I've heard a lot about Dr. Stephen Krashen and his hypothesis about language acquisition, and I have no doubt that his research has been an absolute game changer for anyone learning languages. His Comprehensible Input Hypothesis was first published in 1983, but it wasn't until a few years ago that it became famous and implemented by many of us.

His hypothesis shocked many, not by its complexity, but by its blatant logic—you learn or acquire what you understand. If the input goes into one of your ears and comes out the other, you don't understand and therefore don't learn. But to explain this in a simpler way let's consider a vacuum cleaner, which I think bears a striking resemblance.

According to Dr. Krashen, comprehensible input (dust and fluff) enters our brain (the vacuum cleaner), where it's stored (short-term memory, or in the analogy, the vacuum bag ). The more input we can "absorb," the better—just like with a vacuum: the more we run it, the fuller the bag gets, and the cleaner everything becomes.

However, Dr. Krashen points out that only the input that is comprehensible (usually fluff and dust) is successfully acquired, while the rest (dirty socks, empty pizza boxes, crushed Coke cans, and other random, incomprehensible junk that somehow ends up on the floor) is not because it doesn't fit through the vacuum hose.

Dr. Krashen also says that this has to be done over and over again because our brain tends to "clean house" often (unlike some of us) and only keeps what it thinks is important (see: KonMari Method), allowing it to stay in our long-term memory—the HEPA filter (High-Efficiency Particulate Air in real life and Hoarding Essential Phrases Automatically in the analogy).

Of course, Dr. Krashen's hypothesis is much more sophisticated than just a vacuum cleaner analogy, but I think this comparison might help illustrate the basic concept. Just remember, it doesn't have to be a fancy Dyson—any vacuum will do the job just fine.So, the next time you feel overwhelmed learning a language, think of your brain as a vacuum cleaner. And if you're not making progress, maybe it's because you're trying to "vacuum up" too many dirty socks.