Here's why:
* Contagious refers to the spread of something through contact, often by direct physical contact or close proximity.
* Infectious refers to the spread of a disease caused by a pathogen, like bacteria or viruses.
While both laughter and yawning can spread from person to person, they are not caused by a pathogen. They are involuntary physiological responses.
Therefore, while they can spread easily, they are not infections, but rather contagious behaviors.