Remote Ready Biology Learning Activities has 50 remote-ready activities, which work for either your classroom or remote teaching.
A digital ecosystem, fueled by serendipity.
Serendip is an independent site partnering with faculty at multiple colleges and universities around the world. Happy exploring!
An ongoing conversation on brain and behavior, associated with Biology 202, spring, 1999, at Bryn Mawr College. Student responses to weekly lecture/discussions. A suggested topic was provided, but students were free to write about any other observations, ideas, or questions that particularly interested them.
We had a look between the sensory and motor sides of the nervous system and found, among other things, evidence for "intrinsic variability". Is this a well-defined, useful concept for understanding the nervous system? Does it have implications for better understanding behavior?
Is intrinsic variability the neurological basis for individuality? Does it come down to different pathways in the brain that ultimately determine how we act in different situations? First, I must say that I do not think that the term is very well defined. It seems rather broad in its implications on behavior and kind of seems like a general term to explain the middle steps of processing that we do not quite understand. Further, I am not sure that I entirely agree that this is the only factor involved in intermediate processing, since additional research needs to be done.
We have been discussing in my Psychology class that in order to determine the personality of an individual, one must pay regard to both internal and external factors. The character and the situation play a dual role in determining one's action. Depending on the stress of the situation, one variable is usually more influential. This is easily demonstrated in the analysis of the frog's behavior toward a worm in a cup which, probably is not a stressful situation for the frog. When the size of the cup was reduced to a cup one half the size of the original cup, one would expect that the variability of the jumps would also decrease by half. However, as we saw in the multimedia presentation, it did not, but rather, were still very random (and thus we talked about the possibility of a randomizer). One could be almost certain that a different frog in the exact same situation would produce an entirely different pattern of jumps. Thus, by maintaining the conditions of the situation (as much as possible), the variability can be attributed to the internal characters of the frog. Needless to say, external factors matter too and these contributors are not considered in this model simply by the way the variability is defined as "intrinsic".
I certainly didn't mean to suggest that "intrinsic variability" was "the only factor involved in intermediate procesing", but only that it was an important additional feature of how the nervous system works which happened to have been identified in the course of looking at intermediate circuitry (where, yes, there is indeed more to be explored, other things that have been discovered, and undoubtedly more yet to discover).
I agree too that, along with intrinsic variability, other factors play a role in "personality". These almost certainly include additional intrinsic factors, such as variations in the function and efficacy of some of the "generalized control mechanisms we talked about (I just ran onto an interesting looking article on Neurobiology of the Structure of Personality ...). These in turn, almost certainly, reflect (like everything else) a combination of genetic and external influences. An interesting area to explore further. PG
But I guess what I have been thinking about, this past week, and pretty much this past semester in this class, is how we can be content with just the discoveries of failures. A friend of mine, who took this class last semester, is doing the Neural and Behavioral Sciences concentration for Biology and we were discussing this class. She is trying to decide what she wants to research for her thesis, but now sees her research in a whole new light. What if her hypothesis fails miserably? Then where is she left? True, she does walk away from that year knowing that she did learn something... she learned that the assumption that she took on was wrong. And if you step back and look at the bigger picture, you see that this information could in fact be quite valuable? But what about to that student that has devoted that year to hoping that this hypothesis could in fact be supported? What happens to her? I am just asking, because I know that although we discussed in class that a hypothesis failing could provide necessary information, but where do you go from there? Thoughts from the week...
Interesting and appropriate concern. Yes, it really IS true that hypotheses are, in general, disproveable but not proveable, and that it is the finding that disproves the hypothesis that is most meaningful. Which means one is always a failure? In a sense, yes. But, what one is really doing is not being "wrong" but rather becoming progressively less wrong. Disproving a hypothesis adds meaningfully to the number of observations that have to be effectively summarized in the next hypothesis,and is the motivation for its creation. I don't think of any of our successive frog models as "failures" but rather as the necessary sequential steps to current better understanding. See if that helps your friend who wants to do research? PG
This 'intrinsic variability' is a useful way of understanding present behavior differences as shown in the frog experiment, because this concept of variability ( used because behavior can not be described biologically) or chance could account for differences in personality, preferences and other individual differences.
