Nowadays, the technological growth and the constant changes in every aspect of our lives lead governments and educators to seek for new, interesting teaching tools and practices so as to effectively prepare future citizens. Augmented Reality (AR) arises as one of the most innovative tools utilizing a range of technologies. Moreover, it is regarded as a concept, a system or a set of devices able to present information virtually and three-dimensionally (3D), enabling the users to interact with it in real time [1].

Several definitions have been provided to AR technology: (a) a system combining the virtual and real world by 3D display of items [2], (b) a set of technologies “augmenting” the learning process and experience [3], (c) a technology “blending” virtual and real world to create immersive learning experiences [4], (d) a form of digital technology that facilitates the “co-existence” of the real world with virtual information [5] and others.

AR technology is often mixed up with Virtual Reality. The main difference between them lies in the fact that AR does not deal only with virtual items, but combines digital content with physical reality. Consequently, AR may bridge the gap between the virtual and the real world [6]. A variety of devices is used so as to ensure the simultaneous blend and display of virtual and physical objects: head-mounted displays, glasses, computer monitors, tablets, and smartphones.

AR has been applied in many domains such as medicine, engineering, military, entertainment, architecture, and culture museums. During the last decade, it has been implemented in the educational field too, albeit limitedly [7]. Most frequently applications of AR are found in primary school rather than any other educational setting [8]. AR is implemented in K-12 in the framework of STEAM (Science, Technology, Engineering, Arts, Mathematics) Education, focusing often on Science and Mathematics using augmented 3D models [9], on Art Education [10] and on Programming [11]. Additionally, in the last decade, there have been several studies examining the AR impact on learning regarding Science, Maths, and Language across various educational levels ^[7][12][7,12]. AR learning may encompass principles of Bronfenbrenner’s Development Ecology theory [13] too, which can contribute to our better understanding of the way young learners behave and develop. Based on the Development Ecology model, there are four different environmental systems in which children change, interact, learn and develop: the Microsystem, the Mesosystem, the Exosystem and the Macrosystem [14]. AR technology can be related to these systems and facilitate the children’s knowledge-gain process and skills promotion.

Nowadays, education attracts more and more researchers’ attention so as to investigate AR’s potential impact on students thoroughly [15]. Findings emerging from conducted studies highlight both the advantages and disadvantages of AR applications in school classrooms. Regarding the advantages, gains, such as the following, are mentioned in Garzon et al.’s [8] study: enhanced learning outcomes, increased students’ motivation, a better understanding of abstract ideas, autonomy, “sensory engagement”, improved memory, cooperation, creativity, and accessibility. Moreover, AR technology is believed to contribute to students’ promotion of skills and social interactions ^[12][16][17][12,16,17]. Related to the disadvantages of AR: resistance from teachers, the complexity of equipment, technical difficulties in using AR devices [8] and usability and acceptance of AR tools [18] are identified.

2. Learning through AR

To start with, the AR approach integrates constructivism traits. According to these, the teacher can mentor the students to construct new, useful knowledge based on their own experiences, beliefs and attitudes in order to perceive reality ^[19][22]. Accordingly, in AR activities, learners discover knowledge by reflecting upon previous experiences and gaining information. Furthermore, connectivism comes to add technological and digital character to the constructivist theory, which influences AR practices. Connectivism is a learning approach, according to Goldie ^[20][23], which regards learning as “a network phenomenon”. Therefore, knowledge emerges from connections being supported by technology and social interactions ^[20][23]. Additionally, based on this theory created by Siemens ^[21][24], learning arises in various ways and develops as a lifelong process that can be facilitated by technology. Consequently, it may be enriched through different “connections” that we experience in our environments ^[21][24]. In addition to Connectivism theory that influences AR learning, Thorndike’s “Connectionism theory” ^[22][25] reinforces it as well. Based on this, technology assists learners to have access to different sources of information in their environments. AR technology may support them to interact with them physically in real time by facilitating discovery-based learning. Additionally, AR teaching may be based on the Activity theory. This theory expands Vygotsky’s and illustrates that teacher–children’s interactions and the suitable use of technology tools can influence a learner’s development and may facilitate self-learning in various activity systems that interact with each other ^[23][26]. Furthermore, AR might encompass the framework of twenty-first-century skills. These are competencies that could contribute to success in life, learning, and working places. Typically, these skills are the 4Cs (Critical thinking, Communication, Collaboration, Creativity) ^[24][27], Media-technology skills, and Life-Career skills. All these may be fostered through AR technology, which is thought to create a multi-sensory learning experience ^[25][28]. Based on findings from conducted research, during AR activities, students may be motivated and engaged highly in the learning process while discovering knowledge and learning through the exploration of concepts, phenomena, environments, and places that are beyond the walls of a typical, traditional classroom [1]. Texts, videos, and pictures are used to visualize events not easily accessed in reality [5]. Additionally, traditional teaching tools, for instance, books, can be used together with AR devices and create interactive learning materials ^[26][29], empowering the learning process and placing the students in the center of it. AR tools and materials might positively affect the learning outcomes in subjects such as Engineering [8], Maths ^[27][28][30,31], Science, Physics ^[29][32] Language, Geography ^[30][33] and social studies ^[31][34] in primary school and higher education. Therefore, according to some researchers’ claims, AR technology may arise as an effective educational tool to enhance children’s motivation and engagement in learning and contribute to learners’ creativity ^[27][28][30,31]. Additionally, AR may improve engaged learning together with technology literacy from an early age ^[32][35]. Furthermore, children with autism spectrum disorders (ASD) might be motivated and engaged in interactive learning activities, thus promoting cognitive and social skills through AR technology ^[33][36]. Thus, based on researchers’ claims, AR technology may benefit students’ performance and learning at almost every educational level, as long as suitable instruction and guidance are given ^[34][37]. Yet, preschool is limitedly studied regarding AR effects on learners’ authentic performance, on the promotion of computational thinking skills and on collaborative learning ^[35][38].

