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subgroups of AP and nonAP musicians with a similar early commencement of music train-
ing. Only the AP musicians showed extreme leftward PT asymmetry. Furthermore, Keenan
et al.^13 found that a decrease of the right PT rather than an increase in the left PT deter-
mined the leftward asymmetry of the PT. From these and other studies65,66it appears that
two factors are of importance in acquiring AP: age of commencement of musical training
and an extreme PT asymmetry. In our sample and in other large samples, it is extremely
seldom that someone developed absolute pitch if they did not start musical training or
were exposed to music before the age of seven.
Although the functional significance of the increased leftsided PT asymmetry in AP
musicians is not clear, it has to be examined in the context of their ability to assign any
pitch to a pitch class or category in the absence of a reference tone.^67 Siegel^68 demonstrated
the influence of possession of verbal labels on recognition memory for pitch. In her study,
AP subjects were able to assign different verbal labels to tones that belonged to different
pitch classes resulting in a better performance than nonAP subjects. Comparing different
tones that belonged to the same pitch class did not result in a performance difference
between AP and nonAP subjects since both groups were supposedly using a sensory cod-
ing strategy. These results could be taken as evidence for the categorical nature of absolute
pitch.^68 We designed a functional MRI experiment that aimed to investigate the functional
significance of the increased left-sided PT asymmetry in AP by contrasting two conditions
with each other, a tone and a phoneme memory task. In the tone condition, subjects heard
a string of sine wave tones (each tone was 500 ms long). A two-alternative forced choice
Figure 24.6Two representative brain renderings. The PT is highlighted in each brain. The AP musician has a pro-
nounced leftward asymmetry that is not seen in the nonAP subject.
AP musicianNonAP musician