Communication is truly mysterious.
I stumbled upon a study explaining that musical and vocal expression are alike — and it turns out that both in music and while talking to others, anger and sadness come through much more clearly than happiness, tenderness, or fear.
And this only applies to sound-based communication. Because in other studies, where people looked at each other's faces, happiness was usually at the top!
So what might explain this? The paper's own reasoning is that emotions that share the same energy level, also share the same vocal signature — happiness, anger and fear are all high-energy, so the voice can't really tell them apart. The face is what separates them.
My own hunch, from evolutionary psychology, is the raw need to hear danger in the dark despite not seeing it. Think of the scene from movies where the attacker first angrily calls out his target before hitting him right in the face — you had to hear that coming. Whereas happiness usually happens in peaceful, well-lit situations, like a crowded dinner table where people smile rather than shout that they're happy.
Now, what does this mean for a public speaker?
When talking about a sad or angry moment in your speech, it's more important to carry it with your voice — deepen it and slow down for sadness, push the pitch and pace up for anger. Less attention needs to go to body posture or making an angry or sad face. It's mostly about the voice.
When it comes to the happy moment, it's not that important to emphasize it with a change in pitch, variance or tempo — because your voice will undersell it anyway. What actually works here is a wide, genuine smile of yours.
Citation (APA 7):
Juslin, P. N., & Laukka, P. (2003). Communication of emotions in vocal expression and music performance: Different channels, same code? Psychological Bulletin, 129(5), 770–814. https://doi.org/10.1037/0033-2909.129.5.770