September 30, 2012
Visual Cues – Our Eyes Tell Our Brains What To Think
Alan McStravick for redOrbit.com - Your Universe Online
We´ve all heard the expression, “One hand washes the other”. But according to a recent study, we are learning that an action such as this, or even a mundane task, performed by an estimated 54 percent of Americans daily, such as drinking a cup of coffee, involves a complex set of decisions that our brain must make, often times while hiding the entirety of the decision-making process from us.
In the coffee example, your eyes, as the primary source of information for the brain, must look at the cup, judging the aim of your hand, projecting the weight of the cup and contents, and informing you how to raise and turn the cup so as to ensure that the potentially scalding contents are not spilled.
The study, out of Northwestern University, uses this “salient example,” according to lead author Yangqing ℠Lucie´ Xu, a doctoral candidate in psychology at the university. “When you pick up an object, your brain automatically decides how to control your muscles based on what your eyes provide about the object´s shape. When you pick up a mug by the handle with your right hand, you need to add a clockwise twist to your grip to compensate for the extra weight that you see on the left side of the mug."
"We showed that the use of this visual information is so powerful and automatic that we cannot turn it off. When people see an object weighted in one direction, they actually can't help but 'feel' the weight in that direction, even when they know that we're tricking them," Xu said.
To prove this hypothesis, researchers on the study conducted two experiments. The first asked participants to grasp a vertical stick with a weight hanging from its left or right side. Those performing in the study, even with their eyes closed, had no trouble discerning on which side they felt the weight.
The second part of the first experiment then utilized a set of mirrors that were used to occasionally flip the view of the object, giving the appearance that the weight was on the opposing side from where it actually was located. The study participants were asked to report where they felt the weight was located on the stick. This portion of the experiment showed visual cues strongly influenced their perceptions, especially when the weights were lighter.
The second experiment involved the researchers explaining the “trick” to participants and then asking them to ignore the visual information they were receiving.
“People still could not ignore the visual information,” explains Xu. “In fact, the effect even works on us (researchers), and we designed the experiment!”
Co-author of the study and associate professor of cognitive psychology at Northwestern, Steven Franconeri, explained that the brain is constantly making decisions that we don´t know about or understand.
"These decisions are usually smart and based on vast experience," he said. "In this study's example, your brain is automatically using visual information to tell your hands what they are feeling. We can show that these decisions are happening by manipulating the information your brain receives -- we mirror-reverse the visual information and your brain now tells your hands that they are feeling the reverse of what they are actually feeling. This inference is mandatory -- you feel it even if you know it's not true."
Franconeri said this is not a "bug" in the brain's operation.
"In the vast majority of cases, you want to 'delegate' decisions like this to the unconscious parts of your brain, leaving you free to focus on less straightforward problems, like following driving directions or enjoying your cup of coffee."
Also co-authoring the study were Shelan O´Keefe and Satoru Suzuki. Their findings are published in the current issue of the journal Perception. A visual representation and description of the study can also be found here.