CORAL BLOG

COGNITIVE DEVELOPMENT

The Winner Takes it All: Preschoolers Focus Heavily on Outcome

Written by: Hailey Pawsey 

November 3rd, 2022

image:

If two girls run a race, and one girl is winning but trips on a rock and falls, the other girl might get ahead and win. As adults, we easily can infer that the girl who fell may be a better runner – if she’s in a contest, we might even feel sorry for her, because if she ran the race again and there was no rock on the path, she’d probably win! But do young children understand that sometimes, the person who is better at something doesn’t always win? 


Findings suggests that a lot of preschoolers may struggle with understanding this concept! In one study, researchers created a running task just like the one mentioned above. They explained that the person who was winning the race tripped on a rock, and the other person won. They asked 3-, 4-, and 5-year-olds who they thought was a better runner, and who they thought would win the race next time if there was no rock on the path. Three-year-olds really struggled – they believed that because the person who won the race won, they were the better runner and would win next time. Five-year-olds were successful, correctly inferring that even though the character who lost lost, they were actually faster and also better. What’s interesting is 4-year-olds correctly predicted the person who tripped would win next time, but they still said that the winner was a better runner! 


This focus on outcome is not only reserved for running races, but also building blocks. Another study asked preschoolers to consider different trials and judge from two scenarios which would be easier. In one trial, a girl had to build a tower made of a couple blocks, and another girl had to build a tower out of a bunch of blocks. Preschoolers were able to successfully examine differences in the outcomes (one tower was harder because it had many blocks, whereas the other was easier because it had few), and judge that the girl who built the harder tower was better! In another trial, a girl had a box filled with red blocks and a few blue, and she had to pull out six red blocks. Then there was another girl who had to pull out six red blocks from a box of mostly blue and only a few red. Interestingly, preschoolers couldn’t infer who was better at building blocks, likely because the two girls had the same outcome! This suggests that when preschoolers must integrate both process and outcome information, they really struggle to infer who is better. 


To summarize, current findings suggest that when inferring ability, preschoolers are really focused on outcome information. It may be the case that preschoolers just cannot inhibit information about who won. It’s also possible that preschoolers struggle to consider both process and outcome information, like in the building blocks tasks, and integrate this to determine who is better. 


Interested in the original research? Check out the cited articles below:

If you’re happy and you know it: How do children infer emotions?

By: Jillian Rioux and Shaneene Heupel

June 20th, 2022


The capacity to recognize and understand emotions is one of the most important abilities that one learns in life. This skill matures in the early years and is practiced throughout our lives. Understanding emotions allows us to engage in successful social interactions – such as empathizing with others – but also helps us to regulate our own emotions and behaviors. In almost everything we do, we must attend to our own and others’ emotions. 


When does our understanding of emotions start? 


Research suggests that emotions are something we become attune to as early as the first few months of life! At three months, infants can differentiate smiling from frowning faces, and at five months, they can distinguish between happy and sad vocalizations. By the time they reach their toddler years, children begin to recognize and label basic emotions, such as happiness, sadness, anger, and fear. By four, children understand that emotions can be affected by external causes. For example, they understand that someone who gets their favorite dessert would be happy. As they age, children begin to conceptualize that someone’s emotions can depend on their internal desires and beliefs, and they understand that someone can show mixed emotions towards one situation. This conceptualization of emotions advances progressively throughout their development, with the mastery of some emotions (happy, sad) before others (surprise, fear).


How do children infer emotions? 


There are two leading theories that describe how children infer others’ emotions: by relying on memorized scripts and considering others’ mental states.



Scripts are knowledge structures which consists of sequences of concrete events that allow people to follow common social conventions. For example, you might have a script for a child’s birthday party that guides your behaviours: you show up to the party with a present, you play games, you sing to the birthday child, they blow out their candles, you eat cake, birthday child opens presents, and you get a party favour when you leave. With emotions, children come to learn various scripts and the emotions that accompany them. For example, your child might learn the script that people are happy when they open presents. So, the next time they see someone opening a present, they might infer that the person is happy. 


Researchers from Boston College have found that children as young as 3-years-old are able to use scripts to infer emotions. Given stories about concrete events, they can predict the valence of people’s emotions (e.g., feels good or feels bad), as well as the specific emotion labels (e.g., happy, sad, angry).



