Animal Play: Just for fun?
Bernd Heinrich is in the Department of Biology,
Working out why animals play is no easy task.
The Genesis of Animal Play: Testing the Limits
by Gordon M. Burkhardt
MIT Press: 2005. 518 pp. $50, ?32.95
A kitten batting a ball of yarn, kids on a swing, or an adult wielding a fishing-rod — few would disagree that these behaviours can be described as play. Yet in the study of animal behaviour, the phenomenon of play is an anomaly. It is said to be adaptive and yet it involves the expenditure of much energy, often with no apparent pay-off. When a certain behaviour is found to have obvious pay-offs or functions it is, almost by definition, no longer 'play' but is defined by its function, such as foraging, predator avoidance or mating.
According to the simplest, most short-term definition, play is 'just for fun'. But in the long term it may also be practice for a future role, although the ultimate pay-off may only be determined over a lifetime. Consider the activity of batting a ball around. That's play, isn't it? But if someone got paid for it, would it still be play? Even without pay, it may be for practice. And what about others who expend time and resources to watch this senseless activity? It would be difficult to assign adaptive value to these behaviours, or to measure them objectively. Should play then be defined by internal motivation — pleasure, fun? But the motivation of internal pleasure can apply to many complex behaviours, such as hunting, birdsong, sex or chasing a frisbee, although only the latter is likely to be called 'play'. Is play then only 'senseless' behaviour, or is it simply behaviour for which an ultimate function has yet to be discovered?
Play may be plagued by paradoxes and enigmas, but it is a genuine behavioural phenomenon. It is an appropriate subject for enquiry, if only because we know so little about it, despite the interest of scholars who for centuries have tried to define it, fix its boundaries and fathom its functions. For the most part there has been little progress — instead, the subject has become entangled in a web of definitions and controversies. It is clearly time to re-examine play.
The Genesis of Animal Play does not really explore the limits that I allude to above, but to date it is the most comprehensive and illuminating effort to come to terms with this enigmatic topic. Even though Gordon Burkhardt claims his book "is not meant to be a thorough review of play research in animals or people on either a narrow or broad scale", I believe nevertheless that it does come close. Burkhardt reviews the literature (about 1,300 references are cited) and refers to most of the serious attempts to study play. In his attempt to understand its origins and nature, he incorporates both comparative and multidisciplinary approaches.
In the first part of the book, Burkhardt explores the diversity of play behaviour and the history of various theories, definitions and controversies surrounding it. He also proposes criteria for a modern definition of play. He champions the view of ethology laid down by Niko Tinbergen, which says that any definition of a behaviour must encompass four entirely different types of problem: its causation or mechanisms; its adaptation or function; its development or ontogeny; and its evolution and phylogeny. Burkhardt adds a fifth category: the world of private experience. Researchers using this last criterion would ask whether all play is accompanied by one or a few specific emotions (presumably after play has already been identified, not to identify it).
In the second half of the book, Burkhardt examines the phylogeny of play, reviewing examples from studies of mammals, birds, reptiles, fish and invertebrates. Most of the examples of play in the literature come from a small number of placental mammals, in which play is clear-cut. However, because the focus of the book is the origin and function of play, the most relevant examples are those at the boundaries where play is not readily distinguished from non-play. Even among the mammals and the few birds studied, there is a great variety of play or potential play behaviour, so ecological, social and other potentially relevant factors may shed light even within this narrow taxonomic grouping. At the borders, in fish and invertebrates, descriptions of putative play behaviour remain anecdotal. I suspect that few of these will sustain the five criteria for play that the author sets up, but he remains open-minded to the possibility.
Burkhardt concludes by strongly backing the 'surplus resources' theory as a way to predict where and when we might expect to find playful behaviour. This idea is an elaboration of one proposed in 1795 by the German playwright Friedrich Schiller, who wrote: "An animal may be said to be at work when the stimulus to activity is some lack, and it may be said to be at play when the stimulus is sheer plenitude of vitality." Schiller's idea was further elaborated by Herbert Spencer in 1872. Burkhardt brings it into the social context and adds the adaptive significance — that play not only originates from, but also creates, surplus resources that may be useful on subsequent occasions. I am not sure how or at what point in the life of an animal such surplus resources would manifest themselves or how an ethologist could demonstrate their existence. However, the idea surely applies to the activity of scientific research, and perhaps even to the writing of a book.
March 22, 2005
Hypomanic? Absolutely. But Oh So Productive!
By BENEDICT CAREY
Sometimes when talking to people, I'll tell them that I've just had a lot of coffee, even though it's not true, because I know I fire off in all directions, and I can talk to you about anything - literature, string theory, rock guitar - I once worked for Leo Fender - and one thing I say to people is that, of course, I live near the edge; the view is better."
Laurence McKinney, 60, who lives near the edge of
Among other ventures, he said, he has started pharmaceutical companies, played in rock bands and helped design electric guitars, and written a book about the neuroscience of spirituality. This month, for the first time, he helped start a Web site for people like himself. They are known as hypomanics.
At some point, almost everyone encounters them - restless, eager people, consumed with confident curiosity. Researchers suspect that their mental fever shares some genetic basis with that of bipolar disorder, known colloquially as manic depression, a psychiatric disorder characterized by effusive emotional highs and bouts of paralyzing despair.
