Last week, the website Science Daily reported on a recent study that suggests reading curricula in kindergarten classrooms are deficient. Beyond the simple dearth of words taught, the study criticized kindergarten curricula's word complexity and lack of review, both crucial aspects of vocabulary learning at any age, and worth looking at more closely.

When learning vocabulary, it's important to work with "just right" words. In the kindergarten study, researchers found that curricula introduced words that many kindergarteners were likely already to know. Take for example the word funny, which seemed to be, well, a funny choice for kids who have likely been hearing and using that word for years. Why not focus instead on more complex words such as hysterical?

We take this kind of decision about word complexity very seriously here at When you play the Challenge, we're not sending you random words, or marching you through a one-size-fits-all progression. Rather, from the first few questions you answer, we're building a model of what you know and what you’re ready to learn and then we're actively choosing questions on words that are just right for you. The words you're learning will expand your knowledge, but not too far, building up slowly and filling in gaps in what you, personally, know. 

Reviewing is vital. In the kindergarten study, researchers critiqued a lack of review.

The study found that not enough attention was given to reviewing vocabulary words — or going back over the words in different contexts — and to monitoring whether the students truly grasped their meanings.

"So you're spending time teaching something," [lead researcher and Michigan State University professor of education Tanya] Wright said, "but not spending time checking if the kids ever learned it."

But even if kindergarteners had learned the words at the outset, without proper review they're not likely to retain what they learned. As we wrote in earlier blog posts "The Forgetting Curve" and "Can Forgetting Help You Learn?" research shows that the human brain is designed to discard information it learns within days of encountering it, and the only way to keep this forgetting from happening is through review. In fact, new vocabulary words must be revisited four or more times before they can be trusted to stay put in the brain for any significant amount of time.

That's why, when designing the Challenge, we created algorithms that maximize the brain's natural capacity for memory building by making conscious choices about when and how often you see questions on words. Even after you've mastered a word, it will continue to appear in your Challenge play, to make sure it remains active in your brain.

Unfortunately, the Challenge is not designed for kindergarten use. So, kindergarteners: Come talk to us in fifth grade. The rest of you? Get back to the Challenge — you're making up for lost time!