--- You wrote: Could "stifling his naturally hideous laughter" be viewed in the same light as whispering secret plans into the floppy ears of dogs--unbeknownst to their dopey owners--as the work of a completely healthy juvenile imagination? --- end of quoted material --- sure--it's all part of the game the young narrator is playing with himself--I buy that entirely. But the words--and the idea they describe--take on a completely different meaning when they are remembered by the adult narrator, for once they are spoken in the adult voice they have been filtered, and they Mean Something. That is a big difference between adults and children, since we have been on that subject lately: adults' thoughts go through some sort of filtration system before they are spoken to assure that they have the necessary and intended levels of Meaning, Content, and (a word I hate) Depth. This doesn't necessarily mean that everyone will find meaning in the words, but the point is that adults' public words are calculated, and those of children tend to be less so. In this case Salinger makes good use of this device, allowing a perfectly literal act of childish imagination to also have a more adult meaning.