Title of the article

4.Discussion of the models

Although both models can explain a number of frequently observed patterns like syllable deletions and word size restrictions, there are a number of empirical and theoretical problems related with the models.

First, Fikkert and Demuth & Fee assume that the prosodic development proceeds bottom-up, i.e. from a lower level of representation (the foot or the mora) to the top of the prosodic hierarchy (the prosodic word). Children invariably have to pass trough one stage before they can go to the next. For example, multisyllabic words like ‘elephant’ or ‘crocodile’ have to show a level stress pattern before they can be produced adult-like.

Fikkert explicitly points to that fact. Missing evidence in her data is explained by the recording modalities or is due to the fact that a given stage took a very short time. Demuth & Fee, in contrast, are not explicit with respect to the ordering of the stages. However, they claim that prosodic development proceeds along the prosodic hierarchy. Since in the prosodic hierarchy one constituent strictly dominates the constituent below, stages cannot vary with respect to their temporal order. According to the models, the following realizations for / ‘crocodile’ of Jule, a girl acquiring German, should be chronologically impossible (data from my own corpus):

Example 2.

child form	age	description
	(1;08,12)	the main stressed syllable is realised
	(1;08,29)	a foot with final stress is realized
	(1;10,14)	level stress emerges

As the examples illustrate, level stress can occur after a finally stressed variant of the target word was produced, contrary to the predictions of the models. Such an acquisition order provides empirical evidence against level stress as an obligatory component of prosodic development. Additional empirical support comes from the data of English acquiring children examined by Kehoe & Stoel-Gammon (1997) who also could not find a systematic emergence of level stress.

Level stress as assumed in the models above is problematic also from a grammatical point of view: the representation intended to create level stress (see Figure 4 above) essentially violates the strict layer hypothesis because the two feet are not correctly bounded into the prosodic word. The problem is that the strict layer hypothesis never can be kept by such a representation because there is no gradation in prominence at the word level. According to prosodic theory, two equally stressed feet must not occur within a single prosodic word:
*Wd




F_S F_S

_S _W _S _W

 

Figure 8. The ill-formed representation of the prosodic hierarchy as implied by Fikkert (1994) and Demuth & Fee (1995)
Both models remain vague with respect to the source of level stress: it is unclear how the stages of level stress fit to the assumption that prosodic development is directed by universal prosodic principles. Since they do not discuss the possibility of a child-specific representation, the representation according to the prosodic hierarchy should look like illustrated in Figure 6:

Wd Wd

F_S F_S

_S _W _S _W

 