Are acoustic differences in autonomous fillers salient for the human perception ? Acoustic measurements have been carried out on autonomous fillers from eight languages (Arabic, Mandarin Chinese, French, German, Italian, European Portuguese, American English and Latin American Spanish). They exhibit timbre differences of the support vowel of autonomous fillers across languages. In order to evaluate their salience for human perception, two discrimination experiments have been conducted, French/L2 and Portuguese/L2. These experiments test the capacity to discriminate languages by listening to isolated autonomous fillers without any lexical support and without any context. As listeners have been native French speakers, the Portuguese/L2 experiments aim at evaluating a potential mother tongue bias. Results show that the perceptual discrimination performance depends on the language pair identity and they are consistent with the acoustic measures. The present study aims at providing some insight for acoustic filler models used in automatic speech processing in a multilingual context.