ruminate

(verb) chew the cuds. Example: "Cows ruminate."

(verb) reflect deeply on a subject. Synonyms: chew over, think over, meditate, ponder, excogitate, contemplate, muse, reflect, mull, mull over, speculate. Examples: "I mulled over the events of the afternoon." "Philosophers have speculated on the question of god for thousands of years." "The scientist must stop to observe and start to excogitate."