Biological Bases of Behavior
AP Psychology Topic 1 18:17 English narration · English + 中文 subtitles burned in
Chapters
Transcript
The teacher hands out the exam paper.
老师发下试卷。
Before you have read a single word, your heart is already faster and your hands are cold.
你还没有读到一个字， 心跳就已经变快，手也凉了。
You did not choose that.
这不是你选的。
Something in your body decided it for you, in less than a second.
是你身体里的某个东西替你决定的，用了不到一秒。
This unit is about that something.
这一单元讲的就是那个东西。
Six steps.
分六步。
First, where a trait comes from: heredity and environment together.
第一，一个特质从哪里来：遗传与环境共同作用。
Second, the two halves of the nervous system, and the pair inside one of them that pulls in opposite directions.
第二，神经系统的两大部分，以及其中互相拉扯的一对分支。
Third, exactly how one neuron fires and passes its message on.
第三，一个神经元究竟如何放电并把信息传下去。
Fourth, the chemicals that cross the gap, and the drugs that change them.
第四，跨过缝隙的化学物质，以及改变它们的药物。
Fifth, which part of the brain does which job, and what happens to all of it when you sleep.
第五，大脑的哪个部分负责哪项工作，以及睡觉时这一切会发生什么。
And last, how a sense becomes a signal your brain can use.
最后，一种感觉如何变成大脑能用的信号。
Psychology studies behavior, what a person does, and mental processes, what a person thinks and feels.
心理学研究行为，也就是一个人做了什么；也研究心理过程， 也就是一个人想什么、感受到什么。
Unit one asks where both of those come from.
第一单元要问的是，两者从哪里来。
Every trait grows from two sources, and neither acts alone.
每一个特质都来自两个源头，两者缺一不可。
Heredity is what you inherit from your parents.
遗传是你从父母那里继承的东西。
Environment is everything around you: food, family, school, stress.
环境是你周围的一切：食物、家庭、学校、压力。
Height is a good test of this.
身高是个很好的检验。
It is strongly inherited, and poor nutrition still lowers it.
它受遗传影响很大，而营养不良仍然会让人长不高。
So nature and nurture never compete; the question is always how the two interact.
所以先天与后天从不互相竞争，问题永远是两者如何相互作用。
The evolutionary perspective adds a third question: it explains behavior that once helped ancestors survive and reproduce, which is why a fear of snakes is so easy to learn.
进化论视角再加一个问题：它解释那些曾经帮助祖先生存和繁衍的行为， 这就是为什么怕蛇特别容易学会。
Twin and adoption studies are how psychologists separate the two sources: if identical twins raised apart are still alike on a trait, heredity matters for that trait.
双生子研究和收养研究就是心理学家分开这两个源头的方法： 如果分开抚养的同卵双胞胎在某个特质上仍然相似， 那么遗传对这个特质就是重要的。
The nervous system splits in two.
神经系统分成两部分。
The central nervous system, or C N S, is the brain and the spinal cord.
中枢神经系统，缩写C N S，是大脑和脊髓。
The peripheral nervous system, or P N S, carries messages between the centre and the rest of the body, and it splits again.
周围神经系统，缩写P N S，在中枢与身体其他部分之间传递信息，它还会再分。
The somatic branch moves what you decide to move — voluntary movement, like raising a hand.
躯体分支控制随意运动，也就是你决定要动的东西，比如举手。
The autonomic branch runs the involuntary processes you never think about: heartbeat, breathing, digestion.
自主分支管理不随意的过程，那些你从不去想的事：心跳、呼吸、消化。
Inside the autonomic branch sit two systems that pull against each other.
自主分支里面，有两个互相拉扯的系统。
The sympathetic branch prepares the body for action, which is what happened when the paper landed on your desk.
交感分支让身体准备行动—— 试卷落在桌上时发生的就是这件事。
The parasympathetic branch brings it back down afterwards.
副交感分支随后再把身体带回平静。
This is the part students lose marks on: it is not a switch, it is a balance.
这里正是学生最容易丢分的地方：它不是一个开关，而是一种平衡。
Both are always running, and your state is whichever one is winning right now.
两者一直都在运作，你此刻的状态取决于哪一边占了上风。
Before a neuron can fire, know its parts.
在神经元放电之前，先认识它的各个部分。
Neurons are the cells that carry information, and every one of them has the same four pieces.
神经元是携带信息的细胞，每一个都有相同的四个部件。
The dendrites are the branches at one end; they receive signals from other cells.
