This blog post is based in large part on an article in New Scientist (10 January 2015, 28-31) by Laura Spinney. Although we feel like we are living in the present, we need to construct the present from what has happened in the recent past. First of all, we need to work with data processed by our senses. Different senses process information at different rates. For example, the auditory system can distinguish two sounds just 2 milliseconds apart, whereas the visual system requires tens of milliseconds. It takes even longer to detect the order of stimuli. There is evidence that even at the subconscious millisecond level, our brains make predictions. For example, when we watch a badly dubbed movie, our brains predict that the audio and visual streams should occur simultaneously, but if the lag between them does not exceed 200 milliseconds we stop noticing that the lip movements and voices of the actors are out of synch. Our brains need to blend these different sources of information coming in at different rates into a coherent present, so we can deal with what is happening in what appears to be now, but is actually the future.
Marc Wittman of the Institute for Frontier Areas of Psychology and Mental Health in Freiberg, Germany has developed a model of how this process occurs by drawing on a very large mass of psychophysical and neuroscientific data (Frontiers in Integrative Neurosciece, vol. 5, article 66). He believes that there are a hierarchy of nows, each of which forms the building blocks of the next, until the property of flow emerges into an the illusion of the present.
Virginie van Wassenhove and her colleagues at the French Medical Research Agency’s Cognitive Neuroimaging Unit in Gif-sur-Yvette have been investigating how the brain might bind incoming information into a unified functional moment. They exposed people to sequences of bleeps and flashes. Both occurred once per second, but 200 milliseconds out of synch. Brain imaging was used to reveal the electrical activity produced by these two stimuli. This consisted of two distinct brain waves, one in the auditory cortex and the other in the visual cortex, both oscillating at the rate of once per second. At first the two oscillations were out of phase and the research participants experience the light and sound as being out of synch. But later they reported starting to perceive the beeps and flashes as being simultaneous, the auditory oscillation became aligned with the visual image. So our brain seems to physically adjust signals to synchronize events if it thinks that they belong together (Neuroimage, vol 92, 274). So it appears that even at the subconcious level our brains are choosing what it allows into a moment. But according to Whittman this functional moment is not the now of which we are conscious. This comes at the next level of his hierarchy, the “experienced moment.”
This experienced moment seems to last between 2 and 3 seconds. David Melcher and his colleagues at the University of Trento, Italy provided a good demonstration of this moment. They presented research participants with short movie clips in which segments lasting from milliseconds to several seconds that had been subdivided into small chunks that were shuffled randomly before presentation. If the shuffling occurred within a segment of 2.5 seconds, people could still follow the story as if they hadn’t noticed the switches. But the participants became confused if the shuffled window was longer than 2.5 seconds (Plos ONE, vol 9, pe102248). So our brains seem able to integrate into a cohesive, comprehensible whole within a time frame of up to 2.5 seconds. The researchers suggest that this window is the “subjective present,” and exists to allow us to consciously perceive complex sequences of events. Melcher thinks that this window provides a bridging mechanism to compensate for the fact that ourackf brains are always working on outdated information. Our brains process stimuli that impinged on our senses hundreds of milliseconds ago, but it we were to react with that lag we would not function effectively in the world. Melcher goes on “Our sense of now can be viewed as psychological illusion based on the past and a prediction of the near future, and this illusion is calibrated so that it allows us to do amazing things like run, jump, play sports or drive a car.”
Wittman acknowledges that it is not clear how all this works. The biological of the experienced moment has yet to be found, however neuroscientist Georg Northoff set of the University of Ottawa has proposed one possibility in his 2013 book, Unlocking the Brain. He speculated that implicit timing could be related to slow cortical potentials that provide a kind of background electrical activity measurable across the brain’s cortex. Wittman notes that it’s telling that these waves of electrical activity can last several seconds. He also notes that consciousness itself is kind of filter because it focuses our attention on some things to the exclusion of others. It could be influenced by factors such as emotion or memory, it might tag or label a subset of functional moments as belonging together, to create an experienced moment.
What about meditators who say they are “in the now?” It is clear that it is impossible to be “in the now.” But is it possible that although they appear to be fooling themselves, they are actually accomplish something good? Data indicate that the answer is yes. Wittman did research in which meditators were able to maintain one interpretation of an ambiguous figure longer than non-meditators. Meditators also tend to score higher on tests of attention and working memory capacity. Wittman notes, “If you are more aware of what is happening around you, you not only experience more in the present moment, you also have more memory content.” He also notes, “Meditators perceive time to pass more slowly than non-meditators, both in the present and retrospectively.”
The final paragraph of the New Scientist article merits direct quotation. “This suggests that with a bit of effort we are all capable of manipulating our perception now. If meditation expands your now, then as well as expanding your mind, it could also expand your life. So, grab hold of your consciousness and revel in the moment for longer. There’s no time like the present.”