3. AR in Preschool

Preschoolers are confined to seeing reality only from their own perspective ^[36][39]. Thus, they may encounter difficulties in understanding easily others’ views and it is even harder for them to understand abstract ideas. However, through their interactions and playing with peers, they gradually visualize them. Nowadays, this interaction is enriched by technology and by interesting tools and devices. AR equipment may be one of them that contributes to children’s interactions so as to gain the highest potential learning outcomes and develop useful life-long skills. AR technology integrates and utilizes sound, colorful images and touch stimulating preschoolers’ senses ^[37][40] facilitating them to explore and discover new knowledge [5]. Based on Oranc and Kuntay ^[38][41], AR can be an effective educational tool for preschoolers contributing to their gain of knowledge and skills development. This is facilitated by the fact that by the age of 7 years old, children may develop skills required for the use of AR devices and applications, which can enhance their learning experience ^[39][42]. In educational settings, and especially in preschool, children learn at ease while playing ^[40][43]. In addition to this, education diverts into entertainment and becomes “edutainment” when multimedia tools are utilized ^[41][44]. Accordingly, preschoolers like and want to use AR devices again and again while interacting with AR applications, peers, and teachers ^[42][45]. They are supported to visualize objects in their minds through AR technology, which combines virtual and physical environments and helps them with understanding abstract ideas ^[42][45]. Moreover, the learning process becomes fun and interesting and collaborative learning is promoted. Yet, according to Yilmaz et al. ^[43][46], AR applications may be effective tools in preschool, as long as they are easy to use and can facilitate interactions ^[44][21]. AR technology has been implemented in early childhood in the last decade [10]. Nevertheless, preschool education seems to be limitedly examined compared to other educational levels ^[45][47]. Yet, there have been studies among others examining: (a) preschoolers’ attitudes towards AR picture books ^[43][46], (b) the creation of mathematical learning experiences from AR applications in preschool educational settings ^[46][48], (c) AR as a teaching aid for teaching music ^[47][49], (d) AR technology contributing to interactive educational games ^[48][50], (e) literacy skills’ promotion via AR ^[49][51]. Regarding the gains emerging from the utilization of AR technology in preschool reality:

• It may raise young learners’ attention helping them to focus on activities ^[50][52] and may contribute to children’s cognitive development ^[37][40].
• It may enhance preschoolers’ spatial skills ^[51][53] adding value to playing innovative games and to hands-on ability ^[52][54].
• [16].
  It may motivate young children to get engaged in the learning process by utilizing context (for example, animation) appealing to them ^[53][55].
• It could limit children’s privacy ^[58][60].
  It may create fast, fun and effective learning experiences ^[54][56].
• It could improve Preschoolers’ musical skills helping them to express their emotions easily ^[
• It might confuse young children about where fantasy ends and reality begins [4].
  ^55][57].
  It could enhance children’s creativity and foster their meeting with the arts physically ^[56][58].
• It may support children’s social skills and peer relationships through interactions ^[57][59].

On the other hand, AR technology might have a negative impact on preschoolers as well:

• It may confuse young learners due to its multitasking character [8].
• It may be too complex for preschoolers to use and may cause discomfort to them

Regarding gender and its impact on the potential adoption and benefits of AR, there is little to know. The studies conducted so far focus on the gender effect on students in general and not on preschoolers specifically. For instance, according to Dirin et al. ^[59][61], females aged from 19 to 34 years old may manage New Technologies and AR better than males do because they get more emotionally involved with the content of them and get more enthusiasm from such innovative applications. On the other hand, there have been studies concluding that, in general, males tend to adopt New Technologies more easily than females ^[60][62]. To conclude thus far, while some researchers claim that AR technology may divert the learning process into an interactive action allowing school stakeholders to have control of their learning with less mental effort in a hybrid learning environment ^[61][63], there are others who conclude that AR might cause discomfort and might not facilitate so much young children’s learning ^[4][58][4,60] Moreover, some researchers claim that AR content is inflexible and cannot be tailored easily to children’s interests and needs ^[6][62][6,64].