Weirdnesses in the Vocab tab
I have discovered what seem to be accounting errors in the Vocabulary list, which probably have a negative impact on the usefulness of the 'spaced repetition' algorithm Duo employs.
One of the Portuguese sentences I practiced recently went something like this:
O edifício tem trinta metros e nove andares.
Now, searching in the Vocabulary section for each of the (nontrivial) words, I see this:<pre>
Word Forms Skill Last practiced Strength -------- -------- --------- -------------- -------- edifício edifício Places 22 hours ago XXXX ter ter Possess. 40 minutes ago XXXX trinta trinta Numbers 40 minutes ago XXXX metro metro Measure. 1 month ago XXXX nove nove Numbers 1 week ago XXXX andar andar Household 22 hours ago XXXX</pre>
The first thing to note is that most of the words present in the sentence did not actually register as practiced.
Next, note that many of the word forms used in the sentence don't show up in the Vocabulary, not even on the word details pages. On the other hand, some words show up several times in the same form. Take the verb
ter, for instance. It appears as if the word has been registered separately for each lesson it appears in, even though it is the same word with the same meaning:
Word Forms Skill Last practiced Strength ---- ----- -------- -------------- ------ ter ter Possess. 48 minutes ago XXXX ter ter V. Past 1 week ago XXXX ter ter V. Inf. 13 weeks ago XXX</pre>
I don't know whether these are mistakes in the course, or if they stem from deeper issues in the Duolingo application. Either way, they likely affect the repetition algorithm.
There are a few different places that these discrepancies can pop up... most of them have to do with the way we shuffle and collate word forms together for display in the vocab page (thus they don't effect the spaced repetition algorithm). But some of them do.
If the challenge is what we call a "reverse translate" (where you make up the foreign language sentence), it is known that some words in the sentence you type might not get updated in your vocab. But the key ones will (i.e., the ones our language experts had in mind to teach when they wrote the sentence). For other challenges, all the words should get updated. But thanks for pointing this out, I'll have a look just in case there's something else going on...
As for the verb "ter," these are actually different senses of the verb: "I have a pencil" (possessive) vs. "I have penciled it in" (past/auxiliary), vs. "I want to have the pencil" (infinitive). We track your experience with the different forms and senses separately in a hierarchical model, although I admit that the way the vocab page presents the information is pretty confusing.