The results of the CFA confirmed the factor structure of the cDPMI with excellent fit indices (χ² = 61.093, df = 35, p < .001 RMSEA = .044, SRMR = .040, TLI = .922, CFI = .950). As shown in Table 1, the cDPMI main factor showed acceptable internal consistency for the parents and teachers groups, with Cronbach’s α and McDonald’s ω values greater than .753, and r-bar values greater than .216.

These indices were lower for the children group, with Cronbach’s α and McDonald’s ω values ranging from .542 to .592 and r-bar values below .2, suggesting questionable internal consistency. Similar results were found for the four cDPMI subscales (see Appendix 3): for the parents and teachers groups, Cronbach’s α, McDonald’s ω, and r-hat values were within the acceptable range. The children group achieved acceptable internal consistency for the PI subscale only, r-hat > .202, while internal consistency for the PC, MP subscales was questionable, with r-hat values below .2. Descriptive statistics and deciles for each cDPMI scale are reported in Appendix 4.

Table 2 shows a summary of the FI analyses for user groups and measurement times. As shown in the upper part of the table, the model testing group invariance achieved full configural and metric invariance across the three groups of users. Nevertheless, scalar invariance was only achieved after allowing the intercept of the items “when I practice, I don't play the way my teacher told me to play” and “when I practice, I just play along” to vary. Therefore, the modified model testing group invariance achieved partial scalar invariance across user groups. The lower part of Table 1 shows that the model testing time invariance achieved full configural, metric and scalar invariance across measurement times. All the models computed during the FI analyses had acceptable fit indices, with CFI and TLI values in all cases higher than .869 as well as RMSEA and SRMR values lower than 0.081.

The results of the correlation analysis are reported in Table 3. The cDPMI main factor was positively and significantly related to self-regulation as well as three dimensions of the Big Five short scale (Lang, 2005), namely, extraversion, conscientiousness, and agreeableness. The four cDPMI subfactors showed similar correlation trends with the only exception of mindless practice (MP), which was negatively correlated to most of the variables included in the analysis, as was expected.

The present study aimed at developing and validating the cDPMI, an adaptation of the DPMI for child musicians, especially between 5 and 10 years of age. The questionnaire was designed to be used by music teachers, parents and child musicians, as an evaluation tool for music practice behavior in children.

The cDPMI is composed of 11 items and retains the bifactor structure of the adult DPMI, consisting of a main scale and four subscales. Confirmatory factor analyses confirmed the appropriateness of the cDPMI factor structure with good fit indices. The cDPMI main scale and subscales showed acceptable internal consistency in the parents and teachers groups, but internal consistency indices fell below the acceptable level in the children group. The cDPMI model proved invariant across different groups of users (i.e., children, parents, and teachers) and time of measurement. Finally, the cDPMI main scale and subscales were significantly correlated with self-regulation, as well as three personality traits, namely, extraversion, conscientiousness, and agreeableness.

The analyses revealed a questionable level of internal consistency for the cDPMI main scale and subscales in the children group, except for the process improvement subscale. This may be because practice competences and mindless practice subscales require a degree of introspection and knowledge that the young participants did not have due to their age (mean age = 7.6 years) and still low level of musical expertise. Therefore, the cDPMI may be less reliable as a self-assessment tool for young musicians than as a tool for the teachers and parents to monitor practice behaviors of their students and children. The validity of the cDPMI was assessed by considering multiple aspects. Content validity was assured by the expertise of the reviewers who adapted the DPMI while structural validity was supported by the good fit indices of the cDPMI factor structure. Convergent validity was demonstrated through significant correlations with DP-related constructs, such as self-regulation and personality traits. FI testing evaluated the generalizability aspect of validity while significant correlations between the cDPMI scales and other measures related to DP support the external validity of the new questionnaire. Criteria for configural and metric FI were satisfied. This suggests that the cDPMI factor structure fits similarly well the data from the three user groups, with similar correlation patterns between items. Scalar invariance was achieved only partially. Thus, cDPMI scores collected from different user groups may not be comparable in absolute terms, as intercept values for two items vary substantially across groups. However, group-level comparisons may be reasonably conducted on the PI, PC, and TD subscales, which are computed without the two problematic items. Analyses on the rank order of observations across groups (i.e., correlation analyses) may also be appropriate.

