The Mandela Effect, Streisand Effect, And Other “Effects”

names of types of effects on blue background

You know that thing that happens when you first learn about something and then you start seeing it everywhere? Or when participants in a medical trial start to feel better even though they’ve been taking the pill with nothing in it? Helpfully, there are names for these things.  

In the context of psychology, these “things that happen”—these phenomena—are often referred to as effects, especially in the specific names that have been given to them by the researchers who observe and study them. 

Here are several examples of “effects”—some already well-known and some increasingly part of the cultural dialogue—that may help to explain (and to easily refer to) various strange workings of human minds and behavior.

The Streisand effect

The Streisand effect refers to a phenomenon in which an attempt to hide or censor something causes that thing to get more attention than it would have otherwise. This term was coined by writer Mike Masnick in 2005 and is named after singer Barbra Streisand, who in 2003 attempted to have photographs of her home removed from an online research gallery. As a result of her legal action, Streisand unintentionally created much more interest in the photos than if she had done nothing. The name is now applied to cases in which this happens, especially when it involves a celebrity.

Need to know more? Learn about the term Streisand effect and find real-life examples of its use.

The Mandela effect

The Mandela effect refers to a phenomenon in which a large number of people share a particular false memory. The Mandela effect was named by paranormal researcher Fiona Broome in 2009 after a particular experience she and others had involving false memories of former South African president Nelson Mandela. Broome and many other people have falsely remembered that Nelson Mandela died in prison during the 1980s when in reality he died in 2013, well after his release in 1990. Other common examples of the Mandela effect include the widespread false memory that the series of children’s books was called the “Berenstein Bears” (the name is actually spelled “Berenstain”) or that there was a Shazaam film starring comedian Sinbad (as opposed to the actual movie Kazaam, starring basketball star Shaquille O’Neal).

Explanations for the phenomenon vary, with many of them crediting it to the confusion or conflation or multiple events. More extreme theorists explain these bizarre and widely shared false memories as being the result of alternate universes or timelines.

The CSI effect

The CSI effect—named for the popular TV series CSI: Crime Scene Investigation—refers to an alleged phenomenon in which the popularity of such TV crime dramas has caused the average juror to place a greater importance on forensic evidence and technology. According to those who believe it is real, the CSI effect causes jurors to have the tendency of thinking that forensic evidence is required in every criminal case, is the most important evidence, and is never wrong. However, a number of independent researchers have disputed these conclusions, noting that the effect is not as pervasive as it is purported to be by many legal professionals.

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The IKEA effect

The IKEA effect refers to a phenomenon in which a person places a disproportionately high value on something they helped create. For example, someone will think more fondly of a dilapidated house they built themselves than a brand new one that they didn’t. The IKEA effect is often applied more broadly to say that people are more invested in things they put effort toward. For example, a person might prefer a computer program that required them to set up a user account over an identical one that didn’t.

The IKEA effect is named after IKEA, a popular Swedish furniture brand that sells products that often require self-assembly. The name IKEA effect was coined by Harvard researchers in a 2011 study of the concept. According to the study, people were willing to pay more money for self-assembled products and placed a much higher value on items they had built themselves. Psychologically, the IKEA effect can be explained by people associating positive feelings with successfully completed projects and wanting recognition for their labor.

The placebo effect

The placebo effect refers to the well-known phenomenon in which a person’s belief in a placebo’s healing properties actually causes an improvement in health. A placebo is a substance that has no beneficial health effects, but a person taking it believes or is told that it does. While we don’t know exactly why the placebo effect exists, scientists agree that it is likely due to mental factors, such as pain or depression being alleviated because the brain expects that to happen (and thus causes it to actually happen), combined with the performance of a ritual (taking a pill at the same time each day, for example).

The Pygmalion effect

The Pygmalion effect refers to a phenomenon in which expectations have an impact on performance: positive expectations lead to better performance and negative expectations lead to worse performance. For example, students whose teacher believes they will succeed will perform better than students whose teacher expects them to fail. The explanation behind the Pygmalion effect seems simple: people often try to make the results match the expectations, which in turn significantly increases the likelihood that they do match.

