One of the most important cognitive shifts in the preschool years that occurs between three- to four-year-olds is the development of symbolic thought. Symbolic thought is the ability to mentally or symbolically represent concrete objects, actions, and events (Piaget, 1952). The most obvious sign of the development of symbolic thought in four-year-olds is the significant increase in their use of make-believe play, which becomes more elaborate as they grow. “Do you like my horse?” Sam asks as he rides around his classroom on a makeshift broom. “He’s really fast and loves it when I brush his hair.”

Three-year-olds and some young four-year-olds are considered pre-operational thinkers, which means that they rely solely on the concrete appearance of objects rather than ideas, they focus on only one relationship at a time, and they often see things from only one point of view—their own (Piaget, 1969). Three-year-old Eric looks at a row of six cups that are spaced about three inches apart. Below the row of cups is a second row of cups with the same number as the row above; however, they are spaced one inch apart. When asked which row has more cups, he says that the top row has more because it is longer. Eric makes his decision based on how long the row appears, the physical feature of the line, and doesn’t attend to the absolute number of cups in the row. When his mom counts the number of cups in each row, Eric still says that the longer row has more cups. Clearly, Eric’s thinking is based on what he sees and understands. To a three-year-old, longer means more. When Eric’s mom aligns the cups in the top row with the cups in the bottom row, and they look to be the same length, Eric says that there is the same number of cups. Again, Eric’s decision making is dependent on the appearance of the cups. According to Piaget, Eric does not have conservation of number and will develop this cognitive skill by the time he is five years old.

The same is true for three- and young four-year-olds’ understanding of conservation of quantity. Eric is shown two cups; one cup is tall and thin and the second cup is short and wide. Both hold the same amount of juice. Eric’s mom pours juice from the tall, thin cup into the short, wider cup showing him that the same amount of juice fits into both glasses. When asked what glass of juice he wants, Eric replies, “I want this,” pointing to the tall glass, “because I am really thirsty and I want more juice.” Eric, who just turned four, attends to the most salient feature of the cup—its height. At this age, children are concrete thinkers and solve problems based on physical features.

Three-year-olds have good memories for things in their immediate experiences. However, they have not developed effective strategies for recalling information over longer periods of time. Therefore, structure and routines are important in three-year-olds’ lives. This allows them to anticipate and predict what they will be doing and what is expected of them. However, children’s wonder at this age for things that they have repeatedly experienced is related to their under developed memories. Three-year-olds can repeatedly watch the same puppet or read the same book 40 times and still show the same delight as they did the first time they were engaged in these activities.

Four- and five-year-olds experience important changes in cognitive growth. In general, four- and five-year-olds are beginning to problem solve, think about cause-and-effect relationships, and express these ideas to others. As four- and five-year-olds’ cognition matures, they begin to make the distinction between private thoughts and public expressions.

Four-year-olds are actively manipulating their environment and constructing meaning from their world. At this age, children are very egocentric in their thinking. Egocentrism is the tendency to be more aware of their own point of view than that of others (Piaget, 1952). This explains why four-year-olds have difficulty understanding how the world looks to other people. It is difficult for them to understand why others are not happy when they are happy, sad when they are sad, and hungry when they are hungry. A four-year-old gave her teacher her favorite teddy bear because the teacher said that she was not feeling good. The teddy bear made the four-year-old feel better when she was sick, so the same must be true for her teacher. Because four-year-olds think egocentrically, it is best to present information that is hands-on and is relevant to their own experiences.

Four-year-olds’ thinking and reasoning are concrete, and they typically reason from the particular to the particular as opposed to the particular to the general. (Siegler, 1997). Four-year-old Seth reasons that his dog is friendly, so the dog he passes on his way to school must be friendly, too. Seth likes chocolate, so everyone in his family must like chocolate. At this age, children presume a causal relationship if two events are closely associated in time or in some other way. Bryan sees his teacher at school when he arrives in the morning and leaves her there when he returns home in the afternoon. He reasons that his teacher must live at school.

Concept development is another important aspect of the cognitive development of four-year-olds. They are organizing information into concepts (e.g., chair or animal) based on attributes that define an object or an idea. However, at four years of age, the categories that the concepts are based on are derived from the appearance or the action of the object. Seth calls a small goat that he is allowed to pet at the zoo a “dog.” In his mind, the goat fits all the criteria needed to be a dog: small, furry, and having four legs (Gelman, 1999).

Similarly, when four-year-olds classify objects into categories, they tend to focus on one aspect of the object and ignore the other features. Mary is trying to tell her mother that she does not want fruit for a snack; she wants an apple. She is having difficulty understanding that an apple is a part of the larger category of fruit. Because four-year-olds are beginning to understand part/whole and hierarchical relationships, they have difficulty grasping that objects can be in more than one class. Also at this age, when children are asked to sort objects into specific categories, they are beginning to sort objects on the basis of one attribute (Gelman, 1999). When asked to sort the blocks into groups, Nathan started to put all the blue blocks in one pile and the red blocks in another. At one point, he had put a circular red block in the blue pile because the last block he picked up was circular, and that one was placed in the blue pile. For a moment, Nathan needed to think about what feature of the block he was focusing on for sorting. He confused the shape with the color and soon corrected himself. This ability to focus on one attribute of an object to classify is developing in four-year-olds.

