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Habituation

Source: http://publish.radford.edu/~jsking/Orienting%20Response.doc

An Introduction to the Orienting Response (OR) and its Habituation

It is unfortunate that most texts and courses in Classical and Operant Conditioning omit this topic or only treat them in a cursory fashion. These processes are not only fundamental to other conditioning processes, but form an important link between conditioning phenomena (traditionally the bases for behaviorism) and the more recent emphasis on cognitive influences on learning. Therefore, it is the purpose of this introduction to present the basis phenomena of orienting and habituation and to provide a context for a more complete understanding of classical and operant condition.

The orienting response (OR) is sometimes called the orienting reflex. It was first recognized and reported by the famous Russian physiologist Sechenov in the 1850s in his book Reflexes of the Brain, however, he did not systematically study the OR Pavlov mentioned what we now call the OR as an example of phenomena that can interfere with the expression of a conditioned reflex. He referred to this response as the " What is it?" reflex. It is at this point that we will characterize this reflex.

The Orienting Reflex is a response to novelty. Whenever something occurs that is novel to an organism, the individual stops what it is doing and "turns its sensors to the source of stimulation" (Pavlov, 1927). This is the behavioral component of orienting. Other researchers discovered that orienting is a collection of reflexes that include papillary dilation, a drop in skin resistance and a momentary drop in heart rate.

Some researchers have interpreted the OR as a collection of bodily responses that assist in "receiving" the stimulus and "taking it in" to be processed further. It should be noted that the OR is only a response to novel events that are not aversive. For example a novel sound will elicit an OR unless it is very intense (say 100 db). When very loud, sounds become aversive and elicit a DR (defensive reflex). The DR is sometimes seen as a collection of responses that assist in "blocking out" the event. For example whit a loud sound the pupils constrict and heart rate increases.

It turns out that novelty is a tricky term to define. For example, the sound of a certain person's voice (your mother's) may be routine at home, but may well elicit an OR at a party this Friday night. I know of one case where a man shaved half of his moustache and went to church. By his account only very few people noticed, and they were not his closest friends. Apparently, to his closest friends he was the 'same person' and they noticed nothing out of the ordinary. Only those who relied on his facial characteristics to 'recognize' him noticed the novel event.

I think you can see that it is important for many organisms to be able to detect novelty in their environments. You never know when something new is going to be important. When we start a new job, or take a new course, or play a new sport we expend a lot of effort chasing after things that turn out to be insignificant. It is often an exercise in frustration to figure out what is worthy of our attention and what is not. The more novel events in a new situation, the greater the possibility that some of these are important. Therefore the more difficult the situation. New situations with fewer novel events are less difficult. Can you think of some examples of this in your coursework, hobbies, extracurricular activites?

While it is obvious that building an organism with a "novelty detection" capability is important (even necessary), it is equally obvious that if everything seemed novel that life would be terribly confusing. This can happen with some types of brain damage. If a part of the brain called the hippocampus (and perhaps some structures surrounding it in the anterior temporal lobes of the brain) are destroyed, then the person will have difficulty forming new conscious memories. There is a very famous case of a patient known to us as H.M. who had surgery as a young man (in the 1960s) which removed most of the anterior temporal lobe on both sides of his brain. He has not been able to form new conscious memories since the surgery. Everything and everyone are always new to him. He will carry on a most congenial conversation with you, but if you leave the room (even for a few moments) he will not remember you when you return. His memory for people and things before the surgery is fine. There are some interesting qualifications. For example, after his father died (a few years post surgery), he would have some days when he felt sad, only he did not know why. If reminded that his father had died recently, that would seem to "explain" the sadness. He also learned to do a mirror tracing task, and got quite good at it. When confronted with the task the next day he did not remember it at all, yet he was still quite good at it. That's why I said he was unable to from new "conscious" memories. Apparently these parts of the temporal lobe are also very sensitive to loss of oxygen, because patients who are victims of anoxia (suffocation) seem to have damage to their hippocampi and similar memory deficits to those of H.M.

