Adaptive Behavior and Learning/contents/Chapter 2 - Revision history

Woozle: updated with corrections from temp HTYP

2012-12-11T19:32:16Z

updated with corrections from temp HTYP

Woozle: TOC

2009-11-07T20:22:58Z

TOC

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	[[Adaptive Behavior and Learning~~]]: [[{{PAGENAME~~}}~~\|Chapter 2]]~~		{{Adaptive Behavior and Learning/contents}}
	{{neededit\|"Smart" quotes and other characters did not import properly; italics need to be inserted manually.}}		{{neededit\|"Smart" quotes and other characters did not import properly; italics need to be inserted manually.}}
	[http://psychweb.psych.duke.edu/department/jers/abl/Chapter02.pdf PDF]		[http://psychweb.psych.duke.edu/department/jers/abl/Chapter02.pdf PDF]

Woozle: moved Adaptive Behavior and Learning/Chapter 2 to Adaptive Behavior and Learning/contents/Chapter 2: main article should be about the book, with the contents in subpages

2009-11-07T17:41:25Z

moved Adaptive Behavior and Learning/Chapter 2 to Adaptive Behavior and Learning/contents/Chapter 2: main article should be about the book, with the contents in subpages

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Woozle: moved Adaptive Behavior and Learning: Chapter 2 to Adaptive Behavior and Learning/Chapter 2: reorganizing with subpages

2009-11-07T17:39:23Z

moved Adaptive Behavior and Learning: Chapter 2 to Adaptive Behavior and Learning/Chapter 2: reorganizing with subpages

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Woozle: 7 revisions: migrating from HypertWiki

2009-11-07T17:35:12Z

7 revisions: migrating from HypertWiki

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Woozle: neededit template

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	[[Adaptive Behavior and Learning]]: [[{{PAGENAME}}\|Chapter 2]]		[[Adaptive Behavior and Learning]]: [[{{PAGENAME}}\|Chapter 2]]
			{{neededit\|"Smart" quotes and other characters did not import properly; italics need to be inserted manually.}}
	[http://psychweb.psych.duke.edu/department/jers/abl/Chapter02.pdf PDF]		[http://psychweb.psych.duke.edu/department/jers/abl/Chapter02.pdf PDF]
	=Chapter 2: Variation and Selection of Behavior=		=Chapter 2: Variation and Selection of Behavior=

Woozle: /* Indirect orientation (kineses) */ fig. 2.2, 2.3

2005-08-14T20:27:45Z

Indirect orientation (kineses): fig. 2.2, 2.3

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	Following this pattern, the study of plant movement by Darwin and others led eventually to the discovery of auxins, powerful regulators of the differential growth that underlies movement in plants.3 The movement of bacteria, the next example, is also being traced to complexes of reversible chemical reactions.		Following this pattern, the study of plant movement by Darwin and others led eventually to the discovery of auxins, powerful regulators of the differential growth that underlies movement in plants.3 The movement of bacteria, the next example, is also being traced to complexes of reversible chemical reactions.
	===Indirect orientation (kineses)===		===Indirect orientation (kineses)===
	All living creatures behave; not even a virus is completely inert. Even supposedly primitive animals often show extraordinarily clever behavior. For example, in the l880s the German biologists Engelmann and Pfeffer discovered bacterial chemotaxis (actually a kinesis in the terminology I am ~~using4~~): the ability of bacteria such as Salmonella to move up or down a chemical gradient. By inserting a capillary tube containing a suspension of attractive substance into a medium containing bacteria they showed that more bacteria entered the capillary than would be expected if they simply moved randomly. This is extraordinary behavior for an organism only about 2 ~~Ã¯ÂÂm~~ long, with only the most primitive sensory and motor apparatus, and no nervous system at all.		All living creatures behave; not even a virus is completely inert. Even supposedly primitive animals often show extraordinarily clever behavior. For example, in the l880s the German biologists Engelmann and Pfeffer discovered bacterial chemotaxis (actually a kinesis in the terminology I am using<sup>[[#Note 4\|4]]</sup>): the ability of bacteria such as ''[[wikipedia:Salmonella\|Salmonella]]'' to move up or down a chemical gradient. [[Image:JERS ABL Figure 2.2.png\|thumb\|right\|300px\|'''Figure 2.2''' Flowcharts defining two kinds of [[wikipedia:Hill climbing\|hill-climbing]] process.]] By inserting a capillary tube containing a suspension of attractive substance into a medium containing bacteria they showed that more bacteria entered the capillary than would be expected if they simply moved randomly. This is extraordinary behavior for an organism only about 2 µm long, with only the most primitive sensory and motor apparatus, and no nervous system at all.