树突是一端的分枝，负责接收其他细胞传来的信号。
The cell body adds all those incoming signals together and decides.
细胞体把所有传入的信号加在一起，然后做出决定。
The axon is the long fibre that carries the decision away.
轴突是那条长长的纤维，把决定带走。
Many axons are wrapped in a fatty myelin sheath, which insulates the fibre and makes the signal travel much faster.
许多轴突外面裹着一层脂肪质的髓鞘，它起绝缘作用，让信号传得快得多。
Glial cells are the second kind of cell here.
神经胶质细胞是这里的第二种细胞。
They never carry a signal themselves; they give structure, insulation, and waste removal, and the exam expects you to say so.
它们自己从不传递信号，而是提供结构、绝缘和废物清除，考试要求你写出这一点。
Diseases that damage the myelin or the junction show how fragile this is: multiple sclerosis and myasthenia gravis both break transmission.
破坏髓鞘或神经肌肉接头的疾病说明这套系统多么脆弱： 多发性硬化和重症肌无力都会中断传导。
Now one neuron.
现在看一个神经元。
At rest the neuron sits at a resting potential: ready, not firing.
静息时，神经元处于静息电位：准备好了，但没有放电。
Signals arrive at the dendrites.
信号到达树突。
If the incoming signals reach the threshold, the neuron depolarizes and fires, and the impulse runs down the axon.
如果传入的信号达到阈限，神经元就去极化并放电，冲动沿着轴突传下去。
Here is the rule the exam keeps testing.
下面是考试反复考的规则。
The firing is the same size every time.
每一次放电的大小都是一样的。
A weak signal that crosses the threshold and a very strong one produce exactly the same impulse.
一个刚刚越过阈限的弱信号，和一个非常强的信号， 产生的冲动完全相同。
That is the all-or-none principle.
这就是全或无原则。
So how does your brain know something was strong?
那大脑怎么知道刺激很强呢？
By how often it fires.
靠放电的频率。
Strength is carried by rate, never by size.
强度由频率承载，而不是由大小承载。
One more term belongs here.
这里还有一个术语。
Straight after a neuron fires there is a refractory period, a short pause in which it cannot fire again no matter what arrives.
神经元刚放电之后有一个不应期， 在这段很短的时间里，无论来什么信号它都不能再放电。
The impulse reaches the end of the axon, and now it has a problem.
冲动到达轴突末端，现在遇到一个问题。
Neurons do not touch.
神经元之间并不相接。
There is a gap, called the synapse.
中间有一道缝隙，叫做突触。
The signal crosses it as chemical messengers called neurotransmitters, which fit into receptors on the next neuron the way a key fits a lock.
信号以化学信使的形式跨过去，这些信使叫神经递质， 它们像钥匙插进锁一样嵌入下一个神经元的受体。
Afterwards the chemical is pulled back into the neuron that released it.
之后，化学物质被释放它的神经元重新吸收回去。
That is reuptake, and it clears the gap for the next signal.
这就是再摄取，它把缝隙清空，为下一个信号做准备。
Remember it, because it is how many drugs work.
要记住它，因为很多药物就是靠这个起作用的。
If a drug blocks reuptake, more of the chemical stays in the gap for longer, so the next neuron keeps being stimulated.
如果一种药物阻断再摄取， 就有更多化学物质更久地留在缝隙里， 于是下一个神经元会持续受到刺激。
Put three neurons together and you get the reflex arc, and it explains something you have felt.
把三个神经元接在一起，就成了反射弧，它能解释你亲身有过的感受。
Touch something hot and your hand is already moving.
碰到烫的东西，手已经缩回去了。
Sensory neurons carry the message in from the skin to the spinal cord.
感觉神经元把信息从皮肤送进脊髓。
Inside the cord, interneurons connect straight across.
在脊髓里，中间神经元直接把两边连起来。
Motor neurons carry the command back out to the muscle.
运动神经元再把指令送回肌肉。
All of that happens inside the spinal cord, and the brain is told afterwards.
这一切都发生在脊髓里，大脑是事后才被告知的。
That is why it is so fast: nothing in the loop had to think.
这就是它这么快的原因：这个回路里没有任何一步需要思考。
Now name the chemicals.
现在给这些化学物质命名。
Neurotransmitters are what actually cross the synapse, and every message they carry pushes one of exactly two ways.
神经递质就是真正跨过突触的东西，它们携带的每一条信息只会朝两个方向之一推。
An excitatory message makes the next neuron more likely to fire.
