is it scientifically possible for 2 people to have the same dream?

Hello and Good Evening Everyone

            Recently, a friend of mine and her mother had the same dream which involved an adventure filled with scenery, joy, and happiness.  Then, a catastrophe happens involving a family member.  I know how strange all of this must sound.  Personally, I find it hard to believe myself.  At any rate, is it scientifically possible for 2 people to have the same dream?  Or, is such a situation a very rare coincidence and nothing more?

             Any objective input offered to this question will be greatly appreciated.  I will look forward to everyone's shared thoughts to this rather intriguing occurance.

             Thank you

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How do you define "same"?

It is scientifically possible for 2 people to describe a dream in the same way.
Cornelia YoderArtistCommented:
It is neither real nor coincidence.  Most dreams are based off of something that happened during the day before the sleep.  

Common dreams such as you describe are often a result of a shared experience during the day, perhaps a conversation between your friend and her mother, or a discussion about a planned adventure, or about the family member, any things like that can become part of a later dream.

Then later on, describing the dream to each other takes on significance based on that previous shared waking experience, so each person's dream sounds to the other like the same one, even though it probably wasn't really all that similar.

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JohnBusiness Consultant (Owner)Commented:
No. Dreams come from an individual's thoughts, memories and experiences. No two individuals think exactly the same thoughts.

The best that could happen is two dreams might be similar.

ALL 7 billion people on the planet are unique with unique brains - No two alike.
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Very few things are impossible BUT
Dreams are caused by the brain moving saved memories around. (Boy, that is an oversimplification) but they are caused by actions in the brain. Two brains are highly unlikely to react exactly the same to events.
I suspect that the dreams were not the SAME, similar perhaps, but not exactly the same. I have a hard enough time remembering the general outline of my dreams let alone the exact details.
The people involved will have had similar experiences however, which might result in similar dreams
One thing interesting to note is that it's actually very likely that two people will have very similar dreams.
Let's make up some random numbers.

Let's say there are one billion basic possible dreams.
Let's say everyone is close to an average of four people (parents, spouse, close friend) and that there are about seven billion people in the world.

So 7,000,000,000*4/2 = 14,000,000,000 close relationships.
Let's say you remember an average of one dream per night.
So every year, there are about 365*14,000,000,000 = 5,110,000,000,000 (or about 5 trillion) pairs of dreams to compare.

This means that in the average year, there should be about 5000 pairs of people who are close together who share a dream some night. And that's without the shared memories, which would make the numbers a lot higher.

Coincidence? Sure. That's a good way to describe it.
Suppose your friend calls her mother and says, "I had this incredible dream last night."  And then her mother says, "I did too."

At this point, a scientist breaks in and says, "Stop.  Why don't you two write down all the details you can remember, and then we'll compare them."

Is that how it happened?  Or did  they take turns saying,
 "Exactly."   "Amazing."   and  "Me too."
Scott Fell, EE MVEDeveloper & EE ModeratorCommented:
A long time ago I was going to use random numbers to auto generate usernames.  Before I implemented I did some experimenting in Excel and found many collisions.  

The link and code below can be thought of as 2 people can have 1 of a million different dreams over 10,000 tries or 2 groups of 10,000 people that can each have 1 of a million different dreams.

I'm sure there is some formula for this but my last stats class was too long ago.  As you run this over and over there are about 100 collisions +/- 20.

I think as you read up on dreams, there really are not that many types of dreams.  But individual dreams that 2 people share to the exact detail will of course be a lower probability than something we can all relate to like forgetting to go to 8am stats class all semester until the very last day of finals.  Just about everybody I have talked to has had this type of dream.
<!DOCTYPE html>
<script src=""></script>
  <script src=""></script>
      //Compare to arrays with underscore.js
var list1 = [];
var list2 = [];

var match = [];
totMatch = 0;
for (i = 0; i < 10000; i++) {
for (i = 0; i < 10000; i++) {


var test = _.intersection(list1, list2);

function getRandomInt() {
    var min = 1;
    var max = 1000000;
    return Math.floor(Math.random() * (max - min)) + min;

  <meta charset="utf-8">
  <h2>Random Simulation</h2>
    <li>2 Groups of 10,000</li>
    <li>Each person can have 1 of a million possible outcomes</li>
  <div>Total Matches:
  <span id="match"></span>

Open in new window

Cornelia YoderArtistCommented:
In a word, NO, it's not possible.  Dreams are simply neurons in your brain firing during your sleep, and your brain neuron structure is not the same as someone else's.
Possible.  It's spelled 'occurrence' and dreams often contain stuff that's recently happened.  So, if 2 people have experienced the same stuff then they could dream about it.

Happened to myself and my dad years ago.  We even compared the situation and it was identical.
Scott Fell, EE MVEDeveloper & EE ModeratorCommented:
>Recently, a friend of mine and her mother had the same dream which involved an adventure filled with scenery, joy, and happiness.  Then, a catastrophe happens involving a family member


>Recently, a friend of mine and her mother had the a dream. The friend's dream was a roller coaster with uncle jim on july 4, 2014 where everybody was having a good time. Her mother's dream was about a florida vacation with the family in March 1973.  

