A new study suggests the placebo effect - people perceiving a change simply thanks to being told there is one - affects video games.

Led by University of York human-computer interaction professor and research student Alena Denisova, the study started with 21 participants playing two rounds of survival game Don't Starve.

In the first round, players were told the game's map would be procedurally generated - which it was.

But in the second round, the researchers told subjects they were playing a different version of the game with AI that adapted its difficulty to suit the player.

In actuality, both rounds featured the same game code.

Participants universally noted differences in difficulty in the second round, with some saying it was harder and some saying it was easier.

One player said, "the adaptive AI put me in a safer environment and seemed to present me with resources as needed," while another believed it "reduces the time of exploring the map."

Once confirmed with a second, 40-member experiment, the findings were presented at the CHI PLAY human-computer interaction conference this month.

Cairns and Denisova say developers need to bear the placebo effect in mind when creating and marketing games.

One recent example of the video game placebo effect occurred at gaming site VG247, where a writer played the remastered Uncharted 2, believing it to be Uncharted 4, and wrote a preview article accordingly.