This paper examines the influence of the first language on the accuracy with which trained phoneticians judge isolated monophthongs taken from the phoneme systems of two different languages. The main finding of this study was that the speakers as well as listeners L1 background have a significant influence on judgements which were made by means of the IPA vowel diagram.
This paper consists of 6 sections. In section (1) we will recall the basic principles of the IPA vowel diagram focusing on its layout, proportions, and primary cardinal vowels. In section (2) we will refer to the tradition of using the cardinal vowel system in phonetic studies, particularly in order to plot a vowel sound at a certain point within the space of the IPA vowel diagram. In section (3) we will suggest how the influence of the L1 on articulation and perception of vowels of an unknown language can be investigated with the help of the IPA vowel diagram. The methods which we used during the preparation of recordings and perception experiment, as well as subjects who took part in them, will be described in section (4) and a presentation of the main results will follow in section (5). Finally, we will discuss the results with respect to the three basic dimensions of the vowel sounds: height, backness and rounding.