The Halo Effect: Why People Often Judge a Book by Its Cover

Halo effect


The halo effect is a cognitive bias that causes people’s impression of one aspect of something to influence their impression of other aspects of it. For example, the halo effect can cause people to assume that someone will have an interesting personality, simply because they find that person to be physically attractive.

Essentially, the halo effect means that when we consciously or subconsciously judge a certain entity, whether that entity is a person, a product, or a company, the way we perceive a single notable trait of that entity can significantly influence how we perceive its other traits, as well as how we perceive it overall.

The halo effect is important to understand, since it’s widely prevalent, and can influence both the way that we perceive others, as well as the way that they perceive us. As such, in the following article you will learn more about the halo effect, see examples of how it affects people, and understand what you can do in order to account for its influence.


Examples of the halo effect

One of the best-known examples of the halo effect appears in a 1946 study by psychologist Solomon Asch. The most famous experiment from the study involved presenting participants with one of two descriptions of a person:

A: intelligent—industrious—impulsive—critical—stubborn—envious

B: envious—stubborn—critical—impulsive—industrious—intelligent

Both descriptions are identical in terms of the traits that they contain; the only difference is that description A opens with positive traits (‘intelligent’ and ‘industrious’), and then moves on to more ambiguous traits (‘impulsive’, ‘critical’, and ‘stubborn’), before finally closing with a negative trait (‘envious’), while description B lists these traits in reverse order. However, this small difference promoted a halo effect among participants, which led to a significant difference in how they perceived the person being described:

“The impression produced by A is predominantly that of an able person who possesses certain shortcomings which do not, however, overshadow his merits. On the other hand, B impresses the majority as a ‘problem,’ whose abilities are hampered by his serious difficulties. Further, some of the qualities (e.g., impulsiveness, criticalness) are interpreted in a positive way under Condition A, while they take on, under Condition B, a negative color.”

Another notable example of the halo effect appears in the following story, told by psychologist, economist, and Nobel laureate, Daniel Kahneman:

“Early in my career as a professor, I graded students’ essay exams in the conventional way. I would pick up one test booklet at a time and read all that student’s essays in immediate succession, grading them as I went. I would then compute the total and go on to the next student.

I eventually noticed that my evaluations of the essays in each booklet were strikingly homogeneous. I began to suspect that my grading exhibited a halo effect, and that the first question I scored had a disproportionate effect on the overall grade. The mechanism was simple: if I had given a high score to the first essay, I gave the student the benefit of the doubt whenever I encountered a vague or ambiguous statement later on. This seemed reasonable. Surely a student who had done so well on the first essay would not make a foolish mistake in the second one!

But there was a serious problem with my way of doing things. If a student had written two essays, one strong and one weak, I would end up with different final grades depending on which essay I read first. I had told the students that the two essays had equal weight, but that was not true: the first one had a much greater impact on the final grade than the second.”

— From “Thinking, Fast and Slow

An additional example of the halo effect is a study that showed that what people think about a woman’s personality is influenced by how much she weighs. In the study, participants saw a picture of a woman, together with some background information about her hobbies and about her life in general. One group of participants received an original picture of that woman, while another group received a picture where the woman wore padding, to make her look ~50 pounds heavier.

When asked what they thought about the woman that they read about, the participants who saw the picture of the thinner woman rated her not only as more attractive, but also as having a better personality and as being more likely to achieve success in her career. This is despite the fact that these participants received the same background information about the woman as the participants who saw the picture of the heavier woman, which suggests that they experienced a halo effect, where their perception of the woman’s body influenced their perception of her personality and skills.

Finally, there are many other examples of how the halo effect influences people’s thinking. For instance:

  • When evaluating potential partners for political discussion, people viewed more attractive prospects as more knowledgeable and persuasive, and as better sources for political information.
  • When evaluating essays, people sometimes gave higher ratings to essays that they thought were written by an attractive author, compared to essays that they thought were written by an unattractive one.
  • When evaluating their teachers, students who had a particularly strong opinion regarding one of their teacher’s traits often let that opinion affect their overall rating of that teacher’s performance.

Note: the assumption that physically attractive individuals are more likely to have socially desirable traits than less attractive individuals is generally referred to as the physical attractiveness stereotype or the “what is beautiful is good” stereotype.


Why people experience the halo effect

“The sequence in which we observe characteristics of a person is often determined by chance. Sequence matters, however, because the halo effect increases the weight of first impressions, sometimes to the point that subsequent information is mostly wasted.”

— From “Thinking, Fast and Slow“, by Daniel Kahneman

There are several reasons why people experience the halo effect.

First, people experience the halo effect because once they form an initial impression of someone or something, they often try to prove that that impression is right. Proving that they were right serves two main purposes:

  • It gives the person who formed that impression a positive feeling of accomplishment.
  • It helps that person avoid the negative feeling associated with cognitive dissonance, which in this case occurs if they find out that their initial impression was wrong in some way, which means that they now have to reconcile that impression with a new, better one.

For example, if we’re exposed to a single positive trait of an individual, such as them being funny, we tend to immediately form a positive impression of them, because that’s all the information that we have to go on. Later, when we find out more about them, we try to confirm that initial impression, even if the new things that we discover contradict it, since we don’t want to find out that this impression was wrong.

