Editing G factor (psychometrics) (section)

===Piagetian tasks===

Psychometric theories of intelligence aim at quantifying intellectual growth and identifying ability differences between individuals and groups. In contrast, [[Jean Piaget]]'s [[Piaget's theory of cognitive development|theory of cognitive development]] seeks to understand qualitative changes in children's intellectual development. Piaget designed a number of tasks to verify hypotheses arising from his theory. The tasks were not intended to measure individual differences, and they have no equivalent in psychometric intelligence tests.<ref name="Weinberg 1989">Weinberg 1989</ref><ref>Lautrey 2002</ref> For example, in one of the best-known Piagetian [[Conservation (psychology)|conservation tasks]] a child is asked if the amount of water in two identical glasses is the same. After the child agrees that the amount is the same, the investigator pours the water from one of the glasses into a glass of different shape so that the amount appears different although it remains the same. The child is then asked if the amount of water in the two glasses is the same or different.

Notwithstanding the different research traditions in which psychometric tests and Piagetian tasks were developed, the correlations between the two types of measures have been found to be consistently positive and generally moderate in magnitude. A common general factor underlies them. It has been shown that it is possible to construct a battery consisting of Piagetian tasks that is as good a measure of ''g'' as standard IQ tests.<ref name="Weinberg 1989"/><ref>Humphreys et al. 1985</ref>