Language influences in two-digit number processing across German and French

Whether and how language influences two-digit number processing is not yet clearly understood. Across languages such as English, Polish, German, and Czech, studies have reported different numerical effects, suggesting that number-word structure may shape the processing of multi-digit numbers. We examined whether number-word activation contributes to multi-digit number processing in French and German languages. French- and German-speaking adults (N = 64) performed a two-digit number comparison task manipulating unit–decade compatibility and number range (below vs. above 60). The results showed robust Unit–Decade Compatibility Effects across both language groups and no language-specific interactions were found, suggesting comparable processing across groups. However, within the French sample, reaction times were significantly faster for numbers above 60 than below 60, whereas German participants showed no such difference. This pattern likely reflects properties of the French verbal number system: frequent and highly practiced composite forms may facilitate processing despite their structural irregularity. These findings indicate that, in adults, language may not modulate the UDCE itself but can influence overall processing speed through linguistic transparency and frequency effects. Further cross-linguistic studies are needed to clarify how number-word structure shapes numerical cognition across development.