On Theory of Mind and Geometric Puzzles, scores change from percentile ranks to scaled scores across ages. Why?

Frequently Asked Question:

On Theory of Mind and Geometric Puzzles, scores change from percentile ranks to scaled scores across ages. Why?

Answer:

Neuropsychological tests are not designed to obtain a normal distribution of scores. They are designed to measure constructs that often are not normally distributed in the general population, particularly across age groups, but that are indicative of specific brain-behavior relationships or of atypical development. In addition, the distribution of scores varies across ages as the majority of children master a skill.

The degree to which a distribution is skewed will determine if scaled scores may be generated. Measures that have a slight to moderate degree of skewing may still be converted to a scaled score metric; however, with highly skewed distributions using the scaled score metric is inappropriate. On Theory of Mind, the distribution of children begins to skew heavily toward nearly perfect scores by age 7. Therefore, at age 7 the Theory of Mind Total score switches from a scaled score, to a percentile rank, to better represent the change in the distribution of scores for that age.