Citation	Cognitive Development and Subdomains Studied and Measures Used	Findings	Summary of the Relationship Between Loose Parts and Cognitive Development
Hamadani et al. (2010)	Language—MacArthur Communicative Development Inventory (Words and Gestures) Cognitive and Motor—Family Care Indicator (FCI), Mental Development Index (MDI), and Psychomotor Development Index (PDI)	Most regressions found a significant relationship between play materials and cognitive outcomes. The relationship was no longer significant when children’s nutritional status was controlled. Most regressions found a significant relationship between play activities and cognitive outcomes. The relationship was no longer significant when the analyses controlled for child age. The models explained between 16% (psychomotor) and 31% (language comprehension) of the variance in outcomes.	Play materials: no, when nutritional status was considered as a control variable, the predicting power of play materials was no longer significant Play behaviours: no, when age was considered as a control variable, the predicting power of play behaviours was no longer significant.
Jaggy et al. (2023)	The Tools of the Play Scale (ToPS) evaluated children’s ability to substitute objects, actions, speech, and emotions during pretend play. The Playgroup Educator-Reported Social Pretend Play Competence (RPPC) Questionnaire rated children’s pretend play frequency, social involvement, and quality. Educator reports on social behaviour assess children’s empathy, social behaviour, and peer relationship quality. The Extended Theory of Mind Scale (EToM) evaluated children’s understanding of others’ beliefs and desires. The social-emotional competence subtest from the Intelligence and Developmental Scales (IDS-P) evaluated recognition of emotions and understanding of social situations.	Children in the material condition exhibited more positive changes in pretend play competence (reported by playgroup educators). No differences were found for changes in social pretend play competence measured by the ToPS. No differences between the play tutoring condition and material condition were found for changes in social pretend play competence, emotional understanding and ToM, cooperation, sociability, leadership, and setting limits. No differences between material condition and control group were found for changes in social pretend play competence measured by the ToPS, social-cognitive and emotional skills, social behaviour, and positive peer relationships.	Play materials: yes Play behaviours: not explore
Jaruchainiwat et al. (2024)	Creative thinking behaviour was measured using a frequency record of three categories of behaviour: exploration, participation and enjoyment, and persistence (10 items). Attention span was measured using a frequency record of attention.	Post-test scores measuring creative thinking behaviours were significantly greater than pre-test scores. All three categories of creative thinking behaviour were significantly greater in the post-test recordings.	Play materials: yes Play behaviours: not explored
Lehman (2014)	The Woodcock-Johnson Third Edition (WJ-III) measured literacy through the Letter-Word Identification subtest and math achievement (Applied Problems and Quantitative Concepts subtests). The Peabody Picture Vocabulary Test (PPVT) measured receptive vocabulary. Teacher Questionnaires identified the most frequent activities chosen by the child. Parent Questionnaire gathered information on children’s gender, ethnicity, age, and disability type.	Among children with developmental delay, choosing toys like blocks, LEGOs, or K’NEX during free play in preschool is related to average receptive vocabulary skills. For children without disabilities, choosing alphabet and language materials during free play relates to average receptive vocabulary skills in kindergarten. This relationship could not be compared with children with developmental delays, who prefer building toys. Free-play activity choice in preschool is unrelated to student achievement for five-year-old children. Among four-year-old children with developmental delay, choosing to build toys during free play is related to average applied problem-solving skills in first grade. For four-year-olds without disabilities, choosing alphabet and language materials during free play is related to average receptive vocabulary skills in kindergarten. Free-play activity choice is unrelated to five-year-old children’s academic competence, regardless of developmental delays.	Play materials: yes Play behaviours: no, not significant
Liddell and Masilela (1992)	Total speech was calculated by adding the total number of words spoken by adults and children in a ten-minute transcript. Vocabulary was measured as the total number of words spoken in a ten-minute transcript, scored separately for parents and children. Syntax was coded based on grammatical structure, identifying commands, informs, and questions. School-related concepts were coded by identifying utterances that referred to numbers, colours, comparative estimates, or shapes linked to early scholastic achievement.	Children spoke the fewest words when using miscellaneous and school-readiness materials. Other materials led to more speech. Miscellaneous objects were associated with a limited vocabulary compared to a greater vocabulary for other materials. Children most frequently exchanged information when using drawings/posters and least when using miscellaneous objects. School-related concepts were almost exclusively referred to when using school-readiness materials. Children engaged in symbolic naming most often with drawings/posters and least with miscellaneous objects and school-readiness materials.	Play materials: yes Play behaviours: not explored
Lloyd and Howe (2003)	Play: Observed with the Play Observation Scale, tracking how children played and used materials Convergent Thinking: Picture Completion subtest (WISC-R/WPPSI-R) Peabody Picture Vocabulary Test (PPVT-R) Divergent Thinking: Thinking Creatively in Action and Movement Test (TCAM)	Open-ended materials were linked to both intended and non-intended uses, while closed-ended materials were exclusively associated with intended uses, controlling gender and material type. Closed-ended materials and their intended use were positively correlated with PPVT-R. Solitary-active play with the intended use of materials was positively associated with the total TCAM score, fluency subtest, and originality subtest. Solitary-active play with closed-ended materials was positively correlated with the originality subtest. Partial correlations (controlling for gender) indicated that solitary-passive play was significantly and positively associated with open- and closed-ended materials and their intended use. Reticent behaviour (hesitation to engage or reveal thoughts) was negatively related to convergent and divergent thinking measures, with a stronger relationship observed for divergent measures.	Play materials: yes Play behaviours: yes
Luo (2023)	The Path towards Excellence–Chinese Kindergarten Education Quality Rating Standards (PTE-CKEQRS) measured management guidance, environmental support, curriculum promotion, guarantee of teachers’ qualification, and home-kindergarten-community cooperation. Each had several sub-projects with detailed evaluation indicators using the seven-point Likert scale. The Peabody Picture Vocabulary Test (PPVT) measured receptive vocabulary.	Early achievements in language were weakly to moderately correlated with learning centre planning/materials. Additionally, learning centre planning/material was moderately to highly correlated with psychological atmosphere and curriculum implementation quality. Correlations with all four variables and with early achievement in language were positive. Learning centre planning/materials and outdoor venues/facilities did not directly predict children’s early achievement in language.	Play materials: no Play behaviours: not explored
Lysyuk (1998)	Cognitive (Goal setting) no specific measure	Younger children (groups I and II) predominantly engage in activities characterized by a “one toy: one goal” relationship. Significant changes were observed as children aged, with older children (groups III and IV) increasingly demonstrating more complex relationships, such as “different toys: toy-specific goals” and “different toys: one identical goal.”	Play materials: yes Play behaviours: not explored
Maker et al. (2023)	Problem-solving behaviour observations The study assessed children’s abilities across various domains using specific materials and tasks: Auditory: Children repeated rhythms and tones (closed problems) and created original songs or chants using instruments like a ukulele or keyboard (open problem). Bodily/Somatic: Children balanced on one foot and caught a ball (closed), added movements to a series (semi-open), and created movements to accompany music (open). Emotional/Intrapersonal: Children mimicked emotions (closed), interpreted ambiguous emotions in pictures (semi-open), and used props to describe their feelings (open). Linguistic: Children described toys (closed), explained a picture (semi-open), and made up a story with toys (open). Mathematical: Children counted cubes of different colours (closed), grouped attribute blocks by similarity (semi-open), and created their own groups based on different attributes (open). Mechanical/Technical: Children replicated a gear train (closed), then built their own complex gear train with additional materials (open). Moral/Ethical/Spiritual: Children described and resolved a conflict (semi-open) and depicted qualities of a good person (open). Scientific/Naturalistic: Children identified living things in a desert or ocean (closed), described objects (semi-open), and grouped items by characteristics like function or movement (open). Social/Interpersonal: Children were tasked with building a bridge collaboratively (open), while also being assessed on their social interactions and teamwork. Visual/Spatial: Children replicated a construction (closed), built a car (semi-open), and created a unique construction with provided materials (open).	In the auditory/sound, scientific/naturalistic, and emotional/intrapersonal domains, the percentage of problem-solving behaviours consistently increased each year from age 4 to 6. However, in the mechanical/technical, bodily/somatic, and social/interpersonal domains, some behaviours decreased at age five before increasing again at age 6. Similarly, in the linguistic and visual/spatial domains, most behaviours showed an overall increase from age 4 to 6, with the exception of one behaviour in each domain that decreased at age 6. In the mathematical domain, two behaviours decreased at age five and increased at age 6, while one behaviour decreased consistently at age 6.	Play materials: yes Play behaviours: not explored
Malone et al. (1994)	Categorical and Sequential Play Coding Systems were employed to categorize and analyze the types and complexity of children’s play. Play behaviours were coded. Battelle Developmental Inventory (BDI) was used to measure the children’s cognitive and communication development.	For play behaviours, the independent-play condition showed stronger associations between categorical and sequential play behaviours, with children engaging more in sophisticated play sequences at home than in the classroom. Sequential play measures (e.g., multi-scheme sequences and length of play sequences) were positively associated with cognitive, receptive communicative, and expressive communicative developmental ages in both settings.	Play materials: not explored Play behaviours: yes