Note that, in this case, the halo effect can be viewed as being related to the confirmation bias, which is a cognitive bias that causes us to search for and interpret information in a way that confirms our preexisting beliefs.

Second, in some cases people experience the halo effect because they struggle to disentangle the different traits that an entity is composed of. Essentially, when people try to assess individual qualities in someone or something, they struggle to assess each of these qualities in complete isolation from the others, and their assessment of one quality spills over to their assessment of other qualities.

This means, for example, that when we’re trying to assess someone’s competence in the workplace, we often struggle to assess their competence by itself, without taking into account other factors which may be irrelevant, such as how likable or confident that person is.

In addition, people sometimes experience the halo effect because focusing on a certain trait when judging others reduces their cognitive load. In general, when forming impressions of others, the more factors people look at, and the more complex these factors are, the harder it is for them to form a valid impression.

By taking a single key feature, that stands out either because it’s salient in some way or because it’s relatively easy to process, people can make it easier for themselves to form impressions of others. This, of course, increases the risk of decreasing the accuracy of those impressions, but in many situations people are either willing to accept this potential decrease in accuracy, or they are simply not thinking of it when choosing this type of assessment.

Furthermore, there are situations where the halo effect is based on correlations that people believe in based on their past experiences. Since we often learn that certain traits are correlated with one another, people often assume that the presence of one trait implies the presence of other traits, and in some cases, taking these correlations into account allows people to form impressions that are relatively likely to be accurate.

For example, if over time we come to learn that products that have a pleasant visual design are also reliable from a technical perspective, we might assume that a certain product is reliable, simply because it has a good visual design.

Accordingly, the halo effect also serves as a useful heuristic in some situations. This is because, when we process information we often use mental shortcuts that can be useful when we need to make decisions quickly or when we need to make decisions in situations where we lack certain key pieces of information.

For example, if we have to quickly choose between two products but we’re not sure which one is better in terms of function, we might just look at how the products are designed visually, and choose the one that looks better based on the assumption that the product’s appearance is indicative of its performance.

Of course, the use of the halo effect as a decision-making tool in this way isn’t foolproof, and can sometimes lead us to make the wrong choices. This is especially likely in situations where the person in charge of whatever it is we are assessing is aware of the halo effect, and decides to use it intentionally in order to manipulate our opinion.


How to account for the halo effect

The halo effect and your opinion of others

When it comes to accounting for the halo effect, it’s important to keep in mind that the halo effect influences how you judge others. Accordingly, remembering the way that the halo effect can influence your thoughts, both in a positive as well as in a negative manner, can allow you to assess things more clearly, and to therefore make more rational decisions.

This means, for example, that it’s important to keep in mind that just because someone that you encounter has a single positive trait (e.g. physical attractiveness), that doesn’t mean that you should immediately form a positive impression of them. Similarly, just because someone has a single negative trait, that doesn’t mean that you should immediately form a negative impression of them.

To reduce the likelihood that you will be influenced by the halo effect when you’re assessing others, you can use various cognitive debiasing techniques, such as slowing down your reasoning process. The most effective techniques will be the ones that attempt to address the underlying causes of your halo effect specifically.

This means, for example, that if you notice that you’re experiencing the halo effect because you’re constantly trying to confirm that your initial impression of people was right, then you can reduce the likelihood that you will experience the halo effect by trying to come up with two possible impressions of people when you first meet them, and keep both these impressions in mind until you have more information that will allow you to choose between them.


The halo effect and other people’s opinion of you

When accounting for the halo effect, it’s important to keep in mind that it can influence how other people view you and the things that you create. You can take advantage of this, for example, by realizing that your traits and behaviors in one area influence how other people perceive you in other areas, as well as how they perceive you overall.

For example, one study let students watch an interview with a college professor who spoke English with a foreign accent. There were two groups of students, each of which saw a slightly different version of the interview.

In one version the instructor was warm and friendly, while in the other version he was cold and distant. Students who watched the interview with the warm instructor rated his appearance, mannerisms, and accent as appealing, while students who watch the cold instructor rated the exact same attributes as irritating.

This is an example of how, by taking advantage of the halo effect, you can make simple changes in your behavior, that completely change the way people perceive you.


Variability in the halo effect

Though the halo effect can influence people’s opinions in a variety of situations, it’s important to keep in mind that the halo effect doesn’t always play a role in people’s thinking, and furthermore, that the way in which it influences people’s thinking isn’t always clear.

For example, in the case of people rating essays based on the attractiveness of the purported author, the halo effect played a role only when a man thought that he was rating an essay written by a woman. In the case of women rating an essay written by a woman, and men/women rating an essay written by a man, the physical attractiveness of the author did not play a role in their rating.

This, and similar forms of variability, also appeared in various other studies on the halo effect. This means that while you should certainly take the halo effect into account, you shouldn’t assume that it’s always there, and you shouldn’t assume that it’s the primary factor underlying people’s judgment and decision-making processes.


