Sibling Rivalry > Readers' Letters - 2
[Letters in Spanish]

Sibling Rivalry - Is it really that important? - News reporter's questions.

Are there documented cases of the psychological effects of birth spacing?

Does sibling rivalry in infancy promote later success in life?

Sibling Rivalry - Is it really that important? - News reporter's questions.

From: "Brooks, Khristopher" <>
Subject: Sibling Rivalry - News Reporter's Questions.
Date: Tue, 7 Feb 2006 10:43:10 -0500

Hello Dr. Boyle,

My name is Khristopher J. Brooks and I'm a reporter for the Mount Pleasant Morning Sun in Mount Pleasant, Mich. I'm working on a story about sibling rivalry and I just read your essay. I was hoping I could ask you some more in-depth questions about this if you had time. Believe me, it won't take long, but you'd be helping me a lot with my story. Here they are:

#1) At it's worst, what can sibling rivalry turn into?

#2) I just want to confirm that you suggest not having children back-to-back because they may have the same attention needs.

#3) Does money sometimes become the object of sibling competition?

#4) Does it frequently carry onto adulthood?

#5) Is either gender more prone to verbal or physical abuse of their sibling?

Those are all my questions. Thanks again Dr. Boyle. Hope to hear from you soon.

From: "William Boyle"
To: "Brooks, Khristopher" <>
Subject: Re: Sibling Rivalry -News Reporter's Questions
Date: Thu, 09 Feb 2006 12:07:16 -0500

Hello Mr. Brooks:

Thank you for your message.

Before I answer your questions, I'd like to note that what I am pointing out with my essay (my "thesis" if you like) is that, just as mother-love is the archetype for all human love and friendship, sibling rivalry is the archetype of all human rivalries, enmities, and hate.

Can this situation be handled? The answer is a definite yes. As an example, look in the Bible. In the older books of the Old Testament of the Bible there are many stories of sibling rivalry, e.g., Cain and Abel, Isaac and Ishmael, Jacob and Esau, Joseph and his brothers, and so on. - In the newer books of the Old Testament, or in the New Testament, there are no stories of sibling rivalry - So, the Jewish people learned their lesson! (However, looking at last two thousand years of history, it would seem that the Christian peoples forgot theirs).

And, in many families sibling rivalry is, at most, a mild annoyance or something to joke about - these are the families that have not lost the basic child-rearing techniques of how to defuse or handle sibling rivalry situations before they get out of hand - For them, it's just "the way things are done." For children that have grown up in these families it may be quite difficult to imagine how sibling rivalry may get to be a serious situation, or why anyone in their right mind would possibly allow such a thing to happen. On the other hand, in families that have forgotten this information, rivalry in various degrees among the siblings is just one among many of the symptoms of their dysfunctionality.

Now, my answers to your questions:

>>#1) At it's worst, what can sibling rivalry turn into?

It can turn into lifelong enmity and bickering (see, e.g., many of the entries in my Guestbook) or even murder (e.g., Cain and Abel) - See also many of the sibling rivalry case stories in Frank Sulloway's 1996 in-depth study, "Born to Rebel".

>> #2) I just want to confirm that you suggest not having children back-to-back because they may have the same attention needs.

This is not something I suggest; it just seems like "common sense" - Note that even ancient Jewish law permitted an abortion if the mother already had a child that was less than two years old.

>> #3) Does money sometimes become the object of sibling competition?

Yes. (See some of the entries in my Guestbook).

>> #4) Does it frequently carry onto adulthood?

Yes. (Again, see my Reader's Letters, and many of the entries in my Guestbook).

>> #5) Is either gender more prone to verbal or physical abuse of their sibling?

In the early stages, it might seem that boys might be more physical, and girls more verbal, although this may be a cultural thing. However, in later stages and adulthood both sexes develop into all kinds of devastating "psychological games" (See, e.g., Eric Berne's "Games People Play" - See also the recent article on Sibling Violence by Katy Butler and the Sewell report on Family Violence.)

