Timeline.

Participant recruitment will start in August 2025 and is expected to be completed by October 3, 2025. Intake interviews—including eligibility screening, explanation of the study procedures, and digital informed consent—will take place between September 1 and October 3, 2025, via scheduled video calls. Baseline assessments (T1), including home visits, parent questionnaires, and child interviews, will occur between September 15 and October 17, 2025. The intervention is scheduled to begin in the week of October 20, 2025, and will continue for 18 sessions through the week of March 9, 2026. Posttest assessments (T2), including follow-up home visits and questionnaires, will be conducted between March 16 and April 17, 2026. This timeline ensures a 5-week pretest period, an 18-week intervention period, and a 5-week posttest window. Study results are expected to be available by September 2026 and will be submitted for publication, presented at conferences, and reported in ClinicalTrials.gov.

Incredible Years Small Group Dinosaur Child Program.

The intervention group will receive the IY Small Group Dinosaur Child Program, a structured, manualized cognitive-behavioral intervention originally developed to support young children (ages 3–8) with conduct problems [20,21,24]. The program is designed to enhance emotional regulation, prosocial behavior, and problem-solving abilities through developmentally appropriate, interactive group-based sessions. Although initially developed for children with externalizing difficulties, it is now widely applied in broader populations, including children with internalizing difficulties such as social-emotional or attentional challenges [33]. In this study, the intervention will target children aged 4–8 years who exhibit elevated levels or (sub)clinical levels of conduct problems.

The program will be delivered in ten small groups, each consisting of 5–6 children. Each group will be facilitated by one certified group leader, using the Dutch translation and adaptation of the original IY protocol. Sessions will be held weekly for 18 weeks, with each session lasting approximately two hours. The curriculum will include storytelling with puppets, video modeling, role-play exercises, group discussions, and cooperative games. These elements are intended to foster emotional awareness, frustration tolerance, interpersonal problem-solving, and socially appropriate behavior. Parents in the intervention group will not receive a parallel parent training during the study period.

All groups will be led by one of six certified IY group leaders. Four of these professionals will be licensed child therapists affiliated with Psychologenpraktijk Timmers or Stichting Kumbaya, and two will be affiliated with Tilburg University. Prior to the start of the trial, all trainers will have completed the official IY certification process, which includes delivery of a full intervention cycle and a successful video-reviewed evaluation of fidelity and delivery quality.

Control condition.

Participants assigned to the control condition will be placed on a waitlist and will not participate in any structured group-based intervention during the study period. They will retain access to standard care and community-based services as needed, but will not receive any elements of the IY program during the data collection phase. Information on additional support received will be systematically collected via parental questionnaires.

After completion of the posttest assessment (T2), families in the control group will be offered the opportunity—on a voluntary basis—to participate in the IY Dinosaur Program. This post-trial intervention will be delivered by the same certified group leaders and institutions involved in the study (Tilburg University, Psychologenpraktijk Timmers, or Stichting Kumbaya), but will not be part of the research protocol. This design allows for a controlled comparison of intervention and non-intervention conditions, while ensuring equitable access to support after study completion.

Fidelity monitoring.

To ensure high-fidelity implementation, group leaders will follow a standardized session protocol and complete adherence checklists after each session. Fidelity will be further supported through regular supervision meetings with certified IY consultants. Prior to the start of the trial, all group leaders will have completed the formal IY certification process, including a video-reviewed delivery of the full program. Any deviations from the protocol will be documented and reported in the final study manuscript.

Child temperament.

Child temperament will be assessed using the Child Behavior Questionnaire – Very Short Form (CBQ-VSF), a widely used parent-report instrument [34]. The CBQ-VSF contains 36 items rated on a 7-point Likert scale ranging from 1 (“extremely untrue”) to 7 (“extremely true”). Items cover multiple dimensions of temperament; in the current study, the Negative Affectivity subscale (e.g., “My child gets quite frustrated when prevented from doing something s/he wants to do”) will be used as a moderator. A composite score will be calculated as the mean of the subscale items. The CBQ-SF has demonstrated good internal consistency and construct validity in prior studies [35].

General child sensitivity.

The Highly Sensitive Child – Parent Report (HSC-PR) is a 12-item parent questionnaire that assesses environmental sensitivity in children [36]. Items are rated on a 7-point scale (1 = “not at all” to 7 = “very much”). A sample item is: “My child notices subtle smells or sounds that others do not.” Total scores will be calculated by averaging all items, with higher scores indicating greater sensitivity. The HSC-PR has shown good reliability and factor structure in recent studies [37].

Child emotional variability.

Emotional variability will be operationalized using parent–child dyadic daily assessments collected via the m-Path app [26]. Each evening, parents and children will complete a short diary survey including 2–3 emotion-related items (e.g., “Did your child experience strong emotions today?”) on a 5-point scale (1 = “not at all” to 5 = “very much”). Variability will be calculated based on within-person standard deviations, and changes over time will be explored using a moving window approach [28].

Parent-reported outcomes.

