Microorganisms can significantly influence animal behavior, including that of humans. Parasitic fungi, such as Ophiocordyceps unilateralis, manipulate ants to enhance their chances of being consumed by predators, thus completing their life cycle. In humans, infections like neurosyphilis can lead to cognitive and behavioral changes. Toxoplasma gondii is another notable example, affecting the behavior of rodents and potentially influencing human behavior as well. Other parasites, like those affecting pillbugs, drive them into the open to become prey for birds, facilitating the parasites' reproduction. Additionally, gut bacteria have been shown to alter brain function, impacting behavior. Various studies indicate that significant infections, such as Salmonella or HIV, can also lead to behavioral changes in humans. The discussion highlights the complex interactions between microorganisms and host behavior, suggesting a deeper ecological and evolutionary significance.