兴奋性的信息让下一个神经元更可能放电。
An inhibitory message makes it less likely.
抑制性的信息让它更不可能放电。
Eight of them are examinable.
有八种是要考的。
Dopamine handles reward and movement.
多巴胺负责奖赏和运动。
Serotonin handles mood and sleep.
血清素负责情绪和睡眠。
Norepinephrine handles alertness.
去甲肾上腺素负责警觉。
Acetylcholine handles muscle movement and memory.
乙酰胆碱负责肌肉运动和记忆。
Glutamate is the main excitatory transmitter, and GABA is the main inhibitory one.
谷氨酸是主要的兴奋性递质，γ-氨基丁酸是主要的抑制性递质。
Endorphins relieve pain, and substance P signals pain, so those two are opposites worth remembering as a pair.
内啡肽缓解疼痛，而P物质发出疼痛信号， 这两个正好相反，适合成对记住。
Learn these eight and stop. The exam will not ask you for another.
记住这八种就够了，考试不会问别的。
Hormones do a similar job from outside the nervous system.
激素在神经系统之外做着类似的工作。
Instead of jumping one synapse in a millisecond, they travel through the blood, so they are slower and they last longer.
它们不是在一毫秒内跨过一个突触，而是随血液流动， 所以更慢，作用也更持久。
Five are examinable.
有五种是要考的。
Adrenaline is the alarm that prepares the body for action.
肾上腺素是让身体准备行动的警报。
Leptin turns hunger down and ghrelin turns it up, so a question about appetite is asking about that pair.
瘦素让饥饿感下降，胃饥饿素让它上升， 所以问食欲的题目问的就是这一对。
Melatonin brings on sleep.
褪黑素引发睡眠。
Oxytocin supports bonding and trust.
催产素支持依恋和信任。
Of the glands themselves, only the pituitary gland is in scope, so do not spend revision time on the rest.
至于腺体本身，只有脑垂体在考试范围内，其余的不要花时间复习。
Psychoactive drugs change behavior by acting on that same synapse, and there are only three ways in.
精神药物通过作用于同一个突触来改变行为，而进入的方式只有三种。
An agonist copies the transmitter and encourages firing.
激动剂模仿递质，促进放电。
An antagonist blocks the receptor and discourages it.
拮抗剂堵住受体，抑制放电。
A reuptake inhibitor leaves the transmitter sitting in the gap, so the signal keeps going.
再摄取抑制剂让递质留在缝隙里，于是信号持续下去。
Then learn four categories.
再记住四个类别。
Stimulants speed neural activity up: caffeine, cocaine.
兴奋剂加快神经活动：咖啡因、可卡因。
Depressants slow it down: alcohol.
抑制剂减慢它：酒精。
Hallucinogens distort perception: marijuana.
致幻剂扭曲知觉：大麻。
Opioids relieve pain: heroin.
阿片类药物缓解疼痛：海洛因。
Repeated use builds tolerance, where the same dose does less, and tolerance can lead to addiction, with withdrawal symptoms when the drug stops.
反复使用会形成耐受性，同样的剂量效果变小； 耐受性可能发展为成瘾，停药时出现戒断症状。
Study the brain from the bottom up, because the lower you go the more basic the job.
研究大脑要从下往上，因为越往下，工作越基础。
The brain stem sits at the floor, and inside it the medulla controls breathing and heart rate.
脑干位于最底层，其中的延髓控制呼吸和心率。
Just above, the reticular activating system decides how alert you are.
再往上一点，网状激活系统决定你有多清醒。
The cerebellum, tucked at the back, handles coordination, balance and procedural learning, the kind of skill your hands remember.
小脑藏在后方，负责协调、平衡和程序性学习，也就是手会记住的那类技能。
The limbic system sits deeper inside and holds five structures we will name in a moment.
边缘系统在更深处，包含五个结构，我们马上就要点名。
And over the top of all of it, the cerebral cortex does the thinking, the language and the planning.
而覆盖在最上面的大脑皮层，负责思考、语言和计划。
There is your revision rule: the bottom keeps you alive, the top makes you you.
复习口诀就在这里：下面让你活着，上面让你成为你。
Inside the limbic system, five names, five jobs.
边缘系统里面，五个名字，五项工作。
The thalamus is the relay station: nearly every sense passes through it on the way to the cortex.
丘脑是中继站：几乎每一种感觉在去往皮层的路上都要经过它。
The hypothalamus runs hunger, thirst and body temperature.
下丘脑管理饥饿、口渴和体温。
The pituitary gland releases the hormones we just listed.
