Monkey Sense Without Seeing
November 20, 2013

Monkeys Able To Point To Objects, Even When They Can’t See Them

redOrbit Staff & Wire Reports - Your Universe Online

The human ability to locate and avoid objects in their peripheral field of vision with little more than a sideways glace could also be present in monkeys, according to new research in the journal Animal Cognition.

Lau Andersen of the Aarhus University in Denmark and his colleagues trained five adult male rhesus monkeys in order to perform a short-latency, highly stereotyped localization task.

They taught the creatures to touch one of four locations where an object was presented for a brief period of time on a touch-screen computer. The monkeys were also instructed to perform a second task involving identical stimuli, pressing one of two buttons to indicate whether a specific object was present or missing.

The testing methods are similar to those used on people, allowing for direct comparisons between the two species, and a technique known as visual masking was also used to reduce how easily a visual target could be processed, the researchers explained.

Andersen’s team discovered that the monkeys were capable of locating targets that they could not overtly detect. They were able to complete the tasks with a high accuracy level without the visual mask, and while their performance did drop off some with it, they could still locate targets for which there was no report of said target being presented.

In short, the monkeys were found to be able to detect stimuli even without perceiving them. While the researchers emphasize that the results of their investigation do not firmly establish the presence of phenomenal vision in the monkeys, the discrepancy between visually-guided action and detection were found to mirror the dissociation of conscious and unconscious vision that exists in humans.

“Knowing whether similar independent brain systems are present in humans and nonverbal species is critical to our understanding of comparative psychology and the evolution of brains,” said Anderson.

Earlier this month, researchers from the University of Wisconsin-Madison demonstrated that an ingredient found in the ADHD drug Ritalin could be used to control impulsiveness in rhesus monkeys, improving their ability to forgo instant gratification in favor of a delayed but higher-quality reward.

The research concluded that the substance, methylphenidate, alters the elimination of the brain's reward-neurotransmitter dopamine, allowing a greater amount of the chemical to remain in the brain and altering the rewards-related processing ability of a medicated, normally impetuous monkey. The findings were presented during Neuroscience 2013, the annual meeting of the Society for Neuroscience.