Experiments require resources which are limited.
And after the falsification of intelligence genes, it makes sense to find a psychological cause for delay of gratification first, and test other logical explanations second.
I want to praise you for taking the time to admit that you were wrong about a topic you didn't know much about. It is something that is seen far too infrequently in this world.
Experiments require resources which are limited. And after the falsification of intelligence genes, it makes sense to find a psychological cause for delay of gratification first, and test other logical explanations second.
Edit: I was wrong. Reading Wikipedia article (https://en.wikipedia.org/wiki/Heritability_of_IQ), it seems intelligence is related to both genes and enviroment.