Conservation task

So what are conservation tasks? Such tasks test a child’s ability to recognise that certain properties are conserved, or are invariant, after an object, or set of objects, undergo physical transformations. These properties can include virtually anything – number, volume, length, or amount of matter in an object, for example.

The ability to recognise invariant properties is acquired, or perhaps a better way of putting it, is developed, in the transition between Jean Piaget’s Pre-operational stage, and his Concrete Operations stage. This transition is complete at around the age of seven, although no two children will develop this ability at exactly the same time since there are a multitude of biological and environmental factors that contribute to this development.

A classic test for the ability to conserve number is line up two rows of counters, each containing the same number, and arrange them so that each counter is paired up with another. When asked to compare the two rows, children of course say they are the same. Then one row is spread out so that the space between each counter increases, thus making one row longer than the other. When asked to compare the rows now, the children who have not fully developed the ability to conserve number claim that the longer row has more counters. This can happen even after the child has counted the rows and found them to be the same in number. It appears that the impact of the change in physical size of the row overrides the fact that the two rows were clearly the same in number when they were both of the same length.

The same basic misconception can occur when two identical vessels of liquid are filled to the same level and presented before a child who has not developed fully into Piaget’s Concrete Operations stage. Such children recognise that both vessels contain the same amount of liquid. They also see that when one of the vessels is emptied into a taller and thinner receptacle, the level of liquid is higher in the thinner vessel than in the other original vessel. Pre-Concrete Operations stage children conclude that there is more liquid in the thinner vessel, whereas those who have developed beyond that recognise that the volume of liquid must have remained constant.

The invariance of mass is also effected by size. This is seen when one of two identical balls of clay is re-formed into sausage shape. The child perceives the sausage shape as being bigger, thus concluding that it now has more clay.

There are other more abstract properties that children are unable to conserve before fully reaching the Concrete Operations stage. In a 1989 study by Kreil, children were told of a story where doctors took a horse and through a series of operations, made it look exactly like a zebra. They asked the child; “[when the doctors] were finished, was this animal a horse or a zebra?”. Around 65% of the children tested believed that the horse and actually been changed into a zebra. What this study also highlighted was that pre-operational children could sometimes conserve when the essential defining feature of an object was unchanged, even in the face of dramatic visual changes. This was shown when the aforementioned doctors altered a porcupine to look like a cactus. This time only 25% of the children tested believed that the porcupine had actually become the cactus. The rest recognised that one is an animal, the other a plant and one cannot become the other.

Piaget, having conducted many conservation experiments, concluded that children who are unable to conserve believe that a perceptual change means a quantitative change. Piaget believed that this confusion arose from pre-operational children’s lack of understanding of reversibility. Reversibility is the ability to see physical transformations and then imagine reversing them so that the change is cancelled out. Without being able to imagine, say, pouring the liquid back into the wider vessel mentioned above, the pre-operational child cannot see that the amount of liquid has remained constant throughout. This lack of reversibility causes a child to be dominated by the physical properties they perceive, hence they make incorrect conclusions about the perceived material. Piaget linked this lack of reversibility to pre-operational children’s inability to work out someone else’s viewpoint – i.e. the child believes that everyone perceives the world from the same perspective as their own.

Piaget used his reversibility ideas to formulate the Principle of Invariance. This principle states that there are relevant and irrelevant changes associated with quantity. For instance, addition and subtraction are relevant changes (since they change the quantity of an object or objects), while spreading out a row of counters, or re-forming malleable materials like clay, are irrelevant changes (since they change only physical properties, not quantity).

What is also evident from conservation tasks is that the development from pre-operational to operational is not sudden, but more gradual. For instance, children are able to conserve quantity in the counters problem around a year before they can conserve in the volume of liquid, or amount of matter problems.

Based on conservation experiments, Piaget believed that the invariance principle and children’s lack of reversibility was the reason why they were unable to conserve. But there have been critics of the conservation experiment. Some people claim that the social context in which the experiment takes place effects the results obtained. It is thought that the child is trying to work out what it is the adult, or experimenter, wants from the interaction (since the experimenter is clearly after something). The repetition of the question asked is believed by some to lead the child to believe that they should change their answer as they must have been incorrect before. Such interaction will have happened to the child in the past when they have been asked a question and given the wrong answer - an adult will often ask the question again (with different intonation) in order to get the right answer. The child may see the repetition of the question as the adult implying that the wrong answer was given. This would lead to the child now giving an incorrect answer because they believe that they were wrong before, rather than because they do not understand the invariance principle. It is also argued that even if a child did have a weak understanding of reversibility, this could easily be overridden by social influences as stated above.

The possibility of the above criticism being the case was demonstrated by comparing the results of two conservation experiments, one where the experimenter rearranged a row of counters, the other where a “naughty teddy” puppet did the rearranging, without the experimenter having apparently seen the actions of the impish bear. It was found that the children were more likely to say that the teddy had moved the counters but the rows were still equal in number, as opposed to when the experimenter did it and the usual error was made. However, this experiment has been criticised also. Some believe that a child’s attention may be so focussed on the teddy that the physical change was not noticed. This would lead to a “false positive” result in the experiment. Here it could also be argued that such attentional influences could overwhelm any small understanding of reversibility a child may possess.

Another criticism of Piaget’s theory behind the conservation experiment is that the ability to reverse a perceptual transformation does not mean that the change was irrelevant since relevant changes can be imagined too. For instance if two counters were added to a row, then one can imagine the two counters being taken away.

Piaget believed the determining factor which decides children’s performance in conservation tasks was how developed they were into his Concrete Operations stage. This entailed how well a child had the ability to reverse changes. Whether Piaget’s ideas are right or not, what conservation tasks demonstrate is that children do indeed go though various stages of development and that these stages are transitional. What is also worthwhile is that the difficulties that pre-operational children face have been identified (even if they have not been explained satisfactorily) and this information can be used to help children in education.