I hope this helps.

With my best wishes,

William Antonio Boyle, Ph.D.

"Scientia potestas est." ("Knowledge is power.")
-Ancient Roman proverb

"Shared knowledge is the power to shape our world."

"No power is unlimited."

"The most complex structure in the known universe is each human mind."

Are there documented cases of the psychological effects of birth spacing?

Date: Tue, 4 Jul 2000 10:25:04 EDT
From: S.L.
To: William Boyle
Subject: Psychological effects of birth spacing

Dear William,
       I am a Drama Therapist, writing an article for The Arts in Psychotherapy Journal in which they are doing an issue on female artists who demonstrate how their psychoabiographical history informed their art and later professional therapeutic work. In my article I made reference to my older sister (only 2 years older) who actually resented my presence.
       She was an introverted personality having to deal with me as quite an extroverted "performer" etc. The journal's editors are asking me to cite reference(s) that reenforce my statement that at least 3 years should exist between siblings for more healthy relationships. Your article (on the internet) reflects that statement but you have no references either to studies that sustantiate your statement. Do you know of any?  I enjoyed your article very much and it mirrors my own views. If you can help me on even one academic reference to this point I would appreciate it.

                                     Thank you,
                                     MA, RDT/BCT

Date: Wed, 19 Jul 2000 22:22:27 -0400 (EDT)
From: William Boyle
To: S.L.
Re: Psychological effects of birth spacing

Dear S.L.:

Thank you for your message.

As you have noticed, there doesn't seem to be much in the academic literature on the psychological effects of birth spacing (more on this below).  The only academic journal reference I have been able to find on this topic is:

Tine Westergaard et al., "Exposure to Prenatal and Childhood Infections and the Risk of Schizophrenia," Archives of General Psychiatry, Vol. 56 No. 11, November 1999.

You can find an interesting review of this article in:

An excerpt:

"No association was found between birth order and schizophrenia risk. Short intervals (less than two years) between the birth of the person with schizophrenia and the birth of the nearest oldest or youngest sibling also correlated to an increased risk of schizophrenia. More than 10% of the cases of schizophrenia came from large families or those with close spacing between siblings."

Most references on birth or sibling spacing focus on the medical or physical health benefits, e.g.,

The Jewish law permitting an abortion in the case that the mother already had a child less than two years of age (which I mention in my web essay) is again based on the physical health benefits to the mother and children - see:

-David M. Feldman, 1998.
Birth Control in Jewish Law: Marital Relations, Contraception, and Abortion as Set Forth in the Classic Texts of Jewish Law.
Jason Aronson Publishers.

This emphasis on the medical or physical health benefits of birth or sibling spacing may in part be due to the relative ease in obtaining medical data (e.g., on morbidity and mortality), compared to the difficulty in obtaining unequivocal or unconfounded psychological measurements.

I should also state that what I believe are the prime predictors for healthy sibling relationships are the parents' knowledge of basic parenting skills, their desire to apply these knowledge and skills, and that they have the time and opportunity to apply them with their children - and not birth spacing or sibling gender or temperament.  It is when the parents' knowledge, skills, desire or opportunity are lacking that these other factors become increasingly important.

That is, you CAN have healthy sibling relationships between brothers and/or sisters that are less than three years' difference in age, but I would consider that the result of a virtuoso performance in parenting (and/or of the parents' extraordinary luck in the mellowness of their children's temperaments!) - on the other hand, I think that most parents would have a less strenuous time obtaining these happy results by adequately spacing the births of their children.

Part of my web essay is an attempt to derive the reasons for this from first principles.

Additionally, the fact that there do not appear to be documented cases of the negative psychological effects of insufficient spacing between the births of siblings does not necessarily mean that such negative effects do not exist - it simply means just that:  That such effects have not (yet) been reported in the academic literature; i.e., in this case the absence of evidence is not evidence of absence - What you mention of your own family history with your sister is a case in point.

