Chap.15 Play

鄭先祐 (Ayo) 教授國立台南大學 環境與生態學院

生態科學與技術學系 環境生態研究所 + 生態旅遊研究所

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Play

Defining playTypes and functions of play

Object play Locomotor play Social play A general theory for the function of play

Endocrinological and neurobiological bases of play

A phylogenetic approach to play

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Sea lions Polar bears

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Defining play

Play is all motor activity performed that appears to be purposeless, in which motor patterns from other contexts may often be used in modified forms and altered temporal sequencing.

If the activity is directed toward another living being it is called social play.

This definition centers on the structure of play rather than its function. Purposeless? 不知道，不等於，沒有存在

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Types and functions of play

Object play Refers to play that centers on the use of inanimate

objects such as sticks, rocks, leaves, feathers, fruit, and human-provided objects, and the pushing, throwing, tearing, or manipulating of such objects.

Locomotor play Refers to as locomotor-rotational play

Social play Three functions: (1) long-lasting social bonds, (2)

needed physical skills, (3) development of cognitive skills.

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Leaf-pile pulling. As they go down the slope of a mountain, individuals sometimes walk backwards, pulling handfuls of leaves and then stopping and either walking or somersaulting ( 翻筋斗 ) through the piles of leaves. The (A) photo shows the chimp as he starts to gather a pile of leaves, and the (B) photo shows the same chimp as his leaf pile accumulates.

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Here a cheetah cub comes upon a novel object: a can. Exploring the can appears designed to address the “what is it?” question, while play appears designed to tackle the “what can I do with this object?” question.

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Object play in juvenile ravens

Young animals often have more “free time” than adults to engage in object play.

Mind of the Raven (Heinrish, 1999) Play or exploration? Exploration and play 自然項目有 980items + 44 novel items Exploration and play were directed at novel

items. Benefit of enabling the juvenile ravens to

identify new food sources.

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Various ”hanging games” Heinrich observed in ravens.

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Object play in young cheetahs

Tim Caro examined play in cheetah cubs in the Serengeti National Park in Tanzania for three years (Fig. 15.5).

He observed cubs for more than 2,600 hours and documented many cases of object, social, and locomotor play (Table 15.2).

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In cheetahs, play progressively disappears with age.

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Locomotor play

Two hypotheses: (the function) Provides both exercise and training for

specific motor skills needed later in life. Provides animals with a better

understanding of “the lay of the land”. Pronghorn( 叉角羚 ) play (Fig. 15.7)Physiological effects of elevated

motor activity (Table 15.3)Play and brain development (Fig.

15.8)

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“high-speed running” “fast turns”

“stots”,

jumping with all four legs simultaneously off the ground.

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Mice

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Rats

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Cats

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Social play

Social play and bighorn sheep (Fig. 15.9) Juvenile bighorn sheep who (A)

stayed close to their mothers for extended periods of time play less often than (B) other juveniles.

Social play and cognition Self-assessment

• Young sable antelope like this pair often engage in play, particularly with same-age partners (Fig. 15.10)

Play markers (Fig. 15.11) (play signals) Play face in gorillas (Fig. 15.12)

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(A) Play signals override canine aggression. The dog on the right growls, while the dog on the left “paws”. Pawing is a play signal that can turn a potentially dangerous encounter into a playful one.

(B) Play bows are also often used as signals that the bowing individual wants to play, the dog in this photo is play bowing to another individual.

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Preceding bouts of aggressive play, juvenile gorillas use a facial gesture called a ”play face”, which appears to signal that “what is about to occur is play”.

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Role reversal (self-handicapping)

Older individuals either allow subordinate younger animals to act as it they are dominant during play or the older animals perform some act at a level clearly below that of which they are capable.

The benefits of play (Fig. 15.13) Young animals learn to cooperate during play

(left) and that this might have benefits later in life, when cooperation is necessary– for example, when adult lions are hunting a wildebeest (right).

Role reversal (Fig. 15.14) squirrel monkeys

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In play fighting between older and younger juvenile squirrel monkeys, role reversal sometimes occurs, wherein an older, larger playmate will allow a younger, smaller playmate to act as if he is dominant and to obtain the superior position when they wrestle.

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A general theory for the function of play

Play functions to increase the versatility of movements used to recover from sudden shocks such as loss of balance and falling over, and to enhance the ability of animals to cope emotionally with unexpected stressful situations.

Predictions: The amount of play experienced will affect an

animal’s ability to handle unexpected events. Self-handicapping. The locomotor play should be most common in

species that live in the most variable environments.

mice

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Endocrinological and neurobiological bases of play

Play fighting in young male rodentsFocused on testosterone

Injected neonatal male rats with either testosterone propionate (TP) or an oil substance (as a control).

The presence of testosterone or transformation of testosterone into other substances that affected play fighting in rats.

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Three neurotransmitter systems

Dopamine, norepinephrine, and serotonin Dopamine inhibitors reduce play Siviy experiment

Rat city. This experimental apparatus served as a “play city” for Siviy’s work on rats, play, and neurotransmitters. (Fig. 15.16)

Dopamine may also be involved in the increase in the “chirping’ sound that is often heard during rat play but not at other times.

Fig. 15.17 anticipating play

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Mean number of tunnel crossings in Siviy’s rats. Rats in the “play’ treatment were given a five-minute opportunity to play with a same age partner in a “play city” right before the test. Control animals ha no such opportunity.

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Sexual play in young Belding’s ground squirrels

In natural populations of Belding’s ground squirrels, male initiate much more sexual play than do females. (Fig. 15.18) Females in the testosterone treatment

displayed a significantly increase frequency of sexual play behavior.

Testosterone-treated females displayed sexual behavior at almost the level displayed by same-age males.

Testosterone, play, and food (Fig. 15.19)

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In juvenile Belding’s ground squirrels, males typically display much higher levels of sexual play than do females. Females in the testosterone treatment (T-treated females) increase sexual play. For both young males and females, provisioning (supplementing the diet with a high-fat food) increased rates of sexual play.

Ayo NUTN website:http://myweb.nutn.edu.tw/~hycheng/

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