Interesting problem: does there have to be a "solid pathway or network" for something to be not "vague"? Molecules are actually in random movement all of the time (or at least at temperatures above absolute zero), and so there is, in principle, likely to be some variability in the function of any system constructed of molecules (which neurons, of course, are). It could be that this general variability, rather than any particular pathway or network, accounts for "intrinsic variability". Or it could be that there are particular circuits, as yet to be localized/described, whose activity is the source of the variability observed. Could be an interesting research area. Can you imagine how one could go about looking into the question? Want to try? PG
Yep. And hence, perhaps, implies that "predictability", at least in an absolute sense, is not the objective of "understanding"? Which, in turn, has some interesting implications for what one means by "science"? Is worth further thinking through some of the implications of this. PG
Upon the introduction of “intrinsic variability” Prof.G suggested that perhaps the recent tragedy in Littleton might in some way be addressed in relation to this concept. While this possibility was addressed briefly, upon further reflection it seems that it may be worthwhile to discuss it further.
Although the examples illustrating “intrinsic variability” were extremely simple organisms (and for the most part lacking a cerebral cortex) it was still difficult for me to dismiss the ‘i-function’ as essential to the very nature of the variability in one’s behavior. The compelling simplicity of the ‘Harvard Law of Animal Behavior’ certainly serves as further explanatory evidence for all such “intrinsic variability” without necessitating the involvement of an ‘i-function’. But in humans, what might the possibility of involvement on the part of the ‘i-function’ mean? what might it’s repercussions be?
For the perpetuators of violence as at the massacre at Columbine it would seem that somehow the brain’s “intrinsic variability” capacity proved inactive or thwarted. And that perhaps the very involvement of the ‘i-function’ might have served to only further eliminate potential behavioral options from the repertoire of those, would be, child killers. Certainly there are hundreds of other students at Columbine who suffered similar taunting and harassment as the two identified gunmen -- so what occurred such that the wide range of behavioral options were excluded until only one single deadly action was deemed appropriate or proper for these two individuals. One may postulate as to whether the fault occurred at the level of some “intrinsic variability” component -- or if perhaps some distorted involvement of the ‘i-function’ prevented the brain mechanism to function properly at all.
A further question as to whether the ‘i-function’ in these young murders had even reached full development might be pertanent. Within the teen years a sense of self and self-motivation proves still a some what malleable construct. With an improperly functioning variability mechanism and a malformed or incomplete sense of self there is no safeguard for the elimination of inappropriate and potentially devastating ideas. But if this is the case no amount of boosted school security of school closings will prevent ensuing disaster. As the snowball of school threats plagues our area as well as the rest of the nation -- the ‘variability’ in behavior appears to be growing even more limited. And with the many teenagers yet plagued with a fragile sense of self, our nation should do more than mourn, it should fear.
Thanks for following up on our brief discussion. I share your sense that what happened in Colorado might usefully be thought about in terms of "intrinsic variability" and "I-functions" ... and that, somehow, the students involved ended up with either fewer output options, or less ability to choose among options, than is healthy/desireable. The big questions, of course, are which happened, why, and what can be done to reduce the likelihood of its happening in the future? My own guess, for what its worth, is that the primary problem was reduced output options ... perhaps because, in part, of too little life experience with the significance/usefulness of "choosing" (your "fragile sense of self"?). I'd like to think that giving students more control over their own lives (and hence more experience with "choosing") would reduce the likelihood of incidents like that in Colorado ... but there may well be other factors operating in particular cases as well. I do share your feeling that we want more "variability", rather than less. PG
This also seems to relate to our dicussion of disease labels-- that is disease are labeled based on behavior not on the internal neurobiology. If all the various neurobiological ways to lead to the certain disease behavior could be determined (all the intrinsic variability understood), treatment of a diseaes would be more possilble.
We've got LOTS of explanations for "individual differences". One is differing genomes, and resulting differences in circuits. Another is corollary discharge, as you describe it (and presuming those are different in different people). And a third is "intrinsic variability", which is particularly interesting since it is a variability within one person, and hence perhaps yields an unpredictability even to one's "self". And yes, I agree, there are implications here for the understanding and treatment of "disease". Including your thought that a given "output" (behavior) might have a variety of different neurobiological underpinnings. And perhaps the idea that some degree of unpredictability is a good, rather than a bad thing? PG
For me, intrinsic variability brings about two very different and seemingly contradictory reactions. On one hand, this concept gives me that illusive feeling of "self" where "I" am found. It houses my creativity and my imagination. It is what makes me different from my brother and sister and my peers. Intrinsic variability is the concept that allows the brain and behavior to become unpredictable and a better reflection of how organisms behave. This is what I've been struggling with since we made the assertion that brain equals behavior. All of my doubts concerning this assertion can be calmed by intrinsic variability. It gives me back my free will and choice.
