When this writer was three years old, more than half a century ago, his American family moved into a traditional Japanese house on the outskirts of Tokyo. His landlord and neighbours were scandalised that they wore their shoes inside and kept their large Labrador retriever indoors on the tatami mats.

Over five decades later, shoes are still forbidden but dogs are welcome indoors in most canine-owning Japanese households. Japanese cities abound with prams containing pampered lap dogs allowed to run free in pooch-friendly cafés and houses.

Why have dogs, but not shoes, been permitted in the home? For one thing, the rule against shoes has ancient roots. Shoes and feet have historically been deemed “dirty” in a way that goes beyond simple hygiene.

Taking off one’s shoes at the threshold is one of many rituals – such as washing one’s hands with holy water before entering a shrine – that mark the passage from one space into another. Japanese suicides typically remove their shoes before leaping off a roof or train platform into the next world.

It is true that dogs have often been regarded as dirty, not only in Japan but in the west. In the Bible, Homer and Shakespeare, dogs are often described pejoratively, sometimes as predators and scavengers that feed on corpses and lick their own vomit.

But keeping dogs outside had less to do with hygiene than with the fact that they were kept mainly to guard homes and for hunting – activities that took place outdoors. Dogs tethered on short chains at the entrances to buildings, with signs reading “beware, ferocious dog” were common sights in Tokyo neighborhoods in the 1960s.

The dogs were usually native Japanese breeds, aloof and used to living outdoors.

Most Japanese in those days were unsentimental about dogs, which were valued in purely utilitarian terms for the work they performed. Breeding dogs for companionship, which began in Europe on a large scale in the late 18th century, had yet to reach Japan.

That changed quickly in the 1960s thanks to a combination of interrelated influences. The first was that the spartan mindset of Japan before World War II relaxed as the nation recovered from the conflict and became more prosperous.

Before the war, treating dogs as pets would have been regarded as frivolous. Prosperity allowed Japan’s emotional climate to soften.

Second, the nation’s newly acquired affluence ushered in a change from domestic life lived low to the ground on tatami mats to a more upright western style of daily life based on wood and linoleum floors, tables, chairs, modern toilets, and electrical appliances.

Around the time of the 1964 Tokyo Olympics, the LDK (western style living-dining-kitchen room) began to replace tatami mat rooms as the preferred domestic configