Looking beneath the surface: associations between varied outdoor surfaces and children’s diverse play behaviours in early childhood education and care institutions

Abstract This study assumes that surfaces in outdoor environments in early childhood education and care (ECEC) institutions exert an important influence on children’s play diversity. Gibson (1979) claims that surfaces are important because they are where most action occurs; some surfaces may lead to a diversity of play behaviours, while others afford a narrower range of actions. This study was conducted as part of a three-year mixed-methods project. The sample consisted of 464 video observations (mean duration: 122 seconds) of 79 children’s free play in the outdoor environments of eight ECEC institutions. Multilevel regression analysis, controlled for children’s age and gender, indicated that functional play was positively associated with surfaces resistant to deformation (e.g. rubber) and that constructive play was positively associated with surfaces with low resistance to disintegration (e.g. sand or forest floor). These results can help develop and design outdoor environments that facilitate children’s play diversity in ECEC.


Introduction
This study assumes that the surface of the outdoor environment in early childhood education and care (ECEC) locations is important for children's play diversity.
Within ECEC, play emerges as a universal activity for young children, serving as the primary approach to fulfil their developmental needs.This means that play is also a significant tool for fostering holistic learning (Broström, 2017;Garner & Bergen, 2006).The United Nations Convention on the Rights of the Child (United Nations Children 's Fund, 1989), specifically Article 31, encourages us to view play as a fundamental need and right for all children, urging an understanding from their perspective.This article provides a robust framework that safeguards and legitimises the pivotal role of play in the lives of young children (Kernan, 2007).
According to Sutton-Smith (2009), play is an activity that children engage in for sheer enjoyment, rather than as a means to an end.Children view play as a voluntary and self-controlled endeavour that is fun, active, spontaneous, free, unlimited, natural, and self-initiated (Eberle, 2014;Wiltz & Fein, 2006).Intrinsic motivation is a key aspect of play, which reflects children's genuine interest and enthusiasm.Furthermore, play serves as a catalyst for learning and encompasses skills that are crucial in adulthood (Bjorklund & pellegrini, 2002;pellegrini & Smith, 1998).In the context of pre-school practice, play and learning are intertwined dimensions that stimulate each other (pramling Samuelsson & Johansson, 2006).Environments that offer meaningful contexts for play, learning, and a variety of choices create optimal conditions for children's learning experiences.According to Hirsh-pasek, Golinkoff, and Eyer (2003), such environments empower children to learn to the best of their capacities by following their interests and engaging in activities that are both enjoyable and educational.
The inherent complexity of children's spontaneous free play is evident as it frequently manifests in various forms, types, and stages simultaneously (Hewes, 2014;Sandseter et al., 2020).play forms are commonly classified according to locomotor, object, and social dimensions (pellegrini, dupuis, & Smith, 2007).In their exploration of how playground design affects children's play preferences and behaviours in pre-school settings, dyment and O'Connell (2013) identified prevalent play types, including functional play, constructive play, symbolic play, and non-play activities such as looking on and talking.Functional play occurs when children use their bodies in physical play, including running, riding bikes, sliding, and climbing.Constructive play involves playing with objects and materials, such as building sandcastles and creating huts and shelters.Symbolic play consists of creative and imaginative play, including role-play, dramatic play, and social play.In this study, we employed a modified version of dyment and O'Connell's classification to categorise the diverse forms of children's play (see the section on our methodology).
Generally, outdoor playgrounds are designed to facilitate children's desire to play; thus, they are important factors for the types of play children can engage in Hart (1993;Sawyers, 1994).Herrington and Brussoni (2015) explained that unstructured outdoor play is one of the most valuable activities for children, but opportunities to engage in such play have diminished over the years.despite this trend, given a choice, many children would like to have time to play outdoors (Waller, Ärlemalm-Hagsèr, & Sandseter, 2017).
Research conducted on Australian pre-school centres by Woolley and Lowe (2013) explored the relationship between design approaches and the play value of outdoor spaces.The two authors proposed that environments which support a wide range of play types hold the greatest value.Their study revealed that children's play value increased along a continuum which ranged from traditional playground designs featuring fixed equipment to composite and nature-inspired designs with more manipulative and dynamic elements.
Even though a multitude of materials and surfaces are proven to stimulate children's diversity of play (Heft, 1988;Storli, Sandseter, & Sando, 2020;Woolley & Lowe, 2013), playgrounds have become increasingly uniform.pfautsch, Wujeska-Klause, and Walters (2022) found that since the early 2000s, playground design standards, which are aimed at minimising the risk of serious injury and enhancing universal design to include children with special needs, have led to a decline in the use of natural materials such as grass and sand.Instead, engineered surfaces, including synthetic turf and rubber floors, have become more prevalent (pfautsch et al., 2022).

