Chapter 1 - Learning to Change Flashcards
(25 cards)
Who originally said that change is the only constant? Explain why the author endorses this view? (p. 3)
The Roman philosopher Lucretius said 2,000 years ago, “Change is the only constant.”
Throughout nature, the struggle to survive is an effort to cope with change: The climate changes, prey animals become harder to see, predators become faster, diseases strike without warning, population increases put added stresses on the availability of food, water, habitable space, and other resources. Some changes, such as the movement of continents, take place over eons; others, such as the advance or retreat of glaciers, normally take hundreds or thousands of years; some, such as the changes in climate we are now seeing due to human use of fossil fuels, take decades; still others, such as the rise and fall of the sun or the abrupt lane change of an aggressive driver, occur on a daily basis. The one constant in our lives is change. Any individual or species must be able to cope with change if it is to survive.
Describe why Darwin rejected Malthus’ view of the effects of human population growth. (p. 5)
Thomas Malthus (1798) was a clergyman who did not accept the then-popular idea that human population growth was the path to utopia. On the contrary, Malthus argued that it was the road to ruin. Resources are limited, and eventually an expanding population spells disaster.
Malthus focused on the effects of human population growth, but Darwin realized that all species of animals and plants produce far more offspring than the environment can possibly support, which inevitably leads to competition for resources. Some survive, but most do not. What determines which individuals and species will win out? Clearly the winners must have features that give them an advantage. Those of their offspring that share their parents’ advantage will also tend to survive and reproduce. Over generations, these advantages, some of them very subtle, may accumulate and result in very different species
Describe Darwin’s theory of adaptation based on natural selection. Was Darwin aware of the genetic basis for evolution? Who discovered the genetic basis for natural selection and when? (p. 6)
In Darwin’s day, little was known about how characteristics were transmitted from one generation to the next. As Darwin noted, “The laws governing inheritance are quite unknown. . . .” The Austrian friar and founder of genetics, Gregor Mendel, did not publish his work on inheritance in peas until 1866, and it did not become widely known among scientists until the early 1900s.
Darwin stated that if all members of a species were genetically identical, natural selection would be impossible. Why did he state this, and what is one of the criticisms of Darwin’s theory? (pp. 6–7, 19, 21)
It is important to note that natural selection depends on variations among the members of a species. If all members of a species were genetically identical, natural selection would be impossible. As Darwin wrote, “unless profitable variations do occur, natural selection can do nothing.”
Darwin’s critics have often said that even with variation, natural selection cannot possibly account for the sudden appearance of complex organs such as the human eye. You may be surprised to learn that Darwin agreed. But Darwin went on to say that complex organs do not normally appear suddenly.
Provide examples where change has been very gradual and another example where change has been rapid. (pp. 7–9)
The west coast of Scotland is famous for its cold winters and its warm wool. Until recently the Soay sheep that produced that wool tended to be large, since smaller sheep often succumbed to the cold before reaching reproductive age. Over the past 25 years, however the sheep of this area have been getting smaller and lighter. This reduction in size parallels a change in climate due to global warming: Winters in Scotland have gotten shorter and milder in recent decades, so smaller sheep now are more likely to survive and reproduce.
The brain and the eye - very gradual.
Is natural selection likely if there are no significant changes in the species’ surroundings? Explain your answer. (pp. 7, 25)
Once a species is well adapted to its environment, the rule seems to be: no change in the environment, no change in the species.
We can see this, for example, in the American alligator, a creature that has scarcely changed in 200 million years. The alligator is ideally suited to its habitat, the ponds and wetlands of the American Southeast, particularly the states of Louisiana and Florida, where 2 million of them survive today. The alligator’s territory has shrunk drastically over the millennia, but otherwise changed little.
Why do predators play an important role in natural selection? (p. 9)
The researchers moved wild guppies in Trinidad from a stream that had no predators to a stream with guppy-eating fish. Eight years later Gordon transferred more guppies from the safer stream and compared the survival rate of their young with the young of guppies that had lived among the predators for many generations. The evolved guppies had a survival rate more than 50% higher than that of the newcomers.
What is a reflex? Describe reflexes that exist in the amoeba. Describe the rooting reflex in babies. Describe the salivary reflex. Provide examples where reflexes may not be useful. (pp. 11–13)
A reflex is a relationship between a specific event and a simple response to that event. A reflex is not, as is often thought, a particular kind of behavior. Rather, it is a relationship between certain kinds of events, usually events in the immediate surroundings, and relatively simple forms of behavior.
