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Figure 9. A prosodic representation that incorporates the requirements of the prosodic hierarchy and that allows for level stress
The representation in Figure 6 admits the co-occurrence of two equally stressed feet because every foot projects its own prosodic word. The drawback is that this assumption is ad hoc. There is no motivation for separating a single prosodic word like Dutch / ‘crocodile’ into two prosodic words. In addition, it is an open question which factors could trigger the merging of the two prosodic words into a single one later.

Another problem is that the models described above are primarily based on truncation patterns in multisyllabic words. This is critical from a methodological point of view because it is presupposed that the truncation of syllables is exclusively triggered by prosodic size restrictions. Recent evidence, however, suggests that segmental properties of syllables can also affect the truncation rate. For example, syllables with sonorant onsets seem to be more prone to truncation than syllables with obstruent onsets (Kehoe & Stoel-Gammon 1997).

A comparison of both models suggests that the predictions of the template mapping model of Fikkert (1994) are sometimes too strong. Thus, the prosodic hierarchy model of Demuth & Fee (1995) seems to be superior because of its greater flexibility. First of all, it prevents Fikkert’s circular process of assigning a trochaic structure via prosodic circumscription that actually should be created by the foot template. Furthermore, the prosodic hierarchy model allows for more variability in the productions of children. For example, it allows for the co-occurrence of monosyllabic and disyllabic feet in contrast to Fikkert’s model that only proposes disyllabic trochees for a very long period of time. As the data of children acquiring English suggest, there are doubts on Fikkert’s view that the disyllabic trochee is the unique representation at the early stages (Kehoe & Stoel-Gammon, 1997; Salidis & Johnson, 1997). Moreover, Fikkert predicts a systematic stress shift to the left in disyllabic iambs, a pattern that still needs empirical evaluation. It is also possible that stress shift is rather the result of a complex interplay of factors like edge preferences, weight sensitivity and segmental factors than of a simple template mapping mechanism. If this is true, stress shift can be bidirectional to the left or to the right, depending on the relative importance of the factors involved.

Fikkert’s model is more detailed than the model of Demuth & Fee. It is at best elaborated for stage 1 and 2. With respect to the later stages she remains somewhat inconsistent. For example, she strongly argues for the foot as the relevant prosodic unit, but already at stage 2 the syllable, not the foot, becomes the target of circumscription:

“[...] the child realises both syllables of the target word. However, stress falls on the first syllable. The segmental material of both syllables of the adult word is taken out and mapped onto the child’s trochaic template [...]” (p. 210).
Fikkert also considers the possibility of circumscribing a foot. She concludes that the children circumscribe syllables because the surviving syllables do not constitute a foot in the adult word. But the examples she presents (p. 211) do form two feet within a weight-sensitive model, with each foot containing at least two moras (Example 3):
Example 3.

child form adult target gloss

  ‘elephant’

  ‘pelican’

  ‘locomotive’

  ‘farm’
Fikkert cannot account for this fact because she exclusively assumes weight-insensitive trochees at stage 2. Demuth & Fee’s model, in contrast, would allow for the retention of the foot as the relevant unit since it assumes sensitivity to syllable weight with the emergence of the foot structure.

Demuth & Fee, in contrast, have problems to explain the stress shift to the first syllable in the examples above for two reasons: first, recent evidence suggests that the relationship between distinctive vowel length and the emergence of coda consonants is not as categorial as they claim. In an examination of Fikkert’s data, Salidis & Johnson (1997) found that, contrary to their English acquiring child, the vowel length was not controlled by the Dutch children even if they correctly produced coda consonants. If in turn, children cannot control vowel length appropriately, they cannot assign two moras to a long vowel. The authors relate the divergence between the languages to the impact of vowel quantity on the stress pattern: in English, the long vowels in (C)VV(C) syllables count as heavy and thus attract stress, contrary to Dutch which rather relies on the open-closed distinction. In Dutch, a (C)VC syllable counts as heavy, while a (C)VV does not. Thus, a learner of Dutch presumably does not rely on vowel length as an indicator for stress, while it is crucial for a learner of English to identify the relationship between vowel quantity and stress. Second, given that the absence of the vowel length distinction is an artifact of the investigation and children have mastered the vowel length distinctions if they produce bimoraic feet. Then neither universal nor language-specific constraints could account for the fact that the superheavy finals lose their primary stress in favor of the less heavy ultimates because Dutch follows the universal generalization that a (C)VCC (e.g. //) or a (C)VVC (e.g. //) syllable is heavier than a (C)VV syllable (//,//).

The observation that Dutch children need more time to acquire vowel length distinctions indicates that language-specific properties may influence the prosodic representation in a more detailed way than assumed so far. Thus, further empirical work is needed to shed light on the interplay of universal principles and language-specific conditions in prosodic development.