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closeprevalence of absolute pitch in autists
Posted by DirkvdM on 05 Nov 2012 at 09:13 GMT
The probability of obtaining 3 or more individuals with absolute pitch from a sample of 27 given p = 5/10000 is.0000004. We can therefore robustly reject the null hypothesis that our ASD sample was drawn from the normal population
http://plosone.org/article/info:doi/10.1371/journal.pone.0044084#article1.body1.sec3.sec3.sec1.p1
Lacking any reliable resources concerning the prevalence of absolute pitch in autists, this statement appears to be correct.
However, since absolute pitch is (said to be) more prevalent in autists, the null hypothesis that the ASD sample was drawn from the normal ASD population may very well be valid. Actually, the fact that there are 3 in this sample illustrates this. Even with a prevalence as small as 5/10000 any sample can have 1 occurrence. But 3 out of 27 is so unlikely that one should assume the prevalence to be (much) greater.
So it seems that at the least a second graph without this correction might make sense. But of course one autist with absolute pitch more or less would greatly affect the results. If a reliable source for the prevalence is available, the results can be adapted to fit that. If not, a graph of the various outcomes for different percentages would illustrate the possible range. Far from ideal, but at least it would address the issue, which is at the core of this experiment.
RE: prevalence of absolute pitch in autists
DirkvdM replied to DirkvdM on 05 Nov 2012 at 09:58 GMT
Additional note based on Brown et al (ref 68).
"the prevalence of AP among people with autism may be as high as 1 in 20". (Rimland & Fein, 1988)
"Some data suggest that all infants possess AP, that most lose this ability as they mature, and that music training during an early critical period is necessary for the expression of AP (Saffran & Griepentrog, 2001; Takeuchi & Hulse, 1993)."
This appears to make sense given that less pruning takes place in the autist brain (more (and shorter) connections remain). Without music training, a neurotypical brain removes the absolute pitch since it doesn't seem to be useful to that person. But in an autist this might not happen (is less likely to happen) and AP may persist.