The Pygmalion effect is named after Pygmalion, a Greek mythical character who prayed to the gods to give life to a statue that he had sculpted and fell in love with. Aphrodite, the goddess of love, granted Pygmalion’s wish.

The bystander effect

The bystander effect refers to a phenomenon in which a person is less likely to take action during an emergency or crisis when they are among a group of people. This bystander apathy is often explained in psychology as being due to social influence and/or “a diffusion of responsibility,” a condition in which the personal responsibility that an individual feels actually decreases when there are more people present.

The concept of the bystander effect was popularized by researchers in the late 1960s, when it became strongly associated with the 1964 murder of Kitty Genovese. That case drew widespread media attention due to reports that none of the many people who witnessed the incident attempted to intervene or call the police. However, these reports were later revealed to be inaccurate, and many popular myths formed around the incident.

The Rashomon effect

The Rashomon effect refers to a phenomenon in which an event is described differently, often in contradictory ways, by different people who witnessed the same thing. The explanations behind the Rashomon effect often depend on the specifics of the event in question. For example, each witness might have been in a different physical location, might be unable to accurately remember what they saw, might be trying to give answers that investigators want, or might simply be lying. The Rashomon effect is often used to explain how subjectivity and a witness’s own personal psychology and experiences can affect how they describe an event they saw.

The Rashomon effect is named after Rashomon, a 1950 film directed by Akira Kurosawa. In the film, four witnesses to the murder of a samurai give four different, contradictory accounts as to what happened.

The Hawthorne effect

The Hawthorne effect refers to a phenomenon in which observed subjects tend to change their behavior if they are aware that they are being observed. For example, an experiment designed to see if video games improve reaction speed could result in better reaction speed performance by subjects simply because they want to succeed at the test. Modern science often attempts to minimize the impact of the Hawthorne effect on experiments.

The name Hawthorne effect was coined in the 1950s by researcher Henry A. Landsberger. Landsberger analyzed experiments conducted in the 1920s and 1930s to test the effects of different lighting conditions on worker performance at the Western Electric’s Hawthorne Work electric company located near Hawthorne, Illinois. No matter what changes were made, the subjects’ performance always improved. Landsberger attributed this increased performance to the subjects being aware that they were being observed.

The Dunning-Kruger effect

The Dunning-Kruger effect is a phenomenon in which a person’s lack of skill or competency causes them to believe they are much more skilled or knowledgeable in a particular area than they actually are. The Dunning-Kruger effect is attributed to a cognitive bias caused by a lack of knowledge. Often, a person needs at least a minimal amount of knowledge about something in order to recognize their own lack of skill or mastery. A person who doesn’t even have this bare minimum cannot recognize their own shortcomings and will greatly overestimate how skilled or knowledgeable they actually are.

The Dunning-Kruger effect is named after the scientists who first researched it in 1999, David Dunning and Justin Kruger.

The Baader-Meinhof effect

The Baader-Meinhof effect, also known as the Baader-Meinhof phenomenon, refers to a phenomenon in which the frequency of something seems to increase immediately after a person learns about it—such as when you learn a new word and then see it multiple times soon after. In actuality, this sensation is thought to be due to a cognitive bias in which the brain is putting more emphasis on new information.

The Baader-Meinhof effect is named for the Baader-Meinhof Gang, a 1970s German terrorist group. A man named Terry Mullen coined the name in a letter to a newspaper in which he claimed he to have encountered the mention of the group in the news shortly after having discussed them, despite the group not having been newsworthy for many years. The phenomenon is also sometimes called the frequency illusion.

The halo effect

The halo effect refers to a phenomenon in which a person’s single positive trait or action influences how others see them overall. For example, physically attractive people are often assumed to be nice, smart, charismatic, and funny based purely on their appearance alone. Psychologically, the halo effect is yet another type of cognitive bias—we notice that a person has one positive quality and jump to the conclusion that they must have other ones, too.

The idea of the halo effect was first researched by psychologist Edward Thorndike in 1920. In his research, Thorndike discovered that military officers were more likely to attribute positive qualities such as leadership and intelligence to subordinates that they considered to be physically fit and attractive. Thorndike referred to this bias being caused by what he called the “halo.” The term has since been widely applied by psychologists.

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