Masek et al. (2024)	Math words/phrases per minute were calculated based on each of the three types of math talk: numeracy, spatial, or magnitude. Children’s math comprehension was assessed through three tasks: Point-to-Shape, Point-to-Spatial-Relation, and Point-to-X. In each task, children identified the correct picture for each trial.	Children’s total math talk was positively correlated to children’s age. Children were more likely to use numeracy than other forms of math talk. Children’s math talk was statistically different between materials and was greatest when playing with the grocery shopping set, even when accounting for parent sex and parent dominant language. Numeracy talk was more frequent with the picture book and grocery shopping set than with the shape sorter and magnet board. Spatial talk was more frequent when playing with the magnet board and shape sorter than with the grocery shopping set and picture book. Children were likelier to use magnitudes when playing with the grocery shopping set and the magnet board than with the picture book. They were also more likely to use magnitudes with the magnet board than the shape sorter. Children’s overall math talk showed moderate to large effect sizes on toddlers’ spatial understanding.	Play materials: yes Play behaviours: not explored
McCabe et al. (1996)	Study a and Study b: The McCarthy Scales of Children’s Abilities (McCarthy) assesses general cognitive abilities. The Peabody Picture Vocabulary Test-Revised (PPVT-R) measured receptive vocabulary. The Test for Auditory Comprehension of Language-Revised (TACL-R) includes two sections, Grammatical Morphemes and Elaborated Sentences, used to assess language use.	Study a and Study b: No significant results. The category of play materials did not affect the amount, diversity, or complexity of language used.	Study a and Study b: Play materials: no, not significant Play behaviours: not explored
McCabe et al. (1999)	The McCarthy Scales of Children’s Abilities (McCarthy) assesses general cognitive abilities. The Peabody Picture Vocabulary Test-Revised (PPVT-R) measures receptive vocabulary.	The category of play materials had a significant effect. Functional, constructive, and dramatic play materials each elicited more of their respective types of play and amount of play. Specific toys within each category varied in their effectiveness in engaging children and eliciting expected play types: DUPLOs and markers were effective for constructive play. Dress-up clothes and Fisher-Price houses were effective for dramatic play. The choice of specific toys within each category influenced the type and amount of play observed. The McCarthy GCI and PPVT-R were negatively correlated to the amount of functional play overall and functional play with constructive and dramatic materials. The McCarthy was positively correlated to dramatic play with functional materials whiel the PPVT-R was positively related to overall dramatic and constructive play as well as constructive play with constructive materials. The percentage of dramatic play also accounted for the variance in the number of different words used.	Play materials: yes Play behaviours: yes
Morgante (2013)	The Play Observation Scale was used to record the predominant cognitive play form and social context.	The surface of the sensory table significantly influenced various types of play behaviours. Functional, constructive, and dramatic play all showed main effects based on the surface type, with water encouraging the most functional play and sand and soil promoting the most constructive play. Dramatic play occurred more frequently with water than with rocks. Highly structured objects led to more dramatic play, while minimally structured objects fostered more functional play. Interestingly, highly structured objects, expected to increase social play, instead pulled for more solitary-constructive and solitary-dramatic play. Minimally structured objects promoted greater socialization through parallel and social play and social-constructive play when nested. One significant interaction was found between objects and dyads in parallel-functional play, where heterogeneous dyads engaged in more parallel-functional play with the minimally structured object set than homogeneous male-male dyads. Several significant interactions between surface and object types were observed, particularly in constructive and parallel play. For instance, coupling sand with highly structured objects increased constructive play in heterogeneous dyads, whereas sand paired with minimally structured objects increased parallel play.	Play materials: yes Play behaviours: not explored
Morrissey (2014)	The Pretend Play Observation Scale measured the stages of pretend play in both children and mothers. For children, it assessed the most advanced level of pretend play they showed, from simple actions to complex transformations. For mothers, it focused on their role in modelling and supporting play, evaluating the highest level of pretend play they demonstrated, excluding planning and simple actions. The scale looked at actions and verbal cues to determine the play level.	Children showed a significant increase in the frequency and complexity of pretend play behaviours across three sessions. Play levels advanced from early stages (Stage 1) in Session 1, to higher stages (up to Stage 10) by Session 3, with a noticeable decline in lower-level pretend play and an emergence of more complex play behaviours. Mothers initially engaged in more play behaviours than their children. Still, by Session 3, children’s play frequencies matched or exceeded those of their mothers, reflecting a typical scaffolding pattern where responsibility for play shifts from mother to child. Mothers demonstrated play at more advanced levels than their children, with play ranging from Stages 2 to 10 across all sessions. The gap between mothers’ and children’s play levels narrowed over time, aligning with the scaffolding model. Mothers often modelled play several levels ahead of their children’s abilities rather than just one level ahead.	Play materials: not directly explored Play behaviours: yes
