Given that they were given no guidance on how to regulate their mental activity, each person had their own unique thoughts when carrying out the task – and, when asked, not one of them claimed to have visualized the color red. Nevertheless, after repeatedly carrying out the experiment more than 500 times over three days, volunteers soon began to get the gist of it, and regulated their mental functioning so that, whatever they were thinking about when looking at the black lines, the activity in their primary and secondary visual areas resembled patterns associated with the color red.
In the process, they unknowingly conditioned themselves to associate all grated lines with this type of brain activity, like crimson-slobbered Pavlov’s dogs.
The day after completing this intense associative learning task, the volunteers were shown a number of grated-line patterns of varying colors and asked to describe which colors they saw. Amazingly, those who had been the most successful during the first part of the experiment were more likely to perceive these lines as red, even when they were not. Perhaps more staggeringly, this effect was found to persist five months later.
There is of course a long way to go before this kind of mental trickery can be put to any practical use, although Watanabe hopes to one day use it to help people alter their own brain activity so that patterns associated with depression or autism are corrected. How achievable that is, however, will depend on the outcome of future studies.