Suggestion: Timing the answer to measure word strength
Hi, I think Duolingo should add timing feature to measure how comfort the user uses the words. For example, if user can answer a question in a short time, it somehow proves that he/she learns well the word. If it takes too long for him/her to answer, the word strength should also be decreases. The timer doesn't need to be shown on the screen but it should run to take the statistic and to measure user abilities.
Time is not a very reliable indicator. How can the system know why it took me so long to answer? Maybe I was distracted by someone or made a typo that took too long to correct. This has nothing to do with my comfort with using a specific word. I think mistakes in answers and peeking on the words should be enough to influence word strength.
However, if there were a word drill, this idea would be useful.