Self-paced
A recent study carefully tracked the specific behaviors of five East African chimpanzee groups of one subspecies, and of two West African groups of another subspecies, in activities such as grooming and foraging. ███ █████ █████ ████ ███ ██ ███ ████ ███████ ██████ ███ ████████████ ████ ███████ ██ ███ ████ ███████ ██████ ████ ██ ███ █████ ████ ███████ ███████ ██ ██ █████████ ██████ ████ █████ █████████ ███ ██████████ ██ ████████ ███████ ██████ ████ ██ █████████
Argument Summary
Right off the bat, “A recent study” should make you suspect we’re in phenomenon hypothesis land. We’re gonna learn some observed facts from the study, and expect a causal conclusion pitching us on an explanation of those facts. And indeed that’s what happens in this stimulus:
There are two subspecies of chimps: East ones and West ones. Within these subspecies, there are different chimp groups – some East groups and some West groups. We watched these chimps groom each other and forage around for a while, and it turns out different groups have different styles.
In particular, one of the East groups did a lot of West-style grooming and foraging. That’s interesting. We think this suggests that grooming and foraging styles are probably cultural AND probably not genetic.
Analyzing this argument requires knowing that species are defined genetically. Different subspecies are genetically distinct, and animals within the same subspecies are genetically similar – that’s how we scientists do things.
Anyway, our conclusion really makes two related claims: our explanation is right, and this other explanation is wrong. This gives our anticipation a bit more focus: it’s likely that our correct answer choice will bolster the cultural explanation in a way that undermines the genetic explanation.
16.
Which one of the following, ██ █████ ████████ ███ ████ ███████ ███ ███ █████████
a
Chimpanzees sometimes copy ███ ████████ ██ █████ ████████████ ███████ ██ ███ ████ ███ ███████ ███████ ████████████
The first clause bolsters the cultural explanation by giving evidence that cultural behavior transmission is a real thing that happens. The second clause explicitly controls for genetics – this behavior spread happens regardless of genetic relation.
Causal mechanism
Causal mechanism
Answers that strengthen by shedding light on the "how?" of the cause and effect relationship. For example, high altitude training causes better aerobic performance. How? The causal mechanism could be that the thin air at high altitudes cause physiological changes that support better oxygenation.
b
Chimpanzees that are ███ ██ █ █████ █████████ █████ ████ ████ ███ █████████ ██ ████ ██ ███ ███████ ████████████████
(B) proposes a mechanism of behavioral spread that is both cultural and genetic. Learning that chimpanzees sometimes roll up to a new group and bring in new behaviors into a group arguably bolsters the cultural explanation in much the same way (A) does, by suggesting a means of cultural behavior spread.
But it also bolsters the genetic explanation by suggesting a means for genetic behavioral spread.
c
The chimpanzee groups ███████ ████ █████████ █████████████ ██████████ ███ ██ █████ █████████ █████████ ██ ███████
(C) is silent on the mechanism by which these different groups adapt to their different environmental challenges.
On a tempting reading of (C), perhaps this weird East group that forages in a West-style way is adapting to some West-style environmental challenges. Sure! How are they adapting, though? Is it through the cultural spread of new behaviors, or is it through genetic adaptations that are in the process of turning this group into a new subspecies?
d
The behavioral differences ██ ███ ██████████ ██████ ███████ ███ ██████████ ██ ████ ████ █████ ████████████ ████████ ████ ███ ███ ███████
(D) says you can tell the difference between groups based solely on observing behavior. At its most tempting, (D) seems to repair a supposed weakness “Are you sure you can actually tell the difference between these groups?”
But the answer to that question is “YES,” as established by the premises (which we must take to be true). The study establishes that different groups have observably different behaviors, so reassuring ourselves that we can tell the groups apart provides unnecessary support for an idea that is already supported.
Through a different lens, perhaps (D) is tempting because it suggests these observed behavioral differences are so pronounced and strong that they alone suffice to tell all the groups apart. Like these are really very huge behavioral differences.
The problem there is just that there’s no clear link between big differences and cultural ones. Maybe these big differences come with genetic differences too.
Irrelevant corroboration
Irrelevant corroboration
Answers that provide additional support for a claim that the argument doesn't need more support for.
e
Of the chimpanzee ██████ ████████ ███ ████ ████ ███████ ██████ ████ ██ ██████ █████████ ██ ████ █████ ████ ██ ███ ███ ████ ███████ ███████
(E) perhaps strengthens the idea that cultural behavior spread is more realistic for the East groups than for the West groups because they live so close to one another.
Lots of problems with this, but here’s a clean one: comparing the East subspecies to the West subspecies isn’t relevant to our argument, which compares one specific East group to the rest of the East groups.
We’re not explaining East / West differences, we’re explaining East / Weirdo-East differences.