Published today in Proceedings of the Royal Society B, the study found that while the baboons noticed and responded to a laser mark shone on their arms, legs and hands, they did not react when they saw, via their mirror reflection, the laser on their faces and ears.
It was the first time a controlled laser mark test has been done on these animals in a wild setting and strengthens the evidence from other studies that monkeys don't recognise their own reflection.
The researchers observed 120 Chacma baboons in Tsaobis Nature Park, Namibia, between May and October 2021 to better understand self-awareness among wild non-hominid primates, who have previously been tested almost exclusively in captivity.
Study author Dr Alecia Carter (UCL Anthropology) said: "We define self-awareness as 'the capacity to become the object of your own attention' and we test this capacity by assessing an individual's ability to identify an image of themselves.
"The Chacma baboons we observed in Tsaobis Nature Park certainly enjoyed using the mirrors as a new toy, but throughout our study they didn't quite understand that the mirror's reflection represented their own bodies and that the laser mark in the mirror image was, indeed, on themselves.
Dr Carter continued: "Anthropologists have been trying to measure self-awareness in animals for 50 years, but studies have lacked control conditions and focused on small numbers of animals raised in captivity. Our study is the first controlled laser mark test to be conducted in a wild setting and we hope it will act as a framework for future visual self-recognition studies."
In Namibia, the researchers began by allowing the baboons a period of mirror exposure to learn about the reflective surface. Reflective surfaces are uncommon in the baboons' arid natural habitat, in contrast to primates raised in captivity who may have had more exposure to their own reflection.
As shown in the footage, a red or green laser pointer was first shone on a visible part of the baboon's body, such as their hand or foot, to determine whether the baboon would investigate a mark visible on their own bodies. The baboons found the mark visually compelling, showing their curiosity by touching and scratching the mark.
The laser was then shone on a part of their body the baboon could not see unaided, such as their ear or cheek. While sat in front of a mirror, the baboons did not react or respond to the laser mark in the same way, suggesting they did not identify the baboon in the mirror as themselves.
Overall, interest in the lasers decreased with the age of the baboons and was greater among males than females. They also found that the baboons responded more to the green, rather than the red laser mark. The researchers compared a total of 361 laser experiments across 120 baboons.
Corresponding author Esa A. Ahmad said: "Our study provides a fantastic framework for scientists and anthropologists to continue researching the self-awareness of non-hominid primates in their natural setting.
"As the baboons didn't touch the marks when viewed indirectly, this research confirms that monkeys don't spontaneously recognise themselves in a mirror. But, given the monkeys quickly familiarised themselves with their mirror image, it also suggests that they don't consider their reflection to be a stranger."
Ethical permission to conduct the research was granted by the Namibian National Commission on Research Science and Technology and the Zoological Society of London Ethics Committee.
