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The Mystery of Streetlight Interference

One fine evening, you’re returning home after a long day’s work. As you stroll down the footpath of the street a block away from your house, no one else is around, and you only have the street lamps illuminating your path towards home. Oddly, the street lamp you just walked by suddenly switched off, only turning on again once you’ve passed it. Being the level-headed person that you are, you shrug off what happened as mere coincidence and think nothing more to it. However, three days later, you passed the same row of street lights, and the phenomenon happens again. Even weirder, this time around, three successive lamps are affected, each one suddenly turning off as you approach, only to switch on again as soon as you step away.

What just happened? Was this another random coincidence you should dismiss? Or did you somehow influence the street lights with a hidden energy or power you didn’t know you had?

Many people have personally experienced – or at the very least, witnessed – a streetlight suddenly turning off as someone passes under it. While some may think that this is mere chance, there are also others that suggest this to be an unknown phenomenon caused by a few individuals who supposedly possess an incomprehensible ability to influence electrical devices. Over the years, more and more people have become more open with sharing their unusual experiences involving street lamps, and this phenomenon came to be known as “Street Light Interference” or SLI.


Street Light on road

“Street Light Interference” is a term coined by paranormal scholar and author Hilary Evans to denote the claimed ability of individuals to turn street lights or outside security building lights on or off when passing near them. Experience of this nature are quite common, with many people all over the world claiming that they involuntarily and usually spontaneously cause street lamps to go out. Typically, “the effect is intermittent, infrequent and is without an immediately discernable sequence of cause and effect.”

Although there are many personal anecdotes involving SLI experiences, the circumstances of each case are not always the same as with other instances. Some people report that they have only encountered switching off a single street light close by, while others claim to have influenced as many as a row of street lights in a single instance. There also those that possess the capacity to randomly affect only specific street lights, which makes it difficult to discern a testable pattern in studying SLI. Moreover, though the majority of SLI cases happen while walking, others say the phenomenon also occurs for them while they ride on bicycles, motorbikes, or even the bus.

However, the SLI phenomenon is not limited to streetlights alone. There are also reports of people who supposedly can spontaneously and intermittently affect other electronic devices, which varies from battery-operated wristwatches to railroad crossing to aircraft navigation equipment. Some people also claim to affect volume levels on TVs, radios, and music players, and cause credit cards and other magnetically encoded cards to get damaged and erased while in their possession. There are also those who often experience problems with compasses, causing them to stop or malfunction.

People who supposedly experience the SLI phenomenon are referred to as “SLIders.” Many “SLIders” suffer from a lack of validation for their skeptical family members and friends unless the time comes that they witness the repeated occurrences firsthand. Without sufficient explanation for the phenomenon they experience and with no one to turn to confirm them, SLIders are mostly left with their own devices in imagining and speculating regarding the nature of their supposed power to influence street lamps and other items and devices.


In a modern world where empirical research decides the validity of a theory or a hypothesis, any attempt in determining the main cause of the Street Light Interference phenomenon without thorough scientific investigation is dismissed as mere speculation and intensely rejected by the academic community. This is where the problem with studying SLI arises. As with other reported psychic or paranormal phenomena, SLI is very difficult – if not impossible – to reproduce in a laboratory setting. They seem to occur spontaneously and sporadically without the deliberate intention of the SLIder.

However, there are some informal tests that have been conducted involving this phenomenon, and some of the data gathered in some research and studies are based heavily or solely on the personal anecdotes and subjective reports of the people who claim to have witnessed or experienced SLI for themselves. Even then, these tests and studies have shown that SLIders are usually unable to recreate the SLI effect on demand.

Prior to his death in 2011, the British paranormal scholar Hilary Evans was the foremost authority on SLI. Aside from being a pictorial archivist and authoring numerous books on the Fortean, Evans also helped found the Association for the Scientific Study of Anomalous Phenomena or ASSAP in 1981. And after receiving numerous reports from different people claiming that street lights respond to their presence in an inexplicable manner, Evans decided to uncover the truth behind the mystery. He collected hundreds of accounts of SLI through his research which he referred to as Street Lamp Interference Data Exchange or SLIDE. The culmination of this research was the publication of his final book titled, “SLIDERS: The Enigma Street Light Interference.”