When the amoeba encounters a noxious substance, it immediately withdraws from it; this reflex minimizes the harmful effects of the substance.
Touch a baby’s face, and she will turn toward what touched her; this rooting reflex is useful in finding the mother’s nipple.
Food in the mouth elicits the salivary reflex, the flow of saliva that begins the process of digestion. The presence of saliva and food in the mouth triggers swallowing.
Not all reflexes are useful. Some people have life-threatening allergic reactions to certain foods, such as peanuts. In some people, epileptic seizures can be triggered by flickering lights, a loud noise, a certain kind of music, or a particular odor.
What term is now used for what was once called instinctive behaviour? (p. 13)
Another kind of naturally selected behavior is the modal action pattern (MAP), a series of related acts found in all or nearly all members of a species. They used to be called instincts, but this term fell out of favor.
Modal action patterns resemble reflexes in that they have a strong genetic basis; display relatively little variability from individual to individual or from day to day in the same individual; and often are reliably elicited by a particular kind of event, called a releaser. MAPs differ from reflexes in that they involve the entire organism rather than a few muscles or glands; are more complex, often consisting of long series of reflex-like acts; and are more variable than reflexes, though still rather stereotypic.
Why do modal action patterns (MAP) contribute to the survival of a species? Give examples. (p. 14)
Consider, for example, salmon that migrate upstream to breed. This act often requires the fish to ascend steep cliffs and swim against rushing currents. At one time, returning to the breeding area might have constituted a relatively easy swim up a gently rising stream. As geological changes gradually increased the steepness of the slope, those fish with the ability to make the trip bred successfully and reproduced their kind, whereas those not up to the challenge failed to reproduce.
MAPs evolve through natural selection because they contribute to the survival of the species. They do this chiefly by helping the individual find food, deal with threats to their safety, or pass their genes on to the next generation. The pine bark beetle burrows into pine trees to find a meal. Some spiders spin webs with which they capture prey, while others lie in wait and pounce on an unsuspecting meal as it passes by. The buck moth caterpillar climbs deciduous trees, particularly oaks, to feed on the leaves. Pigs root for worms, larvae, and truffles beneath the ground. Woodpeckers peck on trees to get at the insects that feed there, while the yellow-billed cuckoo and other birds feed on the caterpillars that feed on leaves.
Many MAPs serve to protect the individual from environmental threats, such as predators. The rattlesnake shakes its rattle when approached by an animal, such as a Boy Scout, that may harm it. When confronted by a threatening dog, the house cat arches its back, hisses, growls, and flicks its tail. These acts make the cat appear larger and more formidable than it really is and may therefore serve to put off an attacker. The opossum responds quite differently to predators: It plays dead. Some of the opossum’s predators eat only animals they themselves have killed; others will cover a dead animal they find and return to eat it later, so a “dead” opossum has a chance of surviving.
Are there modal action patterns in human beings? Discuss the prevailing view of this issue. (p. 15)
Today, many researchers maintain that there are no true modal action patterns in people, that the “instincts” previously attributed to them lack the monotonous character of web spinning in spiders and nest building in birds. For instance, for thousands of years, people around the planet obtained food mainly by hunting and gathering, with men typically doing the hunting and women doing the gathering. But the hunting and gathering took different forms in different regions and at different times, and the gender roles were not absolute. And today people are more likely to obtain their food by sitting at a desk than by shooting deer or digging up roots.
Describe the fixed-action pattern of tropical army ants that suggests they are engaging in intelligent behaviour. (pp. 13–14)
An illustration of the unthinking nature of modal action patterns is provided by the tropical army ant. Entire colonies of these ants charge across the forests in what appears to be a highly organized, intelligently directed campaign. However, the ants are merely following a chemical trail laid down by the ants ahead of them. On a flat surface, such as a road, where no obstacles direct the course of the march, the lead ants tend to move toward the ants beside them. The column then turns in on itself, and the ants soon march round and round in a circle. This is not very intelligent behavior.
Define a general behaviour trait. Identify how general behaviour traits differ from fixed-action patterns. (pp. 16–17)
Over the past few decades, a great deal of research has focused on the role of genes in determining what I will refer to here as general behavior traits. By this I mean the tendency to engage in a certain kind of behavior. Examples include the tendency to be shy (or outgoing), aggressive (or mild-mannered), adventurous (or cautious), anxious (or relaxed), and obsessive-compulsive (or impulsive).
