This paper investigates the organization of the vowel space in French speakers. Speakers aged from 4 years to adulthood were recorded in order to generate significant between-speaker variability. Each speaker produced repetitions of the ten French oral vowels /i y u e o o @e oe @? a/. Acoustic analyses show that, despite considerable between-speaker variability in the relative positions of the vowels within the vowel space, speakers tend to produce vowels along a given height degree with a stable F1 value, depending on the speaker, but independently of place of articulation and roundedness. Simulations with the Variable Linear Articulatory Model (VLAM) show that a stable F1 value is basically related to stable tongue heights. The results are discussed in the framework of the Perception-for-Action Control theory (PACT), in which speech units are considered as gestures shaped by perceptual processes.