A.ability B.access. C.admired. D.allowed. E.basically. F.consuming. G.current. H.hiding. I.includes. J.motivation. K.obvious. L.passion. M.premise. N.value. O.wisely The phrase bird-brain may be used to describe someone being silly. But this is not the case for ravens. Long 31___for their intelligence, ravens are now known to be able to plan ahead, a skill previously thought to belong only to humans. Researchers learned ravens could remember key Information for a future task through tests. Until now, some corvids--family of birds that 32_____ravens have shown the 33______to plan beyond the present. For example by 34_____ food for later. But the latest experiments revealed that ravens can 35______forego an immediate reward in order to get a better one in the future. In one of the tests, ravens were trained to use a tool to open a puzzle box in order to 36______reward. And then the ravens were presented with a tool to open a box and immediate reward, but were only 37 ______o choose one or the other. Ravens remembered that the reward in the box was better than the immediate reward. And almost all of them close the tool. Ravens' 38______for planning is still unknown, but it may be similar to ours. The human brain stores memories of past events to guide decision making about 39_____and future events. Planning tends to come about when the higher 40______of a future reward is palpable, or when one imagines the happiness that will come by retrieving food in the future.