Drill 25 · Reading & Writing · Hard Command of Evidence
SAT R&W Command of Evidence (Hard) — Drill 25 is a Reading & Writing practice drill covering Hard Command of Evidence. It contains 5 original questions created by Brian Stewart, a Barron's test prep author with over 20 years of tutoring experience.
Some owls strike prey in the dark by hearing alone, pinpointing a sound's direction from tiny differences between the two ears. This closing set asks you to separate the cue an owl uses for left-right from the cue it uses for up-down, and to read a data display for a difference between conditions. The quotation here is a scholarly, invented excerpt -- no real source -- so judge it only by which line states the claim.
In a darkened arena, a trained owl turns its head toward a hidden speaker, and researchers measure how far off its aim lands. They test the owl with both ears open and again with one ear lightly plugged, varying the speaker's height above or below the owl. Because this owl's ears sit at slightly different heights, blocking one should disturb up-down aim in particular, while leaving left-right aim much as before. If the plugged ear matters for elevation, the owl's error should stay small near its own height and grow as the speaker moves up or down. The graph plots average aiming error against speaker elevation for the two-ears-open and one-ear-plugged conditions.
Question 1. Which statement best captures the difference between the two ear conditions shown in the graph?
Explanation: Correct: The two lines start close near the owl's own height, but the one-ear-plugged line climbs steeply as elevation departs from level while the both-ears line stays flat. That widening gap with elevation is what the graph shows. A: The both-ears line does stay low, but stated alone this ignores the plugged-ear line that the comparison is built on -- it is true yet incomplete. B: It is true that the plugged-ear error is smallest near level, but that single point misses the main pattern, the sharp rise away from level. D: The conditions diverge as elevation changes, so equal error at every elevation is contradicted by the graph.
The owl pinpoints a sound's up-down position far better than most birds. Researchers propose that it reads up-down direction from the difference in loudness between its two vertically offset ears, since a sound from above reaches the higher ear a touch louder. A rival proposal is that the owl instead uses the difference in arrival time between the ears for up-down aim, the same kind of cue many animals use for left-right. The two proposals point to different ear cues, and the team designs a test to separate them.
Question 2. Which finding, if true, would most strongly support the loudness-difference proposal over the arrival-time proposal for up-down aim?
Explanation: Correct: If erasing the between-ear loudness difference -- while leaving timing differences intact -- wrecks up-down aim, then loudness is the cue the owl relies on for elevation. That isolates the proposed cue from its rival. B: Faster turning toward louder sounds concerns reaction, not how the owl judges up-down direction, so it favors neither proposal. C: Accurate aim straight ahead at ear level needs little vertical judgment and does not show which cue handles elevation. D: Plugging both ears equally degrades hearing generally and does not single out the loudness-difference cue.
A student summarizing a review article on owl hearing argues that the ring of stiff feathers forming the owl's flat face is not mere decoration but a sound-gathering structure that channels faint noises toward the ear openings. The student wants a sentence from the review that states this funneling role directly, rather than one that describes the ears or the behavior around it.
Question 3. Which quotation would most effectively support the student's claim about the facial feathers' sound-gathering role?
Explanation: Correct: The claim is specifically that the facial feathers gather and funnel sound, and this sentence says exactly that -- the disc acts as a parabolic reflector collecting faint sounds and directing them to the ears. It names the structure and its sound-gathering function. A: This reports when the owl hunts, not anything about the facial feathers gathering sound. B: This describes the ear openings' placement, a different structure than the facial disc the claim is about. C: This states that the owl hunts by sound but says nothing about the feathers doing the collecting.
Separately, the owl locates left-right direction with great precision. Researchers want to know whether it judges left-right from the difference in arrival time between the two ears or from the difference in loudness, since a sound off to one side both reaches the near ear sooner and sounds slightly louder there. Because the two cues normally travel together, an ordinary sound cannot separate them. To pull them apart, the team can feed the two ears sound through earphones and change one cue while holding the other fixed, then watch which manipulation moves the owl's left-right aim.
Question 4. Which finding, if true, would most strongly support the view that the owl judges left-right direction from arrival-time differences rather than loudness differences?
Explanation: Correct: A pure time delay to one ear, with loudness untouched, makes that ear hear the sound later, so the owl localizes it toward the earlier, undelayed ear. Because only timing changed, the shift shows timing alone drives the horizontal judgment, isolating the arrival-time cue from loudness. A: A faster response to louder sounds is about reaction speed, not whether timing or loudness sets left-right direction. B: That left-right beats up-down accuracy compares two axes but does not say which cue underlies the left-right judgment. D: Equal ear sensitivity is a baseline condition and does not reveal whether timing or loudness carries the left-right cue.
Table: aiming accuracy under four ear conditions
To see what the owl needs for its sharpest up-down aim, researchers test four conditions, noting for each whether the owl's natural ear height asymmetry is preserved and whether its facial disc is left intact. The offset ears supply the loudness cue and the disc gathers the faint sound that cue depends on, so take away either feature and the up-down judgment should suffer. The table reports the average up-down aiming error for each condition.
Question 5. Based on the table, which conclusion is best supported?
Explanation: Correct: The smallest error, 3 degrees, occurs only in Condition 1, where ear asymmetry is preserved and the facial disc is intact. When either feature is removed or disrupted, the error rises, so the table supports the conclusion that the sharpest aim occurred only when both features were present. B: Disrupting the disc (11 degrees) actually harms aim less than removing the asymmetry (14 degrees), so the table does not show the disc mattering more. C: Removing the asymmetry raises the error to 14 degrees, far above the 3 degrees with both intact, so aim is not about as accurate. D: Each single-feature condition (11 and 14 degrees) is much worse than Condition 1, so one feature alone does not give the sharpest aim.