When using light as a zeitgeber, which of the following will cause a larger phase shift?Group of answer choicesDim lightDarknessBright light

To determine what will cause a larger phase shift when using light as a zeitgeber (a cue that helps to regulate biological rhythms), we need to consider the impact of different light conditions on biological systems.

Analysis

1. Dim Light:

   • Dim light is less intense and may have a minimal effect on phase shifting. While it can still signal time of day, it typically results in smaller shifts compared to brighter light.

2. Darkness:

   • Complete darkness can actually serve as a reset mechanism for circadian rhythms but does not induce a phase shift in the same way as light does. It tends to cause a phase delay in some circumstances, especially if followed by bright light.

3. Bright Light:

   • Bright light is a strong cue for the circadian system, and research indicates that it can produce significant phase shifts in biological rhythms, like sleep-wake cycles.

Conclusion

Given these considerations, bright light will cause a larger phase shift compared to dim light or darkness.

Final Answer

Bright light will cause a larger phase shift when used as a zeitgeber.