The interaction Duration: SDLog revealed that, on the whole, as Duration increases, SDLog increases.
While some metrics do include rate-normalization coefficients, the exploration of interactions such as Duration : SDLog allows for a more complete picture of the behavior of vowel durations across different speech.
The first, LemmaFreq: SDLog, indicates that monolingual speakers exhibit less variability in vowel duration (measured in SDLog) for less frequent words.
However, SDLog and PVI themselves are positively (and exponentially) related (PVI~0.02*[2.609.sup.SDLOG]; [R.sup.2]=0.86), which is why it is not surprising to see that this interaction is similar to LemmaFreq : SDLog.
On the one hand, it seems as if the PVI can distinguish the two speaker types over as wide a range of lemma frequencies as SDLog, even if it is two non-consecutive ranges, high- and low-frequencies, but not intermediate ones.