In the real world, Cooper says that the same behaviours can leave us isolated, anxious and disconnected.
The consequences, she says, tend to be cumulative rather than entertaining.
Research analysing around 100,000 lies suggests about 20% are about managing social engagements - getting out of plans or smoothing over awkward interactions in relationships.
Most people tell one or two small lies a day, the study found.
Frequent lying soon becomes a "risky tactic" says Cooper, as there's the possibility of being exposed.
This latent threat changes how we relate to each over.
Even when a lie is not discovered, the deception forces us to interact at more a superficial level.
Conversations become thinner and more guarded, because detail becomes dangerous.
Over time, that self-censorship can be deeply isolating.
"Lying is really lonely," Cooper explains. "You are creating a solo reality and you are out on a little planet by yourself."
While lies can make the moment feel easier, they often make what comes next harder. The emotional cost is what psychologists call cognitive burden.
"We think about surviving that immediate moment and then you don't think about what happens after this," the doctor says.
Maintaining a false story requires constant mental effort: remembering what was said, to whom, and when which can be "a lot to carry".
So, can lying ever be justified?
It depends on the lie, and who is doing it.
Cooper says not all lies are harmful and some can "protect us psychologically or keep us safe".
She explains that children often lie instinctively as a form of self-protection to avoid being told off and adults may also lie automatically in moments of panic.
She describes a spectrum of severity.
Mild lies of omission are forgivable, while "sticky" mid-range deceptions can often be resolved with support and kindness.
But lasting acts of deceit - like long term affairs - are different.
At this extreme end, she says, the lies can last decades, and impact victims just as long.
Cooper's advice is to "always go gently" on yourself as complete honesty is not always possible or appropriate.
You should focus on self-forgiveness and trying to maintain honesty.
One practical step is to find the truth within what you want to say, and communicate that instead.
For example, it might be instinctive to tell a street fundraiser you already donate to that charity or are too busy to stop.
But rather than inventing an excuse, you can simply say: "That's not for me today."
"The truth doesn't have to be brutal or harsh," she adds.
If you don't want to go to a social engagement, instead of lying you can say: "I don't want to come to the party tonight, but let's catch up another time."
"Practise and it gets easier over time.
"It's not about being found out but about integrity and the kind of person you want to be."