O’Connor and Stagnitti (2011)	The Child-Initiated Pretend Play Assessment (ChIPPA) evaluates a child’s ability to engage in pretend play by initiating and sustaining play scenarios. The Preschool Language Scale, Fourth Edition (PLS-4) was used to assess language development, including receptive and expressive language skills. Goal Attainment Scaling (GAS) was used to assess the achievement of specific goals set for an individual. The Penn Interactive Peer Play Scale (PIPPS) was used to assess children’s interactive play behaviours with peers, focusing on their social competence and the quality of peer interactions.	Significant improvements in children’s ability to engage in pretend play (ChIPPA), language, and goal attainment in the play intervention group. When children’s results were explored with baseline scores and age-controlled, there were no significant improvements for the control or intervention group.	Play materials: not directly explored Play behaviours: no, not significant
Pepler and Ross (1981)	Study a: Play sessions were conducted and coded for the following play behaviours: Form-Related, Colour-Related, Representation-Related, Investigation-Related, Construction-Related, and Symbolic. Divergent problem-solving tasks (Village and Structure-Meaning Task) evaluated fluency and originality in generating structures and labels. Convergent problem-solving tasks (Form-Matching, Colour-Matching, and Representation-Matching) measured the number of correct responses and time taken, focusing on accuracy and efficiency. Study b: Play sessions coded for the same play behaviours as study 1. Divergent problem-solving tasks included the same Structure-Meaning Task from study 1 and the Multiple-Use Task, which assessed the originality and number of verbal and demonstrative responses. Convergent problem-solving tasks included four puzzles designed to be matched based on specific cues (form, representation, colour) while disregarding irrelevant distracting cues.	Study a: Children in the convergent play condition focused primarily on the task. In contrast, those in the divergent play condition produced more responses, which were also more unique and engaged in a wider range of behaviours, including investigation, construction, grouping by properties, and symbolic play. The divergent play group demonstrated the highest originality on the structure-meaning task and contributed to increased fluency in divergent problem-solving tasks. Study b: Children in the divergent play condition engaged in more investigative behaviours, such as exploring rolling properties. In contrast, children in the convergent play group spent most of their time on convergent activities. On divergent problem-solving tasks, the divergent play group produced more unique responses than the convergent and control groups, indicating higher originality in problem-solving. There were no significant effects of age or sex. The convergent play group outperformed the control group on form and representation puzzles, requiring fewer runs to complete them.	Study a: Play materials: yes Play behaviours: yes Study b: Play materials: yes Play behaviours: yes
Rogers (1984)	The Thinking Creatively in Action and Movement (TCAM) was used to measure creative ability. The Preschool Embedded Field Test (PEFT) measures cognitive styles of field dependence-independence and analytic functioning.	The results of the present study revealed that the purported relationships between the TCAM variables of fluency, originality, and imagination and the use of unstructured and structured play materials were insignificant. The study did not find significant gender differences in the relationships between TCAM variables and the use of unstructured and structured play materials.	Play materials: no, not significant Play materials: not explored
Saracho (1992)	Play Rating Scale (PRS) measures children’s play by assessing frequency, creativity in communicating ideas, social interaction levels, and engagement in dramatic play The Preschool Embedded Figures Test (PEFT) measures Field-Dependence/Independence	Children with field-independent (FI) cognitive style engaged more in play than field-dependent (FD) children, highlighting the impact of cognitive style on play behaviours. Significant interactions were also found between age and play behaviours, sex and play behaviours, sex and cognitive style, and among age, sex, and play behaviours. The analysis revealed that FI and FD children differed significantly in all play behaviours except frequency of play.	Play materials: not directly explored Play behaviours: yes
Thepsuthammarat et al. (2012)	The Capute scale consists of a Cognitive Adaptive Test (CAT) and Clinical Linguistic and Auditory Milestone Scales (CLAMS). The CAT is used to evaluate fine motor and problem-solving skills, while the CLAMS determine language skills.	Five types of play materials remained significantly associated with higher Capute scale scores after controlling for other factors: natural materials, creative materials, push/pull toys, sound-making toys, and storybooks. Natural materials had the most significant associations with the Capute scale scores, followed by creative materials and pull and push toys. No mention of covariates and how they affected the regression results.	Play materials: yes Play behaviours: not explored
