Just as humans are usually left- or right-handed,many animals favor one side of their body for certain tasks.The strength of this preference varies：some individuals are happy to use either side,while others strongly favor one side（known as being strongly "lateralized"）.
The University of Exeter study found that grey squirrels which strongly favored a side did less well on a learning task.They had to learn to use a paw（爪子），rather than their mouth,to get nuts.
"It has been suggested that being strongly lateralized makes brains more efficient,with each hemisphere（半球）focusing on different tasks," said Dr Lisa Leaver. "This could help animals survive,which would explain the evolution of laterality（向侧性）across the animal kingdom."
"In fish and birds,there is evidence that being strongly lateralized is linked to better cognitive（认知的）performance（brain function）.However,limited data from studies of mammals（哺乳动物）suggest a weak or even negative relationship.Our study measured speed of learning among grey squirrels and,in line with these previous mammal studies,suggests that strong lateralization is linked to poor cognitive performance," said Dr Leaver.
In the study,wild grey squirrels on the University of Exeter's Streatham Campus were presented with transparent tube containing peanuts.Squirrels usually collect food with their mouth,but the tube was too narrow to allow this,so they had to learn to use a paw.By measuring both how quickly squirrels learned and how strongly they favored a particular paw,the researchers could assess both learning and laterality.
More than 30 squirrels were observed,with 12 providing enough data for inclusion in the study.
The relationship between laterality and human cognitive performance is still unclear,though some research has suggested that less lateralized people may be more creative. "More research on mammals is needed to understand the complex relationship between laterality and cognitive performance," Dr Leaver said.



What did the University of Exeter study focus on？ ______

A. The effects of lateralization on learning.
B. The cause of strong lateralization.
C. The evolution process of laterality.
D. The habits of grey squirrels.

What can we know from the fourth paragraph？ ______

A. Fish and birds have similar brain structures.
B. Strongly lateralized birds are better at learning.
C. Most fish and birds have strong lateralization.
D. Strongly lateralized grey squirrels have a higher IQ.

How did the strongly lateralized squirrels act in the study？ ______

A. They were slower to get peanuts.
B. They got more peanuts than others.
C. They got through the tube quickly.
D. They used their paws more skillfully.

What can be a suitable title for the text？ ______

A. Left-handed animals prove more intelligent.
B. Laterality is connected with better brains.
C. Grey squirrels change their habits for food.
D. Strongly "handed" squirrels are less good at learning.