Do Snails Know About Tomorrow?

This started, as apparently quite a lot of my ideas do, while I was doing something completely unrelated.

I was washing the dishes.

Dishes don't require much thought, which means my hands were occupied and my brain was free to wander off unsupervised.

For some reason, it started thinking about consciousness.

More specifically, levels of consciousness.

We tend to talk about consciousness and self-awareness as though there's a line somewhere. On one side are animals we comfortably accept as having some sort of internal experience of themselves and the world. On the other are increasingly simple creatures where everything gets much murkier.

And then something occurred to me.

Animals we regard as highly intelligent or self-aware also seem to have some concept of future.

Not necessarily in the human sense of worrying about the mortgage, booking next year's holiday or lying awake at 3am replaying an argument that hasn't actually happened yet.

But they can anticipate.

They can alter what they're doing now because of something that hasn't happened yet.

And that made me wonder whether one useful way of thinking about intelligence and consciousness might be through temporal awareness.

At the simplest level, an organism responds to what is happening now.

At another level, past experience changes present behaviour.

Beyond that comes anticipation: behaving differently now because something is expected to happen next.

Further still, an animal might represent possible future states, make choices between them, plan towards one of them, or understand itself as something that continues through time.

Humans eventually take this to frankly ridiculous extremes and spend Tuesday worrying about a hypothetical conversation they might have next Thursday.

But where does it start?

How far down the neurological ladder do you have to go before there is nothing resembling a future at all?

Insects?

Molluscs?

And then my brain produced:

Snails.

I became convinced that snails might have some rudimentary concept of future.

There was a reason.

I'd previously watched snails crossing dry, exposed ground during hot weather to reach somewhere damper and more sheltered.

For a snail, crossing a dry path is not an obviously sensible place to be. Yet there they were, trundling determinedly across hostile terrain towards somewhere better.

Obviously this doesn't prove they're thinking, Bloody hell, this paving is awful, but it'll be lovely under that hedge.

They could simply be following gradients of humidity, light, temperature or chemical cues. A surprisingly complicated-looking behaviour can emerge from some very simple rules.

But it left me with a question.

How could you distinguish an animal merely reacting to its current environment from one anticipating a state that doesn't exist yet?

Which eventually led to dinner.

The Snail Experiment

Suppose you kept a small group of garden snails under controlled conditions and fed them at exactly the same time every day.

Same time. Same routine.

After enough repetitions, what would happen before dinner?

If nothing changed until food appeared, fine. They may simply respond to smell or some other immediate cue.

But what if, before any food entered their environment, they started becoming more active?

What if they emerged from their hiding places as feeding time approached?

Better still, what if food was normally presented in one particular location and the snails began congregating there before it arrived?

Now we have something interesting.

Of course, we would have to be horribly suspicious of everything.

Can they smell the food being prepared?

Can they hear or feel me approaching?

Are they responding to changing daylight rather than elapsed time?

Temperature?

Household activity?

Some other cue I haven't thought of because I am not, despite current appearances, a gastropod neuroscientist?

All of those would need controlling as far as reasonably possible.

And eventually there would have to be a test day.

A day when the usual feeding time arrives...

...and dinner doesn't.

Betrayal Day.

If the snails become active or assemble at the expected feeding location despite there being no food present and no food-related sensory cue, we've demonstrated something considerably more interesting than a snail smelling lettuce.

We still haven't proved that Gerald the Experimental Snail is sitting there thinking:

It's eight o'clock. Where the fuck is she?

And that's important.

There is a huge difference between demonstrating an internal timing mechanism, learned temporal association or food-anticipatory behaviour and demonstrating a conscious representation of the future.

The first is experimentally approachable.

The last is an enormous philosophical and neurological claim.

But that's precisely why Gerald interests me.

He isn't really the hypothesis.

He's an attempt to find the bottom edge of it.

Maybe temporal awareness isn't something an organism either has or doesn't have. Perhaps it exists in layers: immediate sensation, memory, anticipation, prediction, planning, counterfactual futures and eventually the elaborate autobiographical sense of time humans experience.

If so, somewhere in evolutionary history, nervous systems crossed from merely reacting to the present into behaving according to something that hadn't happened yet.

I want to know where that line is.

And apparently I'm going to start looking for it in a vivarium full of snails.

Because this is what happens when I wash dishes without adequate supervision.