This data set includes the supplementary material for the article "‘The more, the better?’ An experimental investigation on the role of sentential negation in the acquisition of Italian nessuno". All content is documented in the README.md file. Abstract: This paper presents an experiment on the comprehension of the negative indefinite pronoun nessuno (‘no one’) in different syntactic structures in Italian children aged 4–6. Specifically, the study aimed at determining when the meaning of nessuno is acquired, as well as whether negative concord structures showing both the sentential negation non (‘not’) and postverbal nessuno (e.g., ‘Non l’ha vinto nessuno’, lit. ‘Not it has won no one’) are easier to compute and therefore acquired earlier than structures displaying only preverbal nessuno (e.g., ‘Nessuno l’ha vinto’, lit. ‘No one it has won’) – a prediction following from a decomposition analysis of negative indefinites (Bill et al., 2024, a.o.) coupled with the Transparency Principle (Van Hout, 1998, a.o.). 60 Italian-speaking children were tested via a Truth Value Judgement Task (Thornton et al., 2016) from which it emerged that the comprehension of nessuno is already almost at ceiling at 4 years of age, and that no difference in accuracy rates holds between pre- and postverbal nessuno. Although these findings neither supported nor refuted our predictions – i.e., that the more linguistic material realised, the easier the comprehension – they are particularly interesting as they provide evidence for an early acquisition of nessuno regardless of the syntactic context. This contrasts with accounts attributing the late mastery of the double negation reading of certain Italian sentences featuring a preverbal negative indefinite followed by the sentential negative marker non to difficulties in integrating the negation on the indefinite with that of non (Moscati, 2024; Tagliani, 2019).