This study explores the perceptual vowel space of the Finnish and German languages, which have a

similar vowel system with eight vowels, /A/ /e/ /i/ /o/ /u/ /y/ /æe/ /ø/. Three different prototypicality

measures are used for describing the internal structuring of the vowel categories in terms of the F1

and F2 formant frequencies: The arithmetic mean (centroid) of the F1–F2 space of the category (Pc),

the absolute prototype of the category (Pa), and the weighted prototype of the category (Px), in which

the stimulus formant values are weighted by their goodness rating values. The study gave the following

main results: (1) in both languages, the inter-subject differences were the smallest in Px, and on

the order of Difference Limen (DL) of F1–F2 frequencies for all of the three measures, (2) the Pa and

Px differed significantly from the centroid, with the absolute prototypes being the most peripheric,

(3) the vowel systems of the two languages were similar (Euclidean distances in Px of Finnish and

German 7–34 mels) although minor differences were found in /e/, / ø/, and /u/, and (4) the mean difference

of the prototypes from some earlier published production data was 100–150 mels.