Comparing Milgram’s Obedience and Zimbardo’s Prison Studies

This post corresponds to readings in my online textbook.on two classic social psychology studies:  Stanley Milgram’s Obedience to Authority studies and Phillip Zimbardo’s Stanford Prison Study. I wrote it to help my students better understand the similarities and differences between the two.


Original photo is here


Similarity #1. Participants in both studies had a difficult time ending their participation, and most continued all the way until the end. The reasons for this were similar in both studies.

  • By agreeing to take on the roles they had been assigned, it became very difficult for the participants to back out without breaking the implicit social rule I spoke of earlier.
  • The participants did not want to appear inconsistent by refusing to continue something they had already started.
  • The escalation in violence occurred relatively gradually, so that there was no obvious point at which they could say, “that is enough.”

Similarity #2. Both Milgram and Zimbardo stated reported the effects of personality differences were very limited. For Zimbardo, the only personality characteristic that seemed to have any effect was authoritarianism; and this characteristic was important only for prisoner behavior. Those prisoners who were high in authoritarianism were best able to handle the oppressive conditions in the prison and, thus, remained there the longest. At least four (and maybe five) of the initial group of nine prisoners, on the other hand, had to be released even before the study was ended because of severe stress caused by the conditions.

Based on results such as these, Zimbardo (1975) argued that personality differences were much less important than the social situation. In fact, Zimbardo went even farther than Milgram had by dismissing the importance of personality characteristics for most of our behaviors in everyday life:

Individual behavior is largely under the control of social forces and environmental contingencies rather than personality traits, character, will power or other empirically unvalidated constructs. Thus we create an illusion of freedom by attributing more internal control to ourselves, to the individual, than actually exists. We thus underestimate the power and pervasiveness of situational controls over behavior because: (a) they are often non-obvious and subtle, (b) we can often avoid entering situations where we might be so controlled, (c) we label as “weak” or “deviant” people in those situations who do behave differently from how we believe we would. (p. 115)

Many social psychologists took this extreme position during the 1970’s. In the next chapter (Note: this chapter does not yet appear on this site), I will discuss why they argued for this position and will try to show why it needs to be modified and softened somewhat. In fact, I would imagine that Zimbardo himself would no longer make such a strong claim, although he and many other social psychologists still give social forces a large share of the control over our behavior and mental events.


Original photo is here


Difference #1. A major difference between Zimbardo’s and Milgram’s studies is that, in the prison study, only one experimental manipulation was performed — being assigned to the role of prisoner or guard. This is a major limitation because we cannot know, as we did in the Milgram study, which factors in the situation were most important for the behaviors observed. There is no doubt that each participant’s self-definition as prisoner or guard was important, but it might have helped us to develop a deeper understanding of how such a self-definition can be maintained if Zimbardo and his colleagues had varied other factors in the situation. For example, would wearing normal clothes, which might have caused increased feelings of individuality, have resulted in decreased role-playing? Would a decrease in the reality of the simulation (perhaps by removing the bars on the doors, or having campus security “arrest” the prisoners) have done the same? It would have been very interesting, for example, if we had found that none of these factors were important — that, instead, it was simply the assigning of an arbitrary social role by an authority figure and the voluntary taking on of that role by the subject that was most important for his role-playing behavior. We probably never will be able to find out because, as I will discuss in the next section, it is unlikely that anything similar to this study could ever be performed today.

Difference #2. Milgram attempted to reduce the possibility of harming his participants as much as possible. For example, he debriefed theme as soon as the experimental session was over; and, if they demanded that the session end, he ended it. Because he believed that he had addressed many possible ethical concerns, he continued to perform experiments on obedience for several years.

Zimbardo, on the other hand, stopped his study because of ethical concerns. In fact, years later, he stated that the study was unethical as a whole. What do you think caused him to decide that the study was unethical? Probably the most important aspect of the study making it unethical was the psychological harm that was done to the prisoners. For example, most were extremely distressed by the punishments (e.g., loss of everyday privileges such as being able to go to the bathroom, eat, sleep, and so on) imposed by the guards.

Although some have argued that Milgram’s study also caused much psychological harm (e.g., Baumrind, 1965), the distress felt by the Teachers in that study was temporary (the procedure lasted only an hour), and Milgram showed that almost all had either positive or neutral feelings about the study afterwards.