脑垂体释放我们刚刚列出的那些激素。
The hippocampus writes new memories, so a patient who cannot form new memories has damage there.
海马体写入新的记忆，所以无法形成新记忆的病人是这里受了损伤。
The amygdala handles fear and other strong emotion.
杏仁核处理恐惧和其他强烈情绪。
One exception is worth a mark: smell is the exception to the relay, because it reaches the brain without passing through the thalamus at all.
有一个例外值得一分：嗅觉是中继的例外， 因为它根本不经过丘脑就到达大脑。
The cortex is folded into two hemispheres and four lobes, and each lobe has one headline job.
皮层折叠成两个半球和四个脑叶，每个脑叶有一项主要工作。
The occipital lobes are at the very back and process vision.
枕叶在最后方，处理视觉。
The temporal lobes are at the sides and process hearing and language.
颞叶在两侧，处理听觉和语言。
The parietal lobes hold the somatosensory cortex, which is touch.
顶叶包含体感皮层，也就是触觉。
The frontal lobes do higher-order thinking and executive function: planning, deciding, holding yourself back.
额叶负责高级思维和执行功能：计划、决定、克制自己。
Language has two special areas, and for most people both sit on the left.
语言有两个特殊区域，对大多数人来说都在左边。
Broca's area produces speech, so damage there leaves speech slow and effortful.
布罗卡区负责产生言语，这里受损，说话就变得缓慢费力。
Wernicke's area understands speech, so damage there leaves speech fluent but meaningless.
韦尼克区负责理解言语，这里受损，说话流利却没有意义。
The two hemispheres talk through a thick bundle of fibres called the corpus callosum.
两个半球通过一束很厚的纤维交流，那就是胼胝体。
To treat severe epilepsy, surgeons cut it, and split-brain research studies what those patients can and cannot do.
为了治疗严重的癫痫，外科医生把它切断， 裂脑研究就是研究这些病人能做什么、不能做什么。
The finding is that the halves can work independently.
结论是：两个半球可以各自独立工作。
Researchers show information to one visual field at a time, because each field is processed by the opposite hemisphere, so a word shown on the left reaches only the right side.
研究者每次只向一个视野呈现信息， 因为每个视野都由对侧半球处理， 所以出现在左边的词只到达右半球。
Brain plasticity is the other half of this story: after damage the brain rewires and can move a job somewhere else, which is why recovery is possible at all.
大脑可塑性是这个故事的另一半： 受损之后大脑会重新连线，把一项工作挪到别处， 所以康复才有可能。
Finally, know how researchers look.
最后，要知道研究者怎么观察。
An E E G records electrical patterns and is what identifies the stages of sleep.
脑电图记录电活动的模式，睡眠的各个阶段就是靠它辨认的。
An f M R I shows which areas are active over time.
功能性磁共振成像，缩写f M R I，显示哪些区域在一段时间里活跃。
Case studies and lesioning make up the rest.
个案研究和损毁法构成其余的部分。
Consciousness is your awareness of what is happening inside you and around you, and it changes level all night.
意识是你对体内和周围正在发生的事情的觉察，它整晚都在变化。
The sleep and wake cycle is a circadian rhythm of about twenty four hours; jet lag and shift work are what happens when you break it.
睡眠—觉醒周期是一种大约二十四小时的昼夜节律； 时差反应和倒班工作就是打乱它以后的结果。
Sleep itself runs through four stages, identified by the E E G.
睡眠本身经过四个阶段，用脑电图来辨认。
Stages one to three are N R E M sleep, which just means not REM, and they go from light to deep.
第一到第三阶段是非快速眼动睡眠，缩写N R E M，意思就是不是快速眼动，由浅入深。
Then comes REM sleep, and you cycle back and forth all night.
然后是快速眼动睡眠，整夜来回循环。
REM is also called paradoxical sleep, and the name is the exam answer: the brain looks awake while the body is at its most relaxed, and most dreaming happens here.
快速眼动睡眠又叫异相睡眠，这个名字本身就是考点： 大脑看起来像醒着，而身体最放松，大部分做梦发生在这里。
One more term for the start of the night: hypnagogic sensations are the strange images and the falling feeling as you drop off.
入睡时还有一个术语：入睡幻觉，就是刚睡着时奇怪的画面和坠落感。
Two theories of dreaming are examinable, and only two.
关于做梦，只有两种理论要考。
The activation-synthesis theory says the brain fires more or less at random and then reads a story into it.
