Homing pigeons can be taken from their lofts and transported hundreds of kilometers in covered cages to unfamiliar sites and yet, when released, be able to choose fairly accurate homeward bearings within a minute and fly home. ███
If the birds are using an internal magnetic compass to track displacement, then we would expect distorting magnetic fields to impair their ability to home but it does not reliably do so.
Mechanism ·Conscious navigation to track displacement
If the birds are tracking displacement by consciously tracking their movements (e.g., "I turned left and flew 3 minutes before diving low and then I turned right..."), then we would expect that anesthetizing them would impair their ability to home but it does not at all.
Criticism of Olfactory Hypothesis ·Pigeons cannot distinguish natural air from filtered air
If pigeons did use their sense of smell to create a map, presumably they would be able to tell natural, scent ladened air, from pure, filtered air. But they cannot.
Alternative Explanation ·for Papi's experimental results
Why did Papi's pigeons have trouble homing? It wasn't because they couldn't smell. It was because plugging their noses was a traumatic experience and interfered with their breathing.
When pigeons could not smell but could breathe comfortably, they were able to home. So the mechanism for their map sense is not olfactory.
Passage Style
Critique or debate
Phenomenon-hypothesis (RC)
21.
Given the information in the ████████ ██ ██ ████ ██████ ████ ████ ███ ███ ██████ ██ ███ ███████ █████ ████ █████ ████ █████ ███ ██ ███ █████████ ██████████ █████████ ███ ██████ ███████ ██ ████████
Question Type
Implied
The correct answer is something that both Papi and the author are most likely to agree with. Papi believes that homing pigeons likely home through building an olfactory map. The author believes the map sense hypothesis is plausible, but doesn’t agree that an olfactory map is the most likely way a pigeon builds a map. We can see this from the last paragraph, where the author describes a “problem” with Papi’s hypothesis.
a
The map sense ██ ███████ ██ ████ ████████ ███████ ██ █████ █████████ ██████
Both Papi and the author believe pigeons most likely home using map sense. They don’t agree on the olfactory nature of this map sense, but they do agree on the general mechanism of a map sense.
This is a difficult question.
It is slightly harder than the average question in this passage.
CURVE
Score of students with a 50% chance of getting this right
25%149
157
75%164
Analysis
Implied
Implied
Stems asking us to infer an idea implied by the claims in the passage (as opposed to identifying an idea that appears explicitly). Similar to most strongly supported questions in LR.
Critique or debate passages contain multiple points of view on a particular subject. Sometimes the author takes sides and participates in the critique or debate, other times the author merely reports the debate.
Passages that focus on describing or evaluating potential explanations for a given phenomenon. Causal reasoning features prominently in these passages.
