May 22, 2013 I Louis Proud

Streetlamp Interference: A Modern-day Paranormal Mystery

Let’s say there’s a row of street lamps you pass every day while going to and from work. They are, being typical, modern street lamps, of the low-pressure sodium-vapor variety, emitting a red glow at start up and, once they’re operating fully, a steady monochrome yellow. The lamps automatically switch on at sundown, via the activation of a light-sensitive cell, or photocell. The cell is triggered again when sunlight returns at dawn, switching the lamps off. Generally, rather than each lamp having its own photocell, a single photocell is used to control a whole group of street lamps.

You’re returning home from work on what has so far been a completely typical evening, the street lamps illuminating your way as you stroll down the footpath. No one else is around. Oddly, the street lamp nearest you suddenly blinks out, turning on again as soon as you’ve passed it. A level-headed person, you attribute the event to coincidence and think no more of it. Three evenings later, however, while passing the same row of lamps, the phenomenon occurs again. On this occasion, three successive lamps are affected, each one blinking out as you approach, only to suddenly blink on again the moment you step away.


What on earth just happened? Did you influence the lamps with the power of your mind? Or is there a mundane explanation for these events?

Known as street lamp Interference (SLI), experiences of this nature are common, with people in many different parts of the world claiming “that they involuntarily, and usually spontaneously, cause street lamps to go out. Generally the effect is intermittent, infrequent and without an immediately discernable sequence of cause and effect.”1

These are the words of the British paranormal scholar Hilary Evans, who, prior to his death in 2011, was the foremost authority on SLI. (“SLIder” is the term he coined to refer to someone who reports a SLI experience.) In addition to being a pictorial archivist and author of numerous books on the Fortean, he helped found, in 1981, the Association for the Scientific Study of Anomalous Phenomena (ASSAP). After receiving numerous reports from people claiming that street lamps respond to their presence in an inexplicable fashion, Evans decided to take on the mystery, collecting hundreds of accounts of SLI through his Street Lamp Interference Data Exchange (SLIDE). The culmination of this research – what turned out to be his final book – is the brief yet highly impressive SLIDERS: The Enigma of Street Light Interference (2010). “SLI… can reasonably be regarded as a phenomenon in its own right,” he argued.2 


Frankly, when I first heard of SLI I considered it largely insignificant and boring, regardless of whether or not the phenomenon had a paranormal basis. I hastily concluded that most, if not all, SLI experiences could be accounted for as a result of people perceiving connections that have no basis in reality. For, as everybody knows, street lamps can and do malfunction from time to time, and people are bound to walk past them at the moment these malfunctions occur. After taking a deeper look at the phenomenon, however, I came to the unavoidable conclusion that we’re dealing with a genuine mystery – and, what’s more, an important and fascinating one. I agree with Evans when he says: “If true… claims [of SLI] carry profound and exciting implications for science and for our knowledge of human potential.”3

It’s time we examined some of those claims. Richard M, a professional magician in his thirties who lives in London, England, recalls the moment he became aware of his SLI ability. A teenager at the time, he was taking his dog for a walk when he noticed “that lights were going out when we walked under them and then flickering back on when we had passed.” He continues:

“It didn’t frighten me but I became conscious of it. I remember walking under them trying to make them go out but I couldn’t. The moment I stopped willing it to happen, it would start again – like someone catching me out. I sort of anticipated it for a while and didn’t really tell anyone about it. A few years ago, I noticed it happening again – the first time for a long time. Again, I was with my dog and this time we turned out a number of lights in a car park across the road. I told a close friend when I got home and he came out to watch from the other side of the road. As we walked around the park, they all went out as we passed under them, and then came back on when we had moved away… I seem to recall that both periods coincided with stress, some of it quite intense.4



If SLI involves psychokinesis – or some other form of psi – it figures that the ability would be more inclined to manifest while one is in an abnormal mood or state of consciousness. For, as shown by experiments in parapsychology, our everyday state of consciousness is virtually useless when it comes to psychic functioning. How interesting, then, that the two SLI experiences described by Richard occurred while he was stressed. That a stressed or aroused state of mind encourages SLI ability is suggested by the testimony of a man from Yorkshire, England, referred to as Dan C.