Aim of the study
The primary objective of this study was to investigate how different surfaces in the ECEC outdoor environment are associated with various play behaviours exhibited by children.
An ecological approach to a child-friendly environment Moore (2017) emphasised two central criteria for a child-friendly environment: diversity of environmental resources and access to play and exploration.In ECEC settings, child-friendly surroundings play a crucial role in providing the necessary support and resources for children's growth and development.Miranda, Larrea, Muela, and Barandiaran (2017) elaborated on these ideas, stating that high-quality outdoor environments offer a wide range of spaces, equipment, and materials that encourage diverse interactions and play types while allowing children to explore independently.Gibson (1979) introduced the concept of affordances to describe how the environment offers individuals opportunities for action.He promoted an ecological approach to children's perceptions of their surroundings in relation to play.According to Gibson, affordances are the possibilities for interaction between a person and their environment.Individual differences mean that different people may perceive and act on the same environmental affordances in diverse ways, depending on their unique abilities, experiences, and characteristics.
To further describe the environment, Gibson (1979) proposed a triad consisting of the medium, substances, and surfaces, which allows for a thorough understanding of environmental persistence and change.Surfaces separate the medium (e.g. the air from the substance or the earth), which is the support surface for animals' (and humans') perception and behaviours.Gibson's ecological laws of surfaces state that any surface resists deformation and disintegration based on its viscosity and cohesion, respectively.Furthermore, surfaces have characteristic layouts and pigment textures that are determined by their composition.These factors (hardness, viscosity, density, cohesiveness, elasticity, and plasticity) provide children with different perceptions of the potential affordances of the play environment, which leads to diverse individual actions.Woolley and Lowe (2013) argued that the value of play and development can be enriched by a range of surfaces beyond those with high resistance to deformation and disintegration.Carr (2000) proposed three criteria -transparency, challenge, and accessibility -to evaluate the action potential of play environments.In the context of surfaces, transparency refers to qualities that allow a child to perceive the potential actions of the surface.The challenge criterion pertains to the diverse possibilities for action or play offered by surfaces.Surfaces that facilitate different play types (e.g.functional, constructive, or symbolic play) present greater challenges compared to those directing children to specific, predetermined actions.Accessibility involves the extent of social participation afforded by play materials.For instance, a confined rubber-surfaced space with a swing may only accommodate one child at a time due to safety regulations.In contrast, a large lawn provides abundant space, which allows a group of children to engage in tag play.
In an investigation into criteria for child-friendly environments, Kyttä (2004) identified a positive correlation between children's independent mobility and the actualisation of affordances.The greater the freedom children had to explore and play, the more likely they were to identify and utilise affordances within the play environment.Kyttä divided potential affordances into three subsets, each representing the frameworks that shape their realisation.The promoted action field includes affordances that children interact with while receiving guidance and support from adults, peers, and societal values and norms.Conversely, the constrained action field relates to the restrictions placed on children's potential for action.Internal and external rules, as well as design elements, act as constraints that restrict exploration and play behaviour.Finally, the free action field comprises affordances that children discover independently, thus often surprising adults.This scenario aligns with Carr's (2000) argument that children's unanticipated actions broaden the scope and challenges of play.In this field, children take the initiative in exploring and expanding the possibilities available to them.Kyttä (2004) emphasised that the fields of promoted, constrained, and free action dynamically relate to children's diversity of play.Children continuously challenge and expand the ideas behind the facilitation of various playground surfaces.

