advantage over the novel,unequal-interval scale,which rules out expo-
sure as a factor contributing to performance differences.Not only was
infants’ performance poorer for the equal-step scale,infants were simply
unable to detect the pitch change within that context.These findings are
consistent with the view that unequal-step scales have their origin in per-
ceptual processing predispositions,but they also indicate the potency
of culture-specific exposure.In any case,priority for unequal over equal
steps in scales qualifies as another processing universal.Rhythmic Structure
The diversity of rhythmic structures across cultures makes it easy to
imagine that musical rhythms have their foundation in culture rather
than in nature.To explore this issue,we generated “good”and “bad”
rhythmic organizations of a ten-note melody (Trehub, Hill, and
Kamenetsky 1997a).To identify the best of several “good”rhythms,the
patterns were presented in pairs to musically untrained adults,who were
required to choose the better rhythm.A comparable procedure was used
to ascertain the worst of the “bad”rhythms.The most preferred and least
preferred versions served as “good”and “bad”rhythms for six-month-
old infants (figure 23.6).Half of the infants were required to detect a
pitch change in one tone of the melody with “good”or “bad”rhythm;
the other half had to detect a rhythmic change.Infants performed better
for the pitch and rhythmic changes in the context of adults’ preferred
rhythm,which suggests a natural bias for certain rhythmic forms.Of
interest,the “good”rhythm exemplified gestalt grouping principles and
tone durations related by small-integer ratios;the “bad”rhythm did not.435 Human Processing Predispositions
Figure 23.5
Infant performance on the ascending-descending major,unequal,and equal-step scales.
(From Trehub,Schellenberg,and Kamenetsky,in press.)Fig.23.5