Ruling Out Alternate Explanations (Defender)

After the local bakery switched to using organic flour, the total number of pastries it sold per week increased by 25 percent. The bakery owner concluded that the switch to organic flour caused this increase in pastry sales.

Which one of the following is an assumption on which the bakery owner's argument depends?

In a recent decade-long study of 50 agricultural regions, researchers found that the regions that had adopted a newly developed soil conservation technique experienced a significantly lower rate of topsoil erosion than the regions that continued to rely on traditional methods. Based on this data, the researchers concluded that the adoption of the new technique was responsible for the disparity in erosion rates between the two groups.

Which one of the following is an assumption on which the researchers' argument depends?

Over the past decade, the municipality of Oakhaven implemented a 'Green Streets' initiative, significantly increasing the number of trees and public parks in its downtown district. During this same ten-year period, the incidence of stress-related illnesses reported by downtown residents decreased by 30 percent. Because clinical studies have consistently demonstrated that exposure to urban green spaces lowers cortisol levels, city officials conclude that Oakhaven's newly added green spaces directly caused the local reduction in stress-related illnesses.

Which one of the following is an assumption on which the city officials' argument depends?

A recent workplace study found that employees who regularly use standing desks report 30 percent fewer instances of lower back pain than employees who use traditional sitting desks. Based on this study, a workplace consultant concluded that using a standing desk instead of a sitting desk reduces the risk of developing lower back pain.

Which one of the following is an assumption on which the consultant's argument depends?

Sociologist: A recent corporate study found that employees who participated in an optional weekly mindfulness meditation program reported a 40 percent lower rate of workplace stress compared to employees who did not participate. This demonstrates that practicing mindfulness meditation directly reduces workplace stress.

Which one of the following is an assumption required by the sociologist's argument?

An archaeologist argues: 'Pottery fragments from the ancient Zanthian culture found in coastal excavations are consistently much harder than those found at inland Zanthian sites. This proves that centuries of exposure to salty coastal air chemically strengthened the clay.'

To protect this causal argument from criticism, the archaeologist must assume several 'defender' statements that rule out alternate explanations. Match each alternate explanatory objection below to the specific defender assumption that logically neutralizes it.

Archaeologist: The abandonment of the thriving ancient settlement of Kelior is generally attributed to a century-long regional drought. However, isotopic analysis of soil strata indicates that less than a decade before the abandonment, Kelior's farmers abruptly transitioned from cultivating teff, a highly drought-resistant grain, to a variety of water-intensive marsh-rice. Therefore, it was actually this ill-advised agricultural pivot, rather than the drought alone, that precipitated the settlement's collapse by engineering a catastrophic famine.

The archaeologist's argument relies on which one of the following assumptions?

Sociologist: A comprehensive ten-year study tracked adolescents and their video gaming habits. The researchers found that adolescents who predominantly played cooperative multiplayer video games exhibited significantly higher scores on standardized assessments of real-world conflict resolution than adolescents who predominantly played competitive single-player games. Based on these findings, we can safely conclude that engaging in cooperative multiplayer gaming actively fosters and enhances a teenager's ability to resolve interpersonal conflicts.

Which one of the following is an assumption on which the sociologist's argument depends?

Ten years ago, the national government introduced a substantial tax on plastic packaging used by food manufacturers. Since the tax was implemented, the volume of plastic waste deposited in the nation's municipal landfills has decreased by 30 percent. Economists assert that the tax achieved its intended goal, concluding that the financial penalty forced food manufacturers to switch to biodegradable packaging alternatives, thereby reducing the amount of plastic waste generated.

Which one of the following is an assumption required by the economists' argument?

Wildlife ecologists monitoring the endangered silver-tufted macaque in the Valerius Basin have documented a severe population collapse over the last five years. During this exact same period, the region's population of non-native feral wildcats has nearly tripled. Because feral wildcats are known to hunt small primates in other ecosystems, the ecologists concluded that predation by these wildcats is the primary cause of the macaque population's decline.

Which one of the following is an assumption on which the ecologists' argument depends?

