Politicians don’t answer questions: this is so long established, so easily observed, so universal, that the intricacies of Peter Bull’s research into the subject [pdf download] seem almost decorative, like devising 35 typologies for the Pope’s Catholicism. And yet the York University psychologist, who specialises in micro-analyses of interpersonal communication, has a series of insights, some very broad, some very precise and relating to Theresa May, that have crystallised the process, driven home its necessity, and elaborated its mechanisms so precisely as to have more or less destroyed my faith in public life.

First, Bull details why politicians evade giving direct answers to interviewers: “It’s primarily to do with face; positive face is concerned with making sure they themselves don’t look bad, and negative face is about keeping one’s freedom of action and not committing to anything.” Positive face is, of course, pretty ignoble, and politicians we perceive to be able to say what they really feel, regardless of the flak they get, are admired disproportionately to how honest or talented or effective they demonstrably are.

Negative face, however, is much more of a conundrum. Thinking specifically about current politics, there are very few plain, practical answers May could give to anything, without inhibiting her room for manoeuvre in the near future, even as near as tomorrow. This might explain why, in one interview with Andrew Marr that Bull analysed for The Conversation, she gave a straight answer only 14% of the time. (Bull has found the average explicit answer rate in British political life to be 46%. I was surprised to find it so high, but this is comparable to a 1991 study that put it at 39%).

“A non-reply may include several different forms of not replying,” says Bull. May’s signature evasion is to answer a specific question with a non-specific answer. So, for instance, Marr asked her whether she would prevent a second referendum in Scotland, and she replied: “I don’t think it’s a question of whether there could be a second referendum, it’s whether there should be a second referendum.” Within that leap from specific to non-specific, she rephrases the question, then answers it as she posed it (“that’s a little ploy that politicians often use”).

She also expresses a hope rather than a plan. “She’s making political points all the time,” Bull notes. “Presenting policy, justifying policy, giving reassurance. She often talks in terms of aspirations. In PMQs on Wednesday, she was asked about the border in Ireland. She said: ‘Of course, we don’t want a return to a hard border between north and south.’ Would anyone want that?” This is where aspiration becomes indistinguishable from platitude; people rarely aspire to anything to which anyone else would not aspire.

May is often compared to Margaret Thatcher – they have that ineffable, sphinxish quality so rare in public life (let’s call it, for brevity, being female), but their evasive techniques couldn’t be more different. Thatcher frequently attacked the interviewer, which might have been charmless, but had the desired effect: few stayed on point after a skirmish. (“Theresa May isn’t like that at all. She is very polite.”) Neil Kinnock was known for negative evasion – he would tell the interviewer what he wasn’t going to do, which wasn’t effective at all, encouraging a predictable, punchier response: well, what are you going to do, then?

Bull is sceptical about whether adversarial interviewing styles are the best way of eliciting an answer. “It’s possible to construct a question in such a way that they’re bound to answer. If, for example, Jeremy Corbyn is still there by the next election, and an interviewer said, ‘Can you give us an idea of how things would be different if you were in No 10?’, he’s bound to answer that.”

Tony Blair being grilled by David Dimbleby live on TV in 2001. Photograph: Ken McKay/Rex/Shutterstock

It sounds easy, the Theresa May way, until you try it. I asked Bull to interview me as though I were her.

PB: First of all, prime minister, it’s a great pleasure to have this interview with you. Can you tell us exactly what you are negotiating for in relation to our European partners?

ZW: I’m negotiating for a Britain that is globally respected and prosperous.

PB: I’m sure that’s what we all want, but what specifically would you do?

ZW: Well, I’m going in to the negotiations with a hand, if I tell you what’s in it, I’ll be playing blind and they won’t.

PB: So in effect, you don’t want to say what you’re negotiating for?

ZW: The British people have voted to restore sovereignty to Britain, and that’s what I’m going to get.

PB: Surely parliament is sovereign, so parliament has a right to know?

ZW: This is really hard, isn’t it?

PB: Every time you evade, I follow up. Andrew Marr is much gentler than that.

ZW: OK, give me another.

PB: Obviously, the situation in Syria is causing huge concern. Do you have any plans to involve British troops on the ground?

ZW: There can be no solution to Syria that isn’t taken in concert with international partners, both in Europe and beyond.

PB: Yes, but if the decision was taken internationally to intercede on the ground, would you commit British troops?

ZW: Mmm … well, yes, obviously, if that’s what everyone decided was necessary.

PB: That would be banner headlines, if you said that.

Clearly, politicians are seasoned evaders, and an amateur couldn’t compete. But what struck me is that these conversations are nothing like a civilian evasion, nothing at all like pretending to like a gift or a haircut. They’re not even anything like a deliberate, non-white lie, in which there is at least the challenge of darting away from the matter. It’s like being in a conversation based on a deliberate premise of meaninglessness. You take discourse – which is actually quite a sacred thing, a moment in which people of good faith can get closer to one another – and you turn it into the opposite of that. It’s nebulously humiliating, like being naked in public and having as your best and only tactic the plan of diverting people’s attention somewhere else. I felt genuinely sorry for all of them, even Thatcher.