which test should I use?

#1
Hi
I'm wondering which statistics should I use. I’ve conducted an acceptability judgment task using 7 point scale for 8 different conditions. My study has a 2*2*2 factorial design with two level for each factor, this results in 8 structures mentioned below.
Factor 1: A (-,+)
Factor 2: B (-,+)
Factor 3: C (-,+)

This results in 8 conditions:
Condition 1= A (+) , B (+), C (+)
Condition 2 = A (-) , B (+), C (+)
Condition 3 = A (+) , B (-), C (+)
Condition 4= A (-) , B (-), C (+)
Condition 5 = A (+) , B (+), C (-)
Condition 6 = A (-), B (+), C (-)
Condition 7= A (+), B (-), C (-)
Condition 8 = A (-) , B(+), C (-)

To analyise the data, i’ve used mixed effect model with 3 the three mentioned factors as fixed factors with two levels and with subject and items as random effects. But now i want to check if there is an effect of the subject's dialect (so a new variable other than my three original factors). I have 5 different dialects in my data. I was thinking of testing if there is an affect of dialects on the data in general and then apply the mixed effect model as it is (i.e. by ignoring different dialects and treating all subject in the same way).

My questions are:
(1) how do i test for the affect of dialect on these 8 structures?
(2) Is there a way to test it on all data at once? Or should i check for the effect of dialect per condition?
(3) What type of statistical test should i use?

Thanks in advance!