Chapter 16
Faking Atomic Ache Won’t Get You Out of This: Science Practice Questions
In This Chapter
Getting through the Science Test without blowing up your chemistry set
Sorting through traps and tricks you may see on test day
Question: What happened to the band director when he stuck his finger into an electrical outlet? Answer: Nothing. He was a bad conductor!
If your store of science knowledge is so low that you don’t even understand this joke, don’t worry. You don’t need any specific science knowledge to do well on the Science Test. Everything you need to answer the questions is stated or implied in the passages provided. (If you get the joke but don’t laugh, maybe your standards are higher than our comedic ability!)
This chapter gives you a research-summary passage with twice the usual number of questions. On the actual ACT, a research summary has only 6 questions, not 12, as in this chapter. We give you double the usual number to give you an idea of the various ways in which the ACT can test the same basic points. For now, don’t worry about the format or the timing. Review the material in Chapter 15; then apply that material to the questions in this chapter.
Directions: Based on the following science passage, answer the 12 questions.
Don’t forget to read all the answer explanations after you’re done!
By using electrical recording devices, scientists have shown that many cells in the part of the brain involved with processing visual information respond only to lines of a certain orientation. For example, some brain cells fire when vertical lines are present but do not respond to horizontal lines. Animals that rely on vision must have an entire set of cells so that at least some part of their brains responds when lines of a given orientation are present in their environment.
A major question is how much brain organization is affected by the animal’s environment. The following series of studies investigates this possible environmental role in the development of rat vision.
Study 1
Scientists presented lines of various orientations to newborn rat pups while recording electrical activity from the visual part of the brain. No matter what the orientation, some cells fired while others did not.
These pups were able to walk around both vertical and horizontal obstacles without bumping into them.
Study 2
Scientists conducted the same test used in Study 1 on 6-week-old pups that were raised in a normal environment. Results matched those of Study 1.
Study 3
Scientists raised newborn rat pups for six weeks in a completely dark environment. The scientists recorded very little brain cell activity when the pups were presented with a wide variety of stimuli.
These pups had great difficulty navigating around various mazes. They bumped into both vertical and horizontal obstacles.
Study 4
Scientists placed newborn rat pups in an environment in which all they saw were vertical lines. At 6 weeks, none of their brain cells responded to horizontal lines, but their brain cells had more activity than what was found in Studies 1 and 2 when vertical lines were present.
These 6-week-old pups easily walked around a maze of vertical obstacles but bumped into and could not walk around horizontal obstacles placed in their paths.
Study 5
This study was identical to Study 4 except that the scientists exposed the rat pups to only horizontal lines. At 6 weeks, their brain cells showed no activity in response to vertical lines and, when presented with horizontal lines, showed increased activity as compared to the pups in Studies 1 and 2.
These pups negotiated a maze of horizontal obstacles but could not navigate around vertical obstacles.
Study 6
Scientists placed 6-month-old rats that were raised in a normal environment and had normal vision in a dark environment for six weeks. At the end of this time, these rats displayed a brain-cell firing pattern similar to that of the rats used in Studies 1 and 2.
Study 7
For six weeks, scientists exposed 6-month-old rats with normal vision and a prior normal environment to only vertical lines. Results were identical to those of Study 6.
Study 8
For six weeks, scientists exposed 6-month-old rats with normal vision and a prior normal environment to only horizontal lines. No difference was found between these rats and those of Study 7.
Initial Analysis
This research summary brings on a lot of text. You may be tempted to read through all that mess before you tackle the questions. Don’t waste your time! Even passages that don’t contain many — or any — charts and graphs are best approached by skipping the passage and jumping right into answering the questions.
Use the information in the questions to direct you to the part of the passage you need to go to find the answers. If the question confuses you, get guidance from reading the answer choices. They can tell you what elements to focus on.
1.On the basis of Study 1, can newborn rat pups see vertical lines?
(A)No, because the newborn rat pups could respond to vertical obstacles.
(B)No, because the newborn rat pups could not respond to horizontal obstacles.
(C)Yes, because the newborn rat pups could not respond to horizontal obstacles.
(D)Yes, because the newborn rat pups could respond to vertical obstacles.
This “yes, yes, no, no” question type concerns Study 1. A quick glance at the answer choices tells you that the only data you need to consider is whether the pups responded to vertical and horizontal obstacles. Focus your attention on the first paragraph of the passage. The paragraph clearly states that the pups maneuvered around both horizontal and vertical obstacles. Examine your answer choices more thoroughly. You can immediately eliminate Choices (B) and (C) because they’re not true. The pups in Study 1 avoided the horizontal obstacles.
