Color and touch are separate perceptions but a recent study has suggested that they might be more linked than previously thought. A study reported in Scientific Reports had subjects put their hand on a red or blue surface and the results showed they found the blue surface to feel warmer than the red, even though the surfaces actually had the same temperature.
In the experiment, subjects sat in a dark room and placed their hands on a surface that was either red or blue. The subjects were told to report whether the surface felt warm. Results showed that red surfaces need to be about 0.5oC warmer than the blue surfaces for the subjects to say it was warm.
The study was carried out at the NTT Communication Science Laboratories of the Nippon Telegraph and Telephone Corporation in Japan. Since this laboratory was part of a corporation rather than in a university setting, it was likely carried out with practical applications in mind. The study was likely designed to answer questions about color and hand-held communication devices rather than to answer basic questions about color and touch. The results from their study, however, provide food for thought about the link between color and touch perceptions.
Color perception is a quality of vision. Objects or lights appear as colored based on the relative amounts of different wavelengths of light that reach the eye and are processed by the retina and brain. Long-wavelength light, say between 600 nanometers and 700 nanometers in wavelength, are perceived as red. Short-wavelength light, say between 400 nanometers and 480 nanometers in wavelength, are perceived as blue. Wavelengths in the middle are perceived as green or yellow. Three types of cells in the retina, commonly called red, green and blue cones, receive the light coming into the eye and begin the process of analyzing wavelengths and determine what the color perception will be. The brain receives this information from the optic nerve that extends from each eyeball to the brain.
Touch perception occurs when receptors imbedded in the flesh under the skin respond to mechanical pressure. A special type of touch receptor, called a thermoreceptor, responds to cold or hot stimulation. The signals from the touch receptors then travel through peripheral nerves to the spinal cord, up the spinal cord and then to the brain to create touch, hot or cold perceptions.
The brain must receive information from a sensory system in order for perception to occur. It is therefore not surprising if some sensory systems interact with other sensory systems while the information is being processed by the brain. Some sensory systems are more intertwined together other than others. Smell and taste, for example, are linked to each other in that the smell of foods often affects their taste.
In the reported study on red or blue feeling warm or cold, two perceptions that are not normally associated with each other were linked. The visual perception of red was linked to temperature differently from visual perception of blue, even though not as expected. If the two sensory systems were not linked in some way in the brain, the expectation would be that temperature was perceived to be the same whether the surface was red or blue. A likelihood in this experiment was that the experimental set up was very unusual in that it was very isolated and was not a usual setting found in a house or in nature. Red feeling cooler than blue means color and touch perceptions were interacting in a way that is not normally noticed.
By Margaret Lutze