On the special relationship between fluid and general intelligence: New evidence obtained by considering the position effect

We investigated the influence of the position effect on the relationship between fluid intelligence and general intelligence. The position effect reflects the dependency of responses to items on the position of the items and, therefore, is a possible bias in measurement. A special confirmatory factor model enables the subdivision of the true component of a fluid intelligence measure into ability-specific and position-specific parts. Both parts of the measure of fluid intelligence are related to general intelligence in the framework of a hierarchical model. In a sample of 203 participants the ability-specific part that may be considered as purified fluid intelligence showed an almost perfect relationship to general intelligence. Although the position-specific part also correlated with general intelligence, this correlation was remarkably smaller than the correlation for purified fluid intelligence.