According to Evans, it is theoretically possible that every person who claims to have experienced SLI could be lying. However, since the majority of SLIders have “no ostensible motivation apart from a natural and commendable desire to resolve” this mystery, we can probably set aside deliberate deceit for the time being. And so, based on various research, studies and assumptions from experts that are supportive or skeptical about the validity of the Street Light Interference phenomenon, possible explanations for witness claims of SLI can be grouped into three broad categories –  psychological, paranormal, and mechanical.


In his book about Street Light Interference, Evans raised this primary question: “does SLI occur at all, or are the alleged witnesses deluding themselves?” According to Evans, a decisive answer to this question cannot be produced until the SLI phenomenon is scientifically tested. However, he also mentioned the possibility that SLI could be a shared delusion, much like the widespread delusion that has taken place in the past – such as the witchcraft mania that took place in the 16th and 17th centuries – and even in our more enlightened era – such as the on-going alien abduction mania. However, Evans also noted that SLI does not have the same psychological pay-off as witchcraft or abductions. Those who seek to enhance their special gift of influencing street lamps will not find much to flatter themselves with achieving such a feat. In short, while its possibility cannot be disregarded, it seems highly unlikely that all SLI experiences are delusions.

There are also those that suggest that that the SLI phenomenon might be attributed to people’s tendency to see patterns in “random noise.” Because it is unusual for a light to turn itself on or off when you walk past it, it catches your attention when it does happen. And when it occurs several times consecutively, people have the tendency to think that there is some kind of mechanism at work that makes it possible. And so, some argue that SLI can trace its roots in the power of suggestion, which requires a mix of different factors to work. As such, SLI could be brought about by the normal behavior of bulbs getting older, the witness’s observer bias, and some other important factor that is unknown to the person which would help in making sense of the situation.


Street Light Interference as a paranormal phenomenon is considered by skeptics to be the least likely possibility. By “paranormal,” we are pertaining to what occurs outside the conventionally recognized “normal” scientific parameters. It doesn’t have to mean that a supernatural force or an occult process is involved. If SLI really does occur as SLIders claim, then this phenomenon cannot be confined to the parameters of conventional science. Until now, there is no scientific recognition that the human mind can cause physical effects at a distance, which is what SLIders allege to be the case in SLI. However, the problem with SLI being a paranormal phenomenon is that it will be difficult to conduct experiments to test SLI since the phenomenon happens only at random and it is not produced by the person willing for it to happen.

There are also those who believe that what is causing street lamps to turn off or on could be some kind of “energy” that is emitted by the human body. SLIders report that the instances they spontaneously influence street lamps usually occur while they are tired, stressed, furious, or sad. Others, on the other hand, believe that street lamps are affected by some kind of static electricity that is produced by the body. There are also speculations that SLI might have something to do with the electrical impulses of the brain. At present, these electrical impulses are known to only have an effect within the body of an individual, but if it could somehow have an effect outside the body, then it could be the unconventional remote control that turns street lights off and on for these SLI eyewitnesses.


According to Evans, “The fact that a mechanical device is involved logically suggests that a mechanical explanation should be looked for.” This is precisely why some skeptics suggest that SLI occurs as a consequence of lights nearing the end of their life. Typical modern street lamps are of the low-pressure sodium-vapor variety, which emits red glow at startup and turn into a steady monochrome yellow once they’re fully operating. The lamps automatically switch on at sundown through the activation of a light-sensitive cell or a photocell. When sunlight returns at dawn, the photocell is triggered again, switching the lamps off.

These bulbs take three to four minutes to light up and have a lifespan of 8,000 hours or approximately two years. When a bulb reaches the end of its life, it manifests a behavior that could explain the SLI phenomenon. This behavior is called ���cycling,” which entails street lamps turning on and off every few minutes until the time comes that a technician comes along to replace the bulb. It is also possible that the bulb becomes slightly dislodged from its socket. If that is the case, even a minor vibration – such as that caused by a passing car, bike, or person – is enough to make the lamp blink for a brief moment.

The Street Light Interference is a phenomenon that remains to be a genuine and fascinating mystery to those who believe it, and to those who are open to reserve judgment on it until such a time comes that sufficient empirical evidence is presented that completely disproves it or verifies it. Should it be proven true later on, SLI carries profound and exciting implications for science as well as for our knowledge about human potential.

But speculations aside, we also must not lose sight of the fact that at least some, if not all, incidents of SLI can be attributed to entirely mundane causes. It could simply be a natural event that could be explained by logical reasons, but we are unable to conclude as such because of insufficiency in tangible or verifiable evidence and the influence of psychological factors.



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