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Understanding of Conservation of Number and Mass in Children

Paper Type: Free Essay Subject: Psychology
Wordcount: 1736 words Published: 18th May 2020

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Understanding of Conservation of Number and Mass in Children


One of the most famous child cognitive development theories was coined by Jean Piaget. One of the Piagetian tasks that was used to analyze child development was the conservation task. This task tests if children can reason that a quantity will stay the same regardless of what container it’s in, what shape it changes to and what form it’s in. Children who are in the preoperational stage (ages 2-7) do not fully understand concrete logic so most should fail the conservation task. The next stage in Piaget’s cognitive development theory is concrete operation stage (ages 7-11) where children learn to become more logical and supplicated in their thinking. Children in the concrete operation stage should successfully pass the conservation task. In this study we tested children that were 5 years old and children that were over 7 years old to see if this theory was true. We used two different methods to test children’s knowledge of conservation. Conservation of number and matter. The results show us that although some children under 5 years old are able to complete the number conservation task many of them have trouble performing the matter conservation task. These results highlight Piaget’s cognitive development theory and how children in the preoperational stage (ages 2-7) have not fully learned the concept of conservation even though they may have the ability to perform some conservation tasks.


Jean Piaget’s theory of cognitive development is a theory of the developmental process of a child from birth to adulthood. He believed that there were different stages in development and as children grow older, they obtain the ability to reason, do logical thinking, think abstractly, and more. Piaget found that conservation was not present during the preoperational stage (ages 2-7) but develops once they reach the concrete operational stage (ages 7-11). Conservation is the ability to logically think of quantity staying the same regardless of changes in appearance (Bjorklund, 2012). For example, in Piaget’s famous conservation task he had two cups of water with the same amount of water in each cup. He poured one cup to a tall glass and the other to a short glass. He found that most kids in the preoperational stage would fail this task by believing that the tall glass contained more water. He also discovered that during the concrete operational stage, children were able to easily identify that both cups still had the same amount of water despite their physical appearance showing that they achieve the ability to logically think about conservation. 

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There have been many studies that replicate Piaget’s conservation task and showed that younger children under 7 years old struggle with this task. A notable study that was performed by Olivier Houdé et al. (2011) further elaborated on the idea of number conservation in children using fMRI to explore the brain activities in children that pass the conservation task and also children who fail the conservation task. In this study they performed the number conservation task on young children (under 7 years old) and older children (ages 8-9). They found that the young children group often failed or were slower at answering the conservation questions. Further elaborating on this they reviewed how the fMRI results showed that there is an involvement of an executive parietofrontal network when older children perform the number conservation task (Houdé et al., 2011). This study confirmed Piaget’s theory about a child’s developmental process and idea of conservation while also adding a neuroscience perspective to the literature. Sawat Pratoomraj and Ronald C. Johnson (1966) performed the same conservation task on children at 4 different ages. In this study they wanted to test if the questions being asked had any effect on how the child did on the conservation task. They found that conservation task success increased with age, which is consistent with Piaget’s theory, and also found that the types of questions asked in these tests had no effect on how well children performed in this task. This present study is exploring the conservation task with children that are 5 years old and above 7. There will be two different types of conservation task that will be studied: conservation of number and conservation of matter. Based on existing studies done on conservation, children that are 5 years old in this study should fail the conversation task and children over 7 should have no problem completing the task.



There were 7 participants in this study. Divided into two groups, one group was the preoperational stage group which consisted of 4 children all 5 years old. The other group was the concrete operation stage group, which consisted of 3 children two were 7 years old and one was 8 years old.


There are two phases to this experiment. The first phase was to test children’s knowledge of conservation in number and the second phase was to test children’s knowledge of conservation of matter. 

Phase 1 

In this phase children were shown 5 gold Hershey’s chocolate kisses and 5 silver Hershey’s chocolate kisses. The experimenter laid out the gold and silver chocolates in a row parallel to each other and made sure that the length of both rows was equal. The experimenter then asked the child if there were the same amount of chocolates in each row. Next, the experimenter spreads out a row of chocolate so that one row will appear longer than the other. Both rows still had the same amount of chocolates. The experimenter then asks the children to identify which had more chocolate. After they children gave their answer the experimenter asked them to explain why and their answers were recorded. 

Phase 2

This phase of the experiment was also a conservation task but focused mainly on matter as a unit of measurement. The experimenter rolled up play dough into a ball and made them both the same size. The experimenter then asked the children if the two balls were the same size. After the children stated that they believed the two balls were the same size, the experimenter then squished one ball. The children were then asked the state which ball they believed was bigger. The children were then asked to give an explanation for their answer.  


This present study was testing Jean Piaget’s theory of cognitive development. Specifically, we tested children’s logical thinking ability of conservation in the preoperational stage (ages 2-7) and the concrete stage (ages 7-11). During the first phase of the study, all of the children over the age of 7 correctly identified that the two rows of Hershey’s chocolate were the same length and passed the number conservation task. Surprisingly, all of the 5-year-old children were also able to pass the number conservation task (figure 1). Phase 2 showed slightly different results from phase 1. During phase 2, children that were over the age of 7 were able to correctly identify that the play dough was the same size even after they were squished. Three out of four children who were 5 years old failed the matter conservation task. All 4 of the 5-year-olds agreed that the play dough was the same size when shaped like a ball, but after the ball was squished, three out of the four believed that the squished ball was bigger than the round ball.




 The reason why there were two phases in this experiment was to test whether children fully mastered how to do conservation task. As shown in the results children who were over the age of 7 were able to able to complete both the number conservation and matter conservation task showing that they have reached the concrete operation stage of cognitive development. We hypothesized that children in the preoperational stage group would fail both number and matter conservation. In this study child in the preoperational stage group were all able to successfully perform the number conservation task. We believe that children were able to perform this task because they were able to physically see the amount of chocolate on the table and no matter how far we moved them apart from each other there were 5 chocolates in each row. The children were able to count the chocolate to confirm that the amount of chocolate did not change despite the row looking longer. In matter conservation task only 1 child successfully performed the task from the preoperational stage group. We speculate that this was because children had to rely on actual logical thinking in order to determine that the play dough was still the same size despite the squished play dough looking larger than the round one. One limitation of this study is that it only tested children’s knowledge on conversation of number and mass. There is conservation of liquid, area, volume, and many more. Adding more conservation tasks could specifically show us if older children are able to fully understand the concept of conservation.


  • Bjorklund, D. F., & Causey, K. B. (2017). Children’s thinking: Cognitive development and individual differences. Sage Publications.
  • Houdé, O., Pineau, A., Leroux, G., Poirel, N., Perchey, G., Lanoë, C., … & Delcroix, N. (2011). Functional magnetic resonance imaging study of Piaget’s conservation-of-number task in preschool and school-age children: A neo-Piagetian approach. Journal of experimental child psychology110(3), 332-346.
  • Pratoomraj, S., & Johnson, R. C. (1966). Kinds of questions and types of conservation tasks as related to children’s conservation responses. Child Development, 343-353.


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