Table 3. An overview of studies analysing the early vocal behaviours of infants later diagnosed with Fragile X Syndrome.

Authors	Participants (M/F)	Control group (M/F)	Age range (in months)	Behaviours analysed	Results
Marschik et al. (2014b)	7 (5/2)	–	9-12	Non-linguistic and (pre-)linguistic vocalisations used for communicative purposes*.	5 participants engaged in unspecified vocalisations; 2 participants used babbling for communicative purposes; non-verbal behaviours dominated over pre-linguistic forms of communication. (Proto-)words were not observed. Disagreements discussed.
Belardi et al. (2017)	10 (9/1)	14 (11/3)	9-12	Canonical syllables Canonical babbling Canonical babbling ratio Volubility.	FXS participants were significantly less likely to reach canonical babbling stage by 9-12 months than TD group, participants with FXS produced significantly lower canonical babbling ratios Infants with FXS demonstrated significantly lower volubility than TD infants. 20% of all data double coded, ICC ranged from 0.89-0.94.

^*i.e. unspecified vocalisations, pleasure vocalisations, laughing, crying, fussing, canonical and variegated babbling, onomatopoetics, (proto-)words, word combinations. ICC: Intra-class coefficients, k: Kappa coefficient.