Paying too much attention to your phone is bad for your relationships. This may seem obvious, but it has taken a team of scientists to make us take notice. Phubbing – snubbing someone in your company in order to engage with your phone – has been in the news because researchers in Turkey have found that couples who reported more phubbing also reported less satisfaction in their marriages.

There has been a flurry of research into the impact of phubbing on relationships. Is this because, feeling the effects of myriad micro-ostracisms, we are finally ready to listen? As our phone usage threatens to tip from irksome to destructive, where should the lines of acceptable behaviour be drawn?

If the word phubbing sounds confected, that is because it was coined in 2012 by the advertising agency McCann to promote a dictionary of Australian English. At the time, fewer than half of US adults owned a smartphone, so the idea of being snubbed by someone who owned one must have seemed amusing enough to warrant such a daft word. Of course, we didn’t know then that our relationships were at stake.

“We first started talking about mobile phone etiquette in 2010, 2011, and the problems were nowhere near what we are getting today,” says Liz Wyse, an adviser at Debrett’s, the authority on British etiquette. “We gave very basic guidance: ‘Put it away when you are meeting people,’ that sort of thing.” Her advice hasn’t changed, but “getting out our phones has become such a compulsion that we are doing it unconsciously in inappropriate situations … We are now at a point where it is not manageable. I suppose, eventually, people won’t have the self-consciousness around it to even require etiquette advice,” she says.

It has proved difficult to assert absolute unacceptability in relation to phone habits, or to coalesce around even basic conventions. Do you mind, for instance, if someone you are talking to lowers their eyes momentarily to look at their phone? What about using their phone at the dinner table? Is it OK for you and your partner to scroll while you watch TV together? How many of us can say honestly that we never use the phone in the bathroom?

I spoke to countless people about their mobile phone usage while writing my novel Speak to Me, which features a woman so enraged by her husband’s attachment to his phone that she regards it as the third party in an increasingly high-stakes love triangle. One woman I spoke to had thrown her daughter’s phone out of the window; another had smashed a loved one’s tablet.

People – they were not all women – seethed as they shared the twinge of rage that assailed them every morning when their partner reached for their phone before reaching out to them. There are online forums struggling to soothe the people whose partners check their mobile during sex. My book opens with a scene like this, coitus interrupted by the throbbing of the phone. Surely this is the ultimate phubbing offence?

At home, I strenuously police the no-phones-at-the-table rule. But I have been known – admittedly, only to myself – to play Wordle on the toilet. Does that count as phubbing? Presumably it does if it makes a housemate wait for the bathroom. “Everyone is guilty,” says William Hanson,the executive director of The English Manner, an etiquette and protocol institute.

When did our boundaries get so slack? Should we let them go, in the spirit of progress and transition, or work harder to reinforce them? With the protocol in total confusion, where do the experts see the boundaries?

Using your phone during sex

This includes taking a call, reading a text, checking a notification or even – for the narrator in my novel – pausing when the phone vibrates to look in its direction. As she asks: “When did it become not OK to expect a person’s full attention on a special occasion?”

Diane Gottsman, an etiquette expert and the founder of the Protocol School of Texas, says: “It might be an involuntary reaction. But then put the phone in another room. If it vibrates, we are tempted to look.” If distraction is part of your fun, make it consensual.

Scrolling in the company of your pet

“If the pet needs a walk and you’re on TikTok, the pet takes priority,” Gottsman says. Fair enough. But how about when basic needs are met? What if I am scrolling TikTok while cuddling the cat? I sometimes feel guilty – especially when the cat looks pointedly at my screen. “You get a reprieve,” Gottsman says. “It’s fine, because your pet is also getting petted.” She takes her dog for a walk first thing, then they share a chair while she works on her phone, trying to clear time to have breakfast – with her husband and without her phone.

Waking up and turning to your phone before your partner

This was one of the most common bugbears I came across while researching Speak to Me. “He checks it before he even looks at me, then he rests it on his chest,” said one respondent. Such intimacy! “It’s not as if he’s checking anything important!” Hanson says that he and his husband – the primary victim of his occasional work-related phubbing – try not to have phones in the bedroom: “Get a proper alarm clock. Or put the phone on the other side of the room. It’s good relationship hygiene to greet the humans before the gadgets.”

Taking a call on public transport

I don’t mean talking on loudspeaker in a busy train carriage – all the etiquette experts hate that practice. Taking a call – except the most boringly transactional one, about what time you arrive at the station – is a no-no. “When you are on a bus or train, it’s a confined public space. You are stuck,” says Laura Akano, who teaches etiquette to young people and adults at Polished Manners.

She once got off a bus because another passenger’s conversation became too much. “What they were talking about, and the level,” she says. “I alighted and waited and got on another bus. What makes people not aware of basic decency in a public space?”

As if to bear her out, when I call Wyse, she tells me politely that she is on the bus and asks if she can call me back.

Checking your phone during a meal

“We teach table settings,” says Akano. “No one has created a space yet for the phone or tablet. There is no place for it at the table.”

Staring at a screen while walking

You are alone. There is no one to phub. Right? Wrong! By using your phone while walking along the street, you are phubbing innumerable passersby. “Every time we walk down the street, we make loads of mini-observations and judgments that mean we negotiate the street without inconveniencing other people or barging into them,” says Wyse. “If you look at a phone, you make that impossible.”

Akano sees this often at Victoria railway station in London. “It’s never the young people. It’s always the fully grown adults. Why don’t you move to one side, where you can’t walk into anybody, finish what you are doing, then carry on walking?” she says.

Lowering eyes to a screen during conversation

The narrator of Speak to Me riffs about her husband’s eyelids being “the curtains of the soul”. They are the part of him that she knows best, because he is always looking down. She even considers the possibility of tattooing eyes on to them. “You have to let that be,” Gottsman says. “We have smartphones on our wrist and if you feel the vibration and you take a quick look, it might be involuntary. I think it is important for the person who is doing it to know that, if they look away, it is a disconnect. But I don’t think I can hold judgment against them if they just drop their eyes. We need to give them a bit of grace. It’s human nature.”

Scrolling while watching TV

This is fine if both parties are doing it – and both parties are happy doing it – but not every night. “If my husband and I are in the living room together in the evening, even if we are not talking and we are watching television, that is our time,” Wyse says. “If I was fiddling on my phone, that would be rude.”

Using devices in the bathroom

Taking a phone call while using the toilet “sounds echoey … it’s grim”, says Hanson. It should be inflicted on people only in a medical emergency.

However, although he dislikes the idea of texting on the toilet for hygiene reasons, “it’s not a crime from a manners point of view”, provided you don’t reveal your location to the person you are texting. Hogging the bathroom – for the playing of Wordle, perhaps – is a crime against manners; it becomes a phubbing offence if someone’s bladder is paying the price.

Looking at your phone at a wedding or a funeral

When he had a handset that made it possible, Hanson used to remove his phone’s battery for funerals. “You do not want to be that person who has to touch their phone at a funeral,” he says. Weddings are trickier: “The moment a person gets the phone out to take a picture, they see a message and will be tempted to look.” However, it is not acceptable: “Someone has paid a lot of money for you to be there. For them to see you texting is rude.” He is an advocate of the “do not disturb” feature, which tends to offer a range of settings, plus an emergency override. “The technology is adapting for us to be less distracted,” he says. If only we were more inclined to use it.

Speak to Me by Paula Cocozza is published by Tinder Press (£18.99). To support the Guardian and the Observer, order your copy at guardianbookshop.com. Delivery charges may apply