Apophenia is the spontaneous perception of connections and meaningfulness of unrelated phenomena
Pareidolia is a psychological phenomenon involving a vague or random stimulus (image, sound, etc) being perceived as significant. Pareidolia is a form of Apophenia.
From the perspective of a paranormal researcher, Apophenia arises when we combine small "possible" bits of evidence and draw a conclusion based on it. This is very common when we listen to the stories of our clients, as they have often already drawn these connections. They heard a whisper of their name, and their Grandfather's favorite rocking chair moved by itself. They smell pipe tobacco and swear they saw a shadow slipping into his old bedroom. Oh, and they see things everywhere in the shape of clock hands pointing to 4:13, the time of his death. Conclusion: Grampa is haunting the house.
As investigators we are, by our very focus, opening ourselves up to a constant barrage of the Pareidolia Effect. Is that a face in the window of that photograph? Did I just hear footsteps or is the house settling? Was that mumbled voice on my recorder telling me a name?
Both of these conditions are pitfalls to the paranormal profession, primarily because we often work so hard to find evidence. We listen closely to every second of recorded audio. We scour every shadow and light in our photographs. We concentrate so intently on our evidence that it is easy to matrix all of these items together into a story. After, we are investigators... paranormal detectives if you wish. And detectives fill in the blanks to better understand the big picture.
But we have to be diligent in our review of evidence without seeing something that is not there. Our skeptic side reminds us to throw it out when we are in doubt. But our believing side wants to pick out every bit of evidence that appears even remotely plausible. So do both.
When reviewing your evidence, make not of everything that is out of place. When you are finished, reviewing every bit of that evidence again, only this time ask yourself if you can find any other explanation. Was that sound really just a cat? Could that orb be a light refraction from someone's flashlight? Did that doorknob rattle the same time a big truck went by outside? If you are diligent, you can filter out a great number of false positives on your investigations. There will be times when you need to go back to the location and verify or re-test your possible evidence. Some investigators will arrange to do this prior to the reveal to minimize inconvenience to everyone involved. This should be done sparingly and always with the permission of the client.
In the end, your evidence stands on its own. Are you willing to stand behind it?