激活-综合理论认为大脑差不多是随机放电，然后为它编出一个故事。
The consolidation theory says dreams reflect memory being processed and filed.
巩固理论认为梦反映的是记忆正在被加工和归档。
Sleep as a whole is explained the same two ways: memory consolidation and restoration.
整个睡眠也用同样两种方式解释：记忆巩固和恢复。
The psychoanalytic theory of dreams is outside the scope of this exam, so leave it out.
精神分析的梦理论不在本考试范围内，不要写。
Five sleep disorders finish the topic.
五种睡眠障碍收尾。
Insomnia is trouble falling or staying asleep.
失眠是难以入睡或难以维持睡眠。
Narcolepsy is sleep arriving uninvited in the middle of the day.
发作性睡病是白天睡意不请自来。
Sleep apnea is breathing that stops and restarts.
睡眠呼吸暂停是呼吸停止又重新开始。
Somnambulism is sleepwalking.
梦游就是睡着后走动。
And REM sleep behavior disorder is acting a dream out, because the usual paralysis failed.
快速眼动睡眠行为障碍是把梦演出来，因为平时的肌肉麻痹失效了。
Now the senses.
现在讲感觉。
Sensation is detecting energy from the world and transducing it into a signal the nervous system can carry.
感觉就是探测来自外界的能量，把它转导成神经系统能够传递的信号。
Transduction is the step that does the turning: light into a neural signal at the retina, air movement into a neural signal in the ear.
换能就是完成这一转变的步骤： 在视网膜上把光变成神经信号，在耳朵里把空气的振动变成神经信号。
Two measurements matter.
有两个测量很重要。
An absolute threshold is the smallest amount you can detect half the time.
绝对阈限是你有一半机会能察觉到的最小量。
A just noticeable difference is the smallest change you can detect, and it is a proportion of the original, not a fixed amount.
最小可觉差是你能察觉到的最小变化， 它是原始刺激的一个比例，而不是一个固定的量。
Two more effects are easy marks.
还有两个效应是容易拿的分。
Sensory adaptation is losing sensitivity to something that does not change, which is why you stop noticing a smell.
感觉适应是对不变的刺激失去敏感，所以你会闻不到原本闻得到的气味。
Sensory interaction is the senses working together, and synesthesia is the extreme case, where one sense triggers another and a person hears a colour.
感觉相互作用是各种感觉协同工作， 而联觉是它的极端情形：一种感觉触发另一种，有人能"听见"颜色。
Perception is the next unit: that is interpreting the signal, and it is a different question.
知觉属于下一单元：那是对信号的解释，是另一个问题。
Take the senses one at a time, starting with vision.
感觉一个一个来，先从视觉开始。
The lens changes shape to focus light onto the retina, and that shape change has a name: visual accommodation.
晶状体改变形状，把光聚焦到视网膜上，这个形状变化有个名字：视觉调节。
When it stops working you get nearsightedness or farsightedness.
它失效时，就出现近视或远视。
On the retina sit two kinds of receptor.
视网膜上有两种感受器。
Rods sit around the edge and detect shape and movement in low light, which is why you see a moving thing better from the corner of your eye at night.
视杆细胞分布在周边，在弱光下探测形状和运动， 所以夜里用眼角余光反而更容易看到移动的东西。
Cones are packed into the fovea at the centre and detect colour and fine detail.
视锥细胞密集在中央凹，探测颜色和细节。
Colour needs two theories, not one, and the exam wants both.
颜色需要两种理论，不是一种，考试两个都要。
Trichromatic theory says there are three cone types, for blue, green and red.
三色理论说有三种视锥细胞，分别对应蓝、绿、红。
Opponent-process theory explains what trichromatic cannot: afterimages, where staring at red leaves you seeing green.
对立过程理论解释三色理论解释不了的现象：后像， 也就是盯着红色看之后会看到绿色。
Damage to the occipital lobes can cause prosopagnosia, also called face blindness.
枕叶受损可能导致面孔失认症，也叫脸盲。
Sound is movement in the air, and two of its properties matter.
声音是空气的运动，其中两个性质很重要。
Its wavelength gives pitch, how high or low it sounds.
波长决定音高，也就是听起来多高多低。
Its amplitude gives loudness.
振幅决定响度。
Pitch perception needs three theories working together, and you should be able to name all three: place theory, volley theory and frequency theory.
音高知觉需要三种理论共同解释，三个名字你都要说得出来： 位置理论、齐射理论和频率理论。
Sound localization is how two ears tell you where a sound came from, because it reaches one ear slightly first.
