What makes the yardstick test a direct measurement of reaction time?

The yardstick test is a direct measurement of reaction time primarily because the fall of the yardstick demonstrates a clear, quantifiable relationship between distance and time. When the yardstick is dropped, the distance it falls before being caught is directly related to the speed of the individual's reaction. If the yardstick falls a great distance, it indicates that the person's reaction time was slow; conversely, a shorter distance suggests a quicker response. This cause-and-effect relationship provides a straightforward method for assessing how quickly someone can respond to a stimulus, which is the essence of measuring reaction time.

While the other options may provide additional context, they do not directly address the core principle of how the yardstick test measures reaction time effectively. Numerical markings on the yardstick aid in quantifying the results, but the key aspect is still the distance fallen relative to the reaction speed. Similarly, the design of the yardstick does not specifically cater to measuring reaction time; it simply happens to serve that purpose in this context. Therefore, the first option captures the fundamental reason why this test is effective as a direct measurement of reaction time.