We've learned that if you want to make a man talk, send a pretty woman. And when we want to make a woman talk, we make her jealous. Both theories work amazingly well.

12 seconds sound clip from the The 39 Steps (1937) classic radio play.

You can hear this line at 00:40:32 in the radio play.

Quote context

[...]

- And a properly prepared nation is a nation seldom attacked. The war that they are ready for rarely comes.

- If what I've observed is true, you soldiers who fight with your brains instead of bayonets are finding more and more women as your co-workers.

- How does a woman compare with a man as a spy?

- Very favorably... up to one point.

- A woman's heart will rule her head much more quickly than a man's.

- Today, there is probably one woman to every two men in the world's espionage service.

- We've learned that if you want to make a man talk, send a pretty woman. And when we want to make a woman talk, we make her jealous. Both theories work amazingly well.

- It would appear to me that spying is one activity which provides little or no room for modernization.

- Along with qualifications, I presume that methods have changed little since the days of Moses.

- That's very true. They remain essentially unchanged.

- But there have been radical technical changes in carrying out those essentials.

- For instance, there's a machine, recently developed in this country, so delicate and so accurate that it can etch an invisible secret message on a surface no larger than a grain of corn.

[...]