When Star Trek first appeared on television screens 60 years ago, audiences expected science fiction to offer aliens, monsters and futuristic technology. What they encountered was something far more ambitious.

From its very first broadcast episode on September 8 1966, Star Trek established that its true subject was the exploration of humanity itself. For all its reputation as an action-packed space adventure, the franchise has endured because it repeatedly returned to a universal question: what does it mean to be human?

In that first episode, entitled The Man Trap, the alien antagonist survives by appearing to each observer as the person they most wish to see. Dr Leonard “Bones” McCoy meets a lost love from his past; others see figures shaped by memory, expectation, desire and longing.

The creature, soon dubbed the “salt vampire” by fans of the series, is not simply a shape-shifter. Its power lies in exploiting human perception. Rather than asking viewers to fear an alien with superior strength or advanced weaponry, the episode asks a more profound question: can we trust our experience of reality?

Sixty years on, this question looks remarkably prescient. Modern neuroscience increasingly suggests that perception is not a passive recording of the external world. According to theories of predictive processing, the brain continually generates expectations and compares them with incoming sensory information.

The philosopher Andy Clark has described the brain as a “prediction machine”.........

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