Differences in Inventory Size Affect the Location but not the Precision of Tongue Positioning in Vowel Production

The question addressed by this study was whether native speakers of languages that have a relatively large inventory of vowels maximize the phonetic distance between those vowels by using a relatively wider range of tongue positions than speakers of small-inventory languages. Glossometry was used to measure tongue height in the Spanish vowels /i/, /u/, /a/, /e/, and /o/ and in the English vowels /i/, /u/, /a/, /eI/, and /oU/. These vowels were spoken by eight native speakers each of Spanish and English, normally and with a bite block. The effect of the bite block on average vertical tongue height was negligible, but the tongue was slightly lower in the front of the mouth and higher at the back of the mouth for vowels spoken with, than without, a bite block. Token-to-token variability for vowels spoken in a/b-bV/ context was no greater for the Spanish than for the English subjects despite the smaller vowel inventory of Spanish. The average position of the tongue for the five Spanish and the five English vowels examined did not differ significantly, suggesting that the two languages have the same articulatory "setting". Despite this, the English subjects produced point vowels with a greater range of vertical tongue positions than the Spanish subjects. Taken together, the results suggest the vowel inventory size may affect the location but not the precision of tongue positioning in vowel production.