My sister, for her 8th grade project, attempted to solve this problem in the field of spacial reasoning.
She amazingly found that playing chess DID correlate with better spacial reasoning! She almost made it to the national finals with that project.
The problem was that the experiment was flawed to its core: chess players came from a higher income bracket than-non chess players, had access to tools to train their spacial reasoning, and, really, had many different things that differentiated them form their non chess players as a body.
Because of this, it's hard to draw conclusions about the DIRECT correlation and effects of chess on intelligence, as people who play chess are typically, quite frankly, more affluent than people who don't play chess. Playing chess is a luxury given to those who do not have to worry about the security of their housing or the food on their table tomorrow, and those people typically have the luxury of a forma education [this is a generalization ofc]
She amazingly found that playing chess DID correlate with better spacial reasoning! She almost made it to the national finals with that project.
The problem was that the experiment was flawed to its core: chess players came from a higher income bracket than-non chess players, had access to tools to train their spacial reasoning, and, really, had many different things that differentiated them form their non chess players as a body.
Because of this, it's hard to draw conclusions about the DIRECT correlation and effects of chess on intelligence, as people who play chess are typically, quite frankly, more affluent than people who don't play chess. Playing chess is a luxury given to those who do not have to worry about the security of their housing or the food on their table tomorrow, and those people typically have the luxury of a forma education [this is a generalization ofc]