The thermostat is possibly the feedback device most easily explained: First, the thermostat has a temperature sensing device: usually a long, coiled bi-metal strip. As the dissimilar metals bonded together expand and contract at different rates, movement is created as the temperature around the thermostat changes.
This movement of the bi-metal strip through levers, moves a mercury bulb to a fro until the "tipping point" is reached and the mercury slides from one end of the bulb to the other, either "making" or "breaking" an electrical control circuit to a furnace or boiler. If the the temperature around the thermostat rises, the bulb moves such that the mercury moves away from the contacts and the circuit to the furnace is broken. If the temperature falls, the bulb moves such that the mercury slides back to the contacts and "makes" the circuit to the furnace, ie. turns-on the heat.
Thermostats have either a FIXED setting, say 72 degrees F or a "dial" ADJUSTABLE setting, say from 50 to 90 degrees F. The "setting" of the thermostat is what determines the "tipping point" of the mercury bulb. [Political Aside: This describes the "old style" thermostat which has recently been outlawed! You guessed it: outlawed because the old style thermostat contained, horror of horrors, MERCURY, a poison! Certainly, THE PEOPLE cannot be trusted with such a deadly instrument in their home. Now, more unreliable and expensive mechanisms are required. NOW, mercury MUST enter the home via compact flourescent light bulbs.]
The thermostat is a feedback device because it turns a furnace on and off and uses room temperature "feedback" ("feedback" is evidence from outside regarding the effect of the thermostat's action, its "turning off and on" of the furnace) to maintain a setpoint. A more complicated thermostat might "modulate/gradually adjust" the operation of a heating device instead of turning it on or off. There are innumerable "feedback" devices in the world of mechanics. Another example is a float switch to control water level in a container via a pump. If the water level drops below the desired water level (setpoint) the float switch "turns-on" a pump or water valve.
Ok, so what does this have to do with the human mind? Well, on the most trivial level, the human LITERALLY IS A THERMOSTAT (and simultaneously many other feedback devices as well)! The human (and many animals) can sense local temperature via the skin. When the local temperature departs too far from the preset comfort zone (72 deg. F?), the human becomes increasingly uncomfortable. The discomfort induces the human to cast about to end the discomfort, initially mostly by "trial and error" though there may be some reflexes like shivering and clutching oneself. The human, when "cold" might try moving to a warmer area, exercising to increase metabolism, finding a warmer area (shelter), building a fire, donning animal skins/clothes, hugging nearby humans, . . . and, ultimately, when technology permits, TURNING ON A FURNACE!
Thus, we see that the human is a thermostat with multiple action options to acheive a temperature setpoint based on pleasure/pain feedback. Mechanical thermostats differ only in that they have fewer action options when temperature feedback departs from setpoint. Many thermostats, do, of course, have more than one action. A thermostat might control and air conditioner and/or heat pump as well as a furnace and possibly multiple "backup" furnaces and/or air conditioners.
The more interesting case, of course, is the interpretation of human behaviour, both instinctual and acquired, as controlled by a feedback system. Too often, instincts are viewed more simply only as "pre-programmed" behaviour triggered by specific environmental cues, ie., the stimulus response model. Typically, the "fight or flight" response to dangerous situations (stimulus) is cited in animals and humans as well.
Of course, everyone admits that, though pre-programmed behaviour definitely exists (running, walking, striking-out, etc.) it is gradually modified and perfected in both humans and animals with experience/practice based on "feedback" regarding effectiveness. We are not talking about pure "reflexes" that occur completely outside the influence of the "learning" nervous system like when the "Dr." taps your knee with the rubber hammer.
It must also be admitted that the "fight or flight" response to various dangers in many animals and especially in humans can often be eliminated entirely through training. For instance, to become a good "batter" in the game of baseball, one must overcome the automatic tendency to step away from the potentially deadly fast ball and even stand firm against the "curve ball" that appears to be heading right at you, but experiences teaches may "break" right over the plate! The "stimulus-response" model simply doesn't explain much, so little in fact that many people conclude that beyond reflexes, instincts are a myth.
Many people also militate against the related concept of innate ideas/images in the human mind and insist on Aristotle's tabula rasa theory of the human mind, ie.. that the human mind starts out like a "blank tablet." Obviously if innate ideas/images don't exist, instincts beyond the very simplest reflexes and responses could not exist.
Jung, with his theory of innate archetypes comes the closest to a theory of explaining "instincts." However, due to his "religious mystical" tendency, I believe he dropped the ball. Much like the ancient Greeks, Jung personifies the archetypes as equivalent to "Gods" and becomes "mystically" enraptured.
The easiest way to confirm the existence of archetypes is to review your appreciation for the image of the opposite (or same?) sex as it evolved in your life. From my earliest memories I recall an obsession with the "looks" of girls. I always knew which girl I thought was the prettiest in my neighborhood, classroom, etc. It seemed also that almost all the boys in a class agreed on which girl or couple girls were the prettiest.
The most reasonable explanation for this phenomenon is that boys (at least) have and inborn archetype (image) in their mind that serves as a set-point for evaluating the attractiveness of girls even when they are very young and otherwise not particularly interested in "taking up" with girls as "playmates". Except maybe in dreams, the individual cannot see the archetype directly. However, everything he "sees" in outer reality is automatically COMPARED to the archetype. Each girl he sees is recognized as relevant to the archetype, but the "prettiest" girl provokes a strikingly pleasing emotion indicating a "closest to match" with the inborn archetype.
In my memory, over 60 years ago, when the culture was less "sexualized", the young boys usually just talked amongst themselves about the "prettiest" and then went back to doing "boy stuff". Now, I'm sure, the culture provokes earlier and earlier sexual behaviour based on these archetypes instead of just recognition of the "pleasing" archetype match. Of course, the evolutionary PURPOSE of the archetype match is to induce the boy to take interest in the girl and eventually discover sex and reproduce. The focus on the "prettiest" may be "designed" as an inducement to select the healthiest for reproduction purposes. Presumably, this works in approximately the same way with girls, but in mirror image.
Thus, we see that the inborn image of the opposite sex or archetype functions like a thermostat setting ultimately provoking action toward acquiring a suitable mate for sex and reproduction instead of turning on a furnace. Again, the inborn set-point or archetype acts not DIRECTLY, but indirectly by creating a pleasurable sensation when an outer image is found that "matches" as close as possible the inner, unseen archetype.
It should be added that the inborn archetype (setting) may be adjustable, either consciously or automatically via experience, much like people learn to adjust a thermostat to their liking, but not outside the range ALLOWED by the device. To jump ahead, psychological "problems" from neuroses to psychoses may involve difficulties in adjusting archetypes and/or the response to archetypes. . . (to be continued)