The friends dream later on revealed that when they came back home their dad was in an auto accident and the mom's dream revealed her sister broke her leg.

If you feel that dreams are really symbolism for what is going on in your life, the example George has originally given is easy to compare.    If you break it down to a more exact interpretation, then yes, it will be harder to match and even prove.  But I wonder if you could convert the firing of neurons to some type of binary code, it may again be easy to match that code from within a large group of people as the code is no longer open to interpretation.

When you read up on randomness, it is by no means equates with being unique.
JohnBusiness Consultant (Owner)Commented:
From a scientific viewpoint no two people are alike and no one experience will be interpreted the same way by two people.

To the question asked initially, the answer is no.

Two people can and do have similar dreams. But that is different than what was asked.
GMartinAuthor Commented:
Hello and Good Afternoon Everyone,

              I am currently at work.  Once I get home this evening, I will provide clarification and proper closure to this question.  To be perfectly honest, the question has been answered.  At any rate, I will get back with everyone this evening.  

              Thanks so much for the feedback given because it was exactly what was needed.  By the way, the question is in fact a science question as opposed to a philosophical or religious question.  I will explain tonight when I can sit down and provide an explanation for my view regarding the correct categorization of my question.

Two issues: What is "scientifically"? And what is "same dream"?

As far as the state of 'Science' is today, the answer is a definite "No." But perhaps you have definitions that can lead to useful discussion.

GMartinAuthor Commented:
Hello and Good Evening Everyone

              Between having a couple of misspelled words in addition to a lack of clarity of the question itself, I can certainly understand why there might be some confusion surrounding this thread.  When the word "same" was used in this context, I was referring to my friend's dream having the same content as compared to her mother's dream.  I hope that makes sense because I am unsure how else to describe it.  After talking with her,  it was discovered that the dreams were not exactly the same.  I have to agree with the points outlined by aburr because both my friend and her mother have been sharing very similiar concerns and issues surrounding a sick family member.  

               Moving to the aspect of whether this is a science question or a philosopy/religion question, I am inclined to say this question falls within the realm of science because of the interconnections of psychology and neuroscience.  Let me take a moment to explain.  From a psychoanalytical perspective, much of the content of dreams comes from filtered information within consciousness being passed down to the subconscious level of the mind.  For instance, many social and family issues or concerns which are too painful to deal with at the conscious level often get filtered down to the subconsious which is only accessed through dream analysis.  This notion is perhaps best captured when one reviews the works of the iconic physician and scientist, Dr. Sigmund Freud.  In his approach to treating his patients who suffered from various forms of neurosis, he would have them record their dreams when they would wake.  Their dream log would be kept over a long period of time.  Then, the next part of psychoanalytic therapy would involve going back and looking at common patterns of the dreams in order to gain greater insights into the patients intrapsyche.  In other words, every element, object, color, etc. had great symbolic significance which could be used to gain insights into the patient's emotional state.  In other words, the dream analysis was used as an instrument or tool to help better understand why patients might suffer from anxiety, depression, etc.  Any branch of science, whether it be a biological science or a social science like psychology often imploy a methodology for gathering data to obtain a more objective picture of the issue or concern at hand.

               The notion this question falls within the realm of science is further substantiated by the feedback that John Hurst gave in his initial reply to this question.  His answer made a great deal of sense especially when he indicates that dreams come from memories, experiences, and thoughts stored within the brain.  Since everyone processes and stores information differently, then, naturally it is logical to conclude that no two people can have the exact same dreams because of the uniqueness of the brain structure and activitity.  But, how do we know the brain is unique for each individual?  We do because of science, not philosophy or religion.  

                With respect to closing remarks, I am not a debater or advocate on any particular issue.  My initial goal when asking this question was to obtain objective, informative, and insightful feedback from those who would choose to respond to it.  
The feedback given certainly did just that.  The goal of science is always in search of truth which is what I got from this post.  

                If there should be further comments or corrections on any of my views, please feel free to post them.  I always welcome logical viewpoints even if they might be different from that of my own.  It is all part of being open minded.

                 Thanks again for the feedback shared.  Once again, I apologize for the vagueness and confusion surrounding this question.  

GMartinAuthor Commented:
Hello and Good Evening Everyone

             Thanks so much for the shared input given to this question.  After talking with my friend, she did indicate having a conversation with her mother the day before the dreams happened regarding a sick family member.  It does make sense that the strong personal concerns shared and communicated between her and her mother during their waking hours or conscious state did pass over into their subconscious state which is the state as which dreams manifest themselves.  After they talked about it more, they did come to the conclusion their dreams were actually different in many ways which outweighed any similiarities.  

               Thanks again for helping all of us to make sense out of this situation.

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