If you go on wikipedia or do a search on Google you can quickly find a bunch of articles on the importance of serotonin for impacting the efficacy of learning. Experiments have been run in mice for testing the rate they learn new tasks if 5ht2a is stimulated. There are also studies showing a high degree of correlation between high serotonin levels and high IQs.
If you go far back in history to Timothy Leary's time you find psychologists swearing by psychedelics improving IQ scores, and there is also the Spring Grove LSD experiments where researchers claimed LSD increases IQ scores. If you give someone antipsychotics it blocks 5ht2a, but as a result their thinking also becomes sluggish and processing speed scores on an IQ test decrease.
I get that the fact all psychedelics are illegal makes it fairly hard to study 5ht2a full and partial agonists. Would it not be possible to make a novel chemical hitting that receptor hard, without violating schedule 1? Any other reasons why that research has not been done other than government prohibitions?