Related concepts

The halo effect in marketing

Most commonly, the halo effect is mentioned with regard to its influence on how we perceive other people. In this context, the halo effect can cause us to form an overall opinion of someone that is affected by how we perceive one of their traits, with the influencing trait usually being the first one that we encounter, or one that is salient in some other way.

However, the halo effect isn’t limited to the way we look at people. It can also affect the way that we judge other things, such as products and companies. This means, for example, that if you have a positive impression of a certain brand, you’re more likely to buy products from that brand, even if the positive impression that you have of them is not directly related to the product at hand.

Accordingly, the halo effect is a key effect to consider when it comes to marketing, and it’s often mentioned when it comes to assessing the value of brand names.


The horns effect

The horns effect is a cognitive bias which causes our negative impression of someone or something in one domain to influence our impression of them in other domains. For example, a study on classroom behavior found that when young kids behaved in a defiant manner, teachers were more likely to incorrectly label them as being hyperactive or as having attention-deficit hyperactivity disorder (ADHD).

Similarly, in the context of consumer products, the horns effect could mean, for example, that if you don’t like the way a certain product looks, that might cause you to assume that the product will have poor performance, even though that’s not necessarily the case.

Note that in terms of terminology, the halo effect technically encompasses both positive and negative impressions.

However, in some cases the halo effect is used to refer strictly to positive impressions, while the horns effect is used to refer to negative impressions. This is why the horns effect is occasionally called a reverse halo effect, even though in practice it refers to the same type of cognitive bias as the halo effect.


The origin of the halo effect

The concept of the halo effect is attributed to renowned American psychologist Edward Thorndike, who first wrote about it in his 1920 paper ‘A Constant Error in Psychological Ratings‘. In the paper, Thorndike says the following:

“In a study made in 1915 of employees of two large industrial corporations, It appeared that the estimates of the same man in a number of different traits such as intelligence, industry, technical skill, reliability, etc., etc., were very highly correlated and very evenly correlated. It consequently appeared probable that those giving the ratings were unable to analyze out these different aspects of the person’s nature and achievement and rate each in independence of the others. Their ratings were apparently affected by a marked tendency to think of the person in general as rather good or rather inferior and to color the judgments of the qualities by this general feeling.”

Thorndike then adds further support to this initial study, by showing that when army officers were rated by their superiors based on their physical qualities, intelligence, leadership ability, and personal character, the resulting ratings were strongly and evenly correlated with one another, despite explicit instructions to rate these traits independently from one another. This means, for example, that officers’ intelligence ratings were correlated with the ratings of their physical qualities to a similar degree as they were with the ratings of their leadership ability and personal character, despite the weaker expected association between intelligence and physical qualities.

Thorndike then states that the same issue appeared in the case of aviation officers, whose general ability to perform officer work was highly correlated with their specialized technical ability to fly, to a much higher degree than what could naturally be expected. He notes that this suggests that “a halo of general merit is extended to influence the rating for the special ability, or vice versa”.

Thorndike also mentions related research by Knight and by Boyce, who showed that a similar effect appears when it comes to the rating of teachers. When discussing this, he mentions, for example, that the trait of ‘voice’ was highly correlated with the traits of ‘intelligence’ and ‘interest in community affairs’, far beyond what would normally be expected.

Overall, Thorndike concludes his paper by saying that:

“The writer has become convinced that even a very capable foreman, employer, teacher, or department head is unable to treat an individual as a compound of separate qualities and to assign a magnitude to each of these in independence of the others. The magnitude of the constant error of the halo, as we have called it, also seems surprisingly large…”

Note that Thorndike does not use the term ‘halo effect’ explicitly in the paper, but does use the term ‘halo’ several time when referring to this phenomenon, including in the above quote, where he uses the term ‘constant error of the halo’.

According to the Oxford English Dictionary, the term ‘halo effect’ was first used in a 1938 paper by S. M. Harvey, titled ‘A Preliminary Investigation of the Interview‘, and published in the British Journal of Psychology, which stated that:

“We noted the importance of a general impression gained of the candidate, which was sometimes such as to result in resistance to bias, and sometimes the mechanism through which the bias appeared to operate. Such general impressions, often called ‘ halo ‘ effects, have already been noted to affect the diagnosis of personal qualities…”


Summary and conclusions

  • The halo effect is a cognitive bias that causes people’s impression of one aspect of something to influence their impression of other aspects of it.
  • For example, if people think that someone is physically attractive, the halo effect can cause them to assume that that person has a more interesting personality compared to what they would assume if that person was unattractive.
  • We experience the halo effect for a number of reasons, and specifically because we want to confirm our initial impressions of things, because we struggle to disentangle the different traits of the same entity, because it’s easier to make judgments this way, because we learn to expect certain correlations between different traits, and because halo-based assumptions can serve as helpful heuristics in some cases.
  • It can be beneficial to remember how the halo effect influences the way you view others, since accounting for it will allow you to make more rational decisions, and avoid assuming good or bad things about others in situations where you would be wrong to do so.
  • It can also be beneficial to keep in mind the way that the halo effect influences other people’s perception of you, since it means that your actions in a single domain can significantly influence people’s overall perception of you, either in a positive or in a negative manner.