Concepts are general ideas or terms that can be used to group objects, situations, qualities, or abstractions, that let them become equal in a certain way.

How can the who and what be understandable?

How to divide objects into categories? 

Children use categorical hierarchy to distinguish between categories. The categories are classified into set-subset relation, such as animal-dog-poodle. Small children especially use perceptual categorization: grouping objects that are similar. It can already be seen in children from 3 to 4 months old. As children grow older, they also understand hierarchical and causal relationships between categories. The categorical hierarchies’ children are forming often contain three levels: the superordinate level (for example a plant), the subordinate level (for example an oak tree), and the basic level (for example, a tree). Children mainly learn the basic level first, after the parents help them to gain understanding of the higher levels. In an older age, children establish causal relationships between objects through explanations or the idea of cause and consequences between objects. This helps the child understand the categories and form more categories. 

How to understand others and ourselves?

The naïve psychology focuses on the level of intellect needed to understand other people and themselves. To understand human behavior, three concepts are used: desire, beliefs and actions. There are three remarkable features of these concepts: First, the concepts refer to invisible mental states. Second, the concepts are linked to a cause-effect relationship and third, these concepts develop early in life. 

At the end of the firs, and beginning of the second year of life, babies learn to understand the following four aspects: 

1. understanding other people's intentions,
2. self-awareness, a child understands that it is an individual,  
3. to focus joint attention on an object or situation 
4. intersubjectivity.

At a later age, children develop theory of mind (TOM). TOM is the understanding of how the mind works and how it affects behavior. It develops strongly between the third and fifth year of life. An important component of TOM is understanding relationships between desire and actions. Children develop this at the end of their first year of life. It is well developed when children are two years old. In their third year of life, children develop a certain understanding of the relationship between beliefs and actions. At the same time, the concept is limited. It can be seen through children’s false-belief problems. These are tasks that test whether a child understands that other people behave in accordance with their own beliefs, even though the child knows that these beliefs are incorrect. It shows if children understand that actions of other people are determined by their thoughts in their heads rather than by the objective truth about the situation. Most children have this understanding when they are about five years old.

Nativists believe in the so-called theory of mind module (TOMM). This is a hypothetical brain mechanism, dedicated to understand other people. The researchers believe that certain areas of the brain are constantly activated in representing beliefs across different tasks, and that this brain areas differ in other complex cognitive processes, such as understanding grammar. The idea of ​​TOMM is supported by studies with autistic children. These children have problems with false-belief problems. The problem is related to the limitations in social interactions of these children. This is partly because they have different sizes of and activity in certain areas of the brain. Empiricists believe that TOM develops through interactions with other people. From this point of view, the tendency in autism to not have many conversations with others contributes to the difficulty of understanding others. Another group of empiricists argue that the growth of general information processing is essential for children to understand others. This view states that children with autism lack the necessary information processing skills.

At a given moment, children learn to understand someone else's 'mind' through play. Children around 18 months first play a pretend play. Here they create activities, in which they make new symbolic relations between certain objects, for example pretending that a tree is a horse. Children behave as if they are in a different situation than in reality. Then they use object replacement: a form of pretending, an object is used for something other than what it is meant for. As children grow older, they start with sociodramatic play. They pretend to be someone else in a dramatic situation. For example, playing doctor. Playing with age becomes more complex and social.

Children with autism spectrum disorders (ASD) have difficulty with social interactions, communication and other intellectual and emotional functions. Children with a severe form of it, often show repetitive behavior, barely interact with others, troubles with forming close relationships, barely speak and are more interested in objects than in people. Children with ASD have difficulties with joint attention and are less concerned when others are suffering. They have limited TOM, which makes it difficult for them to understand others. This is also due to more general limitations in planning, adjusting and working memory. If treatment is started at a young age, a lot of progress can be made. 

Many children have an imaginary friend with whom they play, talk and even argue. This is completely normal. Children with imaginary friends (1) are often the first child or the only child, (2) barely watch television, (3) are often socially skilled and (4) often have advanced TOMs. Reasons for creating an imaginary friend are: companionship, entertainment, enjoyment of fantasy, shifting the blame on the friend, venting out, pronouncing things that children would not immediately speak out and comfort when they are sad.  

How to get knowledge of living things?

When children are 4 to 5 years old, they have an impressive amount of knowledge about living things. However, they have many immature views and types of reasoning. First, children often do not understand the distinction between artifacts (made by people with a certain purpose) and living things (which are not made by people). Another weakness is that they cannot yet properly determine which things do or do not live. Some researchers say that children under 7 to 10 years have a superficial knowledge about living things. Other researchers state that children from 5 years of age can understand essential characteristics of living things and what separates them from non-living things, but some points sometimes bring confusion. A third view is that young children have both full-grown and immature understanding at the same time.   

Children can make a distinction between humans and animals in their first year of life. Then also follows the distinction between these two terms (people and animals) and nonliving objects. However, it is difficult to investigate whether children build a general category for living things and which things this category contains. Culture and experience influence the knowledge. For example, children living in rural areas know very well that plants are alive, in contrast to children living in cities. 

Children not yet in school understand the difference between biological processes and psychological processes through invisible processes such as heredity, growth, illness and recovery. Of course, young children still do not understand DNA, but they do understand that there is a big chance that a baby mouse will get the same hair color as its parents. One of the most basic view of children is related to the importance of heredity: essentialism. A perspective saying that living things have an essence in them that makes them who they are. Children who are not yet in school already have an understanding of growth: they know that growth often happens in one direction, from small to large. They also know that a tomato plant that has been scratched can recover again.

