In previous seasons of I'm A Celebrity Get Me Out Of Here, all but one of the winners and runners-up were professional sportspeople. Which is no surprise to Kate Baecher​, the program's resident psychologist. 

They're accustomed to working in groups, Baecher says, so they don't expect others to do everything for them. This endears them to viewers, who punish self-centred contestants by voting them off.

For solo athletes, it can be a different story.

"The ones whose world is very individualistic tend to struggle," she says. "It doesn't occur to them [that] they have to participate as a team."

This interview took place just before the current season began filming. As if proving Baecher's point, tennis player Bernard Tomic and boxer Anthony Mundine subsequently became the first contestants in the show's history to quit.

This isn't exactly shocking. After all, the premise allows for celebrities to quit at any time by shouting the name of the program. But most choose to tough it out – enduring the disgusting food trials and physical challenges – to win money for their chosen charity.

Everyone is different, Baecher stresses, and a person's profession does not determine how they fare on the show. Comedians, for instance, may be advantaged by their embrace of the absurd (which comes in handy when they're forced to eat pigs' eyeballs). On the other hand, those who use humour to distract themselves from unexamined emotions can come undone.

What viewers rarely see is the down time; the endless hours that can be challenging to fill. 

"There's a whole range of things that humans do to avoid all the intrinsic murkiness we have," Baecher says, listing food, social media and smartphones as examples. 

By definition, celebrities exist in relation to their audience. When their connection to fans is severed, they can flounder.

"In the outside world, there is so much more validation and many more accolades," Baecher says. "This [experience] takes everything away. They have to get to know who they are, warts and all. They can't get away from that, they have to face it."

She knows that a person's childhood influences how they interpret – and react to – current situations. Someone whose parents were highly critical, say, could misconstrue a critique as an attack. Perhaps they've developed an acid tongue to defend themselves. Or maybe they unwittingly provoke others to mistreat them as their parents did – not because it feels good, but because it feels familiar.

"There could be a difference between their self-worth based on achievement versus character," Baecher says.

"They're unaccustomed to not achieving."

When this happens, Baecher asks them to analyse their "failure". Sure, they couldn't complete a stunt during filming – but does that justify their feeling worthless?

Sometimes, suffering has more prosaic origins. 

Coffee drinkers invariably underestimate how wretched they'll feel without caffeine. A letter from a loved one – after weeks without contact – can trigger floods of tears. Most find the physical confinement particularly arduous. "Your whole world becomes smaller," recalls former contestant Nazeem Hussain, "and suddenly you're having a passionate fight about who stole Tziporah Malkah's red sock."

Cynics assume that Baecher – who also works with refugess in Bangladesh – is a puppet of the producers, using psychological tricks to manipulate contestants. In fact, the program has no control over her activities. She even has the power to halt production if someone needs urgent attention.

"[The contestants] go through huge changes," she says. "One of the greatest things is that they learn who they are, away from their achievements."

Twitter: @Michael_Lallo