Some behavior traits were once classified as modal action patterns, but they differ from the latter in important ways. As noted previously, modal action patterns are elicited by fairly specific kinds of environmental events, called releasers. The gaping mouth of a fledgling induces the parent bird to provide food; a closed beak does not have this effect. Behavior traits, on the other hand, occur in a wide variety of situations. For instance, under certain circumstances, unpleasant experiences will reliably produce aggressive behaviour in many animals, including people . But unpleasant experience covers a lot of territory. It can include, among other things, an electric shock, a pinprick, a spray of cold water, a threatening stare, an insult, an air temperature above 90 degrees, and so on. All can increase the likelihood of aggressive behavior. Modal action patterns are not released by so many different kinds of events.
Another difference between modal action patterns and behavior traits concerns the plasticity of the behavior. Compare the modal action pattern of the web-spinning spider with the aggressiveness of a shocked rat. Each web-spinning spider spins a web with a specific pattern, and it goes about the task with a remarkable sameness, like someone living a recurrent dream. Moreover, the web spinning of one spider is remarkably like that of other members of the same species (Savory, 1974). But the rat that attacks its neighbor goes about it in a far less stereotypic manner, and there may be considerable difference between the attack of one rat and that of another of the same species.
Describe how genetic engineering has been able to demonstrate the role of genes in behaviour traits. (p. 17)
Today, researchers can use genetic engineering to demonstrate the role of genes in behavior traits. Gleb Shumyatsky, a geneticist at Rutgers University, and his colleagues removed a particular gene from mice and then bred a line of mice without the gene. Although these mice looked and generally behaved normally, the missing gene had a profound effect on one kind of behavior. When mice are placed on an unfamiliar white surface, they normally display caution. The engineered mice, however, were much bolder: They spent twice as much time exploring the area as the ordinary mice did. A similar study identified a genetic component in social dominance.
Selective breeding and genetic engineering are not available as research tools where humans are concerned, but twin studies and studies of specific genes serve researchers well. Researchers have shown that, as in other animals, genes play an important role in fearfulness, excitability, aggressiveness, activity level, drug abuse, and risk-taking.
What are the limits of natural selection? Describe with reference to Gordon’s study of guppies. (p. 19)
Consider Gordon’s study of guppies put into a stream where they were exposed to new predators. The guppies adapted, but it took between 13 and 26 generations. Guppies are short-lived, so those generations occurred over only eight years. Other species take longer to reach sexual maturity and have longer gestational periods, which makes adaptation through natural selection even slower. Humans, for example, reach sexual maturity in their teens and gestation is nine months, so it takes a minimum of about 13 years to produce a new generation. For us to get the kind of adaptive changes seen in Gordon’s guppies would likely take more than 200 years, and that is assuming that women would routinely have children in their teens.
Natural selection is therefore of limited value in coping with abrupt changes.
What are mutations? Describe their relationship to survival and natural selection. (p. 20)
Sometimes abrupt changes in genes, called mutations, appear, and although most of them do not help in the struggle for survival, occasionally they prove useful. When the mutation provides a significant advantage, it may “sweep” through the population and could conceivably ensure the survival of the species.
Why can hybridization help in species adaptation? Provide an example. (p. 20)
Hybridization, the cross-breeding of closely related species, can also aid species adaptation. Mating between different species of animals sometimes occurs in the wild when the species share the same territory. A grizzly bear is known to have mated with a polar bear, for example, producing offspring with characteristics from each parent.
Matings across species should increase the variability of genes in the next generation and thereby lead to useful adaptations
Learning has been described as the acquisition of behaviour. Why has this definition been rejected? What is the definition accepted by Chance? (pp. 21, 24)
The word change is preferred over acquisition because learning does not always involve acquiring something, but it does always involve some sort of change. Joan would like to quit smoking; Bill wants to stop biting his nails; and Mary and Harry would like to quarrel less often. All of these reductions in behavior, if they occur, are examples of learning, but nothing has been acquired - at least, not in the ordinary sense of that word. Learning means a change in some aspect of behavior such as its frequency, intensity, speed, or
form.
Discuss the evidence that covert speech is essentially a diminutive form of speech. Can unconscious thoughts be considered a behaviour? (pp. 22–23)
Neurological evidence supports the idea that our covert speech is essentially a diminutive form of speech. In one experiment researchers found that a kind of magnetic stimulation of an area of the brain involved in language interfered with both overt and covert speech. If thinking were fundamentally different from overt speech, it seems unlikely that stimulation that interferes with one would interfere with the other.
