Positive vs Negative Feedback: Difference and Comparison

Key Takeaways

1. Positive feedback amplifies or reinforces the initial input or stimulus, driving the system from equilibrium and promoting exponential growth or amplification.
2. Negative feedback opposes or counteracts the initial input or stimulus, reducing deviations and bringing the system back to its original state or equilibrium, thus maintaining stability.
3. Positive feedback tends to destabilize systems and can lead to unpredictable outcomes. In contrast, negative feedback promotes stability and control, making it essential for maintaining homeostasis in living organisms and regulating various technological systems.

What is Positive Feedback?

Positive feedback is a process in which an initial change in a system leads to additional changes that amplify or reinforce the original change. In other words, it is a feedback loop in which the output of a system is fed back into the system as an input, which increases the output even further.

A common example of positive feedback is a microphone too close to a speaker. The microphone picks up sound from the speaker, which is then amplified and sent back through the speaker. This amplifies the sound even further, which is picked up by the microphone, and the process continues until the sound becomes distorted.

Positive feedback is associated with instability and can lead to rapid and dramatic changes in a system. However, it can also have beneficial effects in certain situations. For example, positive feedback is important in blood clotting, in which the initial formation of a clot triggers a cascade of further clotting reactions that ultimately result in the formation of a stable blood clot.

What is Negative feedback?

Negative feedback is when an initial change in a system leads to additional changes that counteract or oppose the original change. In other words, it is a feedback loop in which the output of a system is fed back into the system as an input, which then reduces or dampens the output.

A common example of negative feedback is a thermostat that controls the temperature of a room. When the temperature rises above the set point, the thermostat sends a signal to the heating system to turn off, reducing the temperature. When the temperature falls below the set point, the thermostat sends a signal to the heating system to turn on, increasing the temperature. This process continues until the temperature is stabilized around the set point.

Negative feedback is important in maintaining stability and homeostasis in many biological systems. For example, the regulation of blood glucose levels by insulin and glucagon is controlled by negative feedback, in which high glucose levels stimulate the release of one hormone. In contrast, low glucose levels stimulate the release of the other hormone. This results in a finely-tuned feedback loop that maintains blood glucose levels within a narrow range.

Difference Between Positive and Negative Feedback

1. Positive feedback amplifies or reinforces the original change in a system, while negative feedback opposes or dampens the original change.
2. Positive feedback creates instability or exponential growth, while negative feedback promotes stability or equilibrium.
3. Positive feedback can result in runaway effects, while negative feedback provides control and regulation in a system.
4. Positive feedback does not have a threshold and can continue to amplify changes, while negative feedback has a threshold that limits the degree of change.
5. Positive feedback can be found in sound amplification or blood clotting cascade processes. In contrast, negative feedback can be found in systems such as thermostats, blood glucose regulation, or heart rate control.

Comparison Between Positive and Negative Feedback

Parameters of Comparison	Positive Feedback	Negative Feedback
Role in system dynamics	Stabilizes the system around an equilibrium point	It can be found in both simple and complex systems
Time scale	Typically operates on a shorter time scale	Typically operates on a longer time scale
Complexity	Often associated with more complex, non-linear systems	It can decrease variability and promote predictability in a system
Effect on variability	Effect on Diversity	It can increase variability and unpredictability in a system
Effect on diversity	Can reduce diversity by amplifying certain outcomes	Can maintain or increase diversity by opposing certain outcomes

References

1. https://www.sciencedirect.com/science/article/pii/S1631069102015330
2. https://www.tandfonline.com/doi/abs/10.1080/01608061.2017.1423151