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Some Astyanax mexicanus, a river-dwelling fish found in northeast Mexico, have colonized caves in the region. Although there is little genetic difference between river and cave A. mexicanus and all members of the species can emit the same sounds, biologist Carole Hyacinthe and colleagues found that the context and significance of those sounds vary by location—e.g., the click that river-dwelling A. mexicanus use to signal aggression is used by cave dwellers when foraging—and the acoustic properties of cave fish sounds show some cave-specific variations as well. Hyacinthe and colleagues note that differences in sonic communication could accumulate to the point of inhibiting interbreeding among fish from different locations, suggesting that ______
Which choice most logically completes the text?
although A. mexicanus living in rivers are genetically similar to those living in caves, river fish rely on sonic communication less than cave fish do.
although A. mexicanus is a single species at present, it could be in the process of splitting into distinct populations with different characteristics.
although all A. mexicanus emit sounds, the fish living in rivers produce some sounds that the fish living in caves do not, and vice versa.
although A. mexicanus from different locations can interbreed currently, river fish and cave fish are sufficiently genetically distinct that they can be considered separate species.
Psychologists Dacher Keltner and Jonathan Haidt have argued that experiencing awe--a sensation of reverence and wonder typically brought on by perceiving something grand or powerful--can enable us to feel more connected to others and thereby inspire us to act more altruistically. Keltner, along with Paul K. Piff, Pia Dietze, and colleagues, claims to have found evidence for this effect in a recent study where participants were asked to either gaze up at exceptionally tall trees in a nearby grove (reported to be a universally awe-inspiring experience) or stare at the exterior of a nearby, nondescript building. After one minute, an experimenter deliberately spilled a box of pens nearby.
Which finding from the researchers' study, if true, would most strongly support their claim?
Participants who had been looking at the trees helped the experimenter pick up significantly more pens than did participants who had been looking at the building.
Participants who helped the experimenter pick up the pens used a greater number of positive words to describe the trees and the building in a postexperiment survey than did participants who did not help the experimenter.
Participants who did not help the experimenter pick up the pens were significantly more likely to report having experienced a feeling of awe, regardless of whether they looked at the building or the trees.
Participants who had been looking at the building were significantly more likely to notice that the experimenter had dropped the pens than were participants who had been looking at the trees.
Many insects are iridescent, or have colors that appear to shimmer and change when seen from different angles. Scientists have assumed that this feature helps to attract mates but could also attract predators. But biologist Karin Kjernsmo and a team had the idea that the shifting appearance of colors might actually make it harder for other animals to see iridescent insects. To test this idea, the team put beetle forewings on leaves along a forest path and then asked human participants to look for them. Some of the wings were naturally iridescent. Others were painted with a nonchanging color from the iridescent spectrum, such as purple or blue.
Which finding, if true, would most directly support the team's idea?
On average, participants found most of the purple wings and blue wings and far fewer of the iridescent wings.
On average, participants found the iridescent wings faster than they found the purple wings or blue wings.
Some participants reported that the purple wings were easier to see than the blue wings.
Some participants successfully found all of the wings on the leaves.
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