will look similar to each other, even though crossbreeding does not result in as uniform a phenotype as the breeding of purebreds. Often even pups in the same litter will look quite different. Another defining characteristic of designer dogs is that they are usually bred as companion dogs and pets. Working and hunting dogs deliberately crossbred for a particular working purpose are not generally given portmanteau names; they are most often referred to by a type name, such as Eurohounds (racing sled dogs) or lurchers (hunting dogs). These dogs could be considered only as crossbreeds, not as designer animals, since appearance is not the main reason for them to be bred. An exception to this is the Labradoodle, which although having a portmanteau name, is often used as a Guide or Assistance dog as well as being a popular family dog. Although designer dogs are often selected by owners for their novelty, reputable breeders sometimes use crossbreeding in an attempt to reduce the incidence of certain hereditary problems found in the purebred dogs, while retaining their more appealing traits. Jon Mooallem, writing in The New York Times, commented, "Given the roughly 350 inherited disorders littering the dog genome, crossing two purebreds and expanding their gene pools can be 'a phenomenally good idea,' according to one canine geneticist—if it is done conscientiously." Crossbreeding has not been well studied in dogs, although it has been for livestock. The heritability of the desired trait being bred for (such as a hypoallergenic coat) needs to be known; "Heritability is the proportion of the measurable difference observed between animals for a given trait that is due to genetics (and can be passed to the next generation)." In addition, the goals of dog crossbreeding may be harder to define than the goals of livestock crossbreeding; good temperament may be harder to define and measure than high calf weight. Designer dog breeders are often criticised for being more interested in profitable puppy production than in dog health and welfare. Wally Conron, writing in Reader's Digest, comments on the popularity of crosses after his introduction of the Labradoodle: "Were breeders bothering to check their sires and bitches for heredity faults, or were they simply caught up in delivering to hungry customers the next status symbol?" 'Designer dog' puppies sometimes bring higher prices than the purebreds from which they are bred. Fanciers of designer dogs say that all modern