You are at a noisy playground with your little brother, and you hear a child yell, "mom! " you notice a dozen women pause in their conversations, turning their heads to see if it was their child calling for them. this is an example of

Cocktail party effect.

Explanation:

The phenomenon called cocktail party effect is named after the brain's ability to focus on particular stimulus whilst filtering other stimulus. In other words, we are able to distinguish stimulus and filtering those that we consider important; just like individuals in parties can focus on single conversation in a noisy room but are still listening and filtering outside stimulus, or a mother having a conversation in a noisy playground that suddenly listens a yell that calls for "MOM!".

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