They listened to about 1000 examples of requests made during informal conversations between friends, families and neighbours who speak either English, Italian, Lao, the Aboriginal language Murrinh-patha, Polish, Russian, Siwu (Ghana) or Cha'palaa (Ecuador).
The rate some sort of thanks was given in response a request being carried out was just one in 50.
In most cases the response by the person who made a request was for them to continue on with whatever it was they were doing once the other person had helped them.
University of Sydney researcher Professor Nick Enfield, who led the study, said while it seemed standard to say "please" and "thank you" in formal social interactions, people dispense with these niceties almost entirely at home.
However, this doesn't mean they're being rude to their friends and family.
"Instead, it demonstrates that humans have an unspoken understanding we will co-operate with each other," Prof Enfield said.
"Everyday life works because it's in our nature to ask for help and pay back in kind, rather than just in words."
People who spoke English and Italian were found to be more likely to express thanks, while Ecuadorians who speak Cha'palaa never said thank you after someone carries out their request.
The researchers said while English and Italian speakers had relatively high rates of expressions of gratitude, they were still far less often than one might expect given the expectation of politeness in Western cultures.
"In informal interaction between people who know each other well, even English speakers express gratitude just one-out-of-seven times when someone complies with a request," they said in their research paper published in Royal Society Open Science on Wednesday.