David Peat

94 From Certainty to Uncertaintyseries of guesses: Is that a blue moving car or simply the wind disturbingthe reflection of the blue sky on a lake? Is that dark patch a shadowor could it be the black fur of a stalking animal? Is someone hiding inthat bush or is it merely a pattern of foliage?The eyes are constantly looking for certainty while the brain dealsin doubt. This is where the intentionality of vision comes in. Frommoment to moment the brain seeks out what is relevant from withinthe information that it is receiving. It is constantly making hypothesesabout the world around it and, like a Popperian philosopher, it needsadditional information in order to reject some of these hypotheseswhile provisionally accepting others. For this to happen the brain mustinstruct the eye where to look and what to look for. Therefore signalsare constantly being sent to the muscles around the eye in order todirect it to explore various areas of the visual scene and gather moreinformation.Not only is information constantly streaming up the optic nervetoward the brain, but equally important, a series of questions and interrogationsis flowing downward from the brain toward the eye. Thesetwo streams meet at points all along the optic nerve. The signals comingdown from the brain interrogate upcoming raw data and ensurethat only significant information reaches the visual cortex—in otherwords, those answers that help the brain reject certain visual hypothesesand provisionally confirm others.An analogy would be a hypothetical filtering system attached toyour email program. It would scan the content of each message at themoment it is being downloaded from your server. Messages from closefriends and from colleagues relevant to your work get through and aredisplayed on your screen; but junk email, advertising, chain letters, andso on are dumped in the Trash bucket. Moreover, the system is an intelligentone, for it is constantly scanning the work you have been doingon the computer so as to detect what will be significant to you frommoment to moment. In this way you only receive messages of immediateimportance and need not bother about the rest.It is the same with vision. The brain doesn’t want to be overloadedwith everything the eye is detecting. It is only interested in informationrelevant to the scene it is attempting to build up, as well as monitoring