Paleontologist: The extinction of the marine reptile *Thalassadon* was caused by a rapid global cooling event, rather than by a viral pandemic as some scientists have proposed. Fossil records clearly indicate that *Thalassadon* populations drastically plummeted in the higher, colder latitudes hundreds of thousands of years before they disappeared from the warmer equatorial waters.

Statement: The paleontologist's argument logically depends on the assumption that the proposed viral pandemic did not originate in the higher latitudes and slowly spread toward the equator.

An environmental economist observed that cities implementing a 'green canopy' initiative—planting shade trees along commercial corridors—experienced a 15% higher increase in local retail revenue over five years compared to cities without the initiative. The economist concluded that the presence of the green canopy directly stimulated local consumer spending.

Match each potential explanatory objection (left) with the specific 'defender assumption' (right) that the economist's argument must make to effectively neutralize that objection.

Historians recently discovered that medieval European towns with large centralized grain silos experienced significantly fewer winter disease outbreaks than towns with decentralized, individual storage. The historians concluded that the centralized storage system directly caused this improvement in public health.

Match each alternative explanation (causal objection) for this correlation with the specific defender assumption required to rule it out.

A city council implemented a new tax on sugary drinks. One year later, the obesity rate in the city dropped by 5%. The council concluded that the sugary drink tax successfully caused the reduction in obesity.

Match each alternative explanation for the drop in obesity with the defender assumption that would logically neutralize it.

Last month, a local restaurant replaced the fast-paced pop music playing in its dining area with slower classical music. Since this change, the average amount of money spent by each table has increased by 15 percent. The restaurant manager concludes that the switch to classical music is the primary cause of this increase in average spending.

Which one of the following is an assumption on which the manager's argument depends?

Records from the coastal region of Veltierra show that over the last twenty years, the rate of structural failure among seawalls constructed using a newly introduced synthetic material, Duracrete, is significantly higher than the structural failure rate for seawalls built with traditional concrete during the exact same period. Based on these records, a civil engineering task force concluded that Duracrete is inherently less resilient to Veltierra's corrosive marine environment than traditional concrete is.

The task force's conclusion depends on which one of the following assumptions?

A comprehensive analysis of fossilized hominid dental remains from the Pleistocene epoch reveals a distinct pattern: populations residing in high-altitude environments exhibited significantly greater enamel thickness compared to their low-altitude contemporaries. Because thicker enamel provides increased resistance to the rapid abrasive wear caused by masticating tough, fibrous vegetation, anthropologists conclude that the harsh conditions of high-altitude environments must have forced these hominids to rely heavily on such vegetation for their caloric needs.

Which one of the following is an assumption on which the anthropologists' argument depends?

In the 1920s, several textile factories switched their primary power source from steam engines to newly available electric motors. Over the following year, the factories that made this switch reported a substantial drop in the rate of workplace accidents. Based on this record, labor historians concluded that electric motors are inherently safer to operate than steam-powered machinery.

The labor historians' argument depends on which one of the following assumptions?

Read the following argument:

Recently, a major commercial airline switched from standard aluminum cargo containers to containers made from a newly developed carbon composite. In the first year of using the composite containers, the airline reported a 12 percent reduction in overall fuel consumption per flight. The airline's management concluded that the lighter weight of the new composite containers caused the reduction in fuel consumption.

Statement: For the management's conclusion to be logically drawn, the argument must assume that the airline did not simultaneously implement new fuel-efficient flight routing procedures during that same year.

A five-year epidemiological study tracked the neurological health and self-selected dietary habits of two large cohorts of elderly individuals. Cohort A maintained diets highly concentrated in flavonoid-rich berries, while Cohort B consumed diets nearly devoid of them. At the conclusion of the study, Cohort A exhibited a statistically significant lower rate of age-related cognitive decline than Cohort B. Because the researchers rigorously controlled for baseline neurological health at the study's onset, as well as for genetic predispositions and overall cardiovascular fitness, they concluded that the regular consumption of flavonoid-rich berries actively impedes neurological degradation.

Which one of the following is an assumption on which the researchers' argument depends?