Signal in Noise

July 07, 2013  •  Leave a Comment

I better begin this by asking any reader to stick with me on this till the end. We're going somewhere (I'm not sure myself just where right now) and hopefully we do get there and we find the destination worthwhile.

In communication engineering one gets introduced to the "signal to noise ratio" (SNR). The 'signal' is the stuff that the sender intentionally wishes for the receiver to recover, the 'noise' is everything else that the receiver recovers as well in his attempt to acquire the signal. The receiver gets both signal and noise and has to filter out the noise part. This notion of signal and noise can be much more general however. Signal can represent anything that the receiver gets from the environment (surroundings) that has potential to provide some value to the recipient. Noise is everything else in the environment that the receiver also gets but does not use, the stuff that is filtered out in the search for signal. When the 'receiver' is a human being, he/she gets data from the environment via his/her senses: vision, hearing, smell, touch and taste. Since this is a photography web site (it is a photography web site isn't it?) let's concentrate on the vision thing.

During our waking hours, our eyes are continuously bombarded with data. In the sense of the discussion above, I will call it noise. Depending on what we are consciously engaged in at the moment on a subconscious level our brains are filtering that noise looking for signals within it - stuff that matters. What sort of stuff matters? Well it could be signs of a threat to our safety and well-being, e.g. a bear or other threatening wild animal in our path, a run-away automobile bearing down on us, etc. It could be, and thankfully usually is, more benign, e.g. an acquaintance entering one's field of view, a scene or image that reminds one of a pleasant experience, etc. Even if we are consciously engaged in something involving our vision, e.g. reading a book or driving, in which case our vision is consciously engaged in the act of processing some signal, subconsciously our vision is still engaged in filtering noise in the data received by our eyes, for example via our peripheral vision.

The psychologist Daniel Kahneman theorizes that human brains have two distinct components for processing information. In his book Thinking Fast and Slow (a very worthwhile read) he calls these components simply "system 1" and "system 2". System 1 is fast and intuitive, system 2 is deliberate and analytical, but as a result also somewhat slow. Sensory data is initially processed by system 1 - it acts a a gatekeeper if you will - and only passed on to system 2 if system 1 perceives some signal that merits further deliberative attention. While walking along if one's vision suddenly takes in the sight of a lion, system 1 will send a "flight" response to one's muscles, not waiting for system 2 to analyze the situation. After the initial flight response, and while running away, system 2 will be performing analysis of the situation and possibly offer more reasoned additional options beyond just running to insure safety. For another example, when driving a car on a clear straight road with little traffic, system 1 is sufficient to process the visual data in order for the driver to safely control the vehicle. But, when in heavy traffic or on a winding road, then system 2 is called upon to aid in the effort, it must be applied to analyze the incoming visual information and guide our response if we are to remain safe and in control. Now as I recall Kahneman does not use the word 'signal', I am putting it there since I believe it means essentially what he describes as the relevant incoming data to which our brain responds.

Now what about visual arts? Here we leave Kahneman and his theories and go back to my musings. System 1 can initially process our reaction to viewing a piece of visual art. Our quick "I love it" or "Ugh, I hate it" is a fast, intuitive reaction to an image. If our reaction stops there, whether love or hate, and we move on, then the 'art' did not really have much value for such a viewer, essentially the image is noise. Possibly we can consider it to be pleasing noise if the reaction was "I love it" but noise none-the-less. It is only if the viewer was compelled to engage system 2 and consciously and deliberately reflect on the image and seek the signal, seek the message therein, that the image is truly art. The beauty of signal processing within the human mind is that the signal the receiver perceives can have no obvious relation to the message being sent by the  transmitter (whoever or whatever that is). What one person 'sees' in viewing the Mona Lisa, that is the signal his system 2 picks out when his eyes process the data of that image, can be very different from the signal another person discerns when viewing the same image, and both of these can be different from whatever it is Leonardo Da Vinci intended.

I hope that whoever stuck with this item till now finds some signal in the noise of my musings.


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