If letter names are taught first this becomes the 'dominant memory' - the first thing that comes to mind when you see the letter. But beginner readers don't usually need the NAME, they need the sound of letters. The letter names will not help them to read a simple word like 'get'. The names are g (jee), e (ee) and t (tee). The child who hasn't fully established letter sounds may therefore blend those names into 'jeet'. The word won't make sense so the child may simply 'give up'.
With some letters - 'v' for example; the child can say the name /vee/ and from this guess that the sound must be /v/. This is not the case with a number of letters -w,r,y,u,g,c,a, e, i and o and these are the letters than cause name/sound confusions for so many children. Note that ALL the vowels are vulnerable to name/sound confusions.
They letters u/y/w are particularly confusing. Consider the vowel 'U' if the child tries to derive a sound from the name he will come up with 'y' (as in 'yes'). The sound derived from the letter 'Y' would suggest 'w' (as in 'wet')! What does the name 'W' suggest? The child is likely to dismiss 'd' as he has worked out that 'D' says 'd' and respond with 'I don't know'.
Even if the child knows the letter sounds, if the first & dominant memory is a letter's name the child will remember that prior to converting it to sound. This is time consuming and disruptive to the decoding process.
If the child doesn't know the letter sounds, you may get a response similar to the one above (get/jeet). This sort of name/sound confusion, once established is VERY difficult to remediate.
It can be avoided by TEACHING LETTER SOUNDS FIRST,
thereby making the most useful memory the dominant memory.
Then the child can read 'g-e-t' - 'get' and move on.
You may say ... but it is important to teach letter names
- and you are perfectly right. Just - teach the sounds FIRST.