Published in 2012, this study evaluated the effect of chess training on development of cognitive skills for six-year-old children in Turkey. Fifty students who had previously received chess instruction and fifty students who had not were given a concept test that evaluated their understanding of spatial concepts. The children were tested individually by the researcher. The Mann-Whitney U test indicated statistically significant differences between children who had and had not received chess instruction for all tested concepts, resulting in an effect size of 1.600 standard deviation units. The results were statistically significant. This study was eligible for inclusion in the systematic literature review and categorized as a Tier III study. While the study compares the cognitive abilities of children who have and have not received chess instruction, the lack of a pre-test means that the differences between the groups may have been caused by something other than chess, biasing the results.
