Controls: implications stemming from pitch processing and the excluded task

The tasks designed to test an aspect of pitch perception in healthy control

participants raise a number of issues: the effect of identical manipulations of pitch in

speech and music streams, the differences in perceiving short pitch events and longer

ones, and the importance of taking into consideration methodological implications

for the design of tools in the parallel study of language and music. The music

counterpart of the ‘speech pitch’ task was only briefly presented in 4.2. As the performance of controls was very poor, it was thought that employing this task in the

investigations of individuals with impaired processing would serve no meaningful

purpose. However, the control data obtained from this task are worth consideration at

the level of methodology in the parallel study of language and music.

The two pitch tasks required the detection of a pitch difference across a long chunk

in speech and music pitch sequences. That is, in contrast to how pitch perception is

traditionally tested, these tasks did not examine the perception of individual tones or

the detection of off-key tones in a melodic context. Testing controls on these two

tasks pointed to a pronounced dissociation of pitch perception across domains in

healthy participants. The fact that control participants (both musically educated and

musically uneducated) could complete the speech pitch task easily, whereas their

performance was at chance level on its music counterpart is of interest. With respect

to the analogous speech task, another thing that should be noted is that some of the

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stimuli. This suggests that there was a major perceptual difference between the first

part and the second part of the spoken stimuli, when the pitch manipulation was

applied. Such a pronounced difference in the musical stimuli does not seem to have

occurred, as this manipulation did not result in a tone colour difference effect.

Hence, as many controls reported to have perceived parts of the stimuli on the

speech pitch task as belonging to voices of different persons, it can be argued that

this task did not test a pure pitch perception ability. That is, the pitch manipulation

caused a voice quality difference which may not rely solely on pitch perception

abilities. In other words, it can be argued that controls successfully discriminated

between speech stimuli that carried a pitch manipulation extending over half of a

phrase because they identified some difference in the quality of the voice rather than

perceiving a pitch difference. This suggests that the same manipulation in the speech

and the musical domain can, in fact, test different things. That is, in music, one will

not necessarily perceive two music samples played by the same instrument as

samples of different instruments if a small transposition has taken place. Put a

different way, a melody starting two semitones higher than another melody played

on the same instrument will still be perceived as played by the same instrument.

Therefore, in order for the listener to detect the difference between two such

melodies, they should be able to perceive that two melodies started on a different

note. It is possible that placing the transposition in the middle of the melody results

in an even higher degree of processing difficulty. The difficulty in perceiving such a

difference in the music manipulation, while being easily perceived in the speech

manipulation, demonstrated a strong dissociation across domains. This has important

implications both at a theoretical level and at a practical level pertaining to the

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arises as to whether attention to detailed and accurate laboratory manipulations

results in more reliable comparisons. This also pertains to whether precise

manipulations contribute to the understanding of processing of naturally occurring

linguistic and musical stimuli in everyday situations. It can be argued that if –for the

sake of a ‘safe’ comparison– one manipulates stimuli to an analogous degree across domains, these stimuli might acquire a more similar nature than was present in the

original naturally occurring sound streams. That is, manipulating music stimuli in

order to make them comparable to speech stimuli might lead to them both being more likely to be processed in a ‘speech mode’, thus resulting into misleading conclusions about possible differences. Therefore, manipulations aiming to draw

forth a very specific point of comparison can distort the nature of the original

stimulus. After applying this type of manipulation across domains, claiming that

instances of language and music are similar and are processed similarly might be biased by the ‘accuracy’ of manipulation. Alternatively, it can be suggested that it is the manipulated form of instances across domains and not elements of language and

music themselves whose perception is proven to be similar or different. Hence,

although technical manipulations can often guarantee more reliable testing

conditions, examining isolated or manipulated acoustic cues that would not occur in

a natural (out of the lab) context might not be legitimate.

At the same time, the conclusions drawn from these results appear to justify an

assumption that guided the design of the expressive prosody tasks across the

domains. As it was explained in 3.5, the rationale behind the creation of analogous

stimuli was not based on applying exactly analogous manipulations across the

domains. That is, applying identical manipulations across domains might lead to

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occurring stimuli. Moreover, a given manipulation might have a completely different

effect in the speech domain compared to the musical domain and vice versa.

Controlling for a unique pitch manipulation and applying it across domains does not

guarantee that the same type of processing will be engaged across domains. Finally,

making two stimuli across domains comparable by using, for example, music-like

versions of a speech stimulus instead of a real music stimulus does not seem to

constitute a trustworthy method of studying language and music processing.