Having relationship troubles? Then try stroking your partner's arm at the precise speed at which cherry blossom falls.

It might sound bizarre, but an experiment has concluded that gently stroking a line along the inner forearm, between the wrist and the elbow, can significantly improve mood and happiness. 

The stroking – done with a soft paintbrush – should be conducted at just five centimetres a second – the speed at which cherry blossom falls to the ground in spring.

The technique improved mood by up to 50 per cent and works even if you're in a grump. 

In fact, it's so successful it could be used in couples therapy, the study found. 

The experiment, by researchers at Karoli Gaspar University in Hungary, involved 110 men and women quizzed about relationship satisfaction. 

A 10cm (4in) line was drawn along the inner right forearm, starting at the wrist and extending towards the elbow, and electrodes were put on their chest to monitor heart rhythm. 

Participants were first shown images designed to trigger a negative mood. 

Some then had the line stroked by a romantic partner using a watercolour brush at 5cm per second for three minutes. 

Others were stroked by a researcher, while a third group simply looked at their arm without stroking. 

If a romantic partner did the stroking, mood scores improved by 40 to 50 per cent for men and women – even if they weren't completely satisfied in their relationship.

Scores were 20 percentage points higher than if a researcher was involved. 

One theory as to why it works is that nerves called C-tactile fibres in hairy skin respond to slow skin-to-skin contact to trigger social bonding and stress reduction. 

In the International Journal of Psychophysiology, the research team wrote: 'For those who respond well to stroking it might be usable even under difficult emotional circumstances, such as in couples therapy.'