This past weekend, I went to two different holiday parties. While many of the people at the parties were friends, I was also introduced to a couple dozen new people — out of town guests of the hosts, friends of friends, or people from our small town that I somehow had never met. If I run into one of these people at the coffee shop tomorrow, how likely will I be to remember that I’ve met them before? One possibly relevant factor is that I was a designated driver at just one of the two parties.

There’s another factor that has been demonstrated to have a significant effect on whether a face is remembered: the facial expression. In 2004, Arnaud D’Argembeau and Martial Van der Linden found that people who viewed a series of photos of faces were more likely to remember smiling faces compared to angry faces — even when the faces they were later asked to recall had neutral expressions.

In a new study, they wanted to explore the other factors affecting our our ability to remember faces. This time they had 72 volunteers rate 16 faces on one of three different attributes: emotion expressed, intelligence, and nose size. The faces were seen for just five seconds each. Some of the faces they saw were happy, and some were angry. After a one-minute distraction task, there was a surprise memory test. The viewers were shown neutral faces, some of which they had seen before, and some they hadn’t. So which faces did they remember? Here are the results:

As expected, viewers were significantly more likely to remember the happy faces than the angry faces. However, there was also a difference based on the task viewers performed when they initially viewed the faces: Viewers who rated nose size remembered significantly fewer faces than those who rated the facial expression or intelligence of the faces.

But guessing that you might remember a face is different from distinctively recalling it. In a new experiment, D’Argembeau and Van der Linden asked volunteers not just if they recalled seeing a face, but also how strong the recollection was. This graph shows the proportion of respondents who said they distinctly remembered a particular feature of a given face:

As you can see, there’s now a big difference between the viewers who rated intelligence and those rating facial expression. (Pinocchio fans will be disappointed to see that nose length was not rated in this experiment). Even though, as before, there was no overall difference in accuracy for recalling faces that expressed the same emotion, when viewers had rated faces for intelligence previously, they were much more confident in their recollections of faces, with happy faces resulting in the most strong recollections.

So it seems that when viewers pay attention to specific features of faces, such as the facial expression or the nose length, their recollections of that face aren’t as strong as when they attend to general qualities of the person behind the face.

So if you want someone to remember your face, smile. If you want to remember someone’s face, don’t think about the specific details of their face; think about what kind of person they are.

D’Argembeau, A., Van der Linden, M. (2007). Facial expressions of emotion influence memory for facial identity in an automatic way. Emotion, 7(3), 507-515. DOI: 10.1037/1528-3542.7.3.507