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Speculative Execution

Speculative execution is not exactly how thought works, it’s how you work without thinking about it. When philosophers talk about determinism versus free will, they treat the brain as if it were a black box with memory and sensory perceptions going in and actions coming out, with a clear sequence of causality from the first to the last. For the determinists, this is enough. For those who believe in free will, there’s an extra something special added at some point — the Soul, some kind of quantum magic going on in the synapses, whatever sort of swerve away from clockwork perfection seems convincing this decade — but it’s just another station on a linear progression.

Cognitive psychology and neuroscience undermine all of this because the brain doesn’t work like a black box. Without your noticing, it’s continually second-guessing and anticipating in all sorts of different ways. Your visual field is not the beautiful and transparent 360-degree spherical sensorium, God’s own VR headset, that you think it is: it’s a little dot of fine-detailed vision in constant motion with the gaps filled in by how your visual centres have come to assume that the world works. You anticipate what other people are about to say; your own words come tumbling out of your mouth without any conscious composition. The mind isn’t some Cartesian homunculus behind your eyes, marshalling inputs and emitting appropriate commands like some idealised 18th century lord. It’s a democratic and noisy playroom of independently-acting modules, all fighting for what little bandwidth your senses and memory afford them, and only too keen to proceed as far as they can on what guesses they can make.

And just as in CPUs, the goal of all this mess, this willingness to go out on a limb, is efficiency. Err on the side of caution if you think there’s a predator or, more realistically, the hostile or mocking attention of your peers; get distracted by anything which seems promising, an attractive person or an appetising aroma, because who knows that it might not be your last chance.

That’s the evolutionary story, and while we like to locate the life-and-death struggles behind the bundle of hacks we call consciousness in the savage prehistoric past, think of how much more we need to rely on speculative processing in the buzzing and blooming and overcrowded Umwelt we’ve built around ourselves. Sure, we might have evolved on the savannah, but all of these words and walls and works and wills and won’ts are what we’ve built to suit us, and they give our phantom selves such a lot of opportunity to run down the paths of might-have-been.

You’re about to change lanes and you map out the trajectory towards the exit ramp but: there’s someone coming up the inside. Backtrack. You’re indulging in a daydream fantasy about an attractive co-worker and then have to be polite and efficient with him for an hour-long team meeting. Backtrack. You’re following the plot of a movie and then what is he doing? Didn’t she get shot? Backtrack.

And this is just on a small scale. You marry young, anticipating decades of mutual happiness, only to have to unpick it all in a messy divorce in your early thirties. You choose a degree based on a school friend you hero-worshipped but get sidetracked out of it and have to explain it away for the next decade. A swarm of ghost lives, decisions and commitments and purchases and options which, if we’re lucky, we get to retrospectively make sense of, justify, tell ourselves it was destiny or fate, that it was what we were aiming for all along, what we really needed. But perhaps the truth, and it need not be an unkind one, is that a human life needs a sort of virtual scaffolding of possibilities, that the might-have-beens which we’ve unconsciously or consciously rejected are what hold us together.

Certain mental illnesses and mood disorders can be seen as a perversion of this tendency. Depression as the paralysis brought on by too keen an awareness of the sheer volume — number is too narrow a word — of possibilities exploding from every moment: anxiety is a failure of the shielding which lets our minds evaluate them without bothering us with the nagging sense that we are dancing over an abyss. In the manic phase of bipolar disorder there is a dimming of the red light and bell that clangs to signal that it’s time to backtrack, impulses are followed through to their destructive last.

It doesn’t take very much paranoia to imagine that our brain’s talent for speculative execution could be an exploitable vulnerability. Maybe back in the days of the savannah — any predator will have a keen instinct for the false steps and feints of its prey — but now? The misdirection of the magician, the fortune teller’s cold read, the confidence of the con artist, sure in their ability to anticipate just how far down the garden path their marks will lead themselves. The manipulative and abusive, those who gaslight and interrogate, the grandstanding attorney and the demagogue: do they take not take their victim’s or audience’s might-have-beens and magnify them into terrors or seductions? Facebook keeps a record of not only the posts you write, but those you cancel. The algorithms that watch us will have a better map of our shadow self than we will, seeing all the links we follow and then hurriedly click shut, the people we stalk, the products we dare not purchase.

Except that we know from a hundred ads which clumsily ape our ten most recent Google queries that the algorithms are not yet that subtle. The idea that our brains could be hacked by means as delicate as those which can be used to steal the ghosts of data from the might-have-beens of CPU caches is science fiction. And what is fiction, if not a way to coax an audience into the speculative execution of a series of thoughts, a shared illusion, a thing which could never be?

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