Passage Three
　　Questions 31 to 35 are based on the following passage.
　　American scientists have found that some birds are more intelligent than believed. They say birds have abilities that involve communication and different kinds of memory. In some unusual cases, their abilities seem better than those of humans.
　　The findings were presented at the annual conference of the American Association for the Advancement of Science(AAAS). The scientists met for six days last month in Boston, Massachusetts.
　　Irene Pepperberg presented her research about a grey parrot named Griffin. He lives in her laboratory at the Massachusetts Institute of Technology in Cambridge. Pepperberg says Griffin can arrange objects in order of size. The talking bird also can combine words in the right order. For example, he will combine words when asking for food. The researcher says that only humans and other mammals with large brains used to be considered to have the ability to combine objects and words. She believes that birds are able to understand that complex tasks must be done in the correct order. Some birds have other memory skills. For example, they collect and store thousands of seeds in autumn. and find them later in winter.
　　Alan Kamil and Alan Bond of the University of Nebraska are studying the memories of birds called jays and nutcrackers. Their experiments suggest that these birds use natural objects to find the seeds they have stored. They found these birds use at least three objects, such as rocks or trees, to find the stored seeds. Kamil also trained a jay to choose one object instead of another. The bird used this skill to receive a prize, such as food. Scientists say some birds can learn as many as two thousand different songs. They say songs may have developed as a way for birds to communicate with other birds.
　　Verner Bingman of Bowling Green State University in Ohio also presented his research at the science conference in Boston. Bingman believes that birds must have a special guidance system in their brain. He says that understanding how a bird's brain operates may help us better understand the way a human brain processes information.