Understanding another's expectation from action: The role of peripheral sensation

Psychology researchers have long understood and accepted the importance of an individual's brain activity in motor areas when interpreting the actions of others. However, much less was known about the role the body plays in helping individuals process and understand the same information.

With the help of two patients suffering from an extremely rare degenerative neurological condition, a Rutgers-Newark Psychology Professor and his team of researchers have established that the body plays a significant role in helping humans to perceive and understand the actions of others.

In the article, "Understanding Another's Expectation from Action: The Role of Peripheral Sensation," that will appear in the October 2005 issue of Nature Neuroscience, Rutgers-Newark Psychology Professor Guenther Knoblich is among a group of researchers who contend that individuals use the human body's senses to understand others actions and expectations. The researchers reached this conclusion by performing experiments with two individuals suffering from the rare neurological disorder of selective and complete haptic deafferentiation due to sensory neuronopathy. The participants are the only two known individuals in the world whose sense of touch and body movement was completely eradicated by the degenerative disease.

The individuals participated in tasks that tested their ability to gauge the weight of boxes which were lifted by other individuals and their ability to infer weight expectations of the observed individuals. Their performance was compared against a control group comprised of healthy individuals.

"In order for an individual to perform a motor activity simulation, you need to know how it feels to perform the action," Knoblich notes. "The two deafferented individuals do not feel their bodies. They must see their bodies to perform the simplest actions, such as standing upright. We asked whether their lack of body perception would also affect their ability simulate others' actions while observing them."

The tasks involved individuals observing someone lifting a box and attempting to determine and report the object's weight. In some of the instances, the individuals doing the lifting were correctly informed of the boxes weight. In other instances, investigators misled the lifting person about the weight of the box. The patients and control group viewed videos and afterwards either estimated the weight of the box or reported whether or not they thought that the person lifting the box was deceived beforehand about its weight.

"We observed that there was no difference in the responses when the two groups were asked to estimate the object's weight," Knoblich explained. "However, when performing the expectation task and asked to determine whether or not the person lifting the object was deceived about its weight, the patients couldn't do it."

According to Knoblich, the patients were unable to accurately respond to the expectation task because they could not perform a motor simulation. However, they were fully able to process the simple perceptual cues which indicate the weight of the object. Knoblich said these results go a long way toward establishing the view that the body's senses are critical to a human's ability to understand the actions and expectations of others.

"It solidifies the new embodiment view that is becoming increasingly popular in the cognitive and neurosciences," Knoblich notes. "It is interesting that there seem to be parallel developments in science and art. While science questions the assumption that human cognition can be viewed as disembodied, computer-like information processing, many contemporary visual artists and performers seem to move away from abstraction to re-discover the human body as an object of art."