Now all you have to figure out is whether responding to vertical obstacles indicates whether the pups can see vertical lines. Don’t overthink this one. You don’t have to worry that some groundbreaking study in Sweden may have revealed that the eye actually sees horizontal objects as vertical and vice versa. The pups moved around the vertical objects, so they likely saw them. The best answer is Choice (D).
Take the path of least resistance. Pick the most logical answer given the data in the passage.
2.Scientists place a 3-week-old rat pup that was raised in a normal environment in a maze of vertical and horizontal obstacles. Which of the following is the most likely result?
(F)The rat pup bumps into horizontal obstacles but gets around vertical obstacles.
(G)The rat pup bumps into vertical obstacles but gets around horizontal obstacles.
(H)The rat pup bumps into both vertical and horizontal obstacles.
(J)The rat pup negotiates around both vertical and horizontal obstacles.
If a newborn pup can get around the maze and a pup raised in a normal environment for six weeks can get around the maze, then you can logically conclude that a pup raised in a normal environment for three weeks would also be able to do so. Only Choice (J) has a pup that doesn’t need a crash helmet, so it’s your winner.
Did you have Smart Students’ Disease on this question and read more into the question? If you said, “Yeah, but what if …” and started imagining all sorts of horrible and unlikely possibilities (“Maybe the rat OD’d on cheese and staggered around …”), you made this problem much harder than it really was. Keep it simple, okay?
3.Scientists place a 6-month-old rat that was raised in a normal environment in a maze of vertical and horizontal obstacles. Which of the following is the most likely result?
(A)The rat makes no attempt to get around the obstacles.
(B)The rat negotiates around both vertical and horizontal obstacles.
(C)The rat bumps into horizontal obstacles but gets around vertical obstacles.
(D)The rat bumps into vertical obstacles but gets around horizontal obstacles.
Did you try to answer this question based on Studies 1 and 2? Doing so worked for the previous question because it spoke of an age, 3 weeks, that was between newborn (Study 1) and 6 weeks (Study 2). Check the question for details. In this question, the rat is older than the oldest pup in Studies 1 and 2, meaning that you can’t be sure that the present trend continues. (Common sense tells you that the trend probably will continue, but you must be able to distinguish between what will probably happen and what will necessarily happen.)
Skim the studies for ones that provide a more definitive answer comes. In Studies 6, 7, and 8, scientists gave normal rats that had a normal environment for six months an abnormal environment for six weeks. The rat in this question didn’t have to endure an abnormal experience. If the vision of the rats exposed to the abnormal environments turned out okay, then the rat that wasn’t placed in such an environment should also be okay. So the correct answer is Choice (B).
If you were really lost on this problem, you could eliminate Choice (A) right away because it’s much too extreme. Answers with words like rarely and infrequently are right much more often than their dramatic counterparts like no and never. Because nothing indicates a favoring of vertical over horizontal lines or vice versa, you can eliminate Choices (C) and (D) as well.
4.Which of the following was not under the direct control of the experimenters?
(F)the length of time that the rat spent in an abnormal environment
(G)the number of brain cells that responded to horizontal lines
(H)the age at which the rat was tested for visual response
(J)the types of obstacles placed in a maze
This is an experiment setup question, which means you may need to read a little of the introductory material to answer it. When an experimental factor, or variable, is under the direct control of the experimenters, the experimenters can decide exactly how much (or what type) of that factor to use without having to depend on any intervening process. Choice (F) is clearly under the control of the experimenters. The experimenters can let the rat out of the maze (the environment) any time they want. Choice (J) is just as clear. The experimenters can throw in more vertical or horizontal obstacles at will.
Choice (H) is a little tougher to eliminate. You may think that the rat’s age is up to the rat (or at least up to its parents), but the experimenters can decide exactly how old the rats have to be in order to be used in a certain part of the experiment.
By process of elimination, Choice (G) is correct. The experimenters can try to change this factor by changing the environment, but exactly how many cells respond depends on the way the rat’s brain is set up and on how the rat’s brain interacts with the environment.
The basic science info covered in Question 4 comes into play in many different passages. Independent variables — Choices (F), (H), and (J), in this case — are those that experimenters can manipulate independently of any other factor. For example, the experimenter can change the time spent in the dark environment from six weeks to five weeks without changing the type of obstacles in the maze. A dependent variable — Choice (G) in this case — depends on what else was done in the experiment.