In almost every social situation, we make predictions about how someone will act, respond, and feel based on what we know about their mental states, such as their desires, beliefs, and goals. Let’s take our birthday party scenario as an example: Having talked to the birthday child at school, your child knows that the birthday child wants a Lego set. But after opening all their presents, the birthday child realizes that they did not get a Lego set. From understanding the birthday child’s desires, your child will likely infer that the birthday child will be sad. This is an example of taking someone’s mental state into consideration when predicting how they feel! 


Research shows that children’s ability to consider mental states when inferring emotions improves with age. Around age 2, children use people’s desires to infer simple emotions like happiness and sadness. But it is not until around age 7 that they can use people’s beliefs to infer complex emotions, like surprise and fear.                                                 


New research on how children infer emotions:

Probability 


The two theories outlined above, inferring emotions through memorized scripts and mental states, are two prominent theories in the emotion literature. Over the past few years, Dr. Tiffany Doan, a recent PhD graduate from our DLL lab, has proposed an additional way children infer emotions: by using probability. 


What is probability?


Probability is the likelihood of an event happening. For example, winning a contest is a likely event if few people enter, but is an unlikely event if thousands of people enter. Related to our understanding of emotions, how someone feels about the same outcome can differ depending on the probability of it occurring. Someone might feel happier about winning the contest if their odds of winning were low compared to high.


How do children use probability to infer emotions? 


Let’s go back to our birthday party example. If asked to infer how a child feels about not being invited to a birthday party, your child’s inferences might differ depending on information about probability. If the birthday child was allowed to invite 20 classmates, your child might infer that the uninvited child would be very sad since the chances of getting an invite was high. However, if the birthday child was only allowed to invite two classmates, your child might infer that the uninvited child would be less sad, and perhaps even okay, since the chances of getting an invite was low.


A study conducted at the University of Waterloo investigated how children use probability to infer a particular emotion: happiness. In this study, researchers told children a story about a girl and a gumball machine that contained yummy and yucky gumballs. One group of children saw a machine that contained mostly yummy gumballs, and another group saw a machine that contained mostly yucky gumballs. Both groups were told that the girl wanted yummy gumballs, and watched her get two yummy and two yucky gumballs. Children were asked to rate how the girl felt using a happy face scale that ranged from extremely sad to extremely happy. Five- and 6-year-olds rated the girl as happier when the gumballs came from a mostly yucky gumball machine than when they came from a mostly yummy gumball machine. Rating the girl’s happiness differently despite her getting the same outcome suggests that children recognized that a better outcome was likely when the machine held mostly yummy gumballs and a worse outcome was likely when the machine held mostly yucky gumballs. Four-year-olds did not make the same inferences. 


An additional experiment was conducted to see if 4-year-olds can use probability to determine the quality of an outcome, rather than using it to predict someone’s happiness. When given just the outcome of two yummy and two yucky gumballs, 4-year-olds judged that the outcome was better when they came from a mostly yucky gumball machine than when they came from a mostly yummy gumball machine. This suggests that they can use probability to infer the quality of outcomes.


In sum, by the age of four, children can use probability to infer the quality of an outcome, and by five, they can use probability to infer people’s happiness. These findings show that children infer emotions by relying on more than just memorized scripts and people’s mental states.


To summarize, the ability to infer people’s emotions is an important skill to master, and young children may use an array of cues to do so. They can rely on scripts, which are based on their memorization of the events that elicit each emotion. They can consider people’s mental states, like their desires, beliefs, and goals. And they can also use information about probability to infer how people feel.


Interested in the original research? Check out the cited articles below:


How do children determine who is the expert?

By: Venus Ho


In one of our previous blog posts “How do children choose who to learn from?”, we talked about how children use various cues, such as past accuracy, confidence, and expertise, to determine whether a person is a reliable source of information! From a very young age, children are aware that some people are misinformed, so they are constantly evaluating whether people are knowledgeable and trustworthy. In today’s blog post, we will be continuing our discussion on how children are careful learners by sharing more research on how children determine who has expertise!


Studies have shown that children, as young as 3 years old, use a person’s title to determine whether they have expertise in a specific area. Titles, such as “lawyer”, “doctor”, and “car mechanic”, act as a cue to the training and knowledge a person has. For instance, 3-year-olds are able to point out that “car mechanics” are more likely to know about how to fix cars, while “doctors” are more likely to know how to help sick people. As they grow older, children’s ability to do this becomes more advanced and they are able to link titles to broader areas of knowledge. For instance, 4 to 5-year-olds are able to point out that “car mechanics” are more likely to know about how physical objects work in general (e.g., how a yo-yo works), while “doctors” are more likely to know about biological topics in general (e.g., why plants need sunlight to grow).


