LSAT 134 | Section 2 | Logical Reasoning: Q20

LR Question 20 Explanation

QUESTION TEXT: Neural connections carrying signals from the cortex …

QUESTION TYPE: Sufficient Assumption

CONCLUSION: The amygdala has more influence on the cortex than the cortex has on the amygdala.

REASONING: The neural connections from the cortex to the amygdala are less developed than the neural connections from the amygdala to the cortex.

ANALYSIS: This repeats the same terms about 1,000 times so let’s organize the information cleanly. In the reasoning, we see:

1. Neural connections from amygdala → cortex = more developed
2. Neural connections from cortex → amygdala = less developed

Therefore,

1. Amygdala more influence over cortex
2. Cortex less influence over amygdala

As you can see, the reasoning is all about neural connections while the conclusion is all about influence. But right now, we only know that one set of connections is more developed than the other. We are not told what a more developed connection actually means. Does it carry stronger signals? More signals? Does it have any effect on influence at all?

So that’s a pretty big jump to make from more developed neural connections = more influence.

To make that add up, we’d need an assumption that more developed neural connections transmit more influence.

Once you add that, the argument becomes straightforward:

• Connections from the amygdala to the cortex are more developed.
• More developed connections transmit more influence.
• Therefore, the amygdala has more influence on the cortex than the cortex has on the amygdala.

___________

1. The argument only compares the amygdala and the cortex with each other. It says nothing about the rest of the brain.
2. This also changes the comparison. The conclusion isn’t that the amygdala influences the cortex more than every other brain region. It only compares them to each other.
3. Again, this compares the amygdala to all other brain regions, which the argument never does. Even if this were true, it would not tell us whether the amygdala influences the cortex more than the cortex influences the amygdala.
4. Whether another brain region controls the amygdala has nothing to do with comparing the influence between the amygdala and the cortex.
5. CORRECT. Since more developed connections mean more influence, we can safely move from the evidence about neural connections to the conclusion about influence.