Habituation of the OR

Once we orient to a novel event we often find that the event is of no consequence or importance to our life. As mentioned earlier, it would be a tremendous waste of energy if we continued to orient to such an event. Pavlov found that after repeated presentation of the new event it no longer interfered with the conditioned reflex. Some years later, in the 1950s, another Russian scientist, Eugene Sokolov, systematically studied the OR, and the consequences of repeated presentations of novel, but inconsequential events. Sokolov carefully documented what Pavlov had found: With repeated presentations of a novel event the OR becomes weaker and weaker until it no longer occurs. Sokolov termed this gradual decrement in the OR with repeated presentations of a novel stimulus 'habituation'. You might recognize this as a process called 'familiarization'. Indeed habituation is simply the process of becoming familiar with the environment around us. So what's the big deal?? Well, is it true that once we become familiar with things, we no longer 'pay attention' to them? Is orienting and habituation really a matter of attracting (or losing) one's attention. Maybe Attention Deficit Disorder is unusual sensitivity to individual stimuli in the background of what we are attending to, or maybe just a failure (or a slowness) to habituate to unimportant events. While we are at it, if we come to not even notice inconsequential events, do we no longer perceive them?

Sokolov considered this last question, and made one of his most important discoveries. Let me describe one of his experiments in some general terms. Sokolov presented a novel tone to some of his subjects and recorded an OR. As predicted, with repeated presentations, the OR gradually disappeared. You may not be surprised to find that if he changed the tone (made it higher or lower pitch, for example) the OR reappeared. By the way, he termed the reappearance of the OR due to a change in the stimulus 'dishabituation'. You may also not be surprised to find that if he made the tone slightly louder dishabituation also occurred. However (here's the important one) the OR also reappeared if he made the tome softer (less loud).

What's the big deal??? If one learns that the tone is unimportant and no longer processes it, then how is it that a change can be detected? While we may not consciously process the tone (and it no longer gets our attention) our brain must be processing the tone (albeit at a subconscious level) in order to detect the change. One could imagine a gate-like mechanism that would only allow a different or louder tome through, but this won't work to explain dishabituation to the softer tone.

Actually this may not be such a foreign experience. Psychologists quickly pointed out the occurrence of the 'cocktail party phenomenon'. Not that I'm part of the local cocktail party circuit, but such events are characterized by the presence of several small (2-4) groups of people each carrying on their own conversations. While you are aware that the group next to the one in which you are involved is talking, you will have almost no knowledge of exactly what they are saying. (If you switch your attention to the other conversation you immediately 'miss' part of the one you are involved in.) However suppose that someone in the adjacent group mentions your name as part of their conversation. Immediately your attention is 'captured', and you are drawn to that conversation, perhaps only for a few seconds. What's the big deal??? If you had no idea what was being said, how could you have known that someone said your name. Why, they could even accuse you of eavesdropping in on their conversation. Or one of your group could surmise that you weren't really listening to them. Suddenly you are in hot water only because you are a victim of your novelty detection mechanism. There are lots of example of unconscious processing of information and the ability of such information to interfere with our conscious activities. Take a course in Cognitive Psychology to learn more about these.

One last point about dishabituation. Sokolov also found out that if one presents a stimulus at regular intervals, the OR quickly habituates, as predicted. However, if one stimulus in a series of such presentations is left out, then dishabituation occurs. Apparently the omission of an event can itself be an event. A somewhat famous case of this is the Bowery El phenomenon. The Bowery El is a train the regularly runs through the Bowery, a less than desirable section of New York City. In the Bowery the track is lined by some apartment buildings. That residents of these apartments regularly call police to report suspected criminal activity (breakins, assaults) is not so unusual. However, for a period of two weeks in late the 1960s the police received un unusually large number of calls in the middle of the night. Even more confusing was that the police often found no evidence of criminal activity (breakins, peeping toms, etc.) apparently nothing was happening. At least not more than usual. As mentioned, after about two weeks the number of calls reduced down to the usual number. Some astute investigator noticed that at about the time the calls increased in number the Bowery El had stopped its 2:00 AM run. Apparently the residents of the apartments had habituated to the noise in the middle of the night. However once the noise stopped the residents dishabituated and the resulting OR woke them up. Since no one wakes up to nothing, the residents apparently assumed that something unusual had happened and called the police.

As you can see the existence of the Orienting Reflex and its habituation informs us about an essential component of our responses to events in our environments. As you will see these phenomena also serve to demonstrate the relationship between behavioral approaches to understanding behavior and traditional cognitive psychological processes such as attention and perception.