Methods
This mixed-methods study was conducted within the Competence for developing ECEC Institutions' Indoor and Outdoor Environments (EnCompetence) project; it was funded by the Research Council of Norway (grant 270727).The Norwegian Social Science data Services approved the study.The project lasted from 2017 to 2021 and was conducted in partnership with three ECEC providers in Norway (a municipality and two private organisations).data collection involved systematic and randomised video observations of children in outdoor environments during the time allocated to free play.In this type of play, children had the autonomy to choose their activities, select their preferred locations, and decide with whom they wished to interact.

Procedures and sample
Strategically selected from three partner organisations, eight ECEC institutions were selected to represent a diverse range of physical environments and locations.These institutions accommodated varying numbers of children, ranging from 58 to 117, and were established between the years 1989 and 2014.despite differences in outdoor design, all the institutions provided loose materials (e.g.spades, buckets, and tricycles) along with fixed playground equipment and at least one sandbox.From the children whose guardians granted consent for participation, 10 children (five boys and five girls) aged 3-5 years (mean = 4.7) were randomly selected from each ECEC institution, which resulted in a total sample of 80 children.However, one girl was absent during the observation, which reduced the final sample to 79 children (40 boys and 39 girls).In Norway, children typically allocate over 70% of their time outdoors in ECEC during the summer semester and over 30% during the winter semester.(Moser & Martinsen, 2010).To mitigate the impact of seasonal weather, all observations were carried out over a four-week period in October, normally between 12:00 and 15:00.
To maintain uniformity across all institutions, a rigorous data collection protocol was developed.A pre-school teacher from each ECEC institution was recruited as a co-researcher.They utilised a compact handheld Gopro Hero action camera to record the children's play, aiming to minimise disruptions to their behaviours while capturing high-quality video and sound data.The researcher made field notes and ensured compliance with the established protocol.Co-researchers were instructed to approach as closely as possible to capture speech, body language, and facial expressions without disrupting the children's activities.
Each day, two children were observed based on a specific procedure.The first child was filmed for 2 min, followed by a 6-min break; then, the second child was filmed for 2 min, which was also followed by a 6-min break.This process was iterated until each child had undergone six outdoor video observations.If a child expressed a desire not to be filmed or if filming posed ethical concerns, the observation for that child was deferred until the conclusion of the same day's observation cycle.The co-researcher, having familiarity with the children as a pre-school teacher in the institution, refrained from filming in sensitive situations.They engaged in continuous communication with the children to secure their participation without influencing their play.However, the children were not informed when the camera was activated to prevent any disruption to their activities.
The anticipated total count of 2-minute video observations for the 79 children was 474 (six observations per child).However, the ultimate sample comprised 464 observations, with 10 observations omitted.These absences resulted from diverse factors, including parents collecting their children before the observation cycle concluded, instances where the child was obstructed or disturbed by the camera, and technical or human errors.

