Hold a tissue or an unfolded napkin in front of your lips so that it moves when you breathe, and then say “peak.” If you’re a native speaker of one of several varieties of English, including Canadian English, a distinct burst of air should follow your P, causing the tissue to flutter. Now, say “speak.” This time around, the tissue should stay more or less still; it’s the same deal for the P in “leap.”
In linguistics, the name for that puff of air following P is “aspiration,” and in some languages, it makes an absolute difference. In those languages, P, like in “speak,” and P with the puff of air, like in “peak,” are as distinct as P and B are in English — Thai and Hindi speakers, I’m talking about you! In English, however, P’s are P’s whether they are aspirated or not, which (if you’re interested in language) reveals something totally fascinating about sound representation in the mind.
In the language acquisition process, humans learn to group some types of sounds categorically, so that measurably distinct sounds like a “puffy P” and the regular kind of P can be considered the same thing. Experiment after experiment shows that newborns are sensitive to all kinds of subtle linguistic contrasts like aspiration, but as those newborns become infants, their brains start to categorize sounds and focus only on the sound distinctions found in the primary surrounding language(s). So when it comes to picking up relevant sound contrasts and forming sound categories, the brain sure knows its stuff!
