a deterministic universe. They imagine themselves prey to the same traps, the same blunt causal forces, as the digger wasp.

The reason not to fear sphexishness is complexity. The sphex is a misleading example of a living thing with a very simple behavioural pattern. It is not typical of living things. Further, it isn’t even typical of many simple systems which we know to be completely deterministic, yet can yield unpredictable, and endlessly varied, forms.

To illustrate what I’m getting at here, I’m going to tell you about a simple, completely deterministic system that convinced me, viscerally that being a deterministic system didn’t mean being reduced to a simplistic or predictable creature.

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Tell me about cellular automata RULE30; complexity

Skip that, tell me what it means CHAOS; direct link reasons

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1: Dennett attributed the coining of ‘sphexishness’ to Douglas Hoftstader, in his article “Can Creativity be Mechanized?” Scientific American, 247, September 1982, 18-34.

2: A behaviour, incidentally, which may have played a role in Darwin’s loss of faith “I cannot persuade myself that a beneficent & omnipotent God would have designedly created the Ichneumonidae with the express intention of their feeding within … living bodies”: link

3: Watch Richard Dawkins explain the experiments with the digger wasp in the 1991 Royal Institution Christmas Lectures