Additionally, ownership is another cue to expertise that children use. In one study, 4- and 5-year-olds judged that owners of an object were more likely to have knowledge about that object than someone who liked the object but did not own it. This makes sense since owners typically become very knowledgeable of their property through frequent use! 5-year-olds also judged that a person who has deeper knowledge about an object (e.g., knowing how to fix it) was more likely to be the owner of that object than a person who only has superficial knowledge about the object (e.g., knowing what colour the object is). Thus, ownership may also be a strategy that children use to determine who has more expertise and knowledge about objects they want to learn about.


Interested in the original research? Check out the cited articles below:

Imaginary Companions in Childhood and their Psychological Importance 

By: Julianna Lu


Children are known for having remarkable imaginations. Beginning from ages two or three, many children engage with imaginary companions; fictitious people, animals or objects that children create. Talking and playing with an imaginary friend is a normal psychological phenomenon. Interestingly, these imaginary relationships play a role in human thought and can be constructive in children’s development of social relationships and other areas of development such as cognition. For example, playing with an imaginary companion provides children with opportunities to practice skills that are useful for later social interactions and emotional regulation. Indeed, imaginary relationships often mirror real-life relationships in that they are associated with emotion, and the imaginary bonds created can be endured over a period of time.

 

Therefore, there are many benefits to playing with an imaginary friend. Here are three different examples of how having an imaginary friend contributes to child development. 



Research shows that engaging with an imaginary friend may support children’s language development. In

2009, Trionfi and Reese compared the vocabulary and narrative skills between children with or without imaginary companions. Five-year-old children and their mothers were interviewed about the child’s imaginary companion. Children were assessed on their level of engagement with an imaginary companion, on their receptive and expressive vocabulary skills, story comprehension, and ability to retell a story. Findings suggest that children with an imaginary companion told richer narratives when asked to retell a story. However, there was no significant difference in vocabulary skills among children with or without an imaginary companion. Nevertheless, children’s engagement with an imaginary companion contributes to their development of narrative skills, which can, later, bolster children’s reading skills. 

 


Theory of Mind (ToM) is an important social-cognitive ability that develops throughout early to middle childhood. It is defined as the ability to consider one’s own and other people’s mental states. For example, understanding that other people may have different desires and will act accordingly to achieve what they want is one aspect of ToM. Ultimately, ToM is a foundational element for social interaction. 

In a study conducted by Giménez-Dasía, and colleagues in 2014, children with imaginary companions showed better ToM when compared to children without imaginary companions. The creation of an imaginary friend fosters the understanding of mental states. Similar to pretend play, engaging with an imaginary friend requires children to create mental representations. For example, they may create characters who possess different beliefs, desires, and goals. Therefore, playing with an imaginary companion is a great way to foster perspective-taking.

 


In the same study mentioned above, Giménez-Dasía and colleagues found that children who had an imaginary companion were more advanced in their emotional understanding. To measure children’s emotional understanding, participants were evaluated on their ability to recognize basic emotions, their understanding of the impact of external variations on emotions, their ability to understand the impact of beliefs on emotion, and a variety of other features related to emotional understanding. Participants were told a story about a character and after hearing the story, they were asked to label the emotion that best described how the character was feeling. For example, to assess their understanding of the impact of external variations on emotions, they were told the following story: “This girl is being chased by a monster. How is she feeling? Happy, just alright, or scared?” Overall, the findings suggest that children with an imaginary companion had a higher level of emotional understanding than children without an imaginary companion. During these imaginary interactions, children are constructing a reciprocal conversation. They are learning to take different perspectives which allows them to better understand the emotions of another person. 

 

To summarize, having an imaginary companion is a normal and healthy component of play during childhood. Although it was historically viewed as a cause for concern, research on imaginary companions has demonstrated its beneficial role in children’s language development, theory of mind, emotional understanding, and many other areas of child development. But not having an imaginary friend is just fine too – some children enjoy this kind of play and other children find different types of play more fun and rewarding! Nearly every type of childhood play offers specific benefits to cognitive, physical, and language development. 


