Friday , April 16 2021

Monkeys experience the visual world in the same way as humans

rhesus macaque

Credits: Pixabay / CC0 Public Domain

When people look at a visual landscape like a sunset or a beautiful overlook, we experience something – we are aware of what that scene looks like. That awareness of the visual world around us is central to our daily existence, but are humans the only species that the world consciously experiences? Or do other nonhuman animals have the same kind of conscious experience as we do?

Scientists and philosophers have been asking versions of this question for millennia, but finding answers – or even suitable ways to ask questions – has proved elusive. But a team of researchers from Yale recently devised an ingenious way to try to solve this puzzle.

Writing March 29 in Proceedings of the National Academy of Sciences, they claim that one inhuman species – rhesus macaques – also has a conscious awareness of the world around them.

“People have long wondered if animals experience the world the way we experience it, but it was hard to come up with a good way to empirically test this issue,” said Moshe Shay Ben-Haim, a postdoctoral fellow at Yale and the first author of the paper.

Researchers have long known that people can be affected by unconscious subconscious signs – visual stimuli presented just beyond our conscious awareness threshold, said Laurie Santos, a psychology professor at Yale who, along with senior study author her colleague Steve Chang, is an associate professor of psychology and neuroscience. , and Ran Hassin of the Hebrew University.

“We tend to show different learning patterns when we are subjected to subliminal stimuli than we do with consciously experienced or supralimal stimuli,” she said.

If monkeys show the same “double dissociation” pattern as humans, it would mean that monkeys are likely to experience supralimally represented stimuli in the same way as humans — as a conscious visual experience.

Ben-Haim, Santos, and their team devised a new way to investigate whether macaques also show a difference in learning when stimuli are experienced consciously versus unconsciously.

In a series of experiments, they had monkeys, and people guessed whether the target image would appear on the left or right side of the screen. Before the target appeared, participants were given a visual sign – a small star – on the side opposite where the target would subsequently appear. The researchers differed on whether the sign was presented supraliminal or subliminal. When the sign was displayed for a few seconds, human participants successfully learned that the target would appear in the opposite place from the sign. But when the sign was presented subliminally – fast enough to evade people’s conscious perception – participants showed a different pattern of performance; they continued to choose the side that was subconsciously directed, failing to learn the rule that the sign foresaw the opposite side.

Surprisingly, the researchers found that monkeys showed exactly the same response patterns as humans: like humans, macaques were able to successfully look at a target site when signs were consciously presented, but showed an inverted pattern for subconscious signs. This astonishing result suggests that monkeys have two levels of processing just like humans, one of which must be aware.

“These results show that at least one non-human animal shows both unconscious perception as well as conscious human-like visual consciousness,” Ben-Haim said. “We now have a new nonverbal method for assessing whether other non-human beings experience visual consciousness in the same way as humans.”

Athletes perform better when exposed to subliminal signs

More information:
Moshe Shay Ben-Haim el al., “Disassembling Perceptual Consciousness from Unconscious Processing into Rhesus Monkey (Macaca mulatta),” PNAS (2021).

Provided by Yale University

Quote: Monkeys experience the visual world in the same way as humans (2021, March 29) downloaded March 29, 2021 from

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