The contribution of extraneous components to vowel F1 estimation was investigated by constructing a continuum perceived as changing from /ɪ/ to /ε/ as F1 was varied. The phoneme boundary location is a measure of the perceived F1, and hence of the influence of the extraneous component. Adding an extraneous component whose frequency is an integral multiple of F0/2 gives a complex consisting only of components harmonically related to F0/2. This component may thereby be incorporated by acting as a “false harmonic.” Adding a false harmonic on the lower skirt of F1, at a level above the vowel spectral envelope, shifts the phoneme boundary upwards. However, adding a component at any other frequency in this region has a similar effect. The effect of further adding several false harmonics remote in frequency from F1, at levels equal to the spectral envelope of the vowel, is currently being investigated. Preliminary results suggest that adding these components increases the incorporation of the component added in the F1 region, but only if that component frequency is an integral multiple of F0/2. [Work supported by the SERC and the MRC, U.K.]