But there is also some part of me that doesn't quite believe in it. I keep feeling that with enough research something will be discovered that will explain the workings of intrinsic variability. Maybe we will find some new pathway or new chemical that would direct a response in a certain manner. I'm not certain what part of me is thinking in this manner… Is it scientific, maybe? It seems to be the logical way of thinking. Scientific thinking will not ever stop asking questions and so it seems to me that it's not logical to accept this theory as absolute truth. As was said in class on Tuesday, we are never right. There is always a strong possibility that whatever we have accepted as being truth will be later disproved. Almost every piece of knowledge that has ever existed has been proven wrong. What's to say that this isn't also wrong?
Actually, I think we've got lots of explanations for why you are different from your brother/sister/peers (see response to Carly above. But yes, I think "intrinsic variability" is important for creativity/imagination, and, indeed, for choice and free will.
Can you "trust" it ... "intrinsic variability"? Given that there is no "Truth"? Interesting question, needing two somewhat different approaches to an answer. The first is that one is, as you say, always wrong, but one can get "progressively less wrong" (see my reply to Kathy above): as models change some characteristics persist. The second relevant point is that "variability" seems to be pretty deeply rooted, not only in the nervous system, and in biology generally, but in the underlying chemistry and physics as well (see my response to Adrianne above). Taking the two together, my feeling is that believing in "intrinsic variability", and the things that follow from it, is a safer bet than many other things one might choose to believe in. PG
I don't believe that intrinsic variability is a well-defined term because I don't see the difference between it and the Harvard Law of Animal Behavior. Otherwise I do think it is useful in understanding the nervous system. I think it is very interesting that theoretically one could 'keep' a brain 'thinking' even after the death of the human whose brain it is. I am excited yet worried at the implications such an experiment could have. Could there one day be such a thing as a brain transplant, is such an act moral. We harvest other organs of humans and have recent replace body parts such as a hand, what's to stop brains being transplanted? Is this going too far? It seems to me, thinking hypothetically that if brain transplants became the norm than eventually everybody would be intelligent therefore causing the downfall of society because in order for a society to work there must be some inequality for if there wasn't no one would take the jobs deemed for unskilled workers in which case many vital services would no longer be performed.
I definitely think it would have implications for better understanding behavior. Being able to watch a brain function on its own would truly help the understanding of behavior because it is acting without interference. There would be more of a control in any experiment being performed. One could see how it would react to a single input and be able to predict what a human (or any other animal) would most likely do in a given situation.
I don't think one has to worry about brain transplants in the near (or even intermediate) future: there are too many connections that would have to be remade too precisely for it to be practical. Would everyone want to be "intelligent"? I hope not, for reasons other than needing "unskilled workers": humanity needs different kinds of people for much more general reasons. In research terms, though, it would certainly be helpful, for the reasons you mention, to know how much variability isolated nervous system display. PG
Intrinsic Variability alludes to the idea that most living creatures possess a variety of different ways to reach an end. What I find interesting is that this intrinsic variability also varies across individuals. No one individual will have the same pattern of intrinsic variability. (Could this imply that our pattern of variability is in part defined by previous experiences?it would seem so.) I guess in a sense, intrinsic variability may in part account for individual differences. I suppose what makes people unique is the fact that each person will most likely possess an entirely individualized repertoire of behavioral variability.
On a more general note, it seems that the mere possibility of intrinsic variability is what defines a successful and productive existence. This is especially true since adaptation is a very important factor in the life success of any living creature. Without the ability to vary our behavioral responses to reach an ends or goal would definitely detract from our ability to adapt. Much of human psychopathology is based on the notion of rigidity or inability to vary a response given a novel situation or environment. Those people who are least able to rely on a variable behavioral pattern are at a higher risk of suffering from psychological distress. It seems that an inability to accept or rely on our intrinsic variability would detract from our ability to adapt, which would in turn detract from our overall productivity and functionality.
