Darwin smiling

Fig. 20 from Darwin 1872. "Terror"

While I was out of town for the holidays, a news story by Jeanna Bryner reported on research that looked at the facial expressions of blind Paralympians:

The analyses showed sighted and blind individuals modified their expressions of emotion in the same way in accordance with the social context. For example, in the Paralympics, the athletes competed in a series of elimination rounds so that the final round of two athletes ended in the winner taking home a gold medal while the loser got a silver medal.
The blind silver medalists who lost their final matches tended to produce "social smiles" during the medal ceremonies. Social smiles use only the mouth muscles. True smiles, known as Duchenne smiles, cause the eyes to twinkle and narrow and the cheeks to rise.

The “social smile” is interesting because it seems like a way of concealing emotions from others. The conclusion was that visual learning could not account for the socially correct use of these expressions, since people blind from birth follow the same rules.

When I read this story, I couldn’t help but reflect on Darwin’s description of facial expressions, in The expression of the emotions in man and animals. By taking up this topic, Darwin set out on new mode of psychological investigation, distinct in many ways from the experimental psychology tradition. In fact, the major figures in German experimental physiology, such as Wundt, are never mentioned in Expression. This clean separation may have been Darwin’s deliberate attempt to establish psychological inquiry on new ground; his intent was marked in the last section of the Origin:

In the distant future I see open fields for far more important researches. Psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by gradation. Light will be thrown on the origin of man and his history (Darwin 577-578).

Darwin was not alone in pursuing a comparative approach and insisting on continuities between humans and other animals. In some details he followed Herbert Spencer’s psychology. George Romanes picked up Darwin’s own notes on animal behavior as he began to systematize the field; his Animal Intelligence ranged in its examples from invertebrates to man’s best friend, the dog.

Darwin also spends substantial parts of Expression on the expressions of dogs. His analysis, like his description of sexual selection in The descent of man presages later work on signaling. But Darwin’s human examples are some of the most interesting in the book. The picture at the top of this post was drawn “from a photograph by Duchenne” – the same Duchenne (Guillaume-Benjamin-Amand de Boulogne) whose name is commemorated by the “Duchenne smile” as well as the eponymous muscular dystrophy. Duchenne was an experimental physiologist, who among other things used electrical stimuli to contort the facial muscles into their characteristic expressions.

Darwin used the photograph above in Expression, along with others of the same experimental subject. The experimenter at right is Duchenne.

Darwin had other means of obtaining information that the current researchers of Paralympians lack. For instance:

Dr. W. Ogle observed for me in one of the London hospitals about twenty patients, just before they were put under the influence of chloroform for operations. They exhibited some trepidation, but no great terror. In only four of the cases was the platysma visibly contracted; and it did not begin to contract until the patients began to cry. The muscle seemed to contract at the moment of each deep-drawn inspiration; so that it is very doubtful whether the contraction depended at all on the emotion of fear. In a fifth case, the patient, who was not chloroformed, was much terrified; and his platysma was more forcibly and persistently contracted than in the other cases. But even here there is room for doubt, for the muscle which appeared to be unusually developed, was seen by Dr. Ogle to contract as the man moved his head from the pillow, after the operation was over. (Darwin 1872:300-301).

His subsequent discussion is interesting, begun with a characteristic Darwin question: “…I felt much perplexed why, in any case, a superficial muscle on the neck should be especially affected by fear….”

Darwin particularly sought to distinguish the unconscious signs of emotions from the deliberate, and the culturally variable from the universal. In a time when the study of cultural variability was just beginning, Darwin does an admirable job.

His explanations of unconscious expressions presage some of the writings of behaviorists, notably John Watson:

Through steps such as these we can understand how it is, that as soon as some melancholy thought passes through the brain, there occurs a just perceptible drawing down of the corners of the mouth, or a slight raising up of the inner ends of the eyebrows, or both movements combined, and immediately afterwards a slight su?usion of tears. A thrill of nerve-force is transmitted along several habitual channels, and produces an e?ect on any point where the will has not acquired through long habit much power of interference. The above actions may be considered as rudimental vestiges of the screaming-?ts, which are so frequent and prolonged during infancy.
In this case, as well as in many others, the links are indeed wonderful which connect cause and e?ect in giving rise to various expressions on the human countenance; and they explain to us the meaning of certain movements, which we involuntarily and unconsciously perform, whenever certain transitory emotions pass through our minds.

Darwin did discuss the issue of Duchenne smiles and false smiles in Expression. Here is a redacted section from pages 203-204:

Dr. Duchenne has given a large photograph of an old man (reduced on Plate III. fig 4), in his usual passive condition, and another of the same man (fig. 5), naturally smiling. The latter was instantly recognised by every one to whom it was shown as true to nature. He has also given, as an example of an unnatural or false smile, another photograph (fig. 6) of the same old man, with the corners of his mouth strongly retracted by the galvanization of the great zygomatic muscles. That the expression is not natural is clear, for I showed this photograph to twenty-four persons, of whom three could not in the least tell what was meant, whilst the others, though they perceived that the expression was of the nature of a smile, answered in such words as "a wicked joke," "trying to laugh," "grinning laughter," "half-amazed laughter," &c. Dr. Duchenne attributes the falseness of the expression altogether to the orbicular muscles of the lower eyelids not being sufficiently contracted; for he justly lays great stress on their contraction in the expression of joy.

He goes on to examine the muscles involved in the expression with more detail. Darwin’s concern was to connect the smiles of humans with expressions of other primates, and to connect the actions of the facial muscles in a rational way. For example, Darwin suggested that the zygomatic muscles contract during pleasurable emotions, and attempted to relate the characteristic expressions of mental patients having delusions of grandeur to that pattern. Elsewhere, he examines the “grins” of dogs and their relation to play, as well as various reports of smiles in non-human primates.

So, I doubt Darwin would have been surprised by the research on blind athletes.


Darwin CR. 1872. The expression of the emotions in man and animals. John Murray, London.

Darwin CR. 1869. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. John Murray, London. 5 ed.