4. Why You Don't Notice the Refrigerator Humming (But Jump at a Doorbell): A Look at S-R and State System

When you hear a sudden loud noise, have you ever jerked tensely just to disregard it minutes after? The constant hum produced by the refrigerator would be something you ignored until someone explicitly mentions that? These apparently insignificant interactions highlight the two fascinating processes named as habituation and sensitization. However, how do these processes function? Let’s have a look at two important systems at play: the state system and the S-R (Stimulus-Response) system.

Think about a simple reflex that you may have, like blinking in response to someone approaching you. This automatic, timely response is the result of the S-R system. It's essentially a "reflex arc" connecting muscle output, which is blinking, to sensory input, or the item approaching. The S-R system becomes more used to the stimuli with each repetition. This suggests that the brain's response lessens when it views a stimulus as non-threatening. The blinking decreases or even stops, demonstrating the primary feature of habituation—stimulus specificity. 

Now let us have a look at the other important system: The State System (Managing alertness and Reaction Capabilities). So, what happens when there's a loud blast that follows an initially harmless sound? At this point, the state system becomes involved. Unlike the direct relationship of the S-R system, the state system acts more like a conductor, influencing the organism's overall reaction. Events such as the boom that shake the state system increase public sensitivity. Sensitization is the reason why the sound still makes people anxious, even if it was initially disregarded.

Since we all know that the brain is not an isolated organ. So the complex interplay between these systems namely S-R system and state system determines the final response of the individual. The more frequently the S-R system brings about a harmless sound as a habituation signal, the better it can cancel out the state system's heightened arousal (after the bang). On the other hand, a highly aroused situation (such as being chased by a dog) may override S-R habituation and cause you to feel fearful even when you hear familiar sounds. The S-R and state systems provide a solid foundation, but the real world is more complex. Instead of being physically different systems, research reveals that these systems may reflect many brain system processing modalities. Furthermore, the environment, mental emotions, and individual characteristics can all influence the processes of sensitization and habituation. And that's a wrap. Keep reading and learning new things!