There was a story on a topical new program in the 90s (The Day Today) about an experiment looking into the existence of souls that seemed pretty valid, reliable and generalisable to the wider human population.
It was performed on a small sample of mice who were starved for several days.
They were fired at a wall by a special gun (unfortunately killing them in the process).
On a shelf 37.5 cm higher than the impact point of the mouses head were 12.5 grams of cheese.
If the mice had a soul they would be hungry and as they floated up to heaven they would try to eat the cheese.
A special camera that can detect souls was set up to record any evidence of the mouses souls trying to eat the cheese.
I never found out what the results were.