Most of the participants in Zimbardo’s study, on the other hand, became very upset and, for some, this lasted for at least several months. They were brought back on several occasions after the end of the study to discuss their feelings and thoughts about the study. It’s evident from their statements that many or all of them were bothered very much by their own behavior and by the behavior of other participants.

Difference #3. Another ethical problem in Zimbardo’s study — one avoided by Milgram — was the taking on of a dual role. That is, he was both the “prison superintendent” and the principle researcher of the study. Taking on a dual role made it difficult for him to monitor the progress of the study and its effects on the participants objectively. He stopped the study only reluctantly when it was pointed out to him that the prisoners were suffering terribly. Milgram, on the other hand, was never present during the actual procedure itself, so he was able to remain more objective about any harm being done to his participants.


Baumrind, D. (1964). Some thoughts on ethics of research: After reading Milgram’s “Behavioral Study of Obedience.” American Psychologist, 19, 421-423. doi: 10.1037/h0040128
Retrieved November 24, 2011, from

Haney, C., Banks, W. C., & Zimbardo, P. G. (1973). Study of prisoners and guards in a simulated prison. Naval Research Reviews, 9, 1–17. Washington, DC: Office of Naval Research. Retrieved November 25, 2011, from

Milgram, S. (1974). Obedience to authority: An experimental view. New York: Harper & Row Publishing.

Zimbardo, P. G. (1975). On transforming experimental research into advocacy for social change. In M. Deutsch & H. Hornstein (Eds.), Applying Social Psychology: Implications For Research, Practice, and Training (pp. 33-66). Hillsdale, NJ: Lawrence Erlbaum


The “War on Masturbation” (Part 1)

Beginning in the late-nineteenth century and continuing well into the twentieth century, American medical doctors fought a war against an enemy they thought was the primary cause of most societal, mental, and bodily ills: masturbation. According to Hodges (2005),

American doctors, using the most modern “scientific” methods at their disposal, convinced themselves that masturbation was the underlying cause of nearly all social problems and diseases, ranging from rape, divorce, “pederasty,” poverty, and criminal activity, to paralysis, epilepsy, venereal disease, nervousness, heart disease, fever, tuberculosis, apoplexy, insanity, idiocy, and even death.” (p. 722)

Even after medical researchers such as Louis Pasteur and Robert Koch had provided convincing evidence in support of the germ theory of disease, which stated that microorganisms cause many diseases (see Germ Theory) masturbation still was thought to be an important cause of most disease, as well as serious societal and psychological problems. In fact, Hodges (2005) noted that “the medical war on masturbation reached its fever pitch in the 20th century in terms of the numbers of innocent young ‘patients’ forcibly subjected to compulsory and mutilating surgical ‘treatments’” (p. 722).

Simon Auguste David Tissot (1728-1787)

The story begins in the second half of the eighteenth century, after the publication in 1758 of L’Onanisme, Dissertation sur les Maladies Produites par la Masturbation. Its author, Simon Auguste David Tissot, was an esteemed physician and professor at the University of Lausanne in Switzerland.

His highly original argument was carefully constructed and supported by references to earlier authorities…. [H]is erudite book created the partly inaccurate impression that there existed a powerful consensus among the respectable and leading European doctors, in harmony with the views of classical authors, that masturbation was a dangerous and gathering threat to human welfare. (Hodges, 2005, p. 723)


Tissot argued that masturbation was dangerous because physical and mental health required the reabsorption of retained semen. It was the loss of semen that was the root cause of the physical and mental problems caused by masturbation.

Although virtually all medical professionals would have been able to read Tissot’s book in its original Latin version, his arguments would have reached a much wider audience after it was translated into English in 1832.

Benjamin Rush (1745–1813)

Even before its translation into English, many American physicians became aware of Tissot’s book either because they had studied in France, where the book was well known, or had learned of it from those who had. For example, the legendary American physician, Benjamin Rush, fully accepted Tissot’s claims. In 1812, he argued that an excessive “sexual appetite”

becomes a disease both of the body and mind. When restrained, it produces tremors, a flushing of the face, sighing, nocturnal pollutions [wet dreams], hysteria, hypochondriasis, and in women the furor uterines. When indulged in an undue or a promiscuous intercourse with the female sex, or in onanism, it produces seminal weakness [involuntary discharge of semen], impotence, dysury [painful or difficult urination], tabes dorsalis [impairments in movement and sensory disturbances], pulmonary consumption [tuberculosis], dyspepsia [indigestion], dimness of sight [poor vision], vertigo [dizziness], epilepsy, hypochondriasis, loss of memory, manalgia [mental or physical inactivity, lethargy], fatuity [feeblemindedness], and death. (quoted in Hodges, 2005, p. 723).