Measures
This study focused on evaluating children's play behaviours and their utilisation of various surfaces within the outdoor environment as key measures.Additional variables included children's age and sex.Building on previous studies (dyment & O'Connell, 2013; Luchs & Fikus, 2013), children's play behaviour was measured using six categories: functional play, constructive play, symbolic play, mixed play, looking on, and talking.Mixed play represents a combination of different types of play where two or more of the above types overlap without one predominating.The remaining two categories were used when the child was not playing.Looking on indicated that the child was not engaged in play and was sitting, relaxing, walking around looking for something to do, staring into space, or watching activities.Talking was coded when the child was talking to other children or adults about something unrelated to play.
The categories for play were mutually exclusive and coded second by second using Noldus Observer XT 12.5, a type of behavioural coding, analysis, and management software for observed data (Zimmerman, Bolhuis, Willemsen, Meyer, & Noldus, 2009).The researcher applied the coding of the dominant play type when observations could potentially fit into more than one category.This categorisation yielded descriptions of the number of different play types observed.One researcher coded play for the entire sample, while a second researcher ensured consistency by thoroughly examining a random 10% of the video observations.This process led to discussions about the interpretation of specific observations, such as distinguishing between looking on and talking, determining whether all movements constituted functional play, and deciding when to use the mixed-play category.These discussions resulted in a shared understanding of each category and minor adjustments to the initial coding.In the present study, the variables for the three distinct play types (functional, constructive, and symbolic play) were included in the analysis.
Coding was performed to measure children's use of surfaces.These categories were mutually exclusive and measured the surface on which the child was standing, sitting, running, or walking, or the surface below if the child was climbing.Thus, if the child was climbing on fixed playground equipment with a rubber surface below them, this surface was coded even though the child was on a climbing frame.The codes used to measure children's use of surfaces in the outdoor environment were developed in relation to the data and referred to asphalt, sand, gravel, forest floor, grass, rubber, rubber grass mats, artificial grass, and wooden surfaces.
The utilisation of surfaces by children in the observations was coded on a second-by-second basis using Noldus Observer XT (Zimmerman et al., 2009), providing data on the duration of surface usage by each child.To ensure consistency, one researcher carried out the coding for the entire sample.A second researcher randomly examined 10% of the video observations to validate the coding and interpretation of the categories.After conducting this review, minimal modifications were applied to the initial coding, and the overall consistency was deemed satisfactory.The categories for rubber grass mats, artificial grass, and wooden surfaces were merged into 'other surfaces' because of the limited time linked to these categories in the present study.The other six surface categories were included in the analysis.

Analyses
descriptive statistics for the play types and the surfaces were calculated for the total sample and for each of the eight ECEC institutions to highlight the differences among them.Multilevel regression analysis was used to explore the association between children's play behaviours and their use of surfaces.All multilevel analyses employed random-intercept models.dependent variables, including functional play, symbolic play, and constructive play, were examined for their association with surfaces in the outdoor environment.The stepwise inclusion of variables began at the lowest level of the model (Hox, 2010a), wherein the variable characterising the observed surfaces was introduced before considering children's age and sex.Initially, an intercept-only model (M0), devoid of any explanatory variables, was executed.Subsequently, a model encompassing the surface variable (M1) was implemented.Finally, the second-level variables detailing children's age and sex were incorporated into the model (M2).To assess model fit and compare it to preceding ones, metrics such as deviance, the Akaike information criterion, and Schwarz's Bayesian information criterion are provided (Hox, 2010a).

Results
The mean duration of the 464 video observations was 122 s (SD = 3.4).during periods of free play, the children spent most of their time on asphalt (20%) and grass (20%).Rubber was utilised for 17% of the observed duration, whereas gravel was employed 14% of the time.The remaining time was spent on sand (11%), forest floors (7%), and other surfaces (11%).The children engaged in functional play 33% of the time, constructive play 24% of the time, and symbolic play 10% of the time.The remaining time was used for mixed-play behaviours (5%) and non-play activities (28%).Table 1 presents the descriptive statistics for the key variables.
The availability and use of surfaces varied among the participating institutions.Asphalt surfaces were available in all institutions and ranged between 5% use in Institution A and 43% use time in Institution F. Sand surfaces were coded in all the institutions.Still, the amount of time spent on sand varied from 2% in Institution H to 28% in Institution d.Gravel was coded in seven of the eight participating institutions, while forest floor was only coded in four of them.Rubber surfaces were identified in six of the participating institutions, accounting for a time range between 6% and 31% of the observations.
To explore the association between play types and surfaces, multilevel regression analysis was employed.This approach was chosen to account for the nested data structure and the variables of children's age and sex.Random-intercept models were implemented in all multilevel analyses.The data were nested at three levels: the observation level (Level 1, N = 464), the child level (Level 2, N = 79), and the institution level (Level 3, N = 8).The variance partition coefficient (VpC), with a variance limit of 5%, was used to determine the number of levels in the model (Mehmetoglu & Jakobsen, 2017).VpC computations for functional play revealed a 1% variance at the institution level and a 10% variance at the child level.In the case of constructive play, a 4% variance was observed at the institution level and a 14% variance at the child level.As for symbolic play, a 1% variance was identified at the institution level and a 9% variance at the child level.Consequently, two-level models were chosen for subsequent analysis.

