The observer-expectancy effect

24th April 2023. Reading Time: 11 minutes General, Stuff paranormal investigators need to know. 2023 page views. 0 comments.

Otherwise known as the experimenter effect, this is a cognitive bias that can cause us to unknowingly manipulate or misinterpret the results of an experiment. Even the questions we ask or the way we guide subjects during a paranormal investigation can affect the outcome of the experiment.

Otherwise known as the experimenter effect, the observer-expectancy effect is a cognitive bias that can cause us to unknowingly manipulate or misinterpret the results of an experiment.  Even the questions we ask or the way we guide subjects during a paranormal investigation can affect the outcome.  

What is cognitive bias?

A cognitive bias is an error in the way that we think.  It means we are not necessarily thinking with a 'clear mind'.  Our experiences, our beliefs, and our intentions all influence the way we think, the way we make decisions, and the way we interpret our surroundings.  Just the fact that we believe in the paranormal makes us biased.  It means we are more prone to a 'self-fulfilling prophecy' where our brain is likely to interpret certain things to be paranormal when they are not.  We go in looking for the paranormal and our 'brain' makes us find it even if it is not really there.  On the other end, a full sceptic is also biased and will tend to look for a rational explanation discounting any sort of ambiguous event without even looking into the possibility it could be something we don't quite understand.  No one is immune, however, applying critical thinking and taking a moment to really think things through instead of reacting or responding rashly can make a huge difference. 

The experimenter effect

The observer-expectancy effect is also referred to as the experimenter effect and is quite often referenced when it comes to parapsychology studies, particularly those experiments that test ESP.  It is the idea that an experimenter can unknowingly manipulate the results of an experiment by using visual or auditory cues that can influence the results to skew towards their belief that ESP exists and the results of their experiment will prove it.  

JB Rhine Dice Trials (Source Foundation for Research on the Nature of Man)

Psychological research on the experimenter effect has shown higher scores with a warm than with a cold experimenter climate and with an experimenter who expects high rather than low scores. Eight experiments, comprising 12 series, tested for the experimenter effect in psi. Nine of the 12 series had significant results, all in the predicted direction. Six other experiments tested a related hypothesis: that psi experimenters would be self-consistent in obtaining results like their prior ones. Four of these had significant results, all in the predicted direction. 

Gertrude R. Schmeidler

Psi experiments have been under the microscope for decades.  From the Rhine Zener Card trials through to the Ganzfeld experiments, these sorts of studies have not been without heavy criticisms and for good reasons.  When the experimenters attempted to address the problems raised with their trials such as a sensory leak, fraud, and the notion of 'lucky chance', they made the necessary adjustments in the next set of trials, and their success rate was reduced.  Whenever there has been a successful study, it seems it has been difficult to replicate in the next round.  Parapsychology researchers argue that when you are dealing with ESP and PSI it is difficult to replicate due to their nature as it is a psychic phenomena for a reason.  The same could be said about paranormal phenomena.  It seems to be more spontaneous and I guess there is a reason it is called 'paranormal'.  It is because it is something that cannot yet be defined or properly tested.  Critics however believe that the reason these studies could not have the results replicated was because of the experimenter effect influencing the overall results.  When it comes to studies such as Zener Card trials, it is believed that while there was a benchmark of 25% to account for 'lucky guesses' that the element of chance was overlooked when a person scored higher results and was deemed as a success.  While there was a benchmark, of course, it is possible to score higher by sheer luck.  It is also felt that people may have known for example not to guess the same card several times in a row so would change their answers accordingly.  Their body language or even the way they ask a question can unknowingly change the answer a subject will give.  While these may seem like small details, they would ultimately have an effect on the overall percentage.  The experimenter in this case felt anything above the baseline was evidence of ESP because they believed it exists.  Another person analyzing the results would likely draw different conclusions, especially if they were a sceptic.  Their belief system is now influencing how they are interpreting the results to these trials.  This is just one example of how the experimenter effect can come into play.

Double-Blind experiments

It is thought that in order to try and make sure the experimenter effect is not in play would be to introduce what is called a double-blind experiment to properly test the subjects involved.

I propose the following procedure. Take a typical experiment that involves a test sample and a control, for example the comparison of an inhibited enzyme with an uninhibited control in a biochemical experiment. Then carry out the experiment both under open conditions, and also under blind conditions, in which the samples are labelled A and B. In student practical classes, for instance, half the class would do the experiment blind. The other half would know which sample is which, as usual.

If in such tests there are no significant experimenter effects, then for the first time there will be evidence to support the belief that blind techniques are unnecessary. On the other hand, significant differences between the results under open and blind conditions would reveal the existence of experimenter effects. Further research would then be needed to find out whether the experimenters' expectations were influencing experimental systems themselves, or merely the way that the data were recorded or selected.

Rupert Sheldrake

One of the ways that this was implemented in relation to parapsychology studies was a trial into 'gazing' and testing of psychic ability using two sets of groups as Sheldrake mentioned above in order to determine if the experimenter effect was a factor.

