The survival of our ancestors on the savannah depended on their ability to detect change. Change is where the action is. You don't need to know that things are the same, the same, the same.
Our nervous system is biased for the detection of change. Do you feel the watch on your wrist or the ring on your finger? Probably not, unless you have just put them on. You don't see the blind spot of each retina because they are unchanging and filled-in by your brain with information from the visual surround. If the image on your retina is experimentally stabilized, the entire visual field fades in a few seconds and you can see only visual stimuli that move through the field of view. You notice the sound of your home's air control system when it turns-on or turns-off, but not when it's running.
Our perception of changing stimulus amplitude is usually nonlinear. The sensation of loudness grows much more slowly (exponent of 0.6) than the amplitude of the physical stimulus, a reason why rock bands have huge amplifiers and speakers. Perceived brightness grows even more slowly than loudness (exponent of 0.33). The sensation of electric shock grows at an accelerating rate (exponent of 3.5), quickly shifting from a just detectable tingle to an agonizing jolt. Our estimate of length grows linearly (exponent of 1.0); a two-inch line appears twice as long as a one-inch line. We are lousy sound, light, and volt meters, but half-way decent rulers.
We are poor at making absolute judgments of stimulus amplitude, basing decisions on relative, ever changing standards. We judge ourselves to be warm or cool relative to "physiological zero," our adaptation level. The same room can seem either warm or cool, depending on whether you entered it from a chilly basement or an overheated sunroom. The lesson of temperature judgment is applicable to other, more complex measures of change associated with wealth and success. For a highly paid CEO, this year's million dollar bonus does not feel as good as last year's bonus of the same size, the adaptation level. The second term of a presidency does not feel as momentous as the first.
The above exploration of how we perceive changes in anything suggests the difficulty of identifying something that changes everything, from the perspective of the individual. The velocity of change is also critical. Did the Renaissance, Reformation, industrial revolution, or computer revolution, have ordinary people amazed at the changes in their lives? Historical and futuristic speculation about events that change everything features time compression and overestimates the rate of cultural and psychological change. As with previous generations, we may be missing the slow motion revolution that is taking place around us, unaware that we are part of an event that will change everything. What is it?