Time is a concept that four-year-olds have difficulty comprehending (Piaget, 1969). Four-year-olds view time as events occurring immediately or taking a very long time. Anyone who has ever told a four-year-old that he or she will be taking a field trip in a week knows that the child will ask every day if he or she is going on the trip that day.

Four-year-olds are developing their memory skills. They can, with some prompting, remember what they did last weekend. Salient events such as birthday parties, class trips, and a child breaking his or her arm on the playground can easily be remembered. The child can recall main events in a story and can retell a story with some accuracy of the sequence. Four-year-olds have difficulty remembering lists or isolated information. Learning and remembering things at this age are easier if information is presented in a context that is meaningful to the child. Learning and remembering about spiders is easier if the child can study a spider that was crawling on the playground.

At four, children are also beginning to develop a sense about what is real and what is not. This is called the appearance/reality distinction (Flavell, 1992). For example, four-year-old Kate was very frightened of the clown that was at her friend’s birthday party, and she clung to her mother’s leg. As the clown did a magic trick and made her laugh, she said to her mother, “The clown is like a real person. I love her.” Children are beginning to understand what is real and what is not real, what is a dream and what is not a dream.

Five-year-olds think about things. Lee watches the leaves fall off the trees and says that the leaves look like they are dancing. Then he asks, “Why do the leaves fall off the trees?” Five-year-olds are filled with questions about how things work, how things are made, and where things come from. This reflects their interest in understanding the world around them. Their imagination continues to develop, and their play centers around pretending. However, they begin to make distinctions between when they are pretending and when they are not. Classrooms are filled with children saying, “Look at me, I’m pretending to be a kite, or a dog, or a snake.”

Although five-year-olds are egocentric in their thinking, they are beginning to be aware of others’ feelings and points of view (Siegler, 1997). At this age, children can begin to understand that they can be happy when others are not and begin to accept that others do not have to play the exact game that they are playing. They are beginning to understand other children’s likes and dislikes. Gary said at snack time, “You can give me Sam’s graham crackers because I like them and he doesn’t.”

Five-year-olds’ reasoning is still concrete, yet they reason less from the particular to the particular (Gelman, 1999). They may reason that because their dog is friendly, all dogs are friendly. However, they are quick to understand when an adult explains that that may not be the case with all dogs. They are beginning to understand that there are general rules, yet also exceptions to the rules. Also, five-year-olds’ reasoning about concrete information, such as dogs that they see, is easier to accomplish than it is for more abstract information. Understanding that both whales and humans are mammals is a difficult concept for five-year-olds to grasp because it is difficult to demonstrate the similarities of the two in a concrete way.

Five-year-olds continue to become more sophisticated in their development and organization of concepts. With things that children are very familiar with, they can begin to see how different objects fit into different categories. Matthew has both a bunny and a turtle in his classroom. He understands that the bunny is soft and cuddly and eats carrots. The turtle lives in water, and his shell is hard. But when his teacher says that it is his turn to take the animals home for spring vacation, he understands that this means both the turtle and the bunny. He says, “Even though the bunny cannot swim, it still is an animal.” Matthew is developing criteria for his concepts and refining his concepts on the basis of each new experience. His concept of “animal” is becoming more refined as he interacts with other animals and objects and begins to construct his notion of similarities and differences among things.

Five-year-olds are interested in sorting and grouping (Flavell, Miller, & Miller, 1992). They can successfully sort objects on the basis of a single feature, such as color, shape, and size. Sorting things on the basis of more abstract concepts, such as an object’s use, is more challenging. Kim proudly showed her teacher how she sorted all the beads into different color groups. When asked to sort all the toys in the dramatic play area that could be used in the kitchen, the group included spoons, artificial foods, as well as a doll and teddy bear. Kim explained that she frequently played with her doll and teddy in her kitchen at home.

Understanding the concept of time is still a challenge for five-year-olds (Flavell, Green, & Flavell, 1995). They talk about things that happened in the past, yet yesterday means the same thing as last month or last week. However, they are able to understand time in terms of things that they are familiar with. To explain how long it will take to get to the zoo, the teachers say that it will take as long as it takes you to get home from school. Time is relative to things in the children’s immediate experiences. Calendars posted in classrooms and in homes begin to help children conceptualize how long it will be until the field trip or their birthday.

At this age, children have not developed strategies for remembering information. However, with help, they can employ some strategies for remembering (Siegler, 1997). In remembering where they left their sneakers, the teacher can ask specific questions about what and where they were last playing, trying to help them reconstruct events to help them remember. Learning in context and in meaningful ways will increase their chances of recalling information. Five-year-olds can learn the alphabet if it is connected to experiences that they are familiar with. Also, they can recall parts of a story after two readings of a story (Morrow & Smith, 1990).

Five-year-olds are becoming more certain about what is real and what is pretend. At the classroom Halloween party, Jake stood and stared at the frightening witch who entered the room. Then he said, “Hey, Tina, is that you under there? You didn’t fool me.” At this age, children love to play pretend games, and their imaginations are boundless. They are fascinated with magic and think that things really can appear and disappear. Five-year-olds typically believe in the tooth fairy and the magic of Santa Claus. However, they are beginning to ask important questions about how the tooth fairy gets into their house and how she knows where the tooth is. These questions represent the evolution of their thinking and attempts to make concepts fit into what they know about the world.