Functional play and surfaces
The final regression model (M2) pertaining to functional play (Table 3) indicated a positive association between being on rubber surfaces and involvement in this play type.The estimation suggested that the level of functional play during the observation was approximately 33% higher when children allocated 100% of the observed time to rubber surfaces.Being on sand surfaces was negatively associated with engagement in functional play, and the amount of functional play was estimated to be 31% lower when children spent the entire observed time on sand surfaces.
No statistically significant associations were found between engagement in functional play and asphalt, gravel, forest floor, and grass.Children's sex and age were not significantly associated with functional play.M1 was a significantly (p < .001)improved model compared to M0, which used a likelihood-ratio test for functional play.M2 was not a significant improvement on M1.

Constructive play and surfaces
The final regression model (M2) for constructive play (Table 3) showed a positive association between sand and forest-floor surfaces and engagement in this type of play.The estimated level of constructive play during the observation was projected to be 66% higher when children dedicated 100% of their time to sand.Forest floors were anticipated to enhance constructive play by 28%, while rubber surfaces exhibited a negative association with constructive play, resulting in a 16% reduction.Asphalt, gravel, and grass did not show significant relationships with engagement in this play type.No significant associations were found between constructive

Symbolic play and surfaces
The final regression model (M2) regarding symbolic play (Table 5) revealed a negative correlation between asphalt and forest floors and participation in this play type.The estimation indicated that the level of symbolic play during the observation was approximately 12% lower when children devoted 100% of their observed time to asphalt and 15% lower when they spent the entire observation on forest floors.There was no significant association between sand, gravel, rubber, and grass and symbolic play.Age was not significantly related to symbolic play, but boys engaged somewhat  more (6.4%) in symbolic play than girls.For symbolic play, none of the models demonstrated improvement compared to the empty model based on a likelihood-ratio test.This implies that neither the incorporated surfaces nor the child's sex and age exerted influence on engagement in symbolic play.

Discussion
Although Gibson (1979) claimed that surfaces are important because they afford different actions, he recognised that there are also other factors affecting the play value of an environment.Children's freedom to explore, play, and access a variety of environmental resources is regarded as the central criterion of a child-friendly environment by Kyttä (2004) and Moore (2017).Traditionally, outdoor playgrounds are designed to support functional play (Herrington & Brussoni, 2015); however, a child-friendly environment of the kind described by Kyttä (2004) and Moore (2017) should ideally stimulate all types of play.
Our study's overall results (Table 1) align with the findings of dyment and O'Connell (2013) as they indicate that functional play is most prevalent (33%), followed by constructive play (24%) and symbolic play (10%).Given the diverse layouts of the ECEC institutions in this study (Table 2), the distribution of play types is as expected.