Parenting behavior (Explanatory outcome; RQ1). Parenting practices will be measured using the Parenting Practices Interview (PPI) [38]. The PPI includes 73 items rated on a 6-point Likert scale (1 = “never” to 6 = “always”) and covers domains such as positive involvement, inconsistent discipline, and harshness. A sample item is: “When your child misbehaves, how often do you give up trying to discipline him/her?”. Subscale scores will be used to explore potential changes in parenting behavior. Although parents are not enrolled in a formal parenting program, those whose children receive the Dinosaur intervention are indirectly exposed to parenting principles from the IY program. Through weekly letters, reading assignments, and homework exercises derived from the parent book used in the IY parent training, caregivers are encouraged to apply positive parenting strategies at home. The PPI was specifically developed to assess parenting behaviors targeted by the IY parent intervention

Child externalizing behavior (Primary outcome; RQ1). The Child Behavior Checklist (CBCL) will be used to assess children’s behavioral and emotional problems from the parent’s perspective [39]. The CBCL includes 113 items rated on a 3-point scale (0 = “not true”, 1 = “somewhat true”, 2 = “very true”). The Externalizing Problems composite will serve as the primary indicator of behavioral change. To complement this, the Eyberg Child Behavior Inventory (ECBI) will be administered [40]. The ECBI consists of 36 items (e.g., “Refuses to go to bed”) rated for both frequency and problem severity.

Child social behavior (Primary outcome; RQ1). Social competence will be measured using the Social Competence Scale – Parent version (P-COMP) [41]. This 12-item scale uses a 5-point Likert format (1 = “not at all” to 5 = “very well”) to evaluate skills like cooperation, self-control, and empathy. A sample item is: “How well does your child get along with other children?”.

Executive functioning (Primary outcome; RQ1). Parents will complete the Behavior Rating Inventory of Executive Function, Second Edition– Parent form (BRIEF-2) [42,43]. This version includes 60 items rated on a 3-point Likert scale (1 = “never”, 2 = “sometimes”, 3 = “often”) and assesses executive functioning in daily life at home. A sample item is: “Has trouble remembering things, even for a few minutes.” The Global Executive Composite (GEC) score will be used at the primary outcome. The BRIEF-2 has demonstrated strong psychometric properties in both clinical and normative samples [44].

Child language behavior (Primary outcome; RQ1). The Children’s Communication Checklist – Second Edition, Dutch version (CCC-2-NL) [45,46] will be used to assess the child’s communicative/language functioning from the perspective of the parent or caregiver. The CCC-2-NL consists of 70 items covering structural language skills (such as syntax and semantics) as well as pragmatic aspects of communication (e.g., inappropriate initiation, use of context, nonverbal communication). Items are rated on a 4-point scale (0 = “less than once a week or never” to 3 = “several times a day or always”), providing standardized composite scores to identify potential communication difficulties. The General Communication Composite (GCC) derived from the CCC-2-NL will serve as the primary indicator of change in child communicative behavior.

Teacher-reported outcomes.

Child externalizing behavior (Primary outcome; RQ1). The Teacher’s Report Form (TRF) will be used to assess behavioral functioning in the school setting [39]. The TRF mirrors the CBCL and includes 120 items with the same 3-point scale. The Externalizing composite score will be used as a primary outcome.

Child social behavior (Primary outcome; RQ1). Teachers will also complete the Social Competence Scale – Teacher version (T-COMP) [47]. This version includes items similar to those in the parent version and evaluates the child’s social functioning at school. T-COMP scores will be analyzed alongside parent reports to assess cross-contextual consistency in social competence.

Child executive functioning (Primary outcome; RQ1). Teachers will complete the Behavior Rating Inventory of Executive Function, Second Edition – Teacher Form (BRIEF-2) [42,43]. This version contains 61 items, also rated on a 3-point Likert scale, and evaluates the child’s executive functioning in the school setting, including classroom behavior, task focus, and emotional regulation. The Global Executive Composite (GEC) score will be used to parallel the parent-reported outcome and enable comparison across contexts.

Child-assessed outcomes.

Emotional understanding (Primary outcome; RQ1). Children’s emotional awareness will be assessed using the Wally Feeling Test [48], a structured task in which children identify and explain emotions depicted in cartoon vignettes.

Problem-solving skills (Primary outcome; RQ1). Children will complete the Wally Problem Solving Test [49], a structured measure in which social dilemmas are presented in an illustrated format. Children are asked to generate possible solutions for each scenario. Responses are coded for quality and diversity, providing insight into cognitive-behavioral competencies such as perspective-taking, emotional regulation, and flexible problem solving—key targets of the intervention.

Daily diary-based outcomes.

