Influenced by the fashionable beliefs of physiognomy of the 19th century, Duchenne wanted to determine how the muscles in the human face produce facial expressions which he believed to be directly linked to the soul of man.
He is known, in particular, for the way he triggered muscular contractions with electrical probes, recording the resulting distorted and often grotesque expressions with the recently invented camera.
He published his findings in 1862, together with extraordinary photographs of the induced expressions, in the book Mecanisme de la physionomie Humaine (The Mechanism of Human Facial Expression, also known as The Mechanism of Human Physiognomy).

Duchenne believed that the human face was a kind of map, the features of which could be codified into universal taxonomies of mental states; he was convinced that the expressions of the human face were a gateway to the soul of man.
Unlike Lavater and other physiognomists of the era, Duchenne was skeptical of the face's ability to express moral character; rather he was convinced that it was through a reading of the expressions alone (known as pathognomy) which could reveal an "accurate rendering of the soul's emotions".
He believed that he could observe and capture an  "idealized naturalism" in a similar (and even improved) way to that observed in Greek art.
It is these notions that he sought conclusively and scientifically to chart by his experiments and photography and it led to the publishing of The Mechanism of Human Physiognomy in 1862 (also entitled, The Electro-Physiological Analysis of the Expression of the Passions, Applicable to the Practice of the Plastic Arts.
in French: Mécanisme de la physionomie humaine, ou Analyse électro-physiologique de l'expression des passions applicable à la pratique des arts plastiques), now generally rendered as The Mechanism of Human Facial Expression.
The work compromises a volume of text divided into three parts:
General Considerations,
A Scientific Section, and
An Aesthetic Section.

These sections were accompanied by an atlas of photographic plates.
Believing that he was investigating a God-given language of facial signs, Duchenne writes:
In the face our creator was not concerned with mechanical necessity.

He was able in his wisdom or – please pardon this manner of speaking – in pursuing a divine fantasy … to put any particular muscles into action, one alone or several muscles together, when He wished the characteristic signs of the emotions, even the most fleeting, to be written briefly on man's face.
Once this language of facial expression was created, it sufficed for Him to give all human beings the instinctive faculty of always expressing their sentiments by contracting the same muscles.

This rendered the language universal and immutable.

Duchenne defines the fundamental expressive gestures of the human face and associates each with a specific facial muscle or muscle group.
He identifies thirteen primary emotions the expression of which is controlled by one or two muscles.
He also isolates the precise contractions that result in each expression and separates them into two categories: partial and combined.
To stimulate the facial muscles and capture these "idealized" expressions of his patients, Duchenne applied faradic shock through electrified metal probes pressed upon the surface of the various muscles of the face.

Duchenne was convinced that the "truth" of his pathognomic experiments could only be effectively rendered by photography, the subject's expressions being too fleeting to be drawn or painted. "
Only photography," he writes, "as truthful as a mirror, could attain such desirable perfection."
He worked with a talented, young photographer, Adrien Tournachon, (the brother of Felix Nadar), and also taught himself the art in order to document his experiments.
From an art-historical point of view, the Mechanism of Human Physiognomy was the first publication on the expression of human emotions to be illustrated with actual photographs.
Photography had only recently been invented, and there was a widespread belief t
Influenced by the fashionable beliefs of physiognomy of the 19th century, Duchenne wanted to determine how the muscles in the human face produce facial expressions which he believed to be directly linked to the soul of man. He is known, in particular, for the way he triggered muscular contractions with electrical probes, recording the resulting distorted and often grotesque expressions with the recently invented camera. He published his findings in 1862, together with extraordinary photographs of the induced expressions, in the book Mecanisme de la physionomie Humaine (The Mechanism of Human Facial Expression, also known as The Mechanism of Human Physiognomy).
Duchenne believed that the human face was a kind of map, the features of which could be codified into universal taxonomies of mental states; he was convinced that the expressions of the human face were a gateway to the soul of man. Unlike Lavater and other physiognomists of the era, Duchenne was skeptical of the face's ability to express moral character; rather he was convinced that it was through a reading of the expressions alone (known as pathognomy) which could reveal an "accurate rendering of the soul's emotions". He believed that he could observe and capture an  "idealized naturalism" in a similar (and even improved) way to that observed in Greek art. It is these notions that he sought conclusively and scientifically to chart by his experiments and photography and it led to the publishing of The Mechanism of Human Physiognomy in 1862 (also entitled, The Electro-Physiological Analysis of the Expression of the Passions, Applicable to the Practice of the Plastic Arts. in French: Mécanisme de la physionomie humaine, ou Analyse électro-physiologique de l'expression des passions applicable à la pratique des arts plastiques), now generally rendered as The Mechanism of Human Facial Expression. The work compromises a volume of text divided into three parts:
General Considerations,
A Scientific Section, and
An Aesthetic Section.
These sections were accompanied by an atlas of photographic plates. Believing that he was investigating a God-given language of facial signs, Duchenne writes:
In the face our creator was not concerned with mechanical necessity. 
He was able in his wisdom or – please pardon this manner of speaking – in pursuing a divine fantasy … to put any particular muscles into action, one alone or several muscles together, when He wished the characteristic signs of the emotions, even the most fleeting, to be written briefly on man's face. Once this language of facial expression was created, it sufficed for Him to give all human beings the instinctive faculty of always expressing their sentiments by contracting the same muscles. 
This rendered the language universal and immutable.
Duchenne defines the fundamental expressive gestures of the human face and associates each with a specific facial muscle or muscle group. He identifies thirteen primary emotions the expression of which is controlled by one or two muscles. He also isolates the precise contractions that result in each expression and separates them into two categories: partial and combined. To stimulate the facial muscles and capture these "idealized" expressions of his patients, Duchenne applied faradic shock through electrified metal probes pressed upon the surface of the various muscles of the face.
Duchenne was convinced that the "truth" of his pathognomic experiments could only be effectively rendered by photography, the subject's expressions being too fleeting to be drawn or painted. "Only photography," he writes, "as truthful as a mirror, could attain such desirable perfection." He worked with a talented, young photographer, Adrien Tournachon, (the brother of Felix Nadar), and also taught himself the art in order to document his experiments. From an art-historical point of view, the Mechanism of Human Physiognomy was the first publication on the expression of human emotions to be illustrated with actual photographs. Photography had only recently been invented, and there was a widespread belief t
Duchenne de Boulogne