Some of these symptoms are caused by sexually transmitted diseases, such as syphilis. According to Hodges (2005),, attributing them also to masturbation suggests that “doctors at this time were unable or unwilling to make a distinction between sexual activity and the morbidity caused by diseases … contracted during sexual activity with infected partners” (p. 723).

Benjamin_RushBenjamin Rush

Rush’s prominence in the medical community helped to firmly establish the belief among most physicians that masturbation was a dangerous activity that must be aggressively treated.

Sylvester Graham (1794–1851)

xThe medical and scientific literature on the supposed harmful effects of masturbation was popularized by Sylvester Graham. He gave public lectures and, in 1834, published the first edition of a book that warned the American public about not only the scourge of masturbation but also the perilous nature of excessive sexual activity.

Sylvester GrahamSylvester Graham

He agreed with Tissot’s claim that the loss of semen was a major cause of mental, physical, and societal ills. Graham (1834) stated tha

semen may be called the essential oil of animal liquors…. [It] contributes to the support of the nerves…. [Semen] imparts to the body, peculiar sprightliness, vivacity, muscular strength, and general vigor and energy…;—that it causes the beard, hair and nails to grow—gives depth of tone, and masculine scope and power to the voice—and manliness and dignity to the countenance and person; and energy, and ardor, and noble daring to the mind. (quoted in Hodges, 2005, p. 724)

Graham concluded that, because semen is so essential to optimal mental and biological functioning, a single ejaculation

enfeebles the body more than the loss of 20 times the same quantity of blood…. [H]ence the frequent and excessive loss of it, cannot fail to produce the most extreme debility, and disorder, and wretchedness of both body and mind. (Graham, 1834; quoted in Hodges, 2005, p. 724)

But, in a departure from Tissot’s these, Graham asserted that an even greater danger was the sexual activity leading to orgasm. It caused a “nervous excitement” that

rapidly exhausts the vital properties of the tissues, and impairs the functional powers of the organs: and consequently, that it, in a greater degree than any other cause, deteriorates all the vital processes of nutrition, from beginning to end; and therefore, more injuriously affects the character and condition of all the fluids and solids of the body. (Graham, 1834; quoted in Hodges, 2005, p. 275)

Physicians in New England were strongly influenced by Graham’s ideas. A series of articles were published in a prestigious medical journal, the Boston Medical and Surgical Journal, that were reprinted in newspapers. In this way, the warnings about masturbation became well known to a wide audience and, because of their endorsement by medical professionals, gained even more legitimacy among the general public.

In Part 2, I will discuss the evolution of the  “War on Masturbation in the second half of the nineteenth century and into the twentieth century.


Graham S. (1834) A lecture to young men. Providence, RI: Weeden & Cory.

Hodges, F. M. (2005). History of sexual medicine: The antimasturbation crusade in antebellum American medicine. The Journal of Sexual Medicine, 2(5), 722-731. doi: 10.1111/j.1743-6109.2005.00133.x

Tissot, S. A. D. (1832). A treatise on the diseases produced by onanism. New York, NY: Collins & Hannay. Accessed at

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Hypnotizing Chickens?

On the Strange Animals Blog is a post about “chicken hypnosis” (Beredimas, 2014), which is more accurately referred to as tonic immobility–“a state of reduced responsiveness induced by physical restraint” (Bryan Jones & Faure, 1981). Tonic immobility is thought to be an adaptive response to situations that cause chickens to become fearful, similar to animals “freezing” when they become aware of a potential predator.

Tonic immobility can be induced in several ways, but the various techniques typically involve physically restraining the chicken for a short period of time. Here is a video showing one of the techniques (other videos of “chicken hypnosis” induction techniques can be found here).

You can read more about “chicken hypnosis” here and here.