Interested in the original research? Check out the cited articles below:


Moral development: Even your kids can do it!

Written by: Claudia Sehl


The ability to understand the difference between right and wrong is known as morality. Morality is what guides us to make ethical choices and to identify when others are acting badly. Although it may seem like a high-level ability, morality surprisingly emerges early on in development.

 

An American psychologist named Dr. Lawrence Kohlberg raised one of the first theories of moral development in 1958. He believed that people progress through three levels of moral reasoning (preconventional, conventional, and postconventional), with each level consisting of two stages. The first two stages, known as the preconventional stages, correspond to moral development in childhood. At these stages, children try to be well-behaved to avoid punishment. For instance, preschoolers learn not to hit other children because they do not want to get in trouble. Preschoolers are also well-behaved to receive rewards for moral behavior, such as praise or treats for sharing with others. So, from early on in development, children do not automatically know what the right thing is to do. Instead, they rely on feedback from parents and caretakers to guide their behavior. 

 

By late-childhood and adolescence, people start to follow moral conventions, not just for the sake of being rewarded and avoiding punishment. During these conventional stages, adolescents try to live up to societal expectations by being a ‘good’ person. In doing so, they begin to recognize that their behaviour will have social benefits, like friendships. For example, teens realize that it is good to be kind to others, as others will reciprocate this same kindness to them. Additionally, teens start to understand the importance of following fixed rules and laws. 

 

Finally, in the postconventional stages, adults recognize their own personal moral values. They also realize that there may be exceptions to legal rules if moral rights are violated. For instance, stealing necessities such as food and medicine may be considered acceptable in desperate situations. Furthermore, adults at this stage can engage in abstract moral reasoning about ethical principles, such as preserving human life and behaving with integrity. According to Kohlberg, most adults remained at the conventional stages and few adults moved onto the post-conventional stages of moral reasoning.

 

Kohlberg’s work is considered foundational to our understanding of moral development, but some recent research suggests that some stages may occur much earlier than he originally thought. In one experiment, 2.5-year-olds offered their own blanket to a shivering experimenter. Altruistic behaviors such as these suggest that young children are empathetic to others’ distress[1]. In another study, experimenters asked young children if it would be okay to break rules, such as hurting or stealing from others. Four-year-olds knew that it is wrong to do these things, even if parents and teachers said it was okay[2]. Findings like these suggest that our understanding of morality may begin earlier in development than what was previously thought! 

 

Next time you are playing with your child, reflect on these stages of moral development. Can you observe which stage they might be at? What early signs of moral development do you notice?


Interested in the original research? Check out the cited articles below:


[1] Svetlova, M., Nichols, S. R., & Brownell, C. A. (2010). Toddlers’ prosocial behavior: From instrumental to empathic to altruistic helping. Child development, 81(6), 1814-1827.

[2] Smetana, J. G., Rote, W. M., Jambon, M., Tasopoulos‐Chan, M., Villalobos, M., & Comer, J. (2012). Developmental changes and individual differences in young children’s moral judgments. Child development, 83(2), 683-696.

Age-Appropriate Chores that Your Toddler Can Do

Written by: Venus Ho


Did you know that children as young as 2 years old can help out with chores? When toddlers start helping out with chores at an early age, they learn to view themselves as people who contribute and help others, which can promote the development of prosocial skills. Additionally, engaging in chores can be an activity that allows your toddler to both let out their energy and to practice their motor skills. 

 

How do you know what chores are age-appropriate for you child? The key is to look at your child’s gross and fine motor skills and determine what tasks may be achievable for them. However, it is important to keep in mind that toddlers will be sloppier and take longer with the tasks since they are still learning. Therefore, it’s important to manage your expectations and treat chores as a fun, learning opportunity for your child! Below, we list some examples of chores that your toddler may enjoy assisting you with: 

 

1.     Putting away toys after playtime


After playtime, you can encourage your child to put the toys back where they belong. This activity can also be a fun way that your toddler can practice their sorting skills! For example, you can teach them where toy cars vs. toy animals are supposed to go and have them sort them into their respective bins.

 

2.     Helping out with laundry


We all know that toddlers love to throw, pull, and push things! By having them assist with laundry, they can engage in these actions while helping out. Some tasks that your toddler can do are: putting dirty clothes in the laundry bin, throwing clothes into the washer or dryer, taking clothes out of the washer or dryer, folding small items like socks or washcloths.

