Seeing colors -- New study sheds light on sensory system quirk

July 24, 2007

In the psychological phenomenon known as "synesthesia," individuals' sensory systems are a bit more intertwined than usual. Some people, for example, report seeing colors when musical notes are played.

One of the most common forms is grapheme-color synesthesia, in which letters or numbers (collectively called "graphemes") are highlighted with particular colors. Although synesthesia has been well documented, it is unknown whether these experiences, reported as vivid and realistic, are actually being perceived or if they are a byproduct of some other psychological mechanism such as memory.

New research published in the June issue of Psychological Science, a journal of the Association for Psychological Science, sheds some light on the veracity of these perceptions.

Danko Nikolic, a researcher from the Max Planck Institute for Brain Research in Frankfurt, Germany, and his colleagues relied on a variation of a classic psychological method known as the Stroop task to test this. In this task, participants must name the color of the font that a color word is printed in. For example, if the word "blue" was printed in red ink, the participant would say "red" -- a moderately difficult task that requires some mental gymnastics.

To understand Nikolic's version of the experiment, a rudimentary understanding of color perception is required: When anyone views a particular color, specific neurons in the visual cortex area of our brain are activated. These specific neurons will deactivate, however, if a color from the opposite end of the spectrum is presented. So, any neuron activated when the color blue is present will deactivate when it's exact opposite, yellow, comes into the visual field.

Using this logic, Nikolic presented grapheme-color synesthetes with their five most color eliciting letters or numbers. The color of the letter or number was either the same as its common association (congruent), different but not completely opposite of the color association (incongruent independent), or on the opposite end of the spectrum from the associated color (opponent incongruent). The researchers then measured how long it took the participants to name the color of the grapheme.

As expected, opponent incongruent colors made it quite difficult for individuals with grapheme-color synesthesia to respond quickly. It took participants much longer to name opponent incongruent colors than independent incongruent colors. Congruent colors -- colors that matched the association -- actually facilitated the process of naming the colors.

In a separate experiment, the researchers found that this color-opponency system did not work for memories. They presented the same participants with pictures of objects that a color is commonly associated with (a lemon, for example). But like the previous experiment, the objects were in unexpected colors. Reaction times in this experiment were significantly less impeded by the color change and did not differ from reaction times of control subjects who were not synesthetes. Coupled with the results from the first experiment, these findings suggest that synesthetic colors are perceived in a realistic way, just as synesthetes report.
-end-
Author Contact: Danko Nikolic danko@mpih-frankfurt.mpg.de

Association for Psychological Science

Related Brain Articles from Brightsurf:

Glioblastoma nanomedicine crosses into brain in mice, eradicates recurring brain cancer
A new synthetic protein nanoparticle capable of slipping past the nearly impermeable blood-brain barrier in mice could deliver cancer-killing drugs directly to malignant brain tumors, new research from the University of Michigan shows.

Children with asymptomatic brain bleeds as newborns show normal brain development at age 2
A study by UNC researchers finds that neurodevelopmental scores and gray matter volumes at age two years did not differ between children who had MRI-confirmed asymptomatic subdural hemorrhages when they were neonates, compared to children with no history of subdural hemorrhage.

New model of human brain 'conversations' could inform research on brain disease, cognition
A team of Indiana University neuroscientists has built a new model of human brain networks that sheds light on how the brain functions.

Human brain size gene triggers bigger brain in monkeys
Dresden and Japanese researchers show that a human-specific gene causes a larger neocortex in the common marmoset, a non-human primate.

Unique insight into development of the human brain: Model of the early embryonic brain
Stem cell researchers from the University of Copenhagen have designed a model of an early embryonic brain.

An optical brain-to-brain interface supports information exchange for locomotion control
Chinese researchers established an optical BtBI that supports rapid information transmission for precise locomotion control, thus providing a proof-of-principle demonstration of fast BtBI for real-time behavioral control.

Transplanting human nerve cells into a mouse brain reveals how they wire into brain circuits
A team of researchers led by Pierre Vanderhaeghen and Vincent Bonin (VIB-KU Leuven, Université libre de Bruxelles and NERF) showed how human nerve cells can develop at their own pace, and form highly precise connections with the surrounding mouse brain cells.

Brain scans reveal how the human brain compensates when one hemisphere is removed
Researchers studying six adults who had one of their brain hemispheres removed during childhood to reduce epileptic seizures found that the remaining half of the brain formed unusually strong connections between different functional brain networks, which potentially help the body to function as if the brain were intact.

Alcohol byproduct contributes to brain chemistry changes in specific brain regions
Study of mouse models provides clear implications for new targets to treat alcohol use disorder and fetal alcohol syndrome.

Scientists predict the areas of the brain to stimulate transitions between different brain states
Using a computer model of the brain, Gustavo Deco, director of the Center for Brain and Cognition, and Josephine Cruzat, a member of his team, together with a group of international collaborators, have developed an innovative method published in Proceedings of the National Academy of Sciences on Sept.

Read More: Brain News and Brain Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.