Beredimas, D. (2014, February 27). How to hypnotize a chicken. Strange Animals Blog. Retrieved from

Bryan Jones, R., & Faure, J. M. (1981). Tonic immobility (“righting time”) in laying hens housed in cages and pens. Applied Animal Ethology, 7, 369-372. doi: 10.1016/0304-3762(81)90063-8

How not to communicate a scientific discovery

G. S. Brindley made one of the most important contributions to the treatment of erectile dysfunction. He discovered that injecting papaverine into the penis causes an erection. He announced this discovery — in a rather unique way — in 1983 at a meeting of the Urodynamics Society. Laurence Klotz was at that talk and described Brindley’s eccentric (and to some audience members, horrifying) presentation in a paper published in 2005. Here is an extended excerpt from that paper:

In 1983, at the Urodynamics Society meeting in Las Vegas, Professor G.S. Brindley first announced to the world his experiments on self-injection with papaverine to induce a penile erection. This was the first time that an effective medical therapy for erectile dysfunction (ED) was described, and was a historic development in the management of ED. The way in which this information was first reported was completely unique and memorable, and provides an interesting context for the development of therapies for ED….
The lecture was given in a large auditorium, with a raised lectern separated by some stairs from the seats….
Professor Brindley, still in his blue track suit, was introduced as a psychiatrist with broad research interests. He began his lecture without aplomb…. His slide-based talk consisted of a large series of photographs of his penis in various states of tumescence after injection with a variety of doses of phentolamine and papaverine….
The Professor wanted to make his case in the most convincing style possible…. He had, he said, therefore injected himself with papaverine in his hotel room before coming to give the lecture, and deliberately wore loose clothes (hence the track-suit) to make it possible to exhibit the results. He stepped around the podium, and pulled his loose pants tight up around his genitalia in an attempt to demonstrate his erection….
At this point, I, and I believe everyone else in the room, was agog. I could scarcely believe what was occurring on stage. But Prof. Brindley was not satisfied. He looked down sceptically at his pants and shook his head with dismay. ‘Unfortunately, this doesn’t display the results clearly enough’. He then summarily dropped his trousers and shorts, revealing a long, thin, clearly erect penis. There was not a sound in the room. Everyone had stopped breathing…..
He then said, with gravity, ‘I’d like to give some of the audience the opportunity to confirm the degree of tumescence’. With his pants at his knees, he waddled down the stairs, approaching (to their horror) the urologists and their partners in the front row. As he approached them, erection waggling before him, four or five of the women in the front rows threw their arms up in the air, seemingly in unison, and screamed loudly….
The screams seemed to shock Professor Brindley, who rapidly pulled up his trousers, returned to the podium, and terminated the lecture.

Figure 1. What Professor Brindley’s clothed erection may have looked like at his 1983 talk.

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Klotz, L. (2005), How (not) to communicate new scientific information: a memoir of the famous brindley lecture. BJU International, 96, 956–957.  doi: 10.1111/j.1464-410X.2005.05797.x

Note: A pdf of the paper can be found at:

The Confirmation Bias: Seeing What We Expect to See

Anecdotes, the topic of the post at this link, are often used as evidence for claims, even though they have weaknesses that limit severely their value as evidence. Anecdotes are important for another topic we’re discussing in my PSY 101 course: the confirmation bias, which is a strong tendency to readily accept evidence that seems to support beliefs we already have (i.e., our preconceptions) and to examine closely evidence that seems to contradict our preconceptions in order to find problems with the disconfirming evidence that allow us to discount it.

Figure 1. Discounting evidence that disconfirms one's preconceptions can lead to the development of bizarre beliefs that people hold fervently.
Figure 1. Discounting evidence that disconfirms one’s preconceptions can lead to the development of bizarre beliefs that people hold fervently.

In everyday life, however, we often do not even become aware of disconfirming evidence. Sometimes, this is because we can easily avoid it (e.g., we might avoid watching certain news programs that we know will make claims that contradict our beliefs). Other times, our cognitive limitations make it difficult for us to notice the disconfirming evidence (i.e., it doesn’t reach the conscious level). One example of the latter involves the belief that washing our cars causes it to rain. Many of us are able to point to occasions (anecdotes) on which it rained after we washed their cars, which seems to be compelling evidence of the truth of this belief. We often fail, however, to notice (and, therefore, don’t remember) occasions on which these events didn’t occur together. In order to get better evidence for the accuracy of the belief, we would need to make the kinds of observations indicated in the following table.

