Талмуд к Авот 5:18

There are four types of people who sit before the sages. There is one who is like a sponge, one who is like a sifter, one who is like a funnel, and one who is like a sieve. Who is like a sponge? This is the wise student who sits before the sages and learns Tanakh, Mishnah, Midrash, Halakhah, and Aggadah, and just like a sponge absorbs everything, this student absorbs everything. Who is like a sifter? This is the wise and alert student who sits before the sages and listens to them speak about Tanakh, Mishnah, Midrash, Halakhah, and Aggadah, and just like a sifter removes the coarse flour and gathers the fine flour, he lets go of what is useless and gathers what is valuable. Who is like a funnel? This is the stupid student, who sits before the scholars and listens to them speak about Tanakh, Mishnah, Midrash, Halakhah, and Aggadah, and just like a funnel takes something from here and lets it out there, so it is with everything that enters this students ears; it goes in one ear and out the other, one by one, until he has forgotten everything. Who is like a sieve? This is the wicked student, who sits before a sage and listens to Tanakh, Mishnah, Midrash, Halakhah, and Aggadah, and just like the sieve lets out the wine and holds onto the sediment, this student lets go of what is valuable and gathers what is useless.
Rabbi Eliezer ben Ya'akov called him a punctured, shortened horn. Shortened how? This is like a baby who is given a pearl, and then given a piece of bread. He throws away the pearl and takes the bread. Then he is given some pottery, and he throws away the bread and takes the pottery and finds that he is holding nothing but an empty pot in his hands.