Critical Period Hypothesis and Its Research Evidence | 关键期假设及其研究证据

📚 Critical Period Hypothesis and Its Research Evidence | 关键期假设及其研究证据

The critical period hypothesis (CPH) proposes that an organism must receive certain types of environmental input during a limited window of early development in order for a behavior or neural function to develop normally. If the input is absent or disrupted during this time, the function may never be fully acquired. This hypothesis has been studied across ethology, neuroscience, and developmental psychology, making it a central topic in AP Psychology.

关键期假设指出，有机体必须在早期发育的有限时间窗口内接受特定类型的环境刺激，某种行为或神经功能才能正常发展。如果在此期间刺激缺失或受到干扰，该功能可能永远无法完全习得。这一假设在动物行为学、神经科学和发展心理学中都有广泛研究，是AP心理学的核心主题。

1. Key Concepts and Terminology | 核心概念与术语

The critical period hypothesis states that there is a specific time span during development when an organism is especially receptive to certain environmental stimuli. If these stimuli are absent during that window, the associated ability may fail to develop. A critical period is thus often described as a “now or never” window. This is different from a sensitive period, in which an individual is particularly open to influence but retains some plasticity afterwards.

关键期假设指出，在发育过程中存在一个特定的时间窗口，在此期间有机体对某些环境刺激特别敏感。如果该窗口期内缺乏这些刺激，相应的能力可能无法发展。因此，关键期通常被描述为“要么现在，要么永远”的窗口。这不同于敏感期，敏感期个体特别容易受到环境影响，但之后仍保留一定可塑性。

In AP Psychology, the CPH is used to explain how experience tunes developing neural circuits. For example, binocular vision and language are commonly cited as functions with a critical or sensitive period.

在AP心理学中，关键期假设被用来解释经验如何调控发育中的神经环路。例如，双眼视觉和语言通常被视为具有关键期或敏感期的功能。

2. Ethological Evidence: Lorenz’s Imprinting | 动物行为学证据：劳伦兹的印刻

Konrad Lorenz (1935) showed that newly hatched geese will follow the first moving object they see, a process called imprinting. Geese exposed to Lorenz himself during a short window after hatching treated him as their mother. In natural conditions, this window usually opens within hours after hatching and closes after about one day. After that, imprinting is difficult or impossible.

康拉德·劳伦兹（1935）发现，刚孵化的小鹅会跟随它们看到的第一个移动物体，这一过程称为印刻。孵化后的短暂窗口期内，如果小鹅看到的是劳伦兹，它们就会把他当作母亲。在自然条件下，这个窗口通常在孵化后数小时内开启，并在大约一天后关闭。此后，印刻就很难甚至不可能发生。

Lorenz’s research provides an ethological model of a critical period. It demonstrates that a specific behavior depends on a precise timing of stimulus exposure. It also raises questions about whether similar timing constraints exist for more complex human behaviors.

劳伦兹的研究提供了关键期的动物行为学模型。它表明特定行为依赖于刺激暴露的精确时间，也引发了关于更复杂的人类行为是否也存在类似时间限制的问题。

3. Neurobiological Evidence: Visual Cortical Plasticity | 神经生物学证据：视觉皮层可塑性

Hubel and Wiesel (1963) deprived kittens of vision in one eye by suturing the eyelid closed at different ages. When the eye was closed during a critical period (roughly the first few months after birth for cats), that eye permanently lost functional connections in the visual cortex, even after reopening. The same closure in adult cats caused little or no loss of response.

休伯尔和维塞尔（1963）通过缝合眼睑使小猫在不同年龄单眼视觉剥夺。如果在小猫出生后头几个月的关键期内缝合，即使之后重新打开，这只眼睛在视觉皮层中的功能性连接也会永久丧失。成年猫在同样缝合后几乎没有反应损失。

These results show that neural circuits require sensory input during a limited window to develop proper connectivity. Plasticity is high early in life but declines sharply after the critical window. Later experience cannot fully compensate for early deprivation.

这些结果表明，神经环路必须在一定时间窗口内接收感觉输入才能形成正确连接。早期可塑性很高，但关键期过后急剧下降，后来的经验无法完全弥补早期的剥夺。

4. Language Acquisition and the CPH | 语言习得与关键期假设

Eric Lenneberg (1967) applied the critical period hypothesis to human language. He proposed that language is a biologically based capacity that must be exposed to input between age two and puberty. If this does not happen, first language acquisition will be incomplete, especially for grammar and phonology.

埃里克·伦纳伯格（1967）将关键期假设应用于人类语言。他提出语言是一种生物性能力，必须在2岁到青春期之间接触语言输入。如果这期间未发生，母语习得将是不完全的

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