What about unconscious thoughts - are they behavior? No, but they are not thoughts, either. The phrase unconscious thoughts is an oxymoron. True, your brain is routinely engaged in activities of which you are unaware, and some of these activities may affect your behavior (your covert and overt speech, for example). But the same thing can be said of your salivary glands, stomach, liver, intestines, and bone marrow; are the unconscious activities of these organs thoughts? Yet thoughts are not identical to overt behavior. In particular, they often have different effects. If I’m in a stuffy room I can open a window and let in fresh air; thinking about opening a window will not have that effect.
What is a stimulus? Provide original examples of a stimulus. (p. 24)
Stimuli are physical changes in an organism’s environment. They are the changes in air pressure we call sound, the light waves we call sights, the tactile pressures we call touch.
What is experience? Are all changes in behaviour due to experience? Are all experiences learning experiences? Give original examples to support your answers. (p. 24)
Our definition says that learning is due to experience. Experience means changes in the environment, so our definition of learning is, in effect, a change in behavior due to changes in the environment. These changes in the environment are events that affect, or are capable of affecting, behavior. Such events are called stimuli.
Do all changes in behaviour, even those resulting from changes in the environment, qualify as learning? Provide examples. (p. 25)
Not all changes in behavior, even those resulting from changes in the environment, qualify as learning, however. A physician may give an emotionally distraught man a tranquilizer, but we do not then say that the patient learned to be calm. A woman who is usually very agreeable may, following a head injury, become very argumentative. If this change in behavior is due to brain damage, we do not say that she learned to be quarrelsome. Changes in behavior that are due to drugs, injury, aging, or disease do not qualify as learning.
Define habituation. Provide an example of habituation. What factors can influence habituation? (p. 26)
Habituation is a reduction in the intensity or probability of a reflex response as a result of repeatedly evoking the response.
Wagner Bridger (1961) studied habituation in infants and found that when babies first heard a noise, they responded with an increase in heart rate. With repetition of the noise at regular intervals, however, the change in heart rate became less and less pronounced until, in some cases, the noise had no measurable effect.
Variations in the stimulus used to elicit the response affect the rate of habituation. For example, a sudden loud noise will typically elicit the startle reflex - the “jump” you experience when, for example, the wind causes a door to slam shut. But the rate at which habituation occurs depends on the loudness of the sound, variations in the quality of the sound, the number of times the sound occurs, the time interval between repeated exposures to the sound, and other variables.
What is the focus of the nature-nurture argument? What is a major problem with casting nature-nurture questions as a debate? Explain this problem with reference to the idea that humans are (or are not) naturally aggressive. Make reference to the research of Kuo and Wilson. (pp. 28–29)
The trouble with the nature–nurture debate is that it creates an artificial division between the contributions of heredity and learning. The debate wrongly implies that the answer must be one or the other.
Cats provided another example. It seems obvious that cats have a natural attraction to rats—as food, not as playmates. Zing Yang Kuo (1930) of China reared kittens under different conditions. Some grew up with their mothers and had the opportunity to see them kill rats. Others grew up away from their mothers and never saw rats killed. When the kittens matured, Kuo put them together with rats. He found that 86% of the cats that had been reared with their mothers killed rats, but only 45% of the others did. Thus, even something as basic as killing “natural” prey is strongly influenced by experience.
Aggression in humans also seems to be the product of a tangled mix of nature and nurture. Wilson (1978) reports that among the !Kung San, an aboriginal people of Africa, violence against their fellows was almost unknown. But Wilson points out that several decades earlier, when the population density among these people was greater and when there was less governmental control over their behavior, their per capita murder rate rivaled that of America’s most dangerous cities. Wilson (1978) adds that the Semai of Malaya also demonstrated the capacity for both gentleness and violence. Murder is unknown among these people; they do not even have a word in their language for the concept. Yet when the British colonial government trained Semai men to fight against communist guerrillas in the 1950s, the Semai became fierce warriors. One anthropologist wrote that “they seem to have been swept up in a sort of insanity which they call ‘blood drunkenness’” (Dentan, quoted in Wilson, 1978, p. 100). Wilson concludes from such evidence that “the more violent forms of human aggression are not the manifestations of inborn drives . . . [but are] based on the interaction of genetic potential and learning.”