Surfaces with high resistance to deformation and disintegration
According to Table 1, children spent approximately one third of the observation time on hard surfaces with high resistance to deformation and disintegration (37%).Furthermore, 17% of their time was spent on rubber surfaces and 20% on asphalt.The analysis presented in Table 3 reveals a positive association between rubber surfaces and functional play; it estimates a 33% increase in functional play when children spend all their observed time on rubber.However, rubber surfaces exhibit a negative association with constructive play (Table 4) and no significant association with symbolic play (Table 5).This implies that rubber facilitates functional play but limits the range of actions of the other play types.Carr's (2000) criteria for evaluating environmental action potentials suggest that places with rubber surfacing have high transparency for functional play thanks to the material's high viscosity and cohesion, which makes it easily accessible for all children and supportive of universal design.However, our study's analyses of the associations between play types and surfaces show that rubber surfacing affords limited challenge or play diversity, except for functional play.One possible explanation is that rubber, due to its high shock absorbency, is preferred in conjunction with fixed play equipment (e.g.swings and slides), which allows for risky, functional play (pfautsch et al., 2022).In the pursuit of injury prevention, children's activities and play in confined spaces with rubber surfacing are often restricted by rules; this limits other play types (Herrington & Nicholls, 2007), including bringing movable play materials (e.g.tricycles and loose items) onto the rubber surface.This practice aligns with Kyttä's (2004) concept of the field of constrained action, which at times restricts the field of promoted action.Although children have access to play materials that encourage constructive or symbolic play, they are constrained in where and how they can use them because they are not permitted to bring such materials in areas covered with rubber.
Asphalt, another surface with high resistance to deformation and disintegration, exhibits a significant negative association with symbolic play (Table 5) and a negative but not significant association with constructive play (Table 4).However, Table 3 shows a positive, though not significant, association between asphalt and functional play.For practical reasons, Norwegian ECEC institutions typically prefer asphalt as a surface for entrances, as this material permits easy access to delivery and emergency vehicles; asphalt is also simple to maintain.Heft's (1988) functional taxonomy of children's outdoor environments suggests that flat and smooth surfaces afford activities such as walking, running, cycling, and skating.Our findings indicate no positive associations between asphalt and specific play types.This implies that children might not immediately perceive asphalt as a play-friendly surface since it lacks transparency (Carr, 2000) and does not afford anything particularly enticing.However, asphalt is not subjected to the same safety restrictions as rubber surfacing, and this allows children more freedom to define the action potential of asphalt-covered spaces.Children can bring movable objects and loose materials into these spaces, thus enhancing the challenges related to their diverse possibilities for play and action.

Surfaces with low resistance to deformation and disintegration
The children stayed on surfaces with a high degree of plasticity (e.g.sand, gravel, and forest floors) about one third of the time (32%) and on surfaces with intermediate viscosity and cohesion, such as grass, somewhat less (20%).The results in Table 4 show a positive association between engagement in constructive play and sand and forest-floor surfaces.In this study, we coded sand in all eight participating institutions, but forest floors in just four.The amount of constructive play in the observation was 66% higher when the children spent 100% of the observed time on sand surfaces and 28% higher when they were on forest floors.Compared to rigid surfaces (e.g.asphalt and rubber floors), sand provides ample opportunities for deformation (low viscosity) and variable cohesion, depending on factors such as the sand's microstructure, humidity, and temperature (Gibson, 1979;Woolley & Lowe, 2013).For instance, fine-grained, wet sand that is not frozen allows children to build castles, make cakes, or dig deep holes in the ground.In contrast, forest floors are more intricate in both composition and layout.They typically consist of a mixture of small rocks, flowers, plants, fragments of dead trees, leaves, and branches, which create a rough surface.Although the quality of play transparency on forest floors may not be as immediately apparent as it is on sand, the viscosity of the surface creates possibilities for deformation, while its cohesion encourages a myriad of different perceptions.This makes forest floors a surface that poses a high degree of challenge for constructive play.
Sand is often found in enclosed spaces (e.g.sandboxes) and serves as both a surface for play and a play material (a substance).Bergen (2017) argues that substances such as sand, mud, water, and snow are very challenging because they offer children different perceptions of potential affordances that can lead to diverse and individual play actions.In ECEC institutions, constructive play with sand is often encouraged and facilitated by the staff, who provide access to sandboxes, buckets, spades, water, and other play materials.These additions enhance both the transparency and the challenges of the play environment, which makes constructive play with sand more prevalent.This may explain why functional play is negatively associated with sand in Table 1.The field of promoted actions for constructive play overshadows the affordances for functional play.