Table 1. Each cell of this table indicates the observations that would need to be made to determine if washing one's car causes it to rain.
Table 1. Each cell of this table indicates the observations that would need to be made to determine if washing one’s car causes it to rain.

In making observations that would allow us to fill in the cells of the table, we force ourselves to pay attention not only to evidence that supports our belief, but also to evidence that might disconfirm that belief:

  • The cell labelled A shows the number of times we washed the car and it rained.
  • The cell labelled B shows the number of times we washed the car and it didn’t rain.
  • The cell labelled C shows the number of times we didn’t wash the car and it rained.
  • The cell labelled D shows the number of times we didn’t wash the car and it didn’t rain.

Let’s say that we make the relevant observations for one year and get the following results.

Table 2. The cells of the table show, for a one-year period, the proportion (percentage) of days we either washed or did not wash the car and it either rained or did not rain.
Table 2. The cells of the table show, for a one-year period, the proportion (percentage) of days we either washed or did not wash the car and it either rained or did not rain.

Was it more likely to rain on the days we washed the car?

  • Cell A shows that, on 20% of the days, we washed the car and  it rained.
  • Cell B shows that, on 80% of the days, we washed the car and it didn’t rain.
  • Cell C shows that, on 20% of the days, we didn’t wash the car and  it rained.
  • Cell D shows that, on 80% of the days, we didn’t wash the car and it didn’t rain.

Thus, regardless of whether we had just washed our car or not, it rained on 20% of the days that year (and it didn’t rain on 80% of the days). In other words, washing our car was not associated with whether or not it rained.

The confirmation bias is caused, in part, by our unconscious tendency to ignore, avoid, or distort information that would show a preconception to be wrong. In the present example, people tend to pay attention only to the first cell of the table and to ignore the rest. This is because, in general, we are much more likely to notice when something happens than when something doesn’t happen. By forcing ourselves to pay attention to all relevant information in such situations, we are more likely to realize when our preconceptions are inaccurate.


To summarize: Cognitive researchers have found that we have an automatic (unconscious) tendency to seek out and readily accept information that agrees with (confirms) our preconceptions, and to ignore, distort, or discount information that contradicts (disconfirms) them. This confirmation bias serves to maintain and strengthen our preconceptions: we are much more likely to perceive and remember experiences that confirm our prior beliefs, and to discount or reinterpret those that disconfirm them. Thus, over time, the confirmation bias results these beliefs becoming so well established in our minds that eventually we consider them to be common sense (i.e., obviously true). If we wish to minimize the effects of the confirmation bias, we must force ourselves to look for and examine closely both confirming and disconfirming evidence.

Brief Test of Critical Thinking

The development of critical-thinking skills is a fundamental goal of educators, who have tried to devise various ways of assessing critical thinking in their students. Below is one of my attempts .

A cat using its advanced critical thinking skills
A cat using its advanced critical thinking skills

Brief Test of Critical Thinking

1. When your gasoline guage is past Empty, and you are five miles from the nearest gas station, your best option is to:

a. press the accelerator to the floor so that you can get to the gas station before you run out of gas.
b. let some air out of the front tires, put the car in neutral, and coast to the gas station.
c. place a piece of duct tape over the guage so that the engine won’t know that there’s no more gas.

2. You’ve just ridden your bike two miles to a liquor store and are now at the drive-thru window buying a gallon jug of снаряда рвоту vodka. After the clerk hands you the jug, you discover that you don’t have the $2.50 it will take to buy it. It would be best to:

a. break out your beer bong, funnel the vodka, and then pedal as fast as possible until you pass out.
b. settle for the two-liter Bag-O-Bourbon for 99¢ (plus tax), which is on sale until Sunday.
c. a and/or b

3. It’s ten minutes before your college-algebra final is scheduled to begin. You haven’t been to class in weeks, flunked the other tests because you couldn’t remember what X stood for, and have never been able to count past G. Which of the following should you do?

a. Show the teacher your grandmother’s obituary from last year and tell him that you’re really late for the wake.
b. Take the final anyways. Who knows? Maybe you’ll ‘ace’ it!! Hey, anything’s possible, right? Ya’ just gotta think positive!!
c. Tell the teacher that he never returned your last two tests but that you know that you “did really good on ’em” …
d. And that he also incorrectly entered 9% for your score on the first test instead of the 99% that you really got …

4. Critical thinking is:

a. good.
b. bad.
c. crunchy.

