PrepTest 81, Section 4, Question 18

This passage is based on an article written in 1995.

Dowsing is the practice of detecting resources or objects beneath the ground by passing handheld, inert tools such as forked sticks, pendulums, or metal rods over a terrain. For example, dowsers typically determine prospective water-well drilling locations by walking with a horizontally held forked tree branch until it becomes vertical, claiming the branch is pulled to this position. The distance to the water from the surface and the potential well's flow rate are then determined by holding the branch horizontally again and either walking in place or backwards while the branch is pulled vertical again. The number of paces indicates the distance to the water, and the strength of the pull felt by the dowser correlates with the potential well's flow rate.

Those skeptical of dowsing's efficacy point to the crudeness of its methods as a self-evident reason to question it. They assert that dowsers' use of inert tools indicates that the dowsers themselves actually make subconscious determinations concerning the likely location of groundwater using clues derived from surface conditions; the tools' movements merely reflect the dowsers' subconscious thoughts. Further, skeptics say, numerous studies show that while a few dowsers have demonstrated considerable and consistent success, the success rate for dowsers generally is notably inconsistent. Finally, skeptics note, dowsing to locate groundwater is largely confined to areas where groundwater is expected to be ubiquitous, making it statistically unlikely that a dowsed well will be completely dry.

Proponents of dowsing point out that it involves a number of distinct techniques and contend that each of these techniques should be evaluated separately. They also note that numerous dowsing studies have been influenced by a lack of care in selecting the study population; dowsers are largely self-proclaimed and self-certified, and verifiably successful dowsers are not well represented in the typical study. Proponents claim that successful dowsers may be sensitive to minute changes in Earth's electromagnetic field associated with variations in subsurface conditions. They also claim that these dowsers have higher success rates than geologists and hydrologists who use scientific tools such as electromagnetic sensors or seismic readings to locate groundwater.

The last two claims were corroborated during a recent and extensive study that utilized teams of the most successful dowsers, geologists, and hydrologists to locate reliable water supplies in various arid countries. Efforts were concentrated on finding groundwater in narrow, tilted fracture zones in bedrock underlying surface sediments. The teams were unfamiliar with the areas targeted, and they agreed that no surface clues existed that could assist in pinpointing the locations of fracture zones. The dowsers consistently made significantly more accurate predictions regarding drill sites, and on request even located a dry fracture zone, suggesting that dowsers can detect variations in subsurface conditions.

This passage is based on an article written in 1995.

Dowsing is the practice of detecting resources or objects beneath the ground by passing handheld, inert tools such as forked sticks, pendulums, or metal rods over a terrain. For example, dowsers typically determine prospective water-well drilling locations by walking with a horizontally held forked tree branch until it becomes vertical, claiming the branch is pulled to this position. The distance to the water from the surface and the potential well's flow rate are then determined by holding the branch horizontally again and either walking in place or backwards while the branch is pulled vertical again. The number of paces indicates the distance to the water, and the strength of the pull felt by the dowser correlates with the potential well's flow rate.

Those skeptical of dowsing's efficacy point to the crudeness of its methods as a self-evident reason to question it. They assert that dowsers' use of inert tools indicates that the dowsers themselves actually make subconscious determinations concerning the likely location of groundwater using clues derived from surface conditions; the tools' movements merely reflect the dowsers' subconscious thoughts. Further, skeptics say, numerous studies show that while a few dowsers have demonstrated considerable and consistent success, the success rate for dowsers generally is notably inconsistent. Finally, skeptics note, dowsing to locate groundwater is largely confined to areas where groundwater is expected to be ubiquitous, making it statistically unlikely that a dowsed well will be completely dry.

Proponents of dowsing point out that it involves a number of distinct techniques and contend that each of these techniques should be evaluated separately. They also note that numerous dowsing studies have been influenced by a lack of care in selecting the study population; dowsers are largely self-proclaimed and self-certified, and verifiably successful dowsers are not well represented in the typical study. Proponents claim that successful dowsers may be sensitive to minute changes in Earth's electromagnetic field associated with variations in subsurface conditions. They also claim that these dowsers have higher success rates than geologists and hydrologists who use scientific tools such as electromagnetic sensors or seismic readings to locate groundwater.

The last two claims were corroborated during a recent and extensive study that utilized teams of the most successful dowsers, geologists, and hydrologists to locate reliable water supplies in various arid countries. Efforts were concentrated on finding groundwater in narrow, tilted fracture zones in bedrock underlying surface sediments. The teams were unfamiliar with the areas targeted, and they agreed that no surface clues existed that could assist in pinpointing the locations of fracture zones. The dowsers consistently made significantly more accurate predictions regarding drill sites, and on request even located a dry fracture zone, suggesting that dowsers can detect variations in subsurface conditions.