What does it mean when a student confuses 'f' and 'v' in spelling?

Louisa Moats: I had a second grader writing sample this morning and I use the second grade writing sample a lot. This student was writing a list of words ... bed, ship, drive ... and the word drive was spelled 'd'-'a'-'f' ... 'd'-'a'-'f'. So, what I would hope the teacher would be able to do is here, this student was referred for a fluency problem in reading, right? So what does the spelling tell us? It tells us that the student has fuzzy phonology. And what do we mean by that scientific term? It means that what is registering in the student's mind as the constituents of the spoken word — the elements of the spoken word — is a little out of focus because the student wrote an 'f' for the final sound /v/. The difference between 'f' and 'v', or the difference between /f/, the sound, and /v/, the sound is simply voicing ... what we call voicing. Your mouth is doing the same thing

when you say /f/ and when you say /v/ ... the teeth are on the bottom lip. The difference is when you say /v/ as on the end of drive, there's a little buzz in the vocal cords that we call voicing. So it's very logical that ... if the student has what we call a somewhat degraded internal image, if you will, of the spoken word in their mental dictionaries, that they're going to make errors like that in spelling. And it's perfectly transparent to me. The student has not differentiated the finer differences in the speech sounds that are very much alike. So, /f/ and /v/ are a pair. There are nine other pairs of consonants in English that have that same difference of voicing, only voicing ... everything else that the mouth does is the same. /t/, /d/, for example. So if you see that in spelling, it means you need to put a phoneme awareness activity into the code base lesson that requires the student to listen for those differences in those two sounds.

So ... can start with ... are these words the same or different ... fat, vat? And then you get to life, live. And what's the difference between the sounds? You can't just stop with are they the same or different? You have to say, what's the difference? And you can't get to what's the difference unless, in the first place, you've taught the student the identity of the sound. And that's where those speech-sound charts come in. You have to have already identified there is such a thing as /v/, there is such a thing as /f/ ... these two sounds look alike and feel alike. And the difference is what your vocal cords are and are not doing when you make these sounds. So you establish that concept, practice it, relate it to the print, and then look for those errors to disappear with sufficient practice.