Situational Variables are factors in the environment that can unintentionally affect the results of a study. Such variables include noise, temperature, odors, and lighting. For example, let’s say researchers are investigating the effects of caffeine on mood. One day the air conditioning breaks down in the lab. The participants who visit the lab that day to take part in the study get very hot and comfortable, and when filling out the questionnaire to measure their mood most of them report being in a bad mood. The researchers cannot be sure whether the caffeine or the heat caused the participants’ bad mood. Experimenters should try to control for situational variables so they don’t throw off research results.