Downstep
Notation: an exclamation point is used to indicate a downstepped accent. The downstepped accents in ToBI are:
| !H* | a downstepped H* pitch accent |
| !H- | a downstepped phrase accent we'll discuss next quarter |
| H+!H* | a bitonal pitch accent we will discuss next quarter |
Our discussion today will focus on the downstepped pitch accent !H*. In response to a question that Eunjong raised about what triggers the downstepped high pitch accent !H*, Mary Beckman wrote the following reply.
The trigger for downstep in English is very controversial. Pierrehumbert (1980) first proposed that downstep is triggered by any sequence of alternating L and H tones (as in the African tone languages where it was first described), whereas Beckman & Pierrehumbert (1986) proposed that it is only the alternating sequences of bitonal pitch accents that triggers it. Note that in both of these models, there is a bitonal accent H*+L which is missing in ToBI, for which the trailing "L" target is not very low in the pitch range. So an intermediate phrase contour that in ToBI would be transcribed as:
H* !H* L-
would be represented in the Pierrehumbert (1980) or Beckman & Pierrehumbert (1986) models as:
H*+L H* L-
with the downstep that is explicitly marked in ToBI being understood as an automatic consequence of the choice of a bitonal H*+L accent. Similarly, the canonical calling contour that Liberman (1975) described as having a mid tone after the nuclear accent (which is still how Hammond, 1999, describes it in his evidence for the "foot" in English) would be transcribed in ToBI as:
H* !H- L%
but it would be represented in the Pierrehumbert and colleagues model as:
H*+L H- L%
again with the downstep that is explicitly marked in ToBI being understood as an automatic consequence of the choice of a bitonal H*+L accent.
Now, Ladd (1983, 1986) objected to this characterization of downstep, because it meant positing this H*+L accent that typically doesn't have an obvious L target. Gussenhoven and his colleagues have also objected to this, and have always maintained that downstep is a facultative choice that a speaker can make to signal greater cohesion within a prosodic phrase (see, e.g., the van den Berg, Gussenhoven, & Rietveld, 1992, paper in LabPhon2). They have a rather odd way of representing it, in terms of a combination of a H*L accent type for which the L tone typically represents the L- phrase accent, but in cases where the accent is not the nuclear tone, it detaches and reattaches to the following H*L accent, or simply detaches and is a "floating" tone that is realized as downstep. In this system, downstep is represented not as a mark on the accent tones, but as the choice of "float" among the three-way opposition among ways to deal with the L tone (i.e., "spread" for a nuclear accent vs. "reattach" for a what we would transcribe as the leading L tone of a L+H* accent vs. "float" for what we would transcribe as a H* or L+H* accent before a downstepped !H* accent).
Ladd (1986) proposed a different representation again -- namely that downstep be modeled as one term in a binary opposition between two different "register tone" relationships -- adopting Clements's tree model of downstep in African tone languages. So the short story is that no one is sure what triggers downstep. There are competing theories, but no definitive data to decide among them.
Since there is this controversy about the theory, what we decided to do back in 1990, at the first workshop where we started to devise the English ToBI system, was to sidestep the controversy completely, by explicitly marking downstep on the first H tone that is realized in the downstepped pitch range. So downstep can follow any accent that has a H target in it. This is not stated very explicitly in the ToBI conventions, unfortunately, but the correspondence between
H* !H* L- L%
in ToBI, and
H*+L H* L-L%
in Pierrehumbert (1980) is mentioned.
If you want to read the description of how we decided this, by the way, you can look at the Beckman, Hirschberg, & Shattuck-Hufnagel chapter that will appear in the Jun (2004) book. A pdf file for a draft of this paper and wav files for the figure examples are at:
http://www.ling.ohio-state.edu/~tobi/JunBook