Language Development – MCAT Psychology | MedSchoolCoach

Language Development

MCAT Psychology - Chapter 2- Section 5 - Cognition - Language
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Sample MCAT Question - Language Development

Words one can understand are generally described as one’s:

a) Productive vocabulary.

b) Receptive vocabulary.

c) Comprehensive vocabulary.

d) Written vocabulary.

B is correct. Receptive vocabulary comprises the words one can understand. A is incorrect. Productive vocabulary comprises the words one can actively and correctly produce/speak. C is incorrect. Comprehensive vocabulary comprises all the words one is able to understand and produce. D is incorrect. Written vocabulary comprises all the words one can write, not just understand.

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Language Development for the MCAT

When infants are born, they are incapable of producing speech. They can make sounds and cry, but they cannot produce speech. At the age of six to nine months, infants begin to produce pre-speech sounds, called babbling, and from ages nine to 18 months, infants begin to learn words and build their vocabulary. In this post, we’re going to go over several key concepts related to language development that you need to know for the MCAT. 

Naming Explosion/Word Spurt

The rate at which children learn words is not linear. Initially, young children learn words slowly at a rate of approximately 10 words per month. But once they have learned approximately 50 words, they experience what is called a naming explosion. This is also known as a word spurt or a vocabulary spurt. These terms describe the stage in which children begin to learn words at a much higher rate, usually at around 30 words per month.

Fast Mapping

The process by which children learn new words after single exposure is called fast mapping. However, this process often leads children to make common errors, including overextension, underextension, and telegraphic speech.


Overextension is when a child incorrectly uses a word beyond the scope of its meaning. An example would be a child that learns that their pet dog is called a “dog.” Then, when they go outside, they see a furry animal, like a cat, and they call the cat a “dog.” This is overextension.


Underextension is the opposite. This is when a child incorrectly restricts the use of a word. For example, say again that a child learns that their pet dog is called a “dog,” so they call their pet a “dog.” However, when the child goes outside and sees other dogs, they don’t call those dogs “dogs.” This is underextension. 

Telegraphic Speech

Finally, we have telegraphic speech. This is condensed speech that typically only contains the central components of the speech (the nouns and the verbs) and excludes the connective parts of speech. An example would be a child saying, “give toy,” as opposed to the complete speech: “Please give me the toy.”

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