When do you accept a bag search as simple store policy and when would you start to think you're being treated with more suspicion than other shoppers?

Catherine Piota spoke up when she started to suspect she was having her bag searched far more often than white customers at her local shop in the West Australian coastal city of Geraldton.

She said she confronted the shop's manager to complain that she was being singled out because of her skin colour.

"I was told it wasn't the case," Ms Piota said.

"I said, 'well you haven't asked the lady in front of me and you're certainly not going to ask the lady behind me or I'll be watching'.

"So she then checked the bag of the lady behind me because I stood there and watched."

Ms Piota was raised in Switzerland by her Aboriginal mother and Swiss father. She grew up in Switzerland before moving to Australia as a young adult.

Exclusion, suspicion from both sides

Catherine Piota with her kids Naomi, Xavier and Michael Piota in Switzerland in December 2016. ( Supplied: Catherine Piota )

Ms Piota has had no complaints about the police but as an Indigenous woman who did not grow up in her mother's country she has an outsider's perspective on the question of unconscious bias.

She said when she first moved to Australia, Aboriginal people would question her background.

"They didn't think I was Aboriginal," Ms Piota said.

"They'd look at me and say, 'you're not a black fella, you talk funny'."

"Yeah, I know I talk funny because it's not my first language and I'd have to explain that."

As she settled into life in Australia, she said she witnessed bias and prejudice.

"It's a shopping centre, a taxi driver. We have to pay upfront or they won't take us," Ms Piota said.

"I took a taxi from Rangeway [a suburb of Geraldton] one night. He wouldn't take me downtown unless I gave him his $50 in his pocket.

"I was born with club feet. I can't run."

Evolutionary forces underlie bias

West Australian Police Commissioner Chris Dawson last month apologised to Indigenous Western Australians at a NAIDOC week event over "unconscious bias" in the police force.

WA Police Commissioner Chris Dawson makes an apology to Aboriginal people on behalf of the WA Police. ( ABC News: Lindsay Brennan )

Murdoch University psychology researcher David Lewis said unconscious bias was an automatic process in which everyone engaged.

"It could be any category, from a category of race, to a category of age, to a category of gender," Dr Lewis said.

"Everybody's mind is always doing this and I think the real problem is not so much that our minds are doing it, but rather that people are unaware of it and they're scared to know that their minds are doing it."

From an evolutionary perspective, human beings used unconscious bias because it facilitated decision-making, Dr Lewis said.

Murdoch University researcher David Lewis says unconscious bias facilitates decision-making, but doesn't have to lead to prejudice. ( ABC News: Emily Piesse )

"We wouldn't have been very functional organisms if our minds didn't stereotype," he said.

"For example, when you go to the supermarket, you see a bunch of oranges and you assume that all of them are edible oranges. Your mind is actually making a stereotype.

"It's based on previous experience interacting with that type of object, so it's making an assumption that all of those objects themselves are oranges, as opposed to evaluating each individual one. It's not functional to have to evaluate each individual one that you encounter."

Dr Lewis said unconscious bias did not necessarily lead to prejudice or behavioural discrimination.

"Racism is the product of mechanisms in the mind that are designed to track coalition, and so I think the most important thing that we can do is we can create coalitions between individuals that aren't on these lines," he said.

"Although the mind initially tracks race as a cue to coalition, once teams are formed, once groups are formed that are racially mixed, the mind's tracking of race actually disappears."

'Challenge assumptions' to overcome bias: support worker

City of Greater Geraldton youth support worker Simone Mahoney says children are enduring racist slurs and subtle but hurtful racial bias. ( ABC News: Cecile O'Connor )

City of Greater Geraldton youth support worker Simone Mahoney said young Indigenous boys in particular felt singled out by people who suspected them of committing crimes.

"I've had discussions with a lot of kids who've been told Aboriginal kids should be killed," Ms Mahoney said.

"Why should any child be told that another child should be killed? [These are] outright racist slurs towards them.

"If they're walking down the street and people turn their heads away or clutch their handbags a bit tighter, then how do they feel that they belong?"

She said one group of teenagers had told her about being abused by a white woman in a park after her car was hit by rocks.

"It was not the same group of kids. The way they reacted is, first they copped it on the chin until she left, then they were really angry and upset that they'd had to hear 'the children should be killed' and it was 'their fault'."

Ms Mahoney said unconscious bias was one thing, but once people's conscious thought kicked in, it elevated their actions to a new category of severity.

"I believe unconscious bias is unconscious because you're not aware of it," she said.

"As soon you're aware of what you're saying or your actions, it becomes conscious and it leans towards racism.

"I think it's up to us to challenge ourselves in our first assumptions and challenge our mates at a family barbecue. If they're making an assumption about an event, an act of vandalism, ask them for their proof."