 

3.     Taking care of the family pet


Teaching your toddler how they can take care of a pet can help them learn to respect other living things! Some age-appropriate tasks that a toddler can do include refilling the food and water bowls (after you have measured the correct amount) and brushing the pet’s fur.

 

4.     Cleaning

A fun activity you can do is give you toddler a sock and tell them to slip it over their hand. Encourage them to slide their sock-covered hand over a dusty surface to help out with cleaning! Toddlers may also enjoy wiping up small (kid-friendly) spills like juice or milk. Give them a small cloth and show them how they can wipe down the spill!

 

5.     Making the bed


This activity will be too difficult for your toddler to complete on your own, but together, you and your toddler can work together to make the bed! When making the bed together, guide your toddler step-by-step and encourage them to straighten one side of the bed.

 

One thing to remember is that your toddler will not be completing these tasks perfectly and that’s okay! It’s important that you do not go back and immediately correct their work because this may send them the message that their help is not good enough. By not redoing their work, your toddler will take pride in helping you with chores and learn that they can make a difference! 

How Can You Foster Children's Learning?

Written by: Julianna Lu


From birth, children are active participants in the acquisition of knowledge and skills. Through observation, experimentation and participation with other children and adults, children build their understanding of the world. Nevertheless, there are ways in which parents and other caregivers can help children learn more efficiently. One effective teaching method is a concept known as social scaffolding. Based on Vygotsky’s Social Learning Theory, social scaffolding is a technique in which a more competent individual provides a temporary framework to support children’s ability to build on their prior knowledge. This framework enables children to think at higher levels than they could manage on their own. As the name suggests, it functions similarly to the scaffolding used during construction; it provides support during the building, maintenance, and repair of structures.

There are three characteristics of social scaffolding: it is contingent, temporary, and involves a transfer of responsibility. Contingency refers to the way the expert adjusts their level of support based on the learner’s current level of ability. It requires experts to make appropriate judgments about the needs and quality of assistance that would most benefit the learner. For example, when learning how to ride a bike for the first time, it would not be helpful to immediately take off the training wheels. Instead, it might be more appropriate to begin with teaching a child how to steer, pedal and stop with the training wheels.

Social scaffolds are also temporary. As the learner begins to gain competence, support can be reduced. For example, once the learner is comfortable with riding the bike, you can slowly remove the training wheels. The last characteristic is the transfer of responsibility. This occurs when the learner internalizes their new knowledge/skills and can apply their knowledge independently. For example, after learning how to ride a bike smoothly without training wheels, the learner takes control in advancing their skills: learning how to do different turns, stops, etc.

Thus, social scaffolding is an excellent teaching method. It breaks up learning into chucks that are catered to the learner’s current level of ability. By providing this structure, children can incrementally build on their prior knowledge and become experts themselves.

You can try this at home!

·       Pick a goal-oriented activity (e.g., baking cookies)

·       Create a temporary framework (e.g., Show them how to measure out the ingredients. You can support them at first by just having them choose the correct cup with you and watching you scoop and measure and letting them pour it in the bowl carefully.)

·       Slowly reduce the level of support and provide the learner with a more active role (e.g., Once they are comfortable with pouring the measured ingredient in the bowl, let them try doing the measuring part.)

·       During the activity you can pause, ask questions and review – This is an excellent way to check on their understanding and keep them engaged!

Interested in the original research? Check out the cited articles below:

How Parents Can Support Children's Learning During Play

By: Venus Ho


Children love to play since it’s fun and enjoyable. However, play can also be a rich learning opportunity for children since they can freely use their imagination, learn to problem-solve, and engage in hands-on experiences with their environment. During free play, children explore various tasks and activities without the guidance of an adult, which allow for self-expression and creativity. When children play together, they can also learn how to cooperate and share with others. However, despite the benefits of free play, researchers have noted the importance of scaffold play, which is play that is both child-directed and guided by an adult. During scaffold play, the adult can introduce new ideas and concepts to the child, which can help promote learning. Below, we will go over some strategies that adults can use to support children’s learning through play:


Ask questions that stimulate discussion and encourage thinking


Although this strategy seems straight-forward, it may actually be difficult to do since adults are used to instructing children on what to do, instead of asking questions and listening to children’s responses. Research has shown that it can be helpful to give children the opportunity to practice communication by asking questions related to their play. For instance, if children are building a house, adults can ask, “How are you going to build the house?” or “What rooms do you need inside the house?” to encourage extended thinking about the concept. Similarly, if a child is playing with a toy car, adults can ask, “Why do people use cars?” to encourage the child to think about the real-world application of the concept. By inquiring about children’s understanding of a concept, adults can identify gaps in their knowledge and provide more information about the concept if needed. 


