Despite many acoustic, articulatory and phonological studies of Advanced Tongue Root (ATR) vowel contrasts and vowel harmony, studies of the perception of ATR contrasts by speakers of languages with ATR vowel distinctions are lacking. This paper explores how vowels which differ for ATR or height, or both, are distinguished by speakers of Akan, a Kwa language of Ghana. We examine whether the phonological contrastive status of the vowels impacts perception or whether it is driven by acoustic similarity. Results from two experiments reveal that vowels that differ only for ATR are well distinguished, even those that are in an allophonic relationship. Yet, vowels that are contrastive and differ by both ATR and height features, but are acoustically similar, are poorly perceived. We suggest that these vowel contrasts constitute a case of perceptual near-merger.