5.What makes Study 6 important in relation to Study 3?
(A)Study 6 shows that the effects of six weeks in darkness may depend on the rat’s age when scientists place it in such an environment.
(B)Older rats have more reliable brain-cell responses than younger rats.
(C)Study 6 extends the findings of Study 3 by showing that longer periods of darkness also change brain-cell responses.
(D)Study 6 contradicts the findings of Study 3 by showing that, when rats are placed in darkness for a longer period of time, the effect found in Study 3 disappears.
You can dump Choices (C) and (D) immediately because they aren’t true. Study 6 used older rats (ones that have been alive for a longer period of time), but these rats, as well as those of Study 3, were in darkness for only six weeks.
The ACT tests no expert knowledge. You can answer almost all questions based on what the passages state or imply. In other words, you aren’t required to be an expert on rat brain physiology. Because only such experts know whether Choice (B) is true, you can reject it. Six weeks in darkness doesn’t have such a devastating effect when the rats are older. The only answer left is Choice (A), which is correct.
6.Some humans who have suffered brain injuries have been able to recover a lost brain function by having the brain reorganize itself. On the basis of all the rat-vision studies, which of the following humans would be most likely to recover a lost function through brain reorganization?
(F)a 50-year-old man who suffers a stroke (lack of oxygen to a certain region of the brain)
(G)an 80-year-old woman who suffers a stroke
(H)a 30-year-old combat soldier who suffers a bullet wound in the brain
(J)a baby who has had part of the left side of his brain surgically removed along with a tumor
Calm down, calm down — no one expects you to know exactly how each of these brain traumas affects brain functioning. Everything you need to answer this question is there in the passage. The key is to pick up on the ages. Which rats showed a change from the ordinary response pattern when the environment changed? The young rats. Similarly, a young human’s brain is likely to be more flexible than that of an older human. Haven’t you always pointed out to your parents not to be so narrow-minded and set in their ways? Choice (J), which features the youngest human, is the correct answer.
If you’re almost having a stroke right now arguing with us, you probably didn’t notice how carefully the question was worded: “Which of the following humans would be most likely to … ?” True, you don’t know for sure that the baby would have some lost brain function, but all you’re asked is which of the answer choices is the most likely (and, no, “a student studying for the ACT” wasn’t among them).
7.Scientists exposed a 1-year-old rat that was raised in a normal environment and had normal vision to only horizontal lines. Which of the following is the most reasonable prediction?
(A)After three weeks, the cells in the visual part of the rat’s brain fail to respond to vertical lines.
(B)After six weeks, the cells in the visual part of the rat’s brain fail to respond to vertical lines.
(C)After six weeks, the cells in the visual part of the rat’s brain respond to vertical lines.
(D)After six months, the cells in the visual part of the rat’s brain respond to vertical lines.
Study 8 shows that 6-month-old rats exposed to only horizontal lines for six months still have brain cells capable of responding to vertical lines. This info knocks out Choices (A) and (B). After six months, the wiring in the rat’s visual part of the brain seems to be fixed, so you can assume that the 1-year-old rat’s brain has fixed wiring.
Be careful of Choice (D). You can’t say for sure what effects an exposure longer than six weeks will have. Choice (C) is a much safer (and correct!) choice.
Have you been noticing throughout these answer explanations how often you can narrow the answers down to two choices very quickly? If you’re in a hurry or if you’re confused, make a quick guess. Remember that the ACT doesn’t penalize you for wrong answers.
8.In considering all the studies, which of the following is true regarding the brain-cell electrical measurements and the maze results?
(F)The measurements and results are consistent with each other.
(G)The measurements and results are consistent with each other only for newborn rat pups.
(H)The measurements and results are consistent with each other only for rats more than 6 months old.
(J)The measurements and results are inconsistent with each other.
When the electrical measurements showed reduced response to vertical lines, the rats couldn’t negotiate around vertical obstacles. When the measurements showed reduced response to horizontal lines, the rats couldn’t negotiate around horizontal obstacles. The electrical measurements and the maze results always provided the same information regarding what type of lines the rats could handle. So the correct answer is Choice (F).
9.Which of the following studies shows that environmental stimulation can lead to a change in the way the cells in the visual part of a rat’s brain respond?
(A)Study 4 only
(B)Study 4 and Study 5 only
(C)Study 5 and Study 8 only
(D)Study 1, Study 5, and Study 8 only
First, notice that the answer choices only concern Studies, 1, 4, 5, and 8. Don’t waste time evaluating Studies 2, 3, and 7.