I should also mention that there appears to be plenty of empirical evidence that many parents intuitively prefer to space the birth of their children by some two to three years, e.g.,,37922.asp

And, as the data apparently does not yet exist in the academic literature, perhaps research programs should be proposed to investigate topics such as, (a) the psychological effects of birth spacing (e.g., on sibling relationships), preferably taking into account the parents' knowledge of basic parenting skills, and their desire and opportunity to apply these knowledge and skills with their children, and, (b) the reasons why parents prefer specific birth spacing intervals (e.g., medical, psychological, financial, professional career, etc.), again profiling these parents as to their knowledge of parenting skills, their desire and opportunity to apply these skills, as well as on their socioeconomic status, educational level, and so on.

I hope this helps.

With best regards,

William Antonio Boyle, Ph.D.

Does sibling rivalry in infancy promote later success in life?

Date: Sat, 25 Mar 2000 22:02:09 +0800
From: S.W., Singapore

1) Is sibling rivalry a way to succeed in life??

2) The constant competence with each other leads you to success?

3) Do the successful people in real life quarrel with their siblings to succeed?

Date: Fri, 31 Mar 2000 09:04:40 -0500 (EST)
From: William Boyle
To: S.W., Singapore

Dear Ms. S.W.:

Thank you for your very pertinent questions.

To begin with, I think that some degree of sibling rivalry is unavoidable, even in the most cooperative and loving of families - and that it would be hard to say that the "rivalry" had no part in the later success in life of these families' siblings.  However, in these families ALL the siblings would tend to succeed, and their success would probably be more due to each of the sibling's self-confidence and mutual assistance than to their rivalry.

What I decry is unchecked sibling rivalry, of the type which creates feelings of rage and hate, and motivates acts of outright cruelty.  In these family situations, ONE of the siblings tends to succeed, at the expense of his or her siblings' emotional well-being.

This situation is analogous to that of the "Prisoners' Dilemma" in classical game theory (see, e.g., W.J. Baumol, 1972, "Economic Theory and Operations Analysis" Prentice-Hall - and also below) in which the overall total benefit for ALL the prisoners is maximized if the prisoners cooperate, but that the benefit for only ONE of the prisoners is maximized if he or she decides to compete against the others.

So, yes, I am saying that unchecked sibling rivalry would tend to produce "successful" people - in the sense that predatory, manipulative, and abusive people can be "successful" - But, is this "success" worth the cost to his or her siblings, and later to the community?

The human quandary is that, in a sense, each one of us is a "prisoner" for a rather extended amount of time in our particular early family environment, but that the subtleties of the costs and benefits of the "Prisoners' Dilemma" situation would NOT tend to occur naturally to a very young child - which I think is an important point of the Cain and Abel story in the Bible:  The development of cooperative attitudes was a major step in early human social evolution - but this type of attitudes can only be transmitted to the new generations by adults who are aware of the extraordinary value and the importance of the transmittal of these learned traits (Of course, this does NOT mean that children should be taught to cooperate with just "anybody" - Any parent would be quite remiss if he or she did not teach his or her children that there are some VERY nasty people - as well as many others with various degrees of nastiness - out there!).

What this means is that only well-informed and prepared parents can avoid the creation of other Cains within their families.  This in turn implies that families of too young parents, of single parents, and of parents who cannot spend sufficient time with their children (say, because of work obligations) would tend to produce these predatory and abusive "successful" individuals.  And, of course, families with abusive parents will also tend to produce abusive children.

We can also extend the "Prisoners' Dilemma" analogy to the hierarchy of different communities to which each one of us belongs.

I hope this answers your questions.  Let me know if I can be of further assistance.

With best regards,

William Antonio Boyle, Ph.D.

NB:  Some links on the "Prisoners' Dilemma." (Scroll down in the page).

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