Implications
According to Herrington and Brussoni (2015), creating environments that afford play diversity is the best way to ensure that children remain self-motivated and have fun.Especially in ECEC institutions, the outdoor play environment is important because that is where many children stay and play daily, sometimes for several years.
In summary, the results of this study reveal a stronger association between surfaces with low resistance to deformation and disintegration and the diversity of children's play compared to the opposite scenario.pfautsch et al. ( 2022) argued that, since the early 2000s, playground design has seen a rise in engineered surfaces (e.g.synthetic turf and rubber floors), while surfaces with high plasticity, such as sand, gravel, and natural materials, have declined.The future planning and design of outdoor playgrounds must ensure that a focus on safety and universal design does not compromise the variety of play opportunities.
According to Gibson's (1979) ecological laws, surfaces can either afford many actions or restrict actions to a narrow range.Variations in surface hardness, solidity, viscosity, density, cohesiveness, elasticity, and plasticity offer children diverse perceptions and potential experiences in the play environment, thus encouraging an assortment of individual play activities.Therefore, understanding the associations between environmental factors, including surfaces, and children's play is crucial for planning, developing, and facilitating child-friendly outdoor play settings.

Limitations
This study has some limitations.Our research used cross-sectional video observations of children in their everyday environments at ECEC institutions.While this allowed associations between surfaces and children's play to be established, it is important to note that no causal relationships can be inferred from the data.Table 5 shows that there are no significant positive associations between children's symbolic play and any of the investigated surfaces.One possible explanation for this is that certain surfaces might have minor significance when it comes to influencing symbolic play.places in the environment specifically designed for symbolic play, such as playhouses or outdoor play kitchens with relevant equipment (e.g.cups, cutlery, pots, and dolls), could be of greater importance in encouraging symbolic play.The small amount of symbolic play documented and the lack of association between the different surfaces and children's symbolic play could be the result of difficulties in identifying this kind of play, which can occasionally be more subtle and less distinctly expressed than other play types.The assessors frequently coded the play that was most clearly conveyed in the circumstance instead of using different play types as mutually incompatible codes; hence, they may have preferred to code functional and constructive play.dual coding, which would have allowed for more than one form of play to be present at once, would have alleviated this issue, but it would have also complicated and muddled the data.The decision to use 2-min clips as units of analysis may have posed another obstacle to the discovery of symbolic play.The brevity of the duration may have posed a greater challenge for researchers in identifying symbolic play, as this type of play typically requires more time to unfold and become evident to observers.
A limitation of this study is related to the coding of rubber and its association with children's activities, especially those involving play equipment installed on surfaces covered with this material.While our coding approach was designed to ensure consistency and comprehensiveness in data analysis, it raises a valid concern regarding the accurate representation of the play affordances of rubber surfaces.The decision to code activities such as climbing on play structures situated over rubber as 'children's use of a rubber surface' was made to facilitate consistent coding across the video recordings.Therefore, it is essential to acknowledge that rubber serves primarily as a fall surface and may not afford certain play activities.The limitations in our coding approach raise questions about how to precisely categorise activities related to equipment and surface interactions.
Given the above-mentioned shortcoming, future scholars should explore more refined coding schemes that can better capture the complex dynamics of play environments.They may adopt an approach that differentiates between surface use and equipment play more accurately.Still, our study provides valuable insights into the broader relationships between play environments and children's activities.In the future, researchers will be able to build on this foundation to comprehensively address the nuances of play affordances.
Another limitation of this study is the considerable variability in play surfaces across the eight participating institutions.It is important to note that one institution lacked certain play surfaces (grass, forest floor, and gravel), which means that no observations of play on these materials were possible.This variability may have weakened our results in terms of direct comparability.However, we must emphasise that this shortcoming reflects the real-world diversity of play surfaces in different institutions.While our analysis accounted for this variation through

Table 1 .
descriptive statistics for age, play types and surfaces (n = 464 observations).

Table 2 .
Use of different surfaces (% of the observed time) and engagement in play types (% of the observed time) in the eight institutions (a-h).