Self-paced
P1
Many birds that form flocks compete through aggressive interaction for priority of access to resources such as food and shelter. ███ ██████ ██ ████████ ████████████ ███████ █████ ███████ ██ ████ ████ ████ █████ █ ██████████ ██████ ██████ ███████ ██ ███ ████████ ████████ ████ ████████ ██ ██████ ██ █████████ ██████████ ████ ██████ ███████ ███
Phenomenon ·
Status hierarchy in birds
Top bird has best fighting ability which grants them first dibs on food and shelter. Then next bird get their turn, then next, and so on. Each bird has a position on this status hierarchy.
Negative Consequence ·
Maintaining social status is costly: energy, time, and risk of injury
Hypothesis ·
Status signaling hypothesis (SSH)
Instead of actually fighting to establish social status, birds can instead signal their fighting ability and thereby not have to risk actually getting hurt. A bird's plumage is one such signal of fighting ability.
P2
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Rohwer ·
Sparrow plumage supports SSH
Birds with darker throats win conflicts against birds with lighter plumage, controlling for age and sex.
P3
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Critique of Rohwer ·
Data doesn't support his claims
Darker plumage birds don't always win conflicts. Also, age is actually a confounder. Age is a signal of status and plumage just happens to darken with age. Hence, plumage is not a status signal for these sparrows.
P4
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Experimental Evidence for SSH ·
Greater titmouse
Width of black breast-plumage stripe signals status. Experiment controlled for sex, age, wing length, and body weight.
P5
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Experimental Evidence for SSH ·
Greater titmouse
Stuffed titmouse dummies with narrower v. broader breast stripes caused other birds to behave aggressively v. submissively, as predicted by SSH.
Passage Style
Critique or debate
Phenomenon-hypothesis (RC)
18.
Which one of the following ████ █████████ ███ ████████████ ██ ███ ████████
a
A hypothesis is ██████████ ███ ███████ ████████ ██ ███ ██████████ ███ █████████ ███ ██████████
This best captures the organization of the passage as described in the explanation above.
b
A natural phenomenon ██ █████████ ███ ███████ ████████████ ███ ███ ██████████ ███ ████████ ██ ███████
The passage doesn’t provide “several explanations” for a phenomenon. There’s one explanation — the status signaling hypothesis. Then we examine evidence related to that hypothesis.
c
Behavior is described, ████████ ██████████ ██████ ███ ███ ████████ ███ █████████ ███ ███ ██████████ ██ ████ █████ ██ █████████
The author doesn’t describe different potential causes for the behavior described in P1. The author focuses on a single potential cause — status signaling. The rest of the passage examines evidence related to this cause.
d
A scientific conundrum ██ █████████ ███ ███ ███████ ██ ███ █████ ██ ██████████
The passage doesn’t discuss the history of an issue. It discusses evidence related to the status signaling hypothesis and whether that evidence supports the hypothesis.
e
A scientific theory ██ ████████ ███ ████████ ███ ███ ███████ ███ ████████ ██ ████ ██ ███████████ ██████████ ████ ████ ███ █████████
We don’t get any opinion against the validity of the status signaling hypothesis. The author favors the hypothesis, but merely disputes one zoologist’s evidence for that hypothesis. We also don’t get any experiments that suggest the status signaling hypothesis is not correct.