New research helps explain how people with manic or hypomanic tendencies navigate the small triumphs and humiliations of daily life, and provides clues to how some of them quickly shake off the emotional troughs that their ambitious natures should make inevitable.
"It kind of goes against the common assumption, but many people who are inclined to hypomanic or manic symptoms have an underlying resilience," said Dr. Kay Redfield Jamison, a professor of psychiatry at
In a new book, "Exuberance," Dr. Jamison argues that flights of joyous energy similar to hypomanic states frequently accompany scientific and literary inspiration. Psychiatrists have known for more than a century that bipolar disorder, unlike any other mental illness, is often associated with some financial and professional accomplishment. Mania can inspire destructive shopping or gambling sprees, but it can also generate bursts of creative and focused work.
新的研究有助于帮助解释那些有狂躁症和轻度狂躁症倾向的人如果来对待每天的小得成功与羞辱，and provides clues to how some of them quickly shake off the emotional troughs that their ambitious natures should make inevitable。
“这可能有些违反常规，但是很多倾向于轻度狂躁症或者狂躁症的人都有潜在的乐观性” 约翰霍普金斯大学的Dr. Kay Redfield Jamison说，“他们会因为自己的原因被当做垃圾，被看贬，但是他们的反应非常强烈。”
Some studies suggest that first-degree relatives of people with bipolar illness, who are likely to inherit some genetic basis for bipolar disorder, are particularly likely to enjoy high socioeconomic status.
Most recently, researchers have turned their attention to the mild end of the bipolar spectrum, and sliced it into many permutations. Bipolar II, III and IV, for example, each include depressive episodes and varieties of hypomania, or exuberant moods. Cyclothymic disorder involves rapid cycling from moderate depressive to manic symptoms, and hyperthymia is a state of elevated mood.
"When you look across the entire bipolar spectrum, you find that maybe 10 percent to 15 percent of these people never get depressed: they're just up," said Dr. Ronald C. Kessler, a professor of health care policy at
As one psychiatrist put it, Dr. Kessler said, "The goal in life is constant hypomania: you never sleep too much; you're on; you keep going."
最近，研究者转向了对双极性基因的温和末端光谱的研究，将其分割成多个序列。例如双极II III IV型，每一个都包含有抑郁的片断和多个轻度狂躁片断，或者有丰富的感情的片断。循环型精神病患者笼罩于快速的在中度抑郁和狂躁中转变，并且轻度狂躁症是是这其中的过渡状态。
"For some of us, there is a lot of wariness about this tendency to see bipolar disorder everywhere," said Dr. William Coryell, a professor of psychiatry at the University of Iowa School of Medicine, adding that "it's very difficult to determine reliable boundaries between one diagnosis and another" and document the true prevalence of the conditions.
Yet even if bipolar disorders can be reliably diagnosed in only 2 percent of the population, some now believe that hypomania or similar charged states are more prevalent than previously imagined. About 6 percent of college students score high on personality tests that measure hypomanic tendencies, some studies find, and about 10 percent of children rate as temperamentally "exuberant," a related quality.
Outsized delight in small successes may be central to what kindles hypomanic natures and sustains them. In an effort to learn how the joys and sorrows of daily life affect mania and depression, Dr. Sheri Johnson, a professor of psychology at the
In two studies involving 149 people, one completed in 2000 and the other a continuing project, Dr. Johnson has found that personal victories like a promotion
Even when small successes do not arouse manic symptoms, they appear to prompt exaggerated surges of confidence. In one study, scheduled for publication later this year, Dr. Johnson led a team of psychologists who rated a group of 153 college students on a hypomanic scale, which included items like: "There have often been times when I had such an excess of energy that I felt little need to sleep at night," "I often feel excited and happy for no apparent reason," and "I often feel I could outperform almost anyone at anything."
The scale was intended to identify people at risk for developing bipolar disorders.
The researchers gave the students a hand-eye coordination test, then told them that they had scored very well, regardless of their true scores. Offered a choice of which test to take next, the hypomanic group selected a significantly more challenging exam than their peers did. These students not only expected to do very well, Dr. Johnson reports, they were more willing than peers to pursue difficult goals after an initial success.
Researchers do not know whether this surging confidence and hunger for challenge persists, or for how long, but it is a familiar pattern to some psychiatrists who treat mild forms of bipolar disorder.
Dr. John Gartner, a psychiatrist in
"These are people who are always moving the goal posts," Dr. Gartner said in an interview. "If they do well at one thing, they shoot for the moon."
In a footnote in his book, Dr. Gartner recounts the story of how Henry Ford sailed off on a luxury steamer on a whim in 1915 to personally end World War I and bring world peace. "I'll bet this ship against a penny," Ford boasted to the reporters, "that we'll have the boys out of the trenches by Christmas."
This grandiosity practically begs for a tragic fall. Difficult goals are by definition less likely to be achieved, even by those with mental power packs, and there is little question that people with hypomanic tendencies feel disappointment deeply. For some, their fevered, scavenging curiosity may overwhelm any excess rumination: new projects beckon before the old ones can be mourned.
"I'm not so much smarter than other people as faster," said Mr. McKinney, the polymath near
And that is one catch. Dr. Peter Whybrow, director of the
"Usually what happens in the clinical domain," Dr. Whybrow said, "is that these people come in when they've had a business reversal and they're very depressed. They look back on their lives and realize that they were hyperactive, hypomanic, that they started a lot of projects but finished very few of them."
The view may be better, but it is easy to lose your balance.