Sometimes when their trainer gives the hand signal for “Do something creative together," two dolphins circle a pool in tandem and then leap through the air simultaneously.
Conclusion
Dolphins are capable of higher cognitive functions, possibly including the use of language and forethought.
Evidence
When given the "Do something creative together" signal, two dolphins sometimes circle and leap, other times do synchronized backward swims, other times tail-waving.
These behaviors are not simply learned responses to a stimulus.
Evaluate
In a sense this is an Explain Curious Fact argument, because we're trying to interpret how / why the dolphins respond as they do to the hand signal for "do something creative together".
The author explains it as the result of higher cognitive functions (perhaps including language / forethought).
Is there an alternate way to explain it? Could some lower cognitive function account for their behavior?
Goal
When we're strengthening an Explain Curious Fact argument, the correct answer usually makes the author's hypothesis more plausible, but it might involve undermining an alternate explanation.
So let's look for more evidence that dolphins are capable of higher cognitive functions, or look for an answer that undermines some alternate explanation for their "creative" behavior.