5. If you’re making crank phone calls, would it make sense to cover the caller ID so that the person answering the phone doesn’t know who you are?

a. yes
b. only on the weekends
c. Did I already include “yes”? I did? OK, thanks.
d. no


Add up the number of items you either answered or thought about answering or would have answered if you could read, add the number of pints in a meter, multiply by Planck’s Constant (no, not that Planck, the other one), and divide by your age when you were 10.

Did you get a number? No? Good!

This baby received a perfect score.
This baby received a perfect score.

Anecdotes & Testimonials: Good Evidence for Claims?

In my PSY 101 class, we recently discussed some problems with using anecdotes and testimonials as evidence for claims. In this post, I want to begin to explore this issue in more depth. In future posts, I will discuss further some of the issues touched upon here.


One afternoon, Eileen Lipsker was sitting in her family room watching Jessica, her red-headed five-year-old daughter, play with her friends. Eileen later reported that she felt “spaced out” and was “thinking of nothing.” Lenore Terr (1994), a psychiatrist who spoke with her on many occasions, described what Eileen said happened next:

Jessica twisted her head to look at her mother. To ask something? Her chin pointed up in inquiry. She looked up and over her shoulder. Her eyes brightened. How odd! The young girl’s body remained stationary, while her head pivoted around and up…. And at exactly that moment Eileen Lipsker remembered something. She remembered it as a picture. She could see her redheaded friend Susan Nason looking up, twisting her head, and trying to catch her eye.

Eileen, eight years old, stood outdoors, on a spot a little above the place where her best friend was sitting. It was 1969, twenty years earlier. The sun was beaming directly into Susan’s eyes. And Eileen could see that Susan was afraid…. [Eileen] looked away from those arresting eyes and saw the silhouette of her father. Both of George Franklin’s hands were raised above his head. He was gripping a rock. He steadied himself to bring it down. His target was Susan. (pp. 2-3)

Eileen told Terr that this is how she first recovered her repressed memory of Susan Nason’s murder by her father. Eileen’s recounting of the memory recovery is an example of an anecdote: a brief story told by an individual about a personal experience. No matter how interesting or compelling an anecdote may be, it doesn’t provide good evidence for a claim because it is based on interpretations and memories of personal experiences. In other words, an anecdote is inadequate evidence for a claim because it does not control for factors that affect how a personal experience is (a) initially perceived and interpreted, and (b) eventually remembered.

Figure 1. An example of an anecdote used to support the claim that extraterrestrials visit earth
Figure 1. An example of an anecdote used to support the claim that extraterrestrials visit earth


Autistic Disorder is a severe mental disorder that develops in children before the age of three years. It has three main symptoms: a severe impairment in social interaction, a severe impairment in the ability to communicate, and a severely restricted range of interests, activities, and behaviors. On occasion, new treatments for autism are announced that seem to offer hope for either a cure or, at least, a dramatic reduction of symptoms. One such well-publicized treatment used injections of secretin–a hormone that assists in the digestion of food. Some have claimed that secretin improves the social and language skills of autistic individuals by affecting specific behaviors such as the amount of eye contact made, the level of awareness of one’s surroundings, the degree of sociability, and the amount of speech. One proponent of secretin therapy provided the following evidence for this claim:

The good news is that confirmatory evidence of the power of secretin keeps coming. A national newspaper told of Florida pediatrician Jeff Bradstreet’s own four-year-old son, Matthew, shocking his parents by holding his first normal conversation with them the day after his first secretin infusion. And Virginia pediatrician Lawrence Leichtman told me of his “miracle case”: a five-year-old who had previously said only two words amazed all in the office by saying, 15 minutes after his infusion, “I am hungry. I want to eat.” Most cases are much less dramatic, but the autism world is excited, and for good reason. (Rimland, 1998, p. 3)

Is this good evidence for the effectiveness of secretin in the treatment of autism? The evidence consists of two testimonials. A testimonial is an anecdote that describes the supposed merits of a product or service. Testimonials are not good evidence for a claim because they are anecdotes and, as stated above, anecdotes don’t control for factors that might distort our observations and interpretations of a personal experience, as well as how we remember it later on. For example, we may misremember exactly what happened during the event, or may have misinterpreted what we observed during the event.

