Image copyright AFP Image caption The photographs reveal the animals’ personalities, biologist Galarza suggests
Humans pick up on two particular ways in which the emotional state of other animals differs from their own, a study has suggested.
Research by US psychologists shows that – apart from in the case of bizarre behaviour – monkeys and bears are often like us in their patience.
The science journal, Proceedings of the National Academy of Sciences, reports on the study.
The findings are published on the day of Martin Luther King’s birthday.
For the study, the researchers examined 300 individual photographs of monkeys taken over a period of 11 years.
The monkeys – some of which were given information about where they were being photographed – generally held their heads lower than they normally would in a natural world setting.
“We know in theory that people like to sit and gaze at nature, and their level of inclination is of interest to us,” said Maria Galarza, a psychology professor at the University of Texas and co-author of the paper.
Image copyright AFP Image caption Many of the images depicted monkey left-facing rows
One of the reasons the primates made the slight display is that they seek to be noticed by other animals, the researchers suggest.
Overall, most of the photographs portrayed the animals in a way that corresponded to the moral maxim “do unto others as you would have them do unto you”.
The performance was more noteworthy when the photographs were taken outside a human’s natural environment.
The monkeys exhibited the behaviour when “citizen scientists” took photographs that were being compared with some of the original specimens of the same monkey.
The scientists hope that taking a similarly close look at selfies will allow them to better understand the animals’ thinking process.
They also found that the snaps could reveal the animals’ personalities.
A monkey looked “very much like a human”, while another was pictured in “a solitary pose, with no socialising with its peers”, Prof Galarza said.
Yet another looked “very much like a chimp”, and a fourth appeared to be engaging in “selfish behaviour”, Prof Galarza said.
But all of the animals would have looked the same without the photos, she insisted.
The study, in particular, opens up the subject of “how these things shape us,” said Gerhard Dolch, an imaging scientist at Weizmann Institute of Science in Israel, who was not involved in the research.
Image copyright AFP Image caption Alpha and Argus, monkeys shown in one of the photographs were shown to be more solitary than their environment suggested
In theory, to distinguish between different humans, one would need to have access to about five different set of photographs from different settings in order to tell the difference, Dr Dolch said.
The attention to the mood of others and the quality of the images themselves, however, seems to have been shaped by humans.
“This aspect of them is part of their way of being… this is not just a behavioral trait that is somehow formed by having an evolutionary explanation, [although] it is likely one,” said Prof Gurpreet Singh, one of the report’s authors and researcher at Stony Brook University in New York state.
Prof Singh added that he was not surprised by the primate results.
“It is simple psychology,” he said. “It is very intuitive.”
“We already knew that human emotion is reflected in an object, in how it looks, in its expressions, in how it behaves in the presence of others.”
“So, we already knew this about animals in a fundamental way, and very intuitively.”
Image copyright AFP Image caption Many of the photographs the researchers analysed related to the animals’ facial expressions. Image caption This image was taken when the animals were not in the picture
The images provide a glimpse of “how these different emotions affect their behaviour,” Prof Singh said.
“We are happy to know that the behaviour affects them too,” he added.
Dr Dolch added that in human psychology, the most noticeable form of self-regard is also most easily observable.
“That is selfish, in the sense that you express it to others,” he said.
Dr Dolch, who coined the phrase self-regard, has previously argued that the primary subject of any study on self-awareness was how much a subject appreciated themselves.
This study shows what this behaviour does when it is not self-regard, he added.