It was early one morning in 1991, when he was nineteen, that Dan’s history of SLI began. He was heading home from his girlfriend’s house, where the two of them had engaged in a steamy “smooching session,” when a street lamp went out as he approached it. At first he attributed the incident to a “dodgy bulb.” However, the lamp did the same thing the following night. When the incident happened a third time, he “started to think something was up.” Further strange incidents with the street lamp followed. Explains Dan: “Over the months, as I returned home from my girlfriend’s house, the light would always do the opposite as to its original state, i.e. if it was off it would turn on and vice versa. After I’d passed the light-post, it would usually revert to its original state…”5

As was found to be the case for Richard, Dan discovered that the phenomenon behaved according to its own set of rules, largely resisting his attempts to control it. On one occasion, for example, keen to demonstrate his SLI ability to doubting friends, he made them watch while he approached the street lamp, only to make himself look a fool by failing to duplicate the effect. A number of SLI experiences later, involving not just the one street lamp but several different lamps, Dan became aware of a pattern: the phenomenon generally coincided with his being in a particular state of mind. He describes this as “quite tired, on edge, nervous of my surroundings… and I reckon my adrenaline levels must have been up.” He concludes: “This sort of explains why I couldn’t ‘perform’ in front of my friends, having been in a relaxed situation. I have since shut my friends up as I have shown my ability on more than one occasion.”6

poltergiestThere is clearly a connection between sex and SLI. This connection deepens when examined in light of William G. Roll’s recurrent spontaneous psychokinesis (RSPK) interpretation of poltergeist disturbances. According to the RSPK model, these amazing demonstrations of mind-over-matter – of objects flying around houses and electrical equipment going haywire – occur as a result of sexual and emotional tension on the part of the “focus,” who more often than not is a troubled teenager undergoing puberty. Are the mechanisms at work in poltergeist disturbances the same as those involved in SLI?

That the state of arousal produced by sexual activity plays a role in SLI is nowhere more evident than in the case of Bob Lovely, from Montana, USA. Bob says his SLI ability became especially apparent when, at one point in his life, he was dating a woman who lived across the other side of town from him, to whom he paid frequent evening visits. It was while making these nightly trips that Bob occasionally saw rows of street lamps switch off as he passed them in his car, so that “each lamp I passed would go out as I was passing it.” Most interesting of all, however, is that the phenomenon always occurred on those evenings when he and his girlfriend had had intercourse. “On other evenings some lamps would go out but not like on the ones when our passions had been aroused.”7

Whereas some SLIders say they affect only street lamps, other say their ability extends to a whole range of electrical devices, from battery-operated wrist watches to railroad crossings to aircraft navigation equipment. Diana B, an office worker from Texas, USA, belongs to the latter category. Not only do street lamps dim and go out when she approaches them at night, sometimes they also turn on when she approaches them during the day. Regular light bulbs and fluorescent lights also behave oddly in her presence, such as when she goes to a restaurant or enters the home of a friend. There have been occasions, too, when automatic garage doors have suddenly gone haywire on her, opening and closing quickly “in a crazy way.”

According to Diana, her ability to affect electrical devices becomes heightened whenever she’s in a state of excitement or high energy. During these times, she can hold a compass in her hands and the needle will start to spin wildly, coming to a rest the moment she puts the compass down. Handheld tape recorders pose a special problem for Diana, either refusing to record when she wants them to or breaking down altogether. “I went through about 10 of them over a period of a couple of months,” she says. “Once it was so bad it even wiped out what was on the tape.”8


Interestingly, countless instances of malfunctioning electrical equipment, involving recording devices especially, have been observed in relation to psychics like Uri Geller and Matthew Manning, as well as in connection with poltergeist disturbances, UFO sightings and even crop circles. Who isn’t familiar with the scenario whereby an enthusiastic investigator attempts to record some form of paranormal activity on film or cassette, only to find that his equipment has suddenly and inexplicably broken down, or, more frustrating still, that the tape came out blank? Much to the gratification of skeptics – who fail to comprehend that paranormal events are, by their very nature, as slippers as subatomic particles, resisting all attempts to be pinned down – such occurrences are a matter of course.


In terms of what’s known about the human body by contemporary, orthodox science, Diana’s strange talent shouldn’t exist, and therefore she must be either lying or deluded. But if such is the case, why have so many others come forward with similar claims, most of them perfectly normal human beings? Many of those who contacted Evans to inform him of their SLI experiences had never heard of the phenomenon until coming across his research, previously considering their ability unique or doubting their own sanity. To quote one SLIder: “I couldn’t believe this was a phenomenon that others shared with me. I just thought I was nuts…”9