声源定位是两只耳朵告诉你声音来自哪里，因为它会先到达其中一只耳朵。
There are two kinds of hearing loss and mixing them up costs a mark: conduction deafness means the sound never gets in, and sensorineural deafness means the nerve cannot report it.
听力损失有两种，弄混就丢分： 传导性耳聋是声音进不去，感音神经性耳聋是神经报告不了。
Then the chemical senses.
然后是化学感觉。
Olfaction is smell, and it is the only sense not relayed first through the thalamus.
嗅觉就是闻，它是唯一不先经过丘脑中继的感觉。
Gustation is taste, and there are six: sweet, sour, salty, bitter, umami and oleogustus, the taste of fat.
味觉就是尝，一共六种： 甜、酸、咸、苦、鲜味，还有脂味。
The two work together, which is sensory interaction: block your nose and food goes flat.
两者协同工作，这就是感觉相互作用：捏住鼻子，食物就没味道了。
Last, touch, pain, and body position: the senses that report on your own body.
最后是触觉、疼痛和身体位置：报告你自己身体状况的那些感觉。
Skin receptors transduce touch, and there is a neat surprise here: there is no receptor for hot.
皮肤感受器把触觉转化为神经信号，这里有个有趣的意外：并没有"热"的感受器。
When warm and cold receptors fire together, the brain reports hot.
当温感受器和冷感受器同时放电时，大脑报告的就是烫。
Pain is not a simple wire either.
疼痛也不是一根简单的电线。
The gate control theory says the spinal cord holds a gate that pain signals must pass, and other signals can close it.
闸门控制理论说，脊髓里有一道疼痛信号必须通过的闸门， 而其他信号可以把它关上。
That is why attention closes the gate: rub the spot, or get busy, and the pain drops.
所以注意力会关上这道闸门：揉一揉，或者忙起来，疼痛就减轻了。
Phantom limb sensations, pain felt in a limb that is no longer there, prove the same point from the other side: the pain is made in the brain.
幻肢感觉，也就是在已经不存在的肢体上感到疼痛， 从另一面证明了同一点：疼痛是在大脑里产生的。
Two more senses finish the unit.
还有两种感觉给本单元收尾。
The vestibular sense is balance, and it comes from the semicircular canals in your inner ear.
前庭觉就是平衡，来自内耳的半规管。
Kinesthesis is knowing where your arms and legs are without looking at them.
动觉是不用看就知道自己的手脚在哪里。
Let us do one real question, because the shape of the answer is worth as much as the content.
我们来做一道真题，因为答案的结构和内容一样值分。
In the twenty twenty-five Article Analysis Question, students were asked to explain the extent to which the research findings may or may not be generalizable, using evidence from the study.
在二〇二五年的文章分析题里， 学生被要求解释研究结果在多大程度上可以或不可以推广， 并且要用研究本身的证据来支持。
Start with the claim: the findings may not generalize widely.
先写结论：这些结果可能不能广泛推广。
Then the evidence, taken from the study itself: the participants were undergraduate students at one university.
再写证据，取自研究本身：参与者是同一所大学的本科生。
Then link the two: so the sample did not represent the wider population.
然后把两者连起来：所以样本不能代表更广的人群。
Naming the research method is a real answer, but it answers part A, not this one.
说出研究方法本身是有效的回答，但那是A小问的答案，不是这一问的。
Whenever a command word says explain, it wants a claim plus the evidence behind it.
只要指令词是"解释"，它要的就是结论加上背后的证据。
Five things to take with you.
带走五点。
One: heredity and environment interact, so name both, and say how.
第一：遗传与环境相互作用，两者都要写出来，还要说清楚怎么作用。
Two: sympathetic arouses, parasympathetic calms, and both are always running.
第二：交感唤起，副交感平静，而且两者一直都在运作。
Three: all or none means intensity is carried by rate, not by size.
第三：全或无意味着强度由频率承载，而不是由大小承载。
Four: reuptake clears the synapse, and blocking it leaves the next neuron stimulated, which is how a whole class of drugs works.
第四：再摄取清空突触，阻断它会让下一个神经元持续受到刺激， 一整类药物就是这样起作用的。
Five: match the structure to the job before you write a word, and keep sensation, which detects and transduces, separate from perception, which interprets.
第五：动笔之前先把结构和功能对上， 并且把负责探测和转导的感觉，与负责解释的知觉分开。
Now try the practice questions below.
现在去做下面的练习题。