In everyday life, many people report experiences that they believe might have been paranormal. These experiences often have to do with apparent extrasensory perception (ESP)-the acquisition of information without any apparent physical means. For example, someone might think of an old friend that they have lost touch with and not thought about in years, only to receive a telephone call the same day to tell them that their friend has just died. The coincidence may seem so unlikely that the event is taken as evidence of ESP. Other experiences may relate to apparent psychokinesis (PK)-the influence of someone's thoughts upon the physical world. For example, someone might be having a particularly stressful time at work and shout at their computer, which immediately breaks down. They might wonder whether this was evidence of psychokinesis.
Everyday life, however, is messy. There are three main difficulties in taking events such as these as strong evidence that paranormal phenomena exist.
The first problem is that it is difficult to rule out the possibility that normal, physical channels were involved. In the first example given above, a mutual acquaintance might have mentioned that the friend was ill some time before. The person who experienced the coincidence might have forgotten being told this but the unconscious memory might have prompted the idea of the friend's death some time later. This would make the coincidence much less remarkable. In the second example, the person shouting at the computer might have made a sudden movement when they did so. Vibration from this movement might have been enough to trigger a mechanical fault that had been on the verge of happening for some time.