• Repeating effects: This occurs when more efficient processes end up making us do the same things more often. Better appliances have led to higher standards of cleanliness, tempting people to spend the same amount of time on housework.
• Recomplicating effects: As technology improve, the processes become more complex. A lighting system that needs to be operated through an app, making it difficult for a visitor just to flip a switch.
• Regenerating effects: Attempts to solve a problem end up creating additional risks. Pesticides can create superbugs that are resistant to harm.
• Rearranging effects: When costs are transferred elsewhere, so risks shift and worsen. Vacuum cleaners can blow dust mite pellets into the air, making it easier to breathe in.

The more we try to control our tools, the more they can make it worse.

• Before the Industrial Revolution, technology was a tool that served as an extension of the user. In a complex system, the machine is more than a device. It needs parts that interact in unexpected and unwanted ways. For example, the fear of a plane crash prompts the creation of greater safety standards.
• Many revenge effects are the result of attempts to improve safety. To control the acute, it indirectly promotes chronic problems. The removal of asbestos reduced fire safety but moving the material is more harmful than leaving it.

• A revenge effect is not a side effect. It is a revenge effect if it reverses the benefit for at least a small subset of users. Typing on a laptop has increased carpal tunnel syndrome, while the physical effort using a typewriter protected workers from some of the harmful effects.
• The revenge effect is also not a tradeoff - exchanging a benefit for another.

• We can expect revenge effects, even if they cannot be predicted.
• In chains of cause and effect within complex systems, the real benefits are not the ones we expected, and the real threats of not those we feared.
• We should be careful about becoming overconfident about our ability to see the future. The revenge effect may depend on knowledge we don't yet have.
• Before we intervene in a system, assuming it can only improve things, we should be aware that our actions can make it worse or do nothing at all.