When I was a child, I thought science would explain everything. That’s why I loved science. I wanted to know – everything. But when I was an undergrad, the lecturers poured everything science knew into my head and I realized there were things it couldn’t explain. Like, how do you know when someone’s staring at you? Because you do, don’t you? You can feel when someone’s staring at the back of your head, and you can turn and pinpoint them exactly. Exactly! Lock eyes with them. And science can’t explain it. Elizabethans thought the eyes emitted beams. But modern science has no truck with eye beams. Eyes are passive receivers of light waves. So how can you explain our sense of being stared at?

I don’t know, he says. How can you explain it?

Is she demonstrating eye beams? It’s a strong look.

It’s early days, Logan. So no hows. Only hypotheses. Swishing her stick-tail, side to side.

Throw me a bone, he says.

She plods ahead, dropping questions behind her. He’s familiar with the measurement of brainwaves? Does he imagine brainwaves stop at the skull? Does he know there are more than five senses? At least seven more? And that there may be others? Has he considered the evolutionary advantage inherent in a social primate sensing when he or she is the focus of another’s gaze? They have reached a small stream and she stabs her stick into the ground, a pennant.

You are saying there is a sense of – Logan hesitates – what would you call it?

Skoporeception. Beaming from his wife’s wellies to her unbrushed teeth. From skopos, attention. It has been suggested.

But there’s no proof we have such a sense, Logan says.

Only in the experience, she answers. I experience it rather frequently. Don’t you?

No, says Logan. Though it makes perfect sense, looking at her, that she’s the focus of a stranger’s gaze more often than he is.

She giant-steps over the stream, the stick now a lever propelling her forward.

Proof in terms of mechanism – if that’s even achievable – is years away. This is hypothesis. But that’s what you need before you start looking for proof. Goodness knows, we need more sensitive measuring equipment. Assuming we’re even measuring the right thing. And there’s something else.

What?

He follows her, but catches a foot on the far bank, dousing his walking boot. Unbalanced, he stumbles forward, and when she turns to answer him, she has to put a hand on his chest to stop them colliding.

I’m not even sure about the concept of proof in a quantum universe, she says, stepping away and moving on.

He is conscious of the coffee on his breath.

Why?

She sets off again.

The Observer Effect, she says over her shoulder. Heard of the double-slit experiment?

He has, but he doesn’t really get it.