" It costs more energy to ignore a stronger signal," - wait, what, why? Do you have any citation for that? IMHO that has absolutely no basis in how neurons work

" It costs more energy to ignore a stronger signal," - wait, what, why? Do you have any citation for that? IMHO that has absolutely no basis in how neurons work, it does not cost a cell energy to ignore signals. "making it harder for cells to learn to change input signals." this sentence is not even wrong; it essentially presumes that the default behavior is to "not change input signals", which is definitely not how neurons work. "Humans having weaker signals could therefore be related to our ability to learn" - perhaps, but you provide no argument about the direction of causality there (if it's related, perhaps the weaker signals are caused by a different level of learning), nor for elevation of "could be" from mere possibility to why it's likely to be the case. I'm not saying that there is no way that your hypothesis could be right, but you do need to pass a certain (quite high) bar of clearly stating your assumptions and demonstrating that all of the assumptions are reasonable before your hypothesis would be worth reviewing and evaluating, and there is very a big gap between "possible" and "plausible".