Underline the correct form (past simple, present perfect or present perfect continuous). the nature of intelligence for many years scientists tried / have been trying to define the nature of human intelligence. however, they were/ have been unable to agree on whether there is one kind of intelligence, or several kinds. in the early 20th century, psychologist charles spearman came up/ has come up with the concept of ‘g’ or ‘general intelligence’. he gave/ has given subjects a variety of different tests and found/ has found that the people who performed / have performed well in the tests used /have been using one part of the brain, which he called/has called ‘g’, for all the tests. more recently, research found/ has found that this idea may well be true, as one part of the brain (the lateral prefrontal cortex) shows increased blood flow during testing. however, some scientists believe that intelligence is а matter of how much people learned / have learned rather than some ability they are born with. they believe that environment also matters.

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