Yes, I think different people have different repertoires of intrinsic variability (like different finger prints), probably both because of genetic influences and experiences. Not only the particular things one might do in a given situation are different but so too I suspect is the size of the range of things one might do. Which is to say, I think you're right that an interesting way to look at (at least some) psychopathology is in terms of "rigidity or inability to vary a response". Which then raises the question of how one can enhance such abilities? both in cases of psychopathology and generally? PG
I have been looking into the idea of multiple intelligences, an idea proposed by Howard Gardner in his book Frames of Mind. Gardner describes 7 kinds of intelligences: linguistic, logical-mathematical, spatial, bodily-kinesthetic, musical, interpersonal and intrapersonal. I am interested in it from the perspective of children’s development, their educational experience, and the loss of self-worth that can arise from a child not doing well in school. I strongly believe in the idea that people are intelligent in different ways, and think that if these different types of intelligence were honored in our society in the same way that the current definition of “intelligence” is, there would be many benefits. The notion of intrinsic variability gives me a neural jumping-off point from which to explore multiple intelligences. I am planning to explore this is in my final paper.
Maybe you and the science student can get together on this one? Yes, we may indeed get to more specific mechanisms of "intrinsic variability" (see my reply to Adrianne above), but they may well leave us with a fundamental (and I think appealing) indeterminacy, in the brain as in the rest of the world. Here and here are a bit more on this theme, as well as on the importance of valuing the differences between people. And here's some lists of links on education, with one on "learning styles" including multiple intelligences. Looking forward to seeing your paper. PG
The issue of intrinsic variability made me think about all of the times I have been told to “reject” the one data point that’s “too far off” the line. Of course, the experiments I did were not nearly as complicating as behavior, after all I knew that I was “supposed” to get a linear relationship. I was rather shaken up when I learned that in most scientific studies its OK to ignore or not publish a few “really odd ball” data points. I was just reading a study that looked at the actual data books of some scientists who passed away and found that a few points that did not fit with the general trend were simply ignored. This fact did not undermine the relationship that was shown by these investigators, but nevertheless it made me think about what it means to be a scientist. I feel that I fit more into the stereotype of a scientist, that is I do not look at things as “supernatural” occurrences and even in the case of unexplained phenomenon I usually like to think that proper experimental procedures, which are not in our reach at the present moment, can get to the core of it.
One can not devise an experiment to prove something does not occur as is the case of behavior, and any less complex variable. I do not have the answer on how to tackle the problem of variability in behavior and what explanations one can give to Harvard Law of Animal Behavior but I an convinced that students should be guided to think more about the odd ball data points and have try to see beyond the popular “experimental error” idea. More importantly, scientists should publish even the “bad data” points, in an appendix or something. That way there is more room for accepting that there is something more to it all, even if this acceptance entails one to admit that he has no idea what it is.
I'm on your side, both with regard to people publishing the odd data points and with having students (and others) "think beyond ...". Which isn't to say they are always significant ... but it is certainly worth keeping that possibility in mind. A good connection, thanks for making it. And I think too that good science can indeed always "get to the core of it", as long as we admit that the core may in fact involve some fairly fundamental indeterminacy, a position with which at least some "stereotype" scientists are reasonably comfortable at this point. PG
Going to blame "intrinsic variability" for the repeated cutting off short of your writings too? In any case, I like your "physical, biological, and rational entities, all wrapped up in the nervous system". And yes, it doesn't mean we aren't responsible for our choices; in fact it makes responsibility both more free and more meaningful, as you say. A rational animal indeed, with all parts contributing, no part "in charge"? PG
The exploration of how intrinsic variability may help species adaptively is very interesting. Like the idea that the frog may be varying its behavior uncontrollably but to the end that its movement is not able to be as easily predicted by its prey. I am still not clear as to how this could be an adapted feature in any way. But it does seem very useful to be somewhat unpredictable, and the game theory makes a lot of sense. I really like intrinsic variability as a property of the nervous system which is very useful in accounting for the infinite variety of behaviors we all marvel at and disparage of ever explaining entirely.