Each of the two authors recently attempted to replicate studies in which the "receivers" were asked to psychically detect the gaze directed at them by unseen "senders." R. W.'s studies failed to find any significant effects; M. S.'s study gave positive results. The authors then agreed to carry out the joint study described in this paper, in the hope of determining why they had originally obtained such different results. The experimental design was based on each author carrying out separate experiments, but running them in the same location, using the same equipment/procedures, and drawing participants from the same subject pool. The 32 experimental sessions were divided into two sets of randomly ordered trials. Half were "stare" trials during which the experimenter directed his/her attention toward the receiver; half were "non-stare" (control) trials during which the experimenter directed his/her attention away from the receiver. The receivers' electrodermal activity (EDA) was continuously recorded throughout each session. The EDA of R. W.'s receivers was not significantly different during stare and non-stare trials. By contrast, the EDA of M. S.'s receivers was significantly higher in stare than non-stare trials. The paper discusses the likelihood of different interpretations of this experiment

Experimenter effects and the remote detection of staring

Richard Wiseman, Marilyn Schlitz 1997

How could this apply during a paranormal investigation?

A lot of investigations these days tend to be led by a small group of individuals.  Whether it is for your own research or you are attending a public investigation, there is usually at least one person who is running the show.  We know that the type of people is investigating with will completely influence the outcome of the investigation.  

I feel like these two videos can really sum up this influence

Sceptics go ghost hunting for the first time

Superstitious People Go Ghost Hunting For The First Time

While the experimenter effect applies more to actual experiments, you can't help but see the connection with paranormal investigating.  That being said, however, a lot of people do attempt to conduct their own kind of experiments during an investigation.  In this case, they are not following the scientific method and more looking to have a form of a paranormal experience.  The way people use sensory deprivation is an example of this.  Often before leading a group through the experiment of the night, someone may tell you how you might feel.  Just the words a person uses to prepare you for the experiment can influence the outcome. It is likely your belief in the paranormal could influence this as well.

Critical Thinking

It has long been debated that critical thinking can help change the way a person perceives the paranormal.  There was a study conducted in 2005 to see how critical thinking affects people who believe in the paranormal and if their belief can be changed by critical thinking.

A study was conducted to assess the relationship between critical thinking and belief in the paranormal. 180 students from three departments (psychology, arts, computer science) completed one measure of reasoning, the Paranormal Belief Scale (Tobacyk & Milford, 1983), and a scale of paranormal experiences. Half of the subjects filled out the Cornell Critical Thinking Test (Ennis & Millmann, 1985) and the Watson–Glaser Critical Thinking Appraisal (Watson & Glaser, 2002), respectively. The results show no significant correlations between critical thinking and paranormal belief or experiences. Reasoning ability, however, had a significant effect on paranormal belief scores, but not on paranormal experiences. Subjects with lower reasoning ability scored higher on Traditional Paranormal Belief and New Age Philosophy than did subjects with higher reasoning abilities. Results suggest that those who have better reasoning abilities scrutinise to a greater extent whether their experiences are sufficient justification for belief in the reality of these phenomena.

Hergovich, Andreas & Arendasy, Martin. (2005). Critical thinking ability and belief in the paranormal. Personality and Individual Differences. 38. 1805-1812. 10.1016/j.paid.2004.11.008

The results themselves indicate that a person's reasoning abilities make a difference when it comes to changing a belief related to paranormal phenomena.  In a lot of ways, we try to reason with one another on social media.  Someone posts a photo asking for advice and someone offers an opinion.  The problem in these scenarios is usually two-fold.  The person asking for information usually already has their mind made up and they will be unwilling to listen to any explanation that doesn't fit the idea they already have in their head.  On the other end, people can sometimes be aggressive, condescending, and plain nasty when it comes to the delivery of their opinion.  When you approach someone by using passive-aggressive language, even if what you are saying makes sense and you have the facts to back it up, they are not going to listen to you because of the way you have delivered the information.  The key here is the information itself.

Our words have a lot of power.  They can influence a person.  They can educate a person.  They can anger a person.  They can change a person's mind.  How we deliver information can change the way a person behaves.  It can change the way a person investigates the paranormal.  It can change the way we interpret a situation.  I know I have spoken in the past at how much I was influenced in my early days of investigating when I was surrounded by more spiritual people.  I thought almost everything was paranormal.  I knew no different because I had no other point of reference other than those around me.  I can see very easily how people could be unknowingly manipulated or coached during certain trials, especially if it is an area like the paranormal where there is a large population of people who believe in it.    

In the end, knowledge is power.  By educating ourselves about possibilities we are already in a lot of ways prepping ourselves to think critically when on an investigation.  If you are looking at running some experiments, try the double-blind method.  Try not to 'prime' your subjects to expect certain things.  Ensure they are not influenced unknowingly by the tone in a person's voice or even visual cues.  As humans, one of our most powerful tools is the human mind.  It can also become our enemy when it comes to processing information.

Critical thinking can help us explain a lot of paranormal phenomena, but when applied using critical thinking, it can also make us rethink the way we explain these phenomena.  Maybe we are jumping to the 'that's not paranormal' conclusion too quickly.  Extraordinary claims require extraordinary proof.  Whether or not we have that proof we don't know, but the best way to help us find out is to educate ourselves with as much knowledge as possible.  You will be amazed at how much it changes your approach to paranormal investigating.  Knowledge doesn't 'ruin' the way you view the paranormal.  It changes it, and you will end up with even more questions than answers.  


Hergovich, Andreas & Arendasy, Martin. (2005). Critical thinking ability and belief in the paranormal. Personality and Individual Differences. 38. 1805-1812. 10.1016/j.paid.2004.11.008

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