Figure 2. A testimonial from a celebrity about a brand of cigarettes
Figure 2. A testimonial from a celebrity about a brand of cigarettes (circa 1951)

In testimonials about therapeutic treatments, one very important factor that causes distortions of perceptions, interpretations, and memories is people’s expectations for the treatment. These expectations may cause them to conclude that their symptoms improved or disappeared even when they haven’t. This generally happens in one of two ways:

  1. The expectations may cause observers (e,g, patients, family members, doctors) to misperceive or misinterpret the behavior of those receiving a treatment, thereby concluding that the behavior has changed when it really hasn’t.
  2. The expectations may cause observers to experience improvement that has nothing to do with the nature of the treatment itself (e.g., the placebo effect or a self-fulfilling prophecy; see later posts in this series).

Specific examples of some of the problems mentioned here will be described in future posts.

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Pendergrast, M. (1996). Victims of memory: Sex abuse accusations and shattered lives (2nd ed.). Hinesburg, VT: Upper Access.

Rimland, B. (1998). The use of secretin in autism: Some preliminary answers. Autism Research Review International, 12(4), 3. Retrieved January 23, 2013, from

Terr, L. T. (1994). Unchained memories: True stories of traumatic memories, lost and found. New York: BasicBooks.

The Evolution of Domestic Dogs — Part 1

The dog was the first domesticated animal. Domestication is an “evolutionary process [that] has been influenced by humans to meet their needs” (Secretariat, 1992, p. 3). In other words, domestication of a species causes biological changes over generations through selection by humans for favorable traits (i.e., traits that are useful, valuable, aesthetically pleasing, etc.).

Domestication led to extraordinarily large changes in the behavioral characteristics of domestic dogs, as well as in their physical characteristics (which is obvious when one compares the many breeds of dogs). Scientific research on the evolution of dog behavior began in the mid-1800s, most notably in the work of Charles Darwin (Darwin, 1872). In the middle of the twentieth century, a deeper understanding of the evolution of dog behavior was gained by combining behavioral analyses with classical genetic analyses of dog breeds (for a review, see Scott & Fuller, 1965).

Figure 1. An extreme example of the effects of domestication on the physical characteristics of a subspecies of the gray wolf.

Over the past 20 years, archaeological discoveries in combination with the results of highly sophisticated genetic analyses have shed a great deal of light on the evolution of domestic dogs (for a review, see Larson, Karlsson, Perri, et al., 2012). For example, there now is little doubt that domestic dogs evolved from the gray wolf, which is found in many parts of Europe and Asia (Honeycutt, 2010; Wayne & Ostrander, 2007). In fact, domestic dogs (Canis lupus familiaris) are considered to be a subspecies of the gray wolf (Canis lupus lupus). This means that, although dogs and wolves have physical features that often are very different, they can mate and produce fertile offspring.

Nevertheless, there still is much controversy about when and where domestic dogs originated. These disagreements are focused on the answers to two questions: when did domestic dogs “split” from gray wolves and where did this happen? These questions have proved difficult to answer because the results of genetic and archaeological research are complex and, hence, very difficult to interpret.

Genetic research on differences in DNA sequences have led to a wide range of estimates about when dogs and wolves first diverged: sometime between 20,000 to 100,000 years ago. One reason for the wide variation in these estimates is that dogs and wolves probably continued to interbreed, not only over long periods of time but also in many locations (Vilà, Savolainen, Maldonado, et al., 1997).

Archaeological researchers find no clear evidence for the existence of domestic dogs until about 15,000-30,000 years ago (Germonpré, Sablin, Stevens, 2009; Ovodov, Crockford, Kuzmin, et al., 2011). A major difficulty with interpreting archaeological findings, however, is that physical characteristics typically used to distinguish domestic dogs from wolves (e.g., the size and position of the teeth, the size and shape of the skull, etc.) probably varied much more in ancient dog populations than they do today (Larson, Karlsson, Perri, et al., 2012). In addition, nothing is known about the variation of these traits in populations of ancient wolves. In other words, the physical characteristics used to distinguish modern dogs and wolves probably overlapped to a relatively large extent in ancient dogs and wolves, thereby making it very difficult for archaeologists to know if they are looking at the bones and teeth of a wolf or a dog.