Yep, unpredictability is not so hard to understand. Though there are some interesting problems in going from very small unpredictabilities to large scale ones. In many cases, the small scale unpredictabilities "average out". So large scale unpredictabilities imply particular kinds of organization (and not others) of small scale unpredictabilities. Why are you unsure of how frog unpreditability could be "an adapted feature"? If it makes frogs better predators, it would be selected for, no? And yes, it helps to account for diversity of behaviors of which we and other organisms are capable. PG
Pathways within the nervous system and destinations in the brain do not seem to be so well-defined for outputs to specific inputs etc. I think this is essential to having different types of people- people who think, create and make choices different from our own. If people weren't able to think differently there would be no change in our society- no one would look at a situation or idea differently- it would be quite strange.
Variability in behavior also is a benefit in that predators and/or prey (necessary roles in the natural world) are not so predictable. This allows preditors to attack unexpectedly and at the same time affords the prey a chance to get away (by moving differently).
Intrinsic variability seems necessary to the survival of life on earth. Anything predictable or unchanging would not stand a chance. Like the saying goes, "It's good to keep them guessing".
It certainly makes life more interesting. And, I think you're right, necessary for survival. That would certainly seem to be the lesson of evolution. Nice when things are both necessary and fun, no? PG
I'm sorry that I seem to relate everything to sports, but it's a good frame of reference for me. In talking about intrinsic variability, I think about how people sometimes surprise themselves with a movement or skill that they haven't practiced in their sport. This action could seem to just spontaneously happen without it ever being practiced before. Many times we refer to this as "luck." I wonder what the word luck really means in the context that we've been discussing with brain and behavior. Could luck be the intrinsic variability that is present in all of us? Could luck be a temporary glitch in the nervous system, a misfiring of neurons?
There are many different instances of luck outside of sports that seem to be controlled by the brain without the input of the I-function. For instance in car crashes or near misses, sometimes people react without even "thinking" to avoid death. It seems to me that luck could be a figment of our imagination because it could really be controlled by "us" while "we" are just not aware of it.
Thanks. I went to see "The Matrix" last night. Enjoyed it. And no apologies needed for sports as a frame of reference; its a good one. Yes, I agree that people "surprise themselves" with a movement they haven't done before. Probably partly "intrinsic variability". Also being done by "the rest of the nervous system", rather than by the "I-function", no? So "luck" might be a little of both, more of one or the other in different cases perhaps. PG
Good question. Have you an answer? See some of the thoughts of Feyza and Sarah, and my responses. Maybe the notion of "range of possible behaviors" would provide a way to define some kind of line? or at least a zone? PG
In terms of the grander scheme of concepts, I still want a COMMON THREAD! We have done a lot with the nervous system, come to understand it much betteri n a broad, interconnected sense. But there were so many facinating topics brought up in class by people posing questions, to which Prof. G responded, "We will come back to that." but we ran out of time to come back to the finer points of some areas of sensory study. I woudl still love to know more about sight in terms of colorblindness and issues of that nature. Either that, or the point raised today about sleep, dealing with sleep deprevation or insominia. If only there were enough time for all the resolution brought up in this semester's course....
Sounds like you want not so much a "common thread" as more of the strands which make up the thread. Anyhow, I'm glad you "would still love to know more". Me too, for what its worth. And that makes the course a success, for me at least. We indeed ran out of time, in the course (did I really not "come back" to THAT many things? oh well), but there's lots of time ... and plenty of courses/books/journals, and all of ever-expanding cyberspace. Enjoy it. PG
Interesting thoughts. Did the last week help it come together at all? But yes, as I said to Alicia above, if the course worked there should be questions (new ones) coming out the other side. Where does intrinsic variability come from is a good one (see my response to Adrianne above. Even better, how does one get both stability and variation out of a interactive system? I, at least, will go on thinking about that one. Happy to have you join me. PG
Yet, even if I understood how intrinsic variability works, I still do not think I would understand how the nervous system integrates input, or what triggers the generation of output. My understanding of the nervous system has advanced tremendously this semester, but there are still many, many holes in my picture of the nervous system, and what causes behavior. Intrinsic variability seems to be an easy way out of really completely explaining behavior. Yet, I know that our knowledge of the nervous system is incomplete and that we can never fully understand the brain because it changes as we study it. I am forced to wonder why we are seeking these answers. Is this merely curiosity, or does this information serve some purpose?
