Central Ideas and Details: SAT Practice Questions & Study Guide

The following text is adapted from a 2020 article on sleep science. Scientists have long known that sleep deprivation impairs cognitive performance. A newer line of research suggests that the mechanism behind this impairment involves the glymphatic system—a network of channels in the brain that clears metabolic waste products during sleep. During wakefulness, the brain accumulates proteins such as beta-amyloid that are associated with neurodegenerative disease. During deep sleep, the glymphatic system expands and flushes these proteins from neural tissue. This finding implies that chronic sleep deprivation may accelerate neurodegeneration, not merely impair daily cognition. Which choice best states the main idea of the text?

The following text is adapted from a 2021 cultural history essay. Jazz improvisation is often described as a form of spontaneous composition—music created in real time without prior notation. While this description captures something essential, it can obscure the deep structures that organize improvisational performance. Jazz musicians do not improvise from nothing: they work within a vocabulary of scales, chord substitutions, rhythmic figures, and melodic phrases accumulated through years of practice and active listening. What appears spontaneous to the audience has often been assembled from highly internalized materials, recombined in real time according to shared musical conventions. Which choice best states the main idea of the text?

The following text is adapted from a 2022 essay on the economics of attention. Economists traditionally model consumption as the allocation of scarce income across goods and services. But in contemporary digital economies, the relevant scarce resource is often not income but attention. Social media platforms, streaming services, and news organizations compete not primarily for consumers' dollars but for the finite hours in each day. This competition has produced features specifically engineered to maximize engagement—infinite scrolling, autoplay, and variable reward schedules analogous to those used in slot machines. The result is an attention economy in which the incentives of platform designers are often fundamentally misaligned with the long-term interests and preferences of users. Which choice best states the main idea of the text?

The following text is adapted from a 2019 article on ocean plastics. Much public discussion of plastic pollution has focused on large debris—the bags, bottles, and packaging visible on beaches or floating at the ocean surface. Less visible, and arguably more troubling, is the problem of microplastics: fragments smaller than five millimeters that result from the breakdown of larger plastic items or are manufactured at small sizes for use in personal care products. Microplastics have been detected in every ocean on Earth, in the bodies of marine organisms from zooplankton to deep-sea fish, and increasingly in human tissue. Because microplastics are too small to be efficiently removed by current filtration technology, their long-term ecological and health consequences remain incompletely understood. According to the text, why is the microplastics problem particularly challenging?

The following text is adapted from a 2023 philosophy of mind essay. The concept of mental representation—the idea that cognitive states involve internal structures that stand for, or represent, external states of the world—has been foundational to cognitive science since its inception. Computationalist theories of mind build directly on this concept: thoughts are manipulations of mental representations according to syntactic rules, just as a computer manipulates symbols according to its program. Enactivist critics, however, argue that representationalism fundamentally mislocates cognition. Cognition, they contend, does not happen inside the skull but arises in the dynamic interaction between organism and environment. For enactivists, the brain is not a passive decoder of incoming representations but an active participant in a world it continuously helps to shape. Which choice best states the main idea of the text?

The following text is adapted from a 2022 essay on biodiversity conservation. Conservationists have long prioritized the preservation of biodiversity hotspots—regions with exceptionally high concentrations of endemic species and significant habitat loss. This hotspot approach has been critiqued on the grounds that it allocates conservation resources to areas of current richness rather than to areas whose future ecological importance may be higher. Climate models suggest that as temperatures shift, many species will migrate toward cooler latitudes or higher elevations; the areas through which these migrations will pass—often currently species-poor transitional zones—may therefore be as important to long-term biodiversity as today's hotspots. Conservation planners are increasingly advocating for a forward-looking approach that accounts for projected migration corridors alongside present-day species richness. Based on the text, which detail best supports the claim that the hotspot approach may be insufficient as a conservation strategy?

The following text is adapted from a 2021 essay on the history of the Internet. The architects of the early Internet deliberately designed it as a decentralized network—a system with no central control node that could be shut down or captured. This design was not accidental: the ARPANET, the Internet's precursor, was developed partly in response to Cold War concerns about communications infrastructure vulnerable to a single catastrophic attack. The decentralized architecture made the network resilient, but it also made it fundamentally ungoverned. As the Internet scaled from a small academic network to a global communications infrastructure, the absence of central governance created both freedoms and vulnerabilities that its original architects had not fully anticipated. Which choice best states the main idea of the text?

The following text is adapted from a 2023 essay on urban planning and health. The relationship between urban design and population health is more direct than the phrase "built environment" might suggest. Neighborhoods designed around car use—with wide arterial roads, minimal sidewalks, and distant destinations—systematically discourage walking and cycling, contributing to sedentary lifestyles and their associated health outcomes. Conversely, neighborhoods with walkable streets, mixed land uses, and accessible transit have been associated with higher rates of incidental physical activity, lower rates of obesity, and improved mental health outcomes. Urban planners increasingly argue that public health should be treated as a core objective of city design, not merely an incidental benefit of economic development decisions. According to the text, which of the following best explains why car-centric neighborhoods are associated with poor health outcomes?