There are indications that SLI has a physical, measurable component, and that even the run-of-the-mill physicist or biologist would be able to make some headway into penetrating the mystery. For instance, some SLIders, including Diana, have a tendency to accumulate (or perhaps generate within the body itself) a high static charge. She explains: “I… can get very charged with static electricity, so much so that sparks actually fly around me and if anyone else is close by the sparks will connect with them.” Similar comments from other SLIders include, “I build up static electricity like crazy,” and “I seem to get more static shocks than other people.”10

chiOf course, not all SLIders have issues with static electricity, and while it’s true that someone with a high static charge has the potential to interfere with electrical equipment, they cannot do so from a distance; only by means of contact. That a statically charged person would be able to influence a street lamp mounted high above them is therefore extremely unlikely. And let us not forget that some incidents of SLI occur while the individual is seated in their car, a car being a crude form of Faraday cage, blocking static and non-static electric fields. One needn’t be a scientist to realize that the phenomenon is hard to account for in terms of electromagnetism alone, and must therefore involve some other form of energy – perhaps what the Taoists call “chi,” or what Wilhelm Reich dubbed “orgone.”

Speculation aside, we mustn’t lose sight of the fact that at least some incidents of SLI can be attributed to entirely mundane causes, a combination of mechanical and psychological factors. Skeptics of SLI are keen to point out that when the bulbs in sodium-vapor street lamps reach the end of their life they undergo a phenomenon known as “cycling,” switching on and off every few minutes until a technician comes along and replaces the bulb. It can also happen that the bulb becomes slightly dislodged from its socket, so that even a minor vibration – such as that caused by a passing car or a person – is enough to make the lamp blink out for a moment.

Richard Wiseman, a professor of psychology at the University of Hertfordshire, England, was asked to give his opinion on SLI for the Daily Mail newspaper. A dedicated member of the Committee for Skeptical Inquiry (CSI), he cited “observer bias” as the culprit, stating that “street lamps are going on and off all the time… People only have to walk under a couple of lamps going off to think that they might be the cause.”11

Had Wiseman looked at the evidence properly, he’d realize that observer bias is not the whole story. When we eliminate this and other obvious explanations for SLI, we’re left with an exciting possibility: that the phenomenon is due to psychokinesis. Evans discusses this notion in his book, suggesting that some kind of “force” is at work when a SLIder influences a street lamp. He explains that street lamps are designed in such a way as to be protected from operating at too high a voltage, whereby a cut off switch is triggered the moment the voltage reaches a certain level. The lamp will remain off until reactivated the following evening. A similar scenario occurs when the voltage drops below a certain level. Evans puts forward an intriguing theory: that the “force” at work in SLI operates by affecting the voltage of the current, most likely by causing a surge in voltage that triggers the lamp’s internal cut off switch.

“To perform this feat,” he speculates, “SLI would have to be an electro-dynamic force, somehow generated within or through the human biological system, and somehow externalised into the neighbouring environment, where it will act on any appliance which happens to be vulnerable.”12


  1. Hilary Evans, The SLI Effect: Street Lamp Interference – A Provisional Assessment, Association for the Scientific Study of Anomalous Phenomena, 1993.
  2. Hilary Evans, “SLIders: The Mystery of Street Lamp Interference,” Fortean Times, April 2011.
  3. Ibid.
  4. Ibid.
  5. Ibid.
  6. Ibid.
  7. Hilary Evans, The SLI Effect.
  8. Hilary Evans, “SLIders: The Mystery of Street Lamp Interference.”
  9. Hilary Evans, The SLI Effect.
  10. Ibid.
  11. David Derbyshire, “‘Electricity Woman with Amazing Powers’ Causes Lights to Flicker When She Gets Stressed,” Mail Online, 2 February 2008.
  12. Hilary Evans, The SLI Effect.

If you’ve undergone experiences similar to the ones described in this article, or have ever been targeted by lightning, the author would like to hear from you via louisproud(at)gmail(dot)com. 

This article appears in New Dawn Special Issue Vol 7 No 2 – Paranormal Realities & the Unexplained. Click here to obtain your copy.  

Louis Proud

Louis Proud who lives in Melbourne, Australia, is a writer and researcher specializing in paranormal and occult phenomena. His work has been published in Fate, Mysteries, New Dawn, Nexus and Paranormal magazines. His interests include film, radio-controlled models and anything to do with the mysterious and unexplained. His recently published book, Dark Intrusions: An Investigation into the Paranormal Nature of Sleep Paralysis Experiences, is available from Amazon in the USA and the UK. Louis Proud can be contacted at [email protected] Visit his blog:

Join MU Plus+ and get exclusive shows and extensions & much more! Subscribe Today!