Self-regulation is well-known to be a significant predictor of young musicians’ success and a crucial aspect of musical expertise (Bonneville-Roussy & Bouffard, 2015; McPherson & Renwick, 2001; Miksza, 2015; Varela et al., 2016). Extraversion and conscientiousness are typically correlated with the rate of music practice in early childhood (Burak & Atabek, 2023; Marion-St-Onge et al., 2020). Previous studies have shown that extraversion and agreeableness might be significantly higher in musicians than in non-musicians and positively correlated with the duration of musical training (Corrigall et al., 2013; Corrigall & Schellenberg, 2015; Kuckelkorn et al., 2021). Thus, extroversion, conscientiousness and agreeableness could indicate a good compliance with the teacher instructions and promote the continuation of music education in the long term. Neuroticism and openness were not significantly correlated with cDPMI scores. This is surprising, as previous findings suggest that musicians might show higher levels of neuroticism and openness to new experience than non-musicians (Corrigall et al., 2013; Miranda, 2020; Vaag et al., 2018). However, the findings by Kuckelkorn et al. (2021) indicate that the association between personality traits and DP might not be found in novices but rather characterize expert performers. Thus, neuroticism and openness may either develop later in life or be a selection criterion for higher levels of expertise: only musicians who exhibit these traits may have the resources necessary to persist in musical studies.

The results of this study demonstrate a strong conceptual and empirical alignment between the cDPMI and Ericsson’s definition of deliberate practice. Similarly to the DPMI, the cDPMI implements the DP's core principles through subscales that measure children's practical skills, ability to monitor improvement, avoidance of mindless repetition and ability to break down tasks strategically. Moreover, the cDPMI's convergent validity is substantiated by its significant correlations with self-regulation and personality traits such as conscientiousness and agreeableness—traits previously shown to facilitate engagement in DP (Bonneville-Roussy & Bouffard, 2015; Passarotto et al., 2022). The negative relationship between MP (i.e., mindless practice subscale) and these traits also supports Ericsson’s view that passive repetition is insufficient for skill acquisition (Ericsson, 2020). The low reliability of children's self-reports yielded, especially in subscales requiring metacognitive insights (i.e., PC and MP subscales), may reflect the developmental trajectory of self-monitoring skills in young musicians, consistent with Ericsson’s emphasis on expert guidance in early stages of practice (Ericsson, 2008).

This study has important implications for the music education research field. The lower consistency in child musicians’ responses compared to the other groups may depend on the limited understanding of the key aspects of musical practice in this population. While children seem to recognize their own progress and to use the process improvement subscale appropriately, they show uncertainty about their own competencies and a poor understanding of dysfunctional practice behaviors, as evidenced by the improper use of the practice competences and mindless practice subscales (see Appendix 3). This highlights the importance of teachers and their feedback in acquiring the necessary skills to become expert musicians (de Bruin, 2023; Duke & Simmons, 2006). On the other hand, our results discourage music educators from relying too much on the monitoring skills of their young students. Instead, they should involve parents in monitoring their students’ practice behaviors at home and to support the acquisition of good practice habits in the early stages of learning a musical instrument. In addition, our results highlight the importance of teaching methods that prioritize the acquisition of functional behaviors and good practice habits over repertoire mastery in children. In fact, while the latter may be the key to prodigy in the short term, the former promotes a scaffolding process that allows for stable improvements in the long term (Biasutti, 2017; Bolhuis, 2003).

This study comes with some limitations. First, cDPMI subscales such as practice competences and task decomposition, are quite specific to abilities and practice routines that might not be well developed in the children and novices yet. Therefore, these cDPMI subscales may be less applicable as self-report tools, and researchers should be aware of the reliability issues with child self-reports mentioned in the previous paragraphs. Second, due to the limited sample size, we could not evaluate FI across child musicians playing different musical instruments. For the same reason, we were unable to analyze possible age-related differences in how child musicians completed the questionnaires, which may partly explain the poor consistency found in their data. Furthermore, the limited sample size does not allow to produce reliable normative data, which limits the extent to which cDPMI scores can be interpreted in absolute terms. However, we still believe that the cDPMI can already be used with confidence as an educational tool, particularly for monitoring changes in individual behaviors over time. Third, the study was conducted based on the assumption that constructs measured (i.e., deliberate practice, personality traits) are stable and measurable throughout childhood, a premise that may not apply to younger children. Fourth, the different teaching approaches included in the study (i.e., one-to-one and group lessons) may have affected the way child musicians self-evaluated their practice behaviors and potentially contributed to the reliability issues evidenced in the results. Future studies might explore the relationship between the cDPMI scores and the development of psychomotor and auditory abilities in children. In addition, researchers could use the cDPMI to better investigate the role of practice along the path to musical expertise, considering not only the amount of practice but also its quality. Fifth, to receive uninfluenced assessments from parents, no guidelines were provided. Future studies may investigate the effect of guidelines for the targeted observation and assessment of DP in children, as guidelines could prevent undesirable influences from their general behavior and personality traits. Finally, the reduced sample size did not allow us to explore alternative factor solutions that might provide a better fit to our data.

In conclusion, the cDPMI is a valid instrument for measuring DP behavior in child musicians, at least when used with parents and teachers. This compact questionnaire can be used as an external assessment tool as well as a self-assessment tool, although in the latter case the age of the children and the complexity of the constructs underpinning DP may limit the reliability of the measurements. We believe that the cDPMI is a valuable contribution to music education and expertise research fields, providing a standardized measure of the quality of practice in the initial stages of music learning.