LSAT 4 | Section 4 | Logical Reasoning: Q24

LR Question 24 Explanation

QUESTION TEXT: The brains of identical twins are genetically identical…

QUESTION TYPE: Must be False

CONCLUSION: This fact about twins’ brains provides definitive evidence that schizophrenia is caused by damage to the physical structure of the brain.

REASONING: The brains of identical twins are generally identical except when one twin has schizophrenia. Then certain areas of the schizophrenic twins’ brain are smaller.

ANALYSIS: Remember, this is if all of the statements supporting the conclusion are true. We can’t assume the conclusion that physical damage causes schizophrenia is correct.

___________

1. We have no idea what role genetics play – this could be true.
2. We have no idea about controlling symptoms – this could be true.
3. We have no idea what the symptoms of schizophrenia are – this could be true.
4. CORRECT. This could never be true, because genetic twins have identical DNA. Yet one can have schizophrenia while the other does not. You can’t tell who has schizophrenia just from DNA.
5. Since we don’t know what causes schizophrenia, this could be true.

Recap: The question begins with “The brains of identical twins are genetically identical”. It is a Must be False question. Learn more about LSAT MBF questions in our guide to LSAT Logical Reasoning question types.