Thinking Makes it So: Banana Version
The BPS Research Digest blog summarizes a colorful story:
Often…what we actually see is based less on the outside world and more on what our brain expects to be there, like a kind of mentally-generated virtual reality.Now psychologists in Germany have demonstrated this in an elegant experiment involving people’s memory for the colour of everyday fruit and vegetables.
Karl Gegenfurtner and colleagues presented 14 participants with strangely coloured fruits on a computer screen – for example a pink banana – against a grey background.
The participants’ task was to adjust the colour of the onscreen banana until it blended exactly with the grey background. It sounds easy, but the participants couldn’t do it because as they adjusted the colour, they compensated not just for the banana’s actual pink pigmentation, but also for a yellowness that only existed in their mind, thus leaving the banana with a slight bluish hue. That is, their memory for the typical colour of a banana was interfering with their performance.
By contrast, the participants didn’t have any trouble adjusting the colour of anonymous spots of light to make them blend in with the grey background – thus suggesting it wasn’t some quirk of the experimental set-up that was causing the participants difficulties with the fruit and veg.
Cite: Hansen, T., Olkkonen, M., Walter, S. & Gegenfurtner, K.R. (2006). Memory modulates colour appearance. Nature Neuroscience, DOI:10.1038/nn1794.