<p>Researchers (have discovered) that a fish (like a human), (processes) some kinds of information with the right side of its brain (and other) kinds with the left. (no error).</p>
<p>There is no error.</p>
<p>I thought "have discovered" should be "discovered" because the present perfect tense is inappropriate - there discovery is "finished"!</p>
<p>I understand the terms present perfect, past perfect, and simple perfect, but I just cannot apply them!</p>
<p>what does it take? this is so frustrating.</p>
<p>Please help me :)</p>
<p>You would write “discovered” if the sentence referred to the moment of discovery itself. For example, “On Tuesday I discovered that my hair is green.” You write “have discovered” to emphasize that the moment of discovery is unimportant, and that what was discovered continues to be true. This is what happens in your example. Note that facts about the past remain true even when the events they describe are finished. So you would write “Historians have discovered that the Ancient Greeks made wine out of bug juice.”</p>
<p>The same principle is true of many verbs that refer to knowledge and understanding.</p>