Experimenter effect

Imagine you have a toy that you really like, and you want your friend to like it too. So, when you give your friend the toy, you act really excited and show them all the cool things it can do. Your friend might feel happy about the toy too, just because you acted so excited.

This is kind of like the experimenter effect. In science, an experimenter is the person who runs an experiment, or study, to test a hypothesis. The experimenter effect happens when the experimenter's own beliefs or behaviors influence the results of the study, without them realizing it.

For example, let's say a scientist is studying a new medicine to see if it will make people feel better. The scientist might feel hopeful and excited about the medicine, and accidentally give off signals (like Body language or tone of voice) that make the person taking the medicine feel better, even if it's just a placebo. Even though the medicine might not actually be working, the person taking it might report feeling better because of the experimenter's positive attitude.

Scientists try very hard to avoid the experimenter effect by controlling everything in their study very carefully, and by being aware of their own biases and trying to stay neutral. This helps make sure that the results of the study are accurate and not influenced by the experimenter's own beliefs or behaviors.