Want a serious answer? I think "exploring" is a fundamental characteristic of not only the nervous system but all forms of life, from the simplest to the most complex. Does it serve a "purpose" or is it itself "purpose"? A little of both, I think. My guess is that "exploring" is a trick that characterized life from its inception, proved useful (in that it enhanced survivability by providing information in advance of need), and still does. Well, you asked.
Yes, cyclic changes are A form of "intrinsic variability", but a still more interesting form is some degree of randomness/indeterminacy. Where it comes from is a good question for further exploration (see response to Adrianne above. Want to join in? On that, or any of the other holes. You wouldn't really want all the questions answered already, would you? PG
"A cutaneous stimulus delivered to an intact leech sometimes, but not always, triggers swimming behavior. Such input/output variability might, in principle, be attributed to slight variations in the cutaneous stimulus itself, or to differences in other sensory inputs at the time the stimulus is delivered. In fact, as shown in Figure 2B, input/output variablity persists in the isolated nervous system. Identical electrical stimuli delivered to a peripheral nerve sometimes, but not always, triggers swimming."
The cool thing about the leech is that you can remove its nervous system, keep the NS alive, and run experiments on it. That way, you can basicly control all the inputs and observe all the outputs. It's a good organism for this kind of research. The limitation, I guess, is the fact that the leech only has a few limited behaviors (types of outputs?) to observe compared to more complex organisms like frogs. Leeches can't do as much, but are great for studying the nervous system at its most basic level.
Don't let Peter Brodfuehrer hear you say leeches can't do much. But yes, they do/did provide a way to say something quite important about nervous systems in general. And that's likely to continue to be true, of leeches and other organisms. PG
Isn’t that the same type of thing that we see when we recognize a voice (speech pattern), or a gait (walking pattern) or any other kind of motor symphony. They are all different from each other but again they possess all of the necessary components to make them recognizable as being what they are. But within the pattern of each individual voice or walk are variations that can be again attributed to huge number of causes. The person who displays the voice or walk might be frightened or cold, or sick or hurt, etc, which would produce variability within that person’s own unique pattern. Again it is the patterns that make something recognizable as itself. A motor symphony that produces walking we have concluded is caused by a pattern generator. But that pattern has variability within itself.
When Professor Grobstein, studies frog behavior and sees variations
in the snapping behavior of any individual frog or the fact that a frog
does not snap when presented with a worm he concludes that variability
is part of the pattern of behavior that frogs exhibit.
And clearly as we have seen and everyone is thinking and talking about
after last week’s Colorado events, patterns of behaviors, while clearly
possessing the qualities of being behavior are sometimes unimaginably unpredictable.
Why are incarnate objects (snowflakes, rocks, etc) and all living things (animals, plants, cells) different from each other but each still possessing qualities of patterns that make them identifiable as belonging to a particular classification? I’ve been thinking about that question by extending our metaphor of the nervous system as being a series of boxes, to the natural world as boxes within boxes, within boxes? I have a sense (for what ever that’s worth) that one of the reasons has to do with the fact that the myriad of possibilities for the arrangements of things or organisms within themselves (creating individual examples) or in combination with each other do produce unlimited possibilities of combinations. Therefore any and all organisms which exhibit behaviors must posses the qualities necessary to behave, i.e. have responses that recognizes variations/sameness and respond/behave in ways that have intrinsic variability.
Hmmmmm ... Did you mean something sort of like this:
Two conclusions follow from these sorts of considerations. The more
obvious is that the processes underlying the form of living organisms are such as to permit substantial differences
in detail while maintaining some kind of more general invariance. What may be less obvious, but is no less
significant, is the conclusion that the human brain is organized so as to be able to detect such invariances despite
the same quite significant differences in detail.
That comes from
a paper I wrote more than ten years ago which I think posed pretty much the same question you're posing, and was the basis for much of the thinking about variability I've done since. Thanks for reminding me. Do I yet know the answer to the question? No. But I'm learning more about it, and do indeed think it has to do with variability as a property not only of living systems but of non-living things as well. Let's both keep wondering, and see where we get.
PG
| Course Home Page
| Back to Brain and Behavior
| Back to Serendip |
© by Serendip 1994-
- Last Modified: Wednesday, 02-May-2018 10:53:01 CDT