They say social and psychological factors also are at play.

The psychological factors behind all this are not hard to understand.

And, he might have added, the psychological factors were far more important than the physical ones.

And there is the psychological factor of having a world record to break.

There is even evidence that psychological factors come into play.

But I think there is a psychological factor at play, too.

His trust model is based on social and psychological factors.

There may be a psychological factor at work here as well.

And then we have the individual psychological factors which go through our heads.

There are psychological factors to be taken into account, too.