4.2.1 Absolute pitch - a heterogeneous ability
Absolute pitch, the unique ability to be able to name or produce a musical tone without the use of any kind of reference [1] has been said to depend both on genetic factors and on an early sensitive period (see section1.1.3). Specifically it has been acclaimed as
“(...) one of the cleanest examples of a human cognitive ability that arises from the interaction of genetic factors and environmental input during development.
In particular, unlike most other cognitive functions (including language and memory, which are influenced by multiple factors and interact with many gen-eral brain functions), AP is distributed relatively discretely in the population, and its expression is neatly encapsulated, as it seems unrelated to most other cognitive functions.”(Zatorre,Nature Neuroscience, 2003, [47]).
But perhaps absolute pitch is not as clear and “clean” as thought. Other authors, e.g. Wengenroth et al. (2014, [83]), have already argued for a more steadily or even
4.2. General Discussion 31
a uniform distribution of absolute pitch [83]. The present research indicates that autistic traits, cognitive style and brain network connectivity play a role in this abil-ity. But (1) inconsistency of results on cognitive style, (2) the increased, but only in some absolute pitch possessors critically high autistic traits, (3) the missing correla-tion of cognitive style with autistic traits (4) and the brain network characteristics only partly overlapping with autism speak for a heterogeneous ability. The question if and to what extend a co-occurrence of autistic traits and absolute pitch can be ex-plained by shared cognitive and neuroscientific characteristics might therefore only be answered on subgroup level. Or, in other words, autistic traits, cognitive style and brain network connectivity might be related to absolute pitch (and perhaps to each other) only within a subgroup of absolute pitch possessors. However, in the present study, subgroup analysis was not possible because of restrictions with re-spect to sample size.
Nevertheless, the present work shows, that an integrative view of several influenc-ing factors and characteristics of the ability (see Figure 4.1) alongside a brain network perspective is necessary to get more insight into the specific relations between brain, special ability and disability.
FIGURE 4.1: Update: Influences on the acquisition of Absolute Pitch. If and to what extend an individuum exhibits absolute pitch ability relates to various factors indicated with arrows. As a results of the present studies cognitive style and autistic traits are also impor-tant. Interrelation of influencing factors (e.g. autistic traits and brain
network) not shown.
32 Chapter 4. Discussion
4.2.2 Absolute pitch and autism - a common framework?
The question whether the weak central coherence account [132], the enhanced per-ceptional functioning theory [133,137] or other cognitive theories of autism can ex-plain the co-occurrence of autistic traits and absolute pitch cannot finally be resolved in this thesis. Rather it seems that autistic traits and the perceptual-cognitive char-acteristics only comprise one among a range of other influencing factors (see section 4.1). While enhanced auditory disembedding (Publication 3.1), and the tendency towards a more detail-oriented processing of auditory and visual hierarchical stim-uli (Publication 3.2) speak for enhanced perceptual functioning respectively weak central coherence, the inconsistency of the results and the only partially occurring correlations with autistic traits weaken the interpretation.
Based on the results from network analysis (Publication 3.3) it is hypothesized, that both shared and distinct features of autism and absolute pitch exist. Perhaps, while in general, early musical training during a cognitively sensitive period is important for the acquisition of absolute pitch (see section 1.2.3), in a subgroup of AP’s, a life-long tendency for detail-oriented information processing (Publications 3.1, 3.2) and a less integrative brain network (Publication 3.3) might increase the likelihood to develop absolute pitch ability - even later in life [14,46]. The interrelation or even a causal relation of brain connectivity, genetic factors and cognitive style, however, has yet to be explained. Nevertheless, a predisposition for detail-oriented processing or less integrative brain connectivity might explain the on average and individually (often subclinically) higher autistic traits in absolute pitch possessors and the higher incidence of absolute pitch in autism. Therefore, the onset of music exposition might be of less importance in those populations, consistent with the results of Gervain et al. (2013, [46]) and Heaton et al. (1998, [14]).
In conclusion, this might lead to subgroups of absolute pitch possessors that are dis-tinguished by either a more genetically (neurocognitive predisposition) or a more experience based etiology of absolute pitch. However, studies relating genetic influ-ences in the acquisition of absolute pitch to cognitive style, brain network features and autistic traits are missing as are subgroup analyses with much higher sample sizes.
4.2.3 Strengths and Limitations
Several limitations of the studies have to be discussed:
First, no autistic and neurotypical musically matched control groups were included.
A direct comparison with cognitive, neurophysiological and personality traits of autistic people might have helped to understand the differences between relative and absolute pitch possessors. Initially there was indeed a plan to include the two subgroups, but the effort failed due to problems to recrute and motivate autistic in-dividuals to participate in such a long study with several appointments in the lab.
Furthermore, the 10 autistic subjects that could be measured showed a high hetero-geneity of musical experience and comorbid disorders. Therefore an even higher sampled size would have been required to account for all of these covariables. Espe-cially, four of the autistic participants already reported to have absolute pitch ability.
Second, as the present study is a cross-sectional study, no interpretations can be made on the acquisition and development of absolute pitch. Also, the hypothetical interpretation of possibly existing subgroups within the population of absolute pitch possessors can only be proven by subgroup analyses on bigger sample sizes.
Third, no correlation analyses between results from cognitive experiments and brain