Emotional variability and behavior problems (Secondary outcomes; RQ2). To capture within-person variability in emotional and behavioral functioning, daily diary surveys will assess both emotional functioning and behavior problems, completed each evening by the parent–child dyad using the m-Path app [26]. Emotional variability will be measured using a set of seven momentary emotion items derived from the Positive and Negative Affect Schedule for Children (PANAS-C) [29] and the original PANAS [30]. Children will indicate how they felt “at the moment” on a 7-point scale ranging from 1 (not at all) to 7 (very much), for the emotions proud, happy, calm, ashamed, sad, angry, and tense. To enhance developmental appropriateness and alignment with the Dinosaur Child Program, each response option is accompanied by a visual cue: a small-to-large image representing the intensity of each specific emotion, consistent with the emotion cue cards used during the intervention. Behavior problems will be assessed with three items reflecting hostility-related externalizing behaviors, adapted from the externalizing spectrum framework [31]. These include losing one’s patience, saying something mean to someone, and being angry or aggressive towards someone. Responses will be recorded on a 5-point Likert scale ranging from 1 (not at all) to 5 (very often), allowing for sensitive detection of daily fluctuations in child behavior over time.

Parent–child affective dynamics (Secondary outcomes; RQ3). To examine daily relational dynamics between parents and children, both members of the dyad independently complete a daily diary assessing shared emotional moments, negative interactions, emotion regulation, and time spent together. These items were adapted from validated measures of momentary relationship quality [32] and reflect shared emotional experiences, conflict-related emotions, and individual efforts at emotion regulation. This dyadic structure allows for the analysis of affective synchrony, divergence, and co-regulatory processes, which are central to understanding how the intervention impacts family functioning over time. Parents report whether they experienced nice moments with their child (“I had some nice moments with my child today.”) and whether they felt angry toward their child (“I got angry at my child today.”). These items are rated on 5-point Likert scales using either an intensity format (1 = not at all to 5 = very much) or a frequency format (1 = not at all to 5 = very often). In addition, a contextual control item is included to assess the amount of parent–child contact: “How many hours were you with your child today (excluding sleep time)?” (ranging from 0 to 24 hours). Children complete a mirrored set of items: they report whether they had nice moments with their parent, whether they got angry at their parent, how difficult it was to behave well, and what they did to manage their emotions if they felt angry. The regulation item includes a multiple-choice question offering strategies that are taught during the Dinosaur Child Program (e.g., taking deep breaths, doing the “turtle pose,” or thinking of something fun), along with an open-ended “other” option. Ratings use the same Likert formats as in the parent version to ensure comparability.

By collecting matched daily reports across 20 weeks of measurement, this dyadic ILD approach enables rich time-series analyses of both shared and diverging perceptions within the family. It allows the study to examine not only whether parent–child dynamics improve overall, but also whether these improvements are co-experienced and co-regulated — for example, whether decreases in child-reported anger correspond with reductions in parent-reported conflict, or whether increases in positive moments are felt mutually or asymmetrically. The inclusion of contextual time data enables the control of fluctuations in contact intensity, helping to interpret changes in affective dynamics relative to daily routines and caregiving structures.

Preliminary analyses.

To evaluate baseline equivalence between the intervention and control groups, independent samples t-tests (or Mann–Whitney U tests for non-normally distributed variables) will be conducted on demographic characteristics, baseline parenting behavior, and child behavioral outcomes. Any baseline differences that reach statistical significance will be included as covariates in subsequent models.

Hypothesis 1: Group-level behavioral effects.

To assess whether participation in the Dinosaur Child Program leads to greater improvements in children’s emotional, social, behavioral and cognitive functioning, LCS models will be estimated in Mplus for each primary outcome domain: child externalizing behavior, social competence, emotional understanding, and cognitive functioning. Outcomes will be analyzed separately for parent-reported, teacher-reported, and child-assessed measures. LCS models estimate change over time using latent difference scores, thereby distinguishing true change from measurement error. Intervention condition will be tested as a predictor of pre-to-post change examine differential improvements between the intervention and control group. Each latent change score model will estimate the average change over time, interindividual variability in change, and the effect of group assignment on these change scores. Bonferroni-adjusted significance thresholds will be applied to control for multiple comparisons across outcome domains.

Hypothesis 2: Daily variability and behavior problems (ILD-based).

To examine whether the intervention reduces children’s daily emotional variability and behavior problems, multilevel time-series analyses will be conducted on daily parent–child diary data. Daily reports will include ratings of negative affect (e.g., irritability, sadness) and behavior problems (e.g., defiance, tantrums). Repeated observations will be modeled as nested within individuals to capture both group-level trends and within-person variability over time. Fixed effects for time, group, and their interaction will be included to test for differential change trajectories across conditions. In addition, moving window techniques will be employed to capture changes in intra-individual fluctuations and identify evolving temporal patterns of variability throughout the intervention period.

Hypothesis 3: Parent–child dynamics (dyadic ILD-based).

To evaluate whether the intervention enhances the emotional quality of daily parent–child interactions, multilevel time-series analyses will be applied to dyadic daily diary data. These models will examine daily reports of shared positive affect and emotional escalation during conflict, with repeated measures nested within families. Time-by-condition interaction terms will be used to assess whether trajectories of affective dynamics differ between the intervention and control groups. Moving window techniques will be used to derive fine-grained temporal indicators of affective synchrony and escalation, allowing for a dynamic examination of how relational processes evolve across the intervention period. This analytic approach offers a detailed understanding of whether the intervention promotes more stable and positive emotional exchanges between parents and children.