Study 1 was performed with newborn rat pups. With such minimal environmental stimulation, this study can’t show that the environment has an effect. You can eliminate Choice (D).
Study 4 looks good. Exposure to only vertical lines caused a loss of cells able to respond to horizontal lines and a gain of cells able to respond to vertical lines. Because the correct answer must have Study 4 in it, eliminate Choice (C).
Study 5 is very similar to Study 4, except that the roles of the vertical and horizontal lines are reversed. Study 5 shows a loss of cells able to respond to vertical lines and a gain of cells able to respond to horizontal lines. So the correct answer is Choice (B).
To check your work, verify that Study 8 doesn’t work. Study 8 shows that the environment has no effect on 6-month-old rats. This study, taken by itself, lends no support to an environmental contribution.
10.If Study 4 is conducted but Studies 3 and 5 are not, can the scientists conclude that all cells in the visual part of a rat pup’s brain require stimulation in order to function?
(F)Yes, because Studies 3 and 5 test what happens when brain cells are not exposed to vertical lines.
(G)Yes, because Study 4 tests both vertical and horizontal-responding cells.
(H)No, because Study 4 only tests whether brain cells respond to vertical lines.
(J)No, because Study 4 does not test whether vertical-responding cells require stimulation.
This “yes, yes, no, no” question tests whether you understand that experimental results are limited when only certain conditions are tested. Notice that the answer choices indicate that you’re focusing on whether the studies tested responses to horizontal and vertical lines. Eliminate Choices (G) and (H) because they’re not true. Study 4 didn’t test responses to vertical lines.
Choices (F) and (J) provide true statements, but only Choice (J) pinpoints the limitations of Study 4 — that it doesn’t test vertical-responding cells. Studies 3 and 5 did test the vertical factor and allow for a more general conclusion regarding brain cells and environmental input, so they’re necessary to understand the role of all cells. So the answer has to be Choice (J). Study 4 is inadequate.
11.On the basis of all the studies, which of the following best summarizes the role of the environment in the development of a rat’s visual brain-cell responses?
(A)The environment has no effect.
(B)Environmental input early in a rat’s life contributes to the continuation of normal responding.
(C)Environmental input can change the pattern of responses throughout a rat’s life.
(D)The environment is the only factor that influences the responses.
If Choice (A) were true, the pups in Studies 3, 4, and 5 would have normal visual responses. Eliminate Choice (A). If Choice (C) were true, the rats in Studies 6, 7, and 8 would show a change in response patterns. Choice (D) is at odds with Study 1. If the environment is the only factor, why do newborn rats show responses to all types of stimuli? This reasoning leaves only Choice (B), which is correct.
Are you noticing and using the wording in the questions and choices to help you choose and eliminate answers? The conservative language (“contributes to the continuation” rather than “directly determines”) reinforces Choice (B) as the answer. Notice how easily you can contradict Choice (A), which contains the word no, Choice (C), which says throughout, and Choice (D), which includes only.
12.Which of the following studies would probably add the most new information to the work done in this set of experiments?
(F)A study identical to Study 3, except that the pups are in the dark environment for seven weeks.
(G)A study identical to Study 6, except that the rats are in the dark environment for five weeks.
(H)A study identical to Study 6, except that the study uses 1-year-old rats.
(J)A study identical to Studies 4 and 5, except that the rats are exposed only to diagonal lines.
Study 3 shows that six weeks of darkness almost entirely wipes out the cells’ ability to respond. Perhaps seven weeks would cause a complete cessation of responding, but the point made from Study 3 (namely, that lack of visual stimulation leads to impaired brain-cell responding) has already been established. Therefore, the study mentioned in Choice (F) won’t add much.
Study 6 strongly suggests that the response patterns in the visual part of a rat’s brain are fixed enough at six months so that six weeks of an abnormal environment have no noticeable effect. If six weeks have no noticeable effect, why would five weeks be any different? Eliminate Choice (G). If the brain-cell responses are fixed by the time a rat is 6 months old, you can reasonably expect that a 1-year-old rat would show the same responses. Eliminate Choice (H).
The study mentioned in Choice (J) would help because it would show what happens to cells that respond to lines that are in between vertical and horizontal. This study would add some information regarding how precise the brain cells are in regard to lines in the environment. For example, is a diagonal line close enough to a vertical line that the exposure only to diagonal lines still allows the rat to respond to vertical lines? The answer to this question would increase understanding of how the environment interacts with the visual part of a rat’s brain.