Assessing the extent to which inductive thinking is universal and which factors in education and home-environment can explain cross-cultural differences. Testing of primary school pupils ( final years ) and secondary school pupils ( starting years ) in Zambia, Turkey and the Netherlands ( Dutch group and Turkish-Dutch group ). Psychological tests measured inductive thinking, rule classification, rule generation and rule testing, using both figures and letters as stimuli. Furthermore, pupil-related -, school-related - and teacher-related context data were gathered. Eight test batteries used: ITF (Inductive Thinking Figures ), RCF ( Rule Classification Figures ), RGF ( Rule Generating Figures ), RTF ( Rule Testing Figures ), RCL ( Rule Classification Letters ), RGL ( Rule Generating Letters ), RTL ( Rule Testing Letters ). Background variables: basic characteristics/ residence/ household characteristics/ occupation/employment/ education