Figure 2. The 33,000-year-old skull of a wolf-like animal reputed to be a dog (Ovodov, Crockford, Kuzmin, et al., 2011)
Figure 2. The 33,000-year-old skull of a wolf-like animal reputed to be a dog (Ovodov, Crockford, Kuzmin, et al., 2011)

As of now, both the archeological and genetic evidence allow us to conclude with certainty that domestic dogs existed at least 15,000 years ago (Larson, Karlsson, Perri, et al., 2012). It is still an open question, however, if ancient dog populations leading to modern domestic dogs first diverged from wolves earlier than that.

In the next post, I’ll review what recent research seems to tell us about the genetic differences linked to the many physical and behavioral differences between (a) modern domestic dogs and their ancestral species, and (b) the various breeds of modern domestic dogs.

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Darwin, C. (1872). The expression of the emotions in man and animals. London: John Murray. Retrieved January 21, 2013, at

Germonpré M, Sablin MV, Stevens RE, Hedges REM, Hofreier M, Stiller M, et al. (2009). Fossil dogs and wolves from Palaeolithic sites in Belgium, the Ukraine and Russia: Osteometry, ancient DNA and stable isotopes. Journal of Archaeological Science, 36, 473-490. doi: 10.1016/j.jas.2008.09.033

Honeycutt, R. L. (2010). Unraveling the mysteries of dog evolution. BMC Biology, 8(20). doi:10.1186/1741-7007-8-20

Larson, G., Karlsson, E. K., Perri, A., Webster, M. T., Ho, S. Y. W., Peters, J., et al. (2012). Rethinking dog domestication by integrating genetics, archeology, and biogeography. Proceedings of the National Academy of Sciences, 109, 8878–8883. doi: 10.1073/pnas.1203005109

Ovodov, N. D., Crockford, S. J., Kuzmin, Y. V., Higham, T. F. G., Hodgins, G. W. L., & van der Plicht, J. (2011). A 33,000-year-old incipient dog from the Altai Mountains of Siberia: Evidence of the earliest domestication disrupted by the Last Glacial Maximum. PLoS ONE 6(7): e22821. doi:10.1371/journal.pone.0022821

Scott, J. P., & Fuller, J. L. (1965). Genetics and the social behavior of the dog. Chicago: University of Chicago Press.

Secretariat, C. B. D. (1992). The Convention on Biological Diversity. Retrieved December 30, 2012, from

Vilà, C., Savolainen, P., Maldonado, J. E., Amoim, I. R., Rice, J. E., Honeycutt, R.L., et al. (1997). Multiple and ancient origins of the domestic dog. Science, 276, 1687-1689.

Wayne, R. K., & Ostrander, E. A. (2007). Lessons learned from the dog genome. Trends in Genetics, 23, 557–567. doi: 10.1016/j.tig.2007.08.013

Increasing College Costs Causes Autism

Boing Boing‘s Cory Doctorow reported on a spurious correlation of nearly 1.0 between autism and organic-food sales discovered by Jasonp55 on Skeptic Reddit.

This inspired me to look for other extremely high (albeit spurious) correlations with autism. I discovered a correlation of 0.994 between college costs (tuition + fees) and autism rates between the years 1999 and 2007, inclusive.

In the article that I’m certain to get published in Science, my main conclusion will be this: if we want to slash autism rates, we’ll need to drastically reduce college costs by returning educational funding to the levels of previous decades.

Here’s a graph of the cumulative percentages of the two variables that shows clearly their close association.


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Data Sources
1. Office of Special Education Programs, Data Analysis System (DANS), OMB# 1820-0043: “Children with Disabilities Receiving Special Education Under Part B of the Individuals with Disabilities Education Act”
Table 1-11. Number of children and students served under IDEA, Part B, in the U.S. and outlying areas by age group, year, and disability category: Fall 1999 through fall 2008 (Age Group 6-21)
2. National Center for Education Statistics: Digest of Education Statistics 2010 Tables and Figures
Table 345. Average undergraduate tuition and fees and room and board rates charged for full-time students in degree-granting institutions, by type and control of institution: 1964-65 through 2009-10