Time, an Intrinsic Human Phenomenon
In metaphysics, time is a fundamental condition of human experience. Immanuel Kant begins The Critique of Pure Reason by exploring the nature of time, identifying it as the most essential element for human experience.(1) Humans are able to recognize the central role which time plays in experience, but still experience difficulty in grasping the essence of time. One of the most difficult attributes of time to understand is the rate at which it moves, since we have no way to measure time objectively. Time moves for everyone, but depending on the situation, time can be a subjective experience. Humans attempt to eliminate the subjectivity of time by using the Earth’s rotation around the sun to dictate years and days and furthermore dividing up these days into arbitrary units of hours, minutes and seconds. But for anything that moves there must be a rate at which it moves. However it is superfluous to measure the rate of time as 60 second per 1 minute. So then, where is it that humans conceive of the nature of time? By looking at two key examples, we can identify aspects of the brain that may in fact provide hints toward not only the human dependence on time, but the nature of time itself.
The nervous system is able to make minute and highly specialized distinctions between events in time. The communication in the nervous system retains intrinsic sense of time. A simple reaction time is the time it takes to react to a stimulus. The average reaction time is between 200 and 270 milliseconds, although it can be even faster among athletes.(2) Interestingly, it has been conventionally accepted that it takes 500 milliseconds for conscious processing to occur, which manifests as cortical or thalamic activity.(3) Recently, this notion has been challenged by S. Kitazawa whose research has shown conscious sensation takes only 80 milliseconds after the stimulus, and at 500 milliseconds this sensation is “localized in space.”(4) This difference has some very provocative implications toward consciousness and what behaviors are constituted as “conscious.” However, the most important part is not the amount of time delay, but that there is a delay itself. It shouldn’t necessarily be surprising that there is a delay between a stimulus and a response, but the implications of such a situation are huge. Humans cannot ever literally live in the present if they are constantly delayed in reacting to stimuli. It is difficult to say whether the time lapse in a reaction time is a result of the system or a construction of the brain. Regardless, the system of sensation and action in response to experience is one that occurs in the present, but responds to the past. Our brain only has the present moment, but its reaction do not sync with the present reality.(5) Humans can thus never experience any simultaneity with time, since they are confined to action and consciousness in an ever-growing past. It is truly the case that “there is no time like the present,” since for humans the present is eternally fleeting.
It is difficult to engage in a discussion about time without discussing consciousness. Consciousness is required to be able to comprehend the idea that all experience happens within time. We must be conscious of ourselves as in a temporal framework of existence. Thus, there must be something associated with human consciousness which connects to the human sense of intrinsic time. We determine time has passed because there is a change. This perception or recognition of a change necessitates consciousness. Humans accept there are successive and simultaneous events, but regardless of the type of event we accept that there has been a change in time.(6) However, it seems more appropriate to think of change as a sequence of events since we can never react simultaneously with them. If the same event is occurring at T1 and T2 these events are happening at different moments in time, and are therefore sequential. Thus, we can consider time as sequentially ad infinitum.(1) The conscious activity of the brain not only has a sense of time, but also preserves time in its actions. Thus, time is not an abstract concept of existence, but rather a construction of the brain which dictates human experience as we conceive of it. Accepting there is both consciousness and unconsciousness presents us with a difficulty. There is a time delay in the conscious realm, but actions seem to be instantaneous in the unconscious realm, driven by homeostasis. So then, what does this say about conscious human activity and the delay time associated with it? It seems plausible to suppose that free-will may influence human actions during this delay period. Humans can only train their brains to increase reaction times up to a certain point, implying that the brain may have limitations to conscious influence. Thus, conscious human activity will always be based in the past rather than the present.
An additional example of intrinsic time is the human “biological clock.” Humans have a Circadian rhythm, or daily cycle, whose control center is located in the suprachiasmatic nucleus (SCN), a group of cells located in the hypothalamus.(7) The Circadian rhythm is controlled by oscillating amounts of the proteins BMAL/CLOCK and PER/CRY in the brain. This system works on a negative feedback loop, dependent on the nuclear receptor Rev-erb? which is cyclically activated depending on the amount of BMAL/CLOCK protein in the system.(8) It is also known that the cells from the SCN have an intrinsic rhythm which they maintain by regulation of photic and nonphotic cues. Using this knowledge about Circadian rhythms, Czeisler et al. investigated the human circadian timing system. The experiment ran from between 28 to 39 days in a “timeless” environment and found the circadian rhythms ranged between 13 to 65 hours, with a mean around 25 hours, regardless of age and sex.(9) Similar to the reaction time delay, the Circadian rhythm demonstrates there is a physiological system to measure time. The Circadian rhythm demonstrates that humans not only maintain a concept of time on a moment to moment scale, but have a greater sense of the passage of time in the broadest sense. This research suggests we have an internal sense of time—unique from reaction time—which is independent of external stimuli.
Showing that time intrinsically exists in human systems does not allow us to conclude where in the system time is, but simply that it is there. Reaction time and the human Circadian rhythm are two examples of time, but they obviously seem to operate independent of each other. Scientific research is far from being comprehensive on this subject, but it is apparent that there must be a symphony of systems working together so that humans are able to apprehend the basic nature of time both on a macro and micro scale. Time is a fundamental and yet complex unit of our experience, and may be a more internal construction then has ever been appreciated. It is not sufficient to summarize time simply by the Earth’s rotational pattern, but rather, a broader recognition of time is required. This discussion has taken a scientific approach to one of the most controversial debates in philosophy. Novelist Salman Rushdie appropriately identifies this temporal paradox which has been constructed in saying, “Reality is a question of perspective: the further you get from the past, the more concrete and plausible it seems – but as you approach the present, its inevitably seems incredible."(10)
1 There are many philosophers who would disagree that time is continuous, but for all intensive purposes of this paper, I will consider time as real, time as continuous and time as having three properties: past, present and future.
1 Kant, Immanuel. “Transcendental Aesthetic.” The Critique of Pure Reason. Cambridge: Cambridge University Press, 1998.
2 “Reaction Time.” http://en.wikipedia.org/wiki/Reaction_time, Reaction time information on Wikipedia website
3 Libet, Benjamin. “A Short Delay.” http://www.consciousentities.com/libet.htm, Libet’s experiments with consciousness and time awareness from Conscious Entities website
4 Kitazawa, S. “Where Conscious Sensation Takes Place.” http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?CMD=search&DB=pubmed
5 Allot, Robin. “Time and Consciousness.” http://www.percepp.demon.co.uk/time.htm, philosophers main ideas about consciousness
6 Kant, Immanuel. “Second Analogy.” The Critique of Pure Reason. Cambridge: Cambridge University Press, 1998.
7“Circadean Rhythm.” http://en.wikipedia.org/wiki/Circadian_rhythm, Circadian rhythm information on Wikipedia website
8 Logan, Dan. “Sleep Patterns and Circadian Rhythms.” Haverford College, Spring 2006.
9 Moore, Robert Y. “Circadian Rhythms: A Clock for the Ages.” www.sciencemag.org/cgi/content/full/sci;284/5423/2102, Science article discussing Circadian rhythm experiments
10 Rushdie, Salman. Midnight’s Children. New York: Penguin Books, 1981.