fluid cognition in children; integrated construct or discriminated but interrelated?

there are strong relationship and common neural mechanism between working memory, short term storage, executive attention and fluid intelligence.  therefore we can consider these constructs as integrated construct as fluid cognition. to verify this claim, we implemented forward and backward digit and letter spam, visual memory spam. counting spam, stroop, wisconsin card, keep track and cattle iq test on 356 students 8 to 12 years old from elementary schools of tehran. confirmatory factor analyses showed 4 factor structural models have better fit indices than 1 factor structural mode. so we concluded fluid cognitive functions in children are discriminate but interrelated constructs.