Tizard et al. (1976)	Observations of children’s play by measuring duration, organization, material use, social participation, play sequence length, and symbolic themes to assess cognitive and social aspects of their play behaviours. Reynell Developmental Language Scale for language comprehension and expression. Minnesota Non-verbal Intelligence Scale for non-verbal cognitive abilities	There were no consistent correlations between aspects of play and verbal and non-verbal standardized test scores.	Play materials: no Play behaviours: no
Tomopoulos et al. (2006)	The Bayley Scales of Infant Development (MDI) assess cognitive development, focusing on attention, memory, problem-solving, and language skills. The Preschool Language Scale-3 (PLS-3) evaluates receptive and expressive language abilities in children from birth to 6 years and 11 months, helping to identify potential language delays or disorders. Additionally, the Caregiver-Child Interaction Rating Scale observes and rates the quality of caregiver-child interactions, emphasizing aspects such as responsiveness, warmth, and stimulation to understand their influence on child development outcomes.	Symbolic and Fine Motor/Adaptive toys were significant predictors of better language outcomes, and the presence of Fine Motor/Adaptive toys was associated with a decreased likelihood of early intervention eligibility at 21 months. Toys at 18 months were significantly associated with maternal language input but not with mutual communication, which mediated the relationship between resources in the home and developmental outcomes. Including parent–child verbal interactions in regression models reduced the degree to which resources (books and toys) were related to developmental outcomes.	Play materials: yes Play behaviours: not explored
Trawick-Smith (1990)	Transformation observations Type I: Using an object in its conventional way but within a make-believe context. For example, using a toy telephone as if making an actual call or using a cardboard box as if it were a box of animal crackers. Type II: Giving an object a completely new make-believe identity by using it in a way different from its intended function. For example, using a plate as a car’s steering wheel or a wooden rod as an oar for an imaginary boat. Type III: Using a body part or gesture to represent an absent object. For instance, forming a hand as if holding a cup and drinking imaginary water.	More object transformations occurred within realistic environments. Neither age nor sex showed a significant relationship with overall transformations. Type I Transformations were more frequent in realistic play settings, regardless of age or sex. Type II Transformations occurred significantly less often in realistic environments. Until age five, realistic materials elicited the greatest number of overall transformations. After age five, the frequency in non-realistic environments surpassed that in realistic settings. An interaction between age, the realism of play objects, and sex was observed for overall transformations. This interaction was primarily due to a strong correlation between age and transformations for girls in non-realistic environments. For boys, the relationship was less pronounced and not significant, suggesting that realistic materials were more effective in eliciting object transformations among boys even after age five.	Play materials: yes Play behaviours: yes
Vieillevoye and Nader-Grosbois (2008)	The Snijders-Oomen Non-Verbal Intelligence Test (SON) assesses cognitive development, focusing on reasoning and performance through six subtests. It scores mental age, intellectual, reasoning, and performance quotients. The Language Evaluation (ELO) evaluates language skills across vocabulary, phonology, comprehension, and linguistic production, using six subtests that measure receptive and expressive language abilities. The Test of Pretend Play (ToPP) measures various forms of pretend play, assessing object substitution, imaginative acts, and the use of objects or agents in pretend scripts.	Individual and dyadic pretend play explained self-regulation in children of both the typically developping and disability groups. Specifically, in both groups, the higher the symbolic behaviour in the creativity context, the higher self-regulation.	Play materials: not directly explored Play behaviours: yes
Wolfgang and Stakenas (1985)	McCarthy Scales of Children’s Abilities: assessed verbal ability, perceptual performance, quantitative development, memory, and motor development. Play Form Scale explored a form of play (i.e., and the toys associated with it in the home environment. The Play Forms Scale includes five subdomains: Fluid Materials, Structured Materials, Microsymbolic, Macrosymbolic, and Physical. Data on all toys in each child’s home (indoors and outdoors) were collected and catalogued.	The study demonstrated a relationship between toys in the home environment and cognitive development. Findings suggest that different toys and play forms relate to different cognitive development patterns. Structured constructional play/materials influenced perceptual performance, verbal, quantitative, and memory development. Fluid constructional play/materials contributed mainly to perceptual performance, while macro-symbolic play/materials influenced perceptual performance and quantitative and memory development. Micro-symbolic play/materials enhanced memory.	Play materials: yes Play behaviours: yes