Armand’s leap (or Armand’s chasm) is a phenomenon in observational psychology where an observer sees another subject undertake an action and is momentarily paralyzed with the choice of whether they should intervene, do nothing, or do the same thing themselves.¹ The phenomenon is named after Jean-Louis Armand, an 18th-century French clerk best known for his late-in-life writings from St. Lazare.²

Summary

Armand was among the large crowd gathered at Boulogne-sur-Mer to observe Jean-François Pilatre de Rozier and Jules Romain attempt to cross the English Channel by balloon. Armand, along with thousands of others, witnessed the balloon catch fire in the air, suddenly falling from a height of 1,500 feet. Both balloonists were killed instantly. Their deaths greatly affected Armand, who wrote:

Here are two great men of science, attempting a feat in the air heretofore only made possible by the sea, which time and again proves her hunger for human souls. What could have been an Apollonian triumph of human genius over circumstance proved precisely the opposite: the wind blew, the flames escaped the balloon’s silk envelope, & death saw all.⁴

Armand developed a morbid fascination with the event when he learned that Rozier’s fiancée, Susan Dyer, was in the crowd as well, and that she died (possibly by suicide) eight days later. Armand also discovered from the press surrounding the event that Rozier had turned away a nobleman at the last moment from joining him and Romain in the balloon, saying the flight was too dangerous. This combination led to the original formulation of Armand’s leap:

I remember my heart almost leaping out of my chest to shout, “Don’t go! Don’t go!” I had read the letters by the priests in the papers, calling manned flight an affront to God. Whether or not I believed that myself, this inner part of me feared for the lives of these men, steeled by scientific understanding but ultimately offering themselves to the fickle gales of the Channel. Much like the Channel, this cry in my heart stood across an infinite chasm from action—I thought to intervene, but did not intervene, nor did any of the thousands in the crowd. We watched.

The gentleman Rozier turned away must have had precisely the opposite cry to mine in his heart—“I must go! I must go!” It was also whispered that the death of Rozier’s betrothed—Miss Dyer, who saw the entire cataclysm unfold along with all of us—may have been at her own hand. Whether she died in grief or at the prospect of life alone God has not gifted us to know.

I cannot rid myself of this triune impossibility in the face of Rozier’s doomed flight, or any event; all human action, or inaction, seems subject to its relentless logic. We see another person propose an action, or begin to undertake it, and for a moment we are frozen—we must elect within ourselves whether we will join him, stop him, or simply look on…even in memory.⁴

Influence

Armand’s leap is considered an early observation of the bystander effect and similar concepts of human behavior under the influence of crowd dynamics and high-stress situations.

French psychologist Pierre Janet cited Armand in his account of the Dancing Plague of 1518: 

Armand’s options of intervention and non-participation may not have been available to the dancers of Strasbourg. Intervention was heresy, and non-participation its own provincial form of insanity, in the face of all the others swept up in the frenzy. All they could do was dance.⁵

References

1. ^ Harris, Ray (1991). Early History of Observation in Psychology. Taylor & Francis.

2. ^ Durkheim, Émile. (1959) Socialism. London: Routledge and Kegan Paul Ltd.

3. ^ File:Aviation fatality - Pilatre de Rozier and Romain.jpg. Retrieved 14 April 2026.

4. ^ Armand, Jean-Louis Sainte-Marie (1789). Écrits. Paris: Mercure de France.

5. ^ Intro, ibid.