Field experiments occur in the participant's natural environment or real-life setting. Here, the researcher changes the independent variable (IV) but can't control many outside factors, known as extraneous variables.

Pros: High ecological validity - results can apply to real-life scenarios better because they're conducted in the natural environment.

Cons: Less control over confounding variables (other factors that could affect the results), leading to lower internal validity (ability to draw accurate conclusions from the experiment).

Real-World Example: Think of Piliavin, Rodin and Piliavin’s subway study (1969). They played a little act where they would collapse on a subway train and check if anyone would come to help. To change the IV, some actors used a cane while others appeared drunk, carrying a bottle.

Just like field experiments, natural experiments occur in the participant's natural setting. However, the researchers don't manipulate the IV. Instead, the IV is a natural occurrence.

Pros: High ecological validity (just like field experiments) and can be used when it's unethical to manipulate the IV.

Cons: Lower internal validity because of less control over confounding variables.

Real-World Example: A good example would be comparing the development rates in adopted orphans and those who stayed in the orphanage. The IV here (adoption or staying in the orphanage) naturally occurred.

Interesting fact: All natural experiments are also known as quasi-experiments because the IV isn't manipulated by the researcher!

Here, the researcher manipulates the IV in a controlled lab setting.

Pros: We can infer causation because it's easier to control confounding variables.

Cons: The results might not apply as well to real-life scenarios due to low ecological validity.