Many studies have tried and failed to determine the cause of this.

A similar study in 1974 failed to find any two year old fish breeding.

A later study, in 1990, failed to indicate any ability to identify events at a level greater than chance.

But later studies failed to back up those earlier findings.

The company's studies in depressed children failed to show any positive effect.

Two other studies had failed to show a link to gulf war service.

But clinical studies have failed so far to make the case.

This could explain why so many studies have failed to find evidence of performance persistence.

If the study fails, then no federal funding will be provided.

A second study also failed to show any evidence of probing.