Giving enough time for children to answer questions


In addition to asking questions that encourage children to think, it is important for adults to give ample time for children to formulate their responses. Oftentimes, children may take longer to answer questions because they are thinking about their response and how to express it. This is important for adults to keep in mind because adults often follow up with another question or provide an answer to the question before the child has had enough time to answer. By giving children enough time to think about their responses, children are better able to practice their language skills.


Providing Feedback and Comments


Adults can also support children’s learning by providing comments on what children are doing. For instance, if adults ask, “What are you playing with?” and the child answers with the word “car”, adults can respond with “Oh, you are playing with a toy car.” This allows children to hear their response incorporated in a complete sentence, which can help with language development. Additionally, adults can provide definitions about concepts. For example, if a child is playing with a pencil, the adult can say, “You are playing with a pencil. Pencils are used for writing things.” This can enhance children’s knowledge about different concepts. Furthermore, adults can connect new concepts with background knowledge that the child already has. For example, if a child is playing with a train, the adult can bring up situations where the child has been previously exposed to trains, such as in a TV show or a book (“Is that train similar to the one we were reading about yesterday?”).


Therefore, adults can play an important role in children’s learning during play. By using these strategies, adults can support children’s learning by introducing new ideas and allowing children to practice their communication skills.

 

Resource: https://link.springer.com/article/10.1007/s10643-016-0827-5 

I Can't See it, But it's Still There! Fostering Object Permanence in Children.

By: Venus Ho


One of the major developmental milestones that children attain is the understanding of object permanence. Although the concept sounds complex, object permanence is simply understanding that an object continues to exist even if it cannot be seen or heard. When babies are very young, they do not understand that an object still exists when they cannot sense it. It's literally "out of sight, out of mind"! During this phase, when a toy is covered with a blanket, your child may give up searching for it quickly because they do not understand that it still exists.

The concept of object permanence was originally developed by Jean Piaget, who proposed that the skill did not develop in children until they were 8 months old. However, research by Baillargeon and colleagues has now shown that babies can understand object permanence much earlier, even when they are just 5 months old! Below, we have outlined some activities for you and your child that can help foster the development of object permanence.

Peekaboo is one of the simplest and most popular games to play with your baby to foster object permanence. You can either hide your face behind your hands or anything that can cover your face (e.g., blanket, book) and then shout "Peekaboo" as you reveal your face again.

This is another easy and fun activity you can do with your child. You can simply hide a toy under a blanket and then take it out again to reveal that it still exists. This activity can be even more fun if you have a toy that makes noises. When you cover the toy with the blanket, you can make sounds with the toy, showing your child that even though they cannot see it, the toy is still there!

For babies that are starting to learn how to walk, you can hide toys around your home in places that your child can easily find them. After hiding the toys, you can ask your child to find them. To make it easier, you can give your child cues about where the toy is (e.g., "You're getting closer!"). This activity can show them that even though they cannot see their toy, it has not disappeared and can be found again. This activity is also great for promoting muscle development and motor coordination skills!

This final activity requires collecting tube-like materials, such as PVC pipes or the leftover cardboard tubes from paper towel rolls. You will also require a small round object, such as a ball, that can fit through the tube. Next, you can choose to tape the tube vertically to a wall or hold the tube yourself. Now, when you put a ball inside the top of the tube, it will fall out from the bottom of the tube. With this activity, your child will be learning that even though the ball cannot be seen inside the tube, it is still there! Children also love playing with gravity, so this activity will definitely be a favourite.

Interested in the original research? Check out the cited articles below:


Baillargeon, R., Spelke, E. S., & Wasserman, S. (1985). Object permanence in five-month-old infants. Cognition, 20(3), 191-208. https://doi.org/10.1016/0010-0277(85)90008-3


https://activeforlife.com/baby-object-permanence/ 


https://calgarypreschools.ca/blog/3+Simple+Games+to+Teach+Your+Child+About+Object+Permanence+/37