Nativists and empiricists have different opinions about the development of a child's biological understanding. Nativists believe that people were born with a so-called biological module, which is similar to TOM. They have three arguments for this:

During earlier periods in our evolution, it was crucial for the survival that children quickly learned about animals and plants.

Children around the world are fascinated by plants and animals and learn about it quickly and easily.

Children around the world organize information about plants and animals in more or less the same way.

Empiricists believe, however, that the biological understanding of a child arises from personal experiences and information they receive from their environment (parents, teachers and culture). Empiricists also note that the knowledge of children reflects the view of their culture.  

In conclusion, it seems that nature and nurture both play an important role in obtaining biological understanding. Young children are naturally fascinated by animals, but their learning is also influenced by the environment. Nature always responds to nurture.  

How to understand the why, where, when and how much?   

First of all, children develop categories through questions about 'who' and 'what'. Later, children develop categories through questions about 'where', 'when', 'why', and 'how much'.

How does an understanding of causality develop?

The nativists and empiricists also disagree on the development of causality. According to the nativists, babies have an innate causal module, or core theory, making it possible for them to observe the causal relations between events. According to the empiricists, babies understand the causal relationships between events through innumerable observations of events in the environment and through observation of the effects of their own actions. What both sides agree on is that from infancy on children show impressive causal reasoning. 

From 6 months onwards, babies can observe causal relationships between physical events. Babies from 9 to 11 months can often reproduce consecutive actions if there is a causal relationship between the actions. At the end of their second year of life, children can derive the causal impact of a variable on the basis of information about another variable. Children aged 4 seem to understand that, if a variable has a certain effect, this effect must be consistent. If inconsistency occurs, they deduce that there must be another variable that has caused a certain effect. When children are about 5 years old, they are also interested in, for example, magic tricks, because they know that there is no clear causal mechanism that can cause the effect.

Children live in a world where fantasy and reality are more entangled than it is the case for adults. Children believe in fantasy and magic, children aged 4 to 6 think that they can influence others by 'effectively wishing'. How can this be combined with the fact that children do have a certain understanding of physical causes and effects? It is important to remember that children may have some conflicting ideas. The more children learn about real causes, the less they explain events in magical terms. The world of fantasy is the most present between 3 and 6 years but can continue until the 9th year of life.

How does understanding of space develop?

Nativists believe that children possess an innate module that specializes in spatial representations and learning about space. They think that spatial information differs from other information processing processes. Empiricists believe that children acquire a spatial representation through the same learning mechanisms and experiences originating through cognitive growth. They also believe that children adapt to the changing environment, and that language and other cultural resources form the spatial developments. Ultimately, the nativists and empirists agree on certain aspects. One aspect is that children understand some spatial concepts, such as up, down, right, left, and turn away. A second aspect is that self-generated movement stimulates the processing of spatial information. Another aspect is that certain parts of the brain are specialized in coding a certain type of spatial information. A fourth aspect is that geometric information is very important in spatial information processing.

Children can code the location of objects in relation to their own body. According to Piaget, children are only able to form representations during the sensorimotor period, namely: egocentric spatial representations. This is the coding of spatial locations in relation to one's own body, without paying attention to the environment. 

Babies of 6 months can already use landmarks to locate objects that are hidden. For such young children, however, it must be the only clear point of reference and it must be close to the hidden object. Children, like adults, have difficulty in forming a spatial representation when they walk around in an environment with no noticeable landmarks or when the landmarks are far from the target location. The extent to which people develop spatial skills depends strongly on the importance of these skills in their culture. 

In addition, spatial thinking can not only be based on seeing, but also on other senses, such as hearing. It is true that absence of visual experience in the first months of life creates a limited and changed spatial development. Still, the blind have an impressive good feeling for space, even though they have never seen the world.

How does the understanding of time develop?

Babies have a sense of time in their first year of life. Even of sequence and duration of certain situations/ events. Small children can also distinguish between short-term and long-term events. At the age of about 4 years, children realize the sequence of events a long time ago. During the middle of childhood, children become more and more adept at reasoning about time.

How does an understanding of numbers develop?

Again, nativists and empiricists have different opinions. Nativists believe that children are born with a core concept about figures, containing a special mechanism. The mechanism allows a child to learn about the numbers and numbers of objects in a set, count, or simply add and subtract. Empiricists believe that children learn about numbers and counts through the same experiences and learning mechanisms that acquire other concepts. According to them, the innate numerical competence of children is not nearly as big as nativists state.

The most basic concept in numbers is the so-called numerical equality. This is the realization that a N number of objects has something in common. Babies already have a certain understanding of it, but in a non-linguistic way. The distinction between numbers is becoming more and more precise during the first year of life and beyond.   

There are five principles about counting that young children develop to count a certain number of objects:

1. One-one correspondence: each object must be labeled with one number.
2. Stable order: the numbers must always be listed in the same order.
3. Cardinality: the total number must correspond to the last number.
4. Order irrelevance: objects can be counted from left to right, from right to left and in any other order. 
5. Abstraction: every set of discrete objects can be counted.

Piaget stated that babies only have a general, undifferentiated concept of size and no specific concepts of space, time and numbers. In some research, children show both the general undifferentiated concept of size and the more specific concepts of space, time and numbers.