The Calm Diffuser by Citroën releases synthetic pheromones to soothe anxious pets in cars, extending the brand's comfort identity beyond humans. Plenty of dogs love car rides, but for millions of pet owners, getting their dog or cat into a vehicle is a real ordeal. Dogs pant and tremble; cats yowl from their carriers. It's a problem most owners have learned to live with rather than solve. French automaker Citroën, working with agency BETC Paris, wants to change that with the Calm Diffuser — a plug-in device that releases vet-approved synthetic pheromones mimicking the calming olfactory signals mother animals produce for their young. Undetectable to humans, the pheromones are designed to reduce anxiety in dogs and cats. The product extends the brand identity Citroën has built over more than a century. The company has long treated comfort as a core differentiator, from its hydropneumatic suspension to the more recent Seetroën glasses for motion sickness. But that promise has always been implicitly human.…