Robert Zajonc

What is the mere-exposure effect?

Robert Zajonc (1923-2008) is well known in social psychology for his research on the mere-exposure effect. His popularity also flashed in the popular press, including the New York Times. Not only did the New York Times cover some of his professional work but also his death and personal history.

For many of us, of a different generation and touched by war only through tv, his early life reads like a harrowing Hollywood movie, a little surreal.1, 2, 3

At the beginning of WW II, Zajonc’s parents were killed, and he was badly injured during a German air raid in Warsaw, Poland. Zajonc eventually ended up in a Nazi work camp, from which he escaped only to be recaptured. Then the same cycle began in a different country. Zajonc was sent to a political prison in France only to escape again. This time, instead of being captured, he ended up in the French resistance and the University of Paris. His life then took him to England to work as a translator for the American forces in 1944, back to Paris to work for the United Nations Relief and Rehabilitation Administration, and then to Germany to study psychology at the University of Tübingen.

With a back-story like this, the rest of his life seems almost boring. This nomadic existence stopped with his emigration to the United States in 1948. Not only did he obtain his bachelor’s, master’s, and doctoral degrees at the University of Michigan, he stayed there to work as a professor until his retirement in 1994. After retirement, well, he went back to work — as an emeritus professor at Stanford University until his death of pancreatic cancer in 2008.

During the “boring” part of his life, he became well known for a number of findings in social psychology such as the mere-exposure effect, the confluence model, and social facilitation. My roundabout point with this list is he did a lot of well-recognized work, and that work made its way into journal articles, textbooks, and newspapers.

In this post, we’re focusing on the mere-exposure effect. The gist of the effect is the more a person is exposed to an item, the more that person will prefer it. Increase exposure, increase liking.

He developed the mere-exposure effect in his classic 1968 article titled “Attitudinal Effects of Mere Exposure.”4 Zajonc was not the first person to test or suggest the existence of this phenomenon, but he was the first person to provide scientific evidence for it. Zajonc started his classic article with this hook:

“On February 27, 1967, the Associated Press carried the following story from Corvallis, Oregon: A mysterious student has been attending a class at Oregon State University for the past two months enveloped in a big black bag. Only his bare feet show. Each Monday, Wednesday, and Friday at 11:00 A.M. the Black Bag sits on a small table near the back of the classroom. The class is Speech 113—basic persuasion. . . . Charles Goetzinger, professor of the class, knows the identity of the person inside. None of the 20 students in the class do. Goetzinger said the students’ attitude changed from hostility toward the Black Bag to curiosity and finally to friendship [italics added].”

I love a good hook.

Zajonc’s point with this example is that students’ liking of the Black Bag could have increased simply through exposure, in other words, from seeing it over and over and over again. Everyday life is full of anecdotes to get us thinking. Now, let’s get to the science for some evidence.

The basic format of Zajonc’s experiments (in technical speak “paradigm”) was to repeatedly expose people to an item and then test their preference for it. In his classic article, Zajonc examined people’s preference for made-up “Turkish” words, Chinese characters, and men’s faces – neutral items that people had not seen before. Specifically, in Zajonc’s third experiment, people viewed a man’s face 0, 1, 2, 5, 10, or 25 times. After viewing the faces, people indicated how much they might like each man on a seven-point scale. On average, the more people saw a picture of a particular man, the more they thought they would like the man. Hence, simply repeatedly viewing something (“mere exposure”) affects preference.  Zajonc argued that this effect is best for unfamiliar items.

Flash forward to 2001 to Zajonc’s article titled “Mere Exposure: A Gateway to the Subliminal.” This is 33 years after his original work. Now, Zajonc calls the mere-exposure effect, the mere-repeated-exposure effect. He also offers an explanation for how an item repeatedly touching your senses increases your liking of the item. He suggests that it’s a form of classical conditioning.

For a refresher on classical conditioning, go here. In short, a neutral item gets associated with an item that naturally and automatically elicits some sort of a response. After a while, the neutral item alone will elicit the response.

The omnipresent example involves a bell (the neutral item), food (the item that automatically elicits a response), and a dog salivating (the response).

Keep in mind, food automatically causes a dog to salivate but the bell does not.

Now ring a bell during a dog’s feeding time, preferably within 500 ms of presenting the food. Rinse and repeat. Bring in the food; ring the bell. After a few of such trials, the food and bell link together, and ringing the bell (without any food around) will cause the dog to salivate.

Conditioning has occurred. Huzzah!

Let’s see how this process could have occurred in the mere-exposure experiments.

Zajonc argued in the 2001 article that the innate response to an environment not trying to kill you is a positive feeling. After all, survival is important. (Remember his early life.) In the just-described experiment from Zajonc’s 1968 article, people saw men’s faces within a nice environment: The room was nice; the experimenter was nice; the task was – well nice. The automatic response to such an environment is a warm, fuzzy feeling. Repeatedly viewing the faces within this environment resulted in a link between the men’s faces (the neutral item) and environment (the item that automatically elicits a response). After a while, the faces alone elicited the warm, fuzzy feeling (the response).

Conditioning has occurred. Huzzah!

Is this what’s happening behind the mere-exposure scene?


What we know with quite a bit of certainty is the mere-exposure phenomenon is very robust. It’s been shown over and over again in different experiments and across species. My husband even thinks that’s how he got me to marry him. Through mere-exposure.





1 Fox, M. (2008, December 6). Robert Zajonc, who looked at mind’s ties to actions, is dead at 85. The New York Times. Retrieved April 23, 2014, from

2 Diane Swanbrow, D. (2008, December 9). Obituaries: Robert Zajonc. The University Record Online: News for Faculty and Staff. Retrieved Retrieved April 23, 2014, from

3 Plous, S. (2005, July 24). Rober Zajonc. Social Psychology Network. Retrieved April 23, 2014, from

4 Zajonc, R. B. (1968). Attitudinal effects of mere exposure. Journal of Personality and Social Psychology, 9(2), 1-27. doi:

5 Zajonc, R. B. (2001). Mere exposure: A gateway to the subliminal. Current Directions in Psychological Science, 10, 224-228.

Picture Attribution

Wikimedia Commons: Robert Zajonc by Linda A. Cicero/Stanford News Service