Subject: Re: Absolute pitch discussion From: yund <yund@xxxxxxxx> Date: Fri, 31 Aug 2007 15:43:21 -0700 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>Contrary to Braun's claim, a bimodal distribution like that of Fig. 1 in the PNAS paper, is not strong (or even weak) evidence for a simple genetic factor. A skill will show such a bimodal distribution if it is something that is not learned in normal everyday activities. Those who take up activities that teach the skill will be on one end of the distribution and us others will be on the other end. Of course, there will also be some individuals in the intermediate range (as in the cited Fig. 1) due to statistical properties of testing, incomplete learning, generalization from other abilities, or something else. Another possible explanation (also more likely than a simple genetic factor) is an early environmental factor that biases development of the trait. I am not an expert in genetics, but I have often heard my wife (who does have these credentials) vent her frustrations at claims of a simple genetic factor on the basis of such non-evidence. Bill Yund ------------------------------------------ E. William Yund, Ph.D. Hearing Loss Research Laboratory (151/MTZ) VA Northern California Health Care System 150 Muir Road Martinez, CA 94553 yund@xxxxxxxx (925)372-2296 FAX (925)228-5738 ------------------------------------------ Martin Braun wrote: > Dear Robert, Diana, Henkjan, Roy, and others, > > Robert Zatorre asked (concerning the recent PNAS study): > > "Could it be, therefore, that the over-representation of AP in the > distribution represents a sampling bias?" > > Yes, of course. But the crucial question is: Could the bimodal > distribution (clear APers vs. clear non-APers) be the result of a sampling > bias? And here the answer definitely is "No". There is nothing in the > design > of the web study that could have attracted zero-APers on the one hand and > excellent APers on the other hand, but then could have repelled moderate > and > low performance APers. > > Thus the bimodal distribution, as shown in Fig. 1 of the study, has to be > regarded as an empirical fact. The consequences of this finding are > far-reaching. All human traits that are of purely environmental origin only > show one mode in the distribution of its strength. > > If a trait shows two modes in the distribution, as is the case with many > pathological traits, we can be certain that a relatively simple genetic > factor is involved. In conclusion, after this new PNAS study, we are now > compelled to expect that a relatively simple genetic factor is involved in > the development of the cognitive version of absolute pitch (AP). > > This does not mean that the environmental factors that were mentioned in > this discussion have become less important. But it is now clear that > environmental factors are not sufficient for the development of the AP > trait. > > The crucial Fig. 1 of the study is easily available here: > > http://www.pnas.org/cgi/reprint/0703868104v1 > > > Martin > > --------------------------------------------------------------------- > Martin Braun > Neuroscience of Music > S-671 95 Klässbol > Sweden > web site: http://w1.570.telia.com/~u57011259/index.htm > > > > > ----- Original Message ----- From: "Robert Zatorre" > <robert.zatorre@xxxxxxxx> > To: <AUDITORY@xxxxxxxx> > Sent: Wednesday, August 29, 2007 6:21 PM > Subject: Re: Absolute pitch discussion > > > I would agree with Roy's point that the whole issue of AP is > complicated, so let's not look for simple solutions. The paper by > Deutsch et al is very interesting, but note that its results can be used > just as well as evidence either for genetics or for early tone-language > exposure, since the higher incidence of AP was found in ethnically > Chinese students as compared with non-Chinese; so they were comparing > two populations with different genomes as well as different language > histories. > > As for the PNAS study, it also presents very interesting and valuable > data, and I like the web-based approach they used. However, I wonder if > the two subpopulations seen in the distribution are somehow a > consequence of the recruiting system used. People were not entered into > the test randomly, rather they self-selected to participate, and people > who know they have AP would naturally want to test themselves to see how > they score. Could it be, therefore, that the over-representation of AP > in the distribution represents a sampling bias? > > Robert > -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > > Robert J. Zatorre, Ph.D. > Montreal Neurological Institute > 3801 University St. > Montreal, QC Canada H3A 2B4 > phone: 1-514-398-8903 > fax: 1-514-398-1338 > e-mail: robert.zatorre@xxxxxxxx > web site: www.zlab.mcgill.ca > >