chewing over, cogitating, considering, contemplating, debating, deliberating, entertaining, eyeing(or eying), kicking around, meditating, mulling (over), perpending, pondering, poring (over), questioning, revolving, ruminating, studying, thinking (about or over), turning, weighing

musing (upon), reflecting (on or upon), reminiscinganalyzing, exploring, reviewingconcluding, reasoningsecond-guessing, speculating (about)brooding (about or over), dwelling (on or upon), fixating (on or upon), fretting (about or over), obsessing (about or over)believing, conceiving, opiningabsorbing, assimilating, digesting, drinking (in)

beating one's brains out (about), chewing on, cudgeling one's brains (about), looking at