An emotion is a response to an emotional, psychological, or environmental stimulus. The emotion resulting from a certain situation is unique to each individual, their past and their life story, their intellectual abilities, and their psychological state. Emotions involve physical effects of initial psychological responses: sadness can cause tears, fear can trigger a scream, sometimes urinary discharge, or joy can generate a big smile, and even tears. Similar situations involve different emotions depending on the individual concerned, the context, and implications. Emotion differs from sensation, which appeals to sensory perception, and feelings, which are felt, but in the absence of physical manifestations.