	Bacteria have no distance receptors; they cannot detect the source of a chemiÃ‚Âcal in the way that we can detect an illumination source, from a distance, by looking at it. (Mammals have no distance receptors for chemical gradients either, of course, nor is such a thing possible. Hence, dogs follow a scent trail in much the same ways as moths and bacteria.) The only way to find the source of a diffusing chemical is by means of a process called hill climbing (sometimes also called gradient descent/ascent ~~Ã¢â‚¬â€~~ depending one whether the source is good or bad), where the hill to be climbed is the chemical gradient. Hill climbing can be explained by the simile of a blind man trying to find his way to the top of a hill. His simplest course is just to sample a direction: If it is downhill or level, sample again, but if it is uphill, follow it for one step, then sample again, and so on. A more efficient type of hill climbing is the method of steepest ascent: Here the man samples different directions from his current position and picks the one that gives the biggest increment. The logic of these two strategies is illustrated by flowcharts in Figure 2.2. Both require a small memory, sufficient to store a single slope value, but in addition the steepest-ascent method requires a stopping rule to tell the man when to cease sampling at each step. Still more complex, and more efficient, variants of hill climbing are possible (indeed, all adaptive behavior can be thought of as a sort of hill climbing).		Bacteria have no ''distance receptors''; they cannot detect the source of a chemiÃ‚Âcal in the way that we can detect an illumination source, from a distance, by looking at it. (Mammals have no distance receptors for chemical gradients either, of course, nor is such a thing possible. Hence, dogs follow a scent trail in much the same ways as moths and bacteria.) The only way to find the source of a diffusing chemical is by means of a process called ''[[wikipedia:Hill climbing\|hill climbing]]'' (sometimes also called ''gradient descent/ascent'' – depending one whether the source is good or bad), where the hill to be climbed is the chemical gradient. Hill climbing can be explained by the simile of a blind man trying to find his way to the top of a hill. His simplest course is just to sample a direction: If it is downhill or level, sample again, but if it is uphill, follow it for one step, then sample again, and so on. A more efficient type of hill climbing is the ''method of steepest ascent'': Here the man samples different directions from his current position and picks the one that gives the biggest increment. The logic of these two strategies is illustrated by flowcharts in Figure 2.2. Both require a small ''memory'', sufficient to store a single slope value, but in addition the steepest-ascent method requires a ''stopping rule'' to tell the man when to cease sampling at each step. Still more complex, and more efficient, variants of hill climbing are possible (indeed, all adaptive behavior can be thought of as a sort of hill climbing).

	The essential process in hill climbing is comparison of two heights, which define the gradient. There are only two ways a bacterium can detect a chemical gradient. One is by a comparison of chemical concentrations across the minusÃ‚Âcule length of the body (simultaneous comparison), which would involve detecÃ‚Âtion of concentration differences of as little as one part in 10,000, a formidable task. This mechanism would allow for directed movement up the gradient, a taxis in the classification of Fraenkel and Gunn (1940), whereas the observed movements look almost random with respect to the gradient. The second possibility is for comparison across time (successive comparison), allowing modulation of a largely undirected pattern of movement by increases and decreases in concentration. This kind of orientation mechanism is termed a kinesis in the Fraenkel and Gunn scheme.		The essential process in hill climbing is comparison of two heights, which define the gradient. There are only two ways a bacterium can detect a chemical gradient. One is by a comparison of chemical concentrations across the minusÃ‚Âcule length of the body (simultaneous comparison), which would involve detecÃ‚Âtion of concentration differences of as little as one part in 10,000, a formidable task. This mechanism would allow for ''directed movement'' up the gradient, a ''[[wikipedia:Taxis\|taxis]]'' in the classification of Fraenkel and Gunn (1940), whereas the observed movements look almost random with respect to the gradient. The second possibility is for comparison ''across time'' (successive comparison), allowing modulation of a largely undirected pattern of movement by increases and decreases in concentration. This kind of orientation mechanism is termed a ''kinesis'' in the Fraenkel and Gunn scheme.

			[[Image:JERS ABL Figure 2.3.png\|thumb\|right\|400px\|'''Figure 2.3''' The panels show the appearance in the dark-field microscope as an increasing proportion of bacteria cease tumbling and begin swimming in a straight line: The field is illuminated stroboscopically. so that when the camera shutter is left open for a brief period a smooth swimming bacterium shows up as a series of white dots. The graph shows the proportion of organisms tumbling as a function of time since the attractant (serine) was added at time zero. (From Koshland. 1977.)]]

	Macnab and Koshland (1972) showed that temporal comparison was the key in ingenious experiments with two species of bacteria: Salmonella typhimurium, the agent of common food poisoning, and Escherichia coli, a resident of the human gut much used in molecular biology. First, they showed that the movement pattern of the bacteria was the same at different absolute concentrations of an attractant. Then they subjected the bacteria to a sudden, Ã¢â‚¬Å“stepÃ¢â‚¬Â change in concenÃ‚Âtration, and looked at them immediately after mixing was complete. If the organismÃ¢â‚¬â„¢s behavior is guided by comparison between the concentrations at its Ã¢â‚¬Å“headÃ¢â‚¬Â and Ã¢â‚¬Å“tail,Ã¢â‚¬Â there should be no effect of the sudden change. But if their movement was determined by a difference across time, then a sudden drop in concentration should produce the same effect as swimming down a gradient.		Macnab and Koshland (1972) showed that temporal comparison was the key in ingenious experiments with two species of bacteria: Salmonella typhimurium, the agent of common food poisoning, and Escherichia coli, a resident of the human gut much used in molecular biology. First, they showed that the movement pattern of the bacteria was the same at different absolute concentrations of an attractant. Then they subjected the bacteria to a sudden, Ã¢â‚¬Å“stepÃ¢â‚¬Â change in concenÃ‚Âtration, and looked at them immediately after mixing was complete. If the organismÃ¢â‚¬â„¢s behavior is guided by comparison between the concentrations at its Ã¢â‚¬Å“headÃ¢â‚¬Â and Ã¢â‚¬Å“tail,Ã¢â‚¬Â there should be no effect of the sudden change. But if their movement was determined by a difference across time, then a sudden drop in concentration should produce the same effect as swimming down a gradient.

Woozle: /* SIMPLE ORIENTING MECHANISMS */ Fig. 2.1

2005-08-14T19:47:22Z

SIMPLE ORIENTING MECHANISMS: Fig. 2.1

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	Two forces are at work here, one directed and one undirected. The upward growth of the plant is a directed movement, a taxis; the direction is opposite to the force of gravity (negative geotropism). The way taxes work is described in the next chapter. But the turning movement is undirected Ã¢â‚¬â€ until the moving tip encounters a vertical obstacle such as a stick or the stem of another plant. Once such an obstacle is encountered, the turning movement, together with upward growth, ensures that the plant will twine about it and be lifted to a higher (and usually more satisfactory) location.		Two forces are at work here, one directed and one undirected. The upward growth of the plant is a directed movement, a taxis; the direction is opposite to the force of gravity (negative geotropism). The way taxes work is described in the next chapter. But the turning movement is undirected Ã¢â‚¬â€ until the moving tip encounters a vertical obstacle such as a stick or the stem of another plant. Once such an obstacle is encountered, the turning movement, together with upward growth, ensures that the plant will twine about it and be lifted to a higher (and usually more satisfactory) location.

			[[Image:JERS ABL Figure 2.1.png\|right\|thumb\|300px\|'''Figure 2.1''' Tracing of circumnutation of the plant ''[[wikipedia:Hop-clover\|Trifolium subterraneum]]'' on horizontal glass, illuminated from above, from 8:40 A.M. July 23 to 10:30 P.M. July 24. (From Darwin. 1880, Figure 92.)]]
	Most plants also possess a second taxic mechanism, phototropism. This comÃ‚Âbines with upward growth to direct the tip of the plant toward the lightest part of the sky. The efficient light-seeking of the plant can, therefore, be explained by the combined effects of three separate adaptive mechanisms: negative geotropism, circumnutation, and positive phototropism.		Most plants also possess a second taxic mechanism, phototropism. This comÃ‚Âbines with upward growth to direct the tip of the plant toward the lightest part of the sky. The efficient light-seeking of the plant can, therefore, be explained by the combined effects of three separate adaptive mechanisms: negative geotropism, circumnutation, and positive phototropism.

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	Paramecium and many other ciliates show essentially the same pattern as Oxytricha, reacting to negative gradients by retreating and turning. As with the bacteria, this process serves both to avoid bad regions and seek good ones. If a bad region surrounds a good one, the process keeps the animal within the good region.		Paramecium and many other ciliates show essentially the same pattern as Oxytricha, reacting to negative gradients by retreating and turning. As with the bacteria, this process serves both to avoid bad regions and seek good ones. If a bad region surrounds a good one, the process keeps the animal within the good region.

	==REFLEX MECHANISMS==		==REFLEX MECHANISMS==
	The beauty of simple orienting mechanisms is that we can capture in one or two simple processes the entire behavioral repertoire of the animal. The familiar psychological cateÃ‚Âgories of motivation, cognition, sensation, and perception are all fused in a harmonious combination of mechanisms that initiate action, respond to stimulation, and guide the animal toward things that will aid its survival and reproduction. Behavior such as the avoiding reaction of Paramecium Ã¢â‚¬â€ reversal of movement in response to a sudden Ã¢â‚¬Å“change for the worseÃ¢â‚¬Â Ã¢â‚¬â€ makes sense as part of a system of reactions that combine to produce adaptive behavior. With animals like birds or mammals, on the other hand, it is more difficult to see how things fit together. Because of this complexity, researchers often succumb to the natural tendency to look for some particular type of behavior Ã¢â‚¬â€ like the Ã¢â‚¬Å“reflexÃ¢â‚¬Â or the Ã¢â‚¬Å“operantÃ¢â‚¬Â Ã¢â‚¬â€ as the key to behavior in general, when the real key is no behavior in particular, but rather how all behaviors fit together to yield adaptation to a niche. The behavior of mammals and birds is so varied and so dependent on individual history, and their ecological niches are so poorly understood, that we cannot grasp as a whole the functional relations among the various elements in their repertoire.		The beauty of simple orienting mechanisms is that we can capture in one or two simple processes the entire behavioral repertoire of the animal. The familiar psychological cateÃ‚Âgories of motivation, cognition, sensation, and perception are all fused in a harmonious combination of mechanisms that initiate action, respond to stimulation, and guide the animal toward things that will aid its survival and reproduction. Behavior such as the avoiding reaction of Paramecium Ã¢â‚¬â€ reversal of movement in response to a sudden Ã¢â‚¬Å“change for the worseÃ¢â‚¬Â Ã¢â‚¬â€ makes sense as part of a system of reactions that combine to produce adaptive behavior. With animals like birds or mammals, on the other hand, it is more difficult to see how things fit together. Because of this complexity, researchers often succumb to the natural tendency to look for some particular type of behavior Ã¢â‚¬â€ like the Ã¢â‚¬Å“reflexÃ¢â‚¬Â or the Ã¢â‚¬Å“operantÃ¢â‚¬Â Ã¢â‚¬â€ as the key to behavior in general, when the real key is no behavior in particular, but rather how all behaviors fit together to yield adaptation to a niche. The behavior of mammals and birds is so varied and so dependent on individual history, and their ecological niches are so poorly understood, that we cannot grasp as a whole the functional relations among the various elements in their repertoire.

Woozle: PDF link

2005-08-14T19:23:41Z

PDF link

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	[[Adaptive Behavior and Learning]]: [[{{PAGENAME}}\|Chapter 2]]		[[Adaptive Behavior and Learning]]: [[{{PAGENAME}}\|Chapter 2]]

			[http://psychweb.psych.duke.edu/department/jers/abl/Chapter02.pdf PDF]
	=Chapter 2: Variation and Selection of Behavior=		=Chapter 2: Variation and Selection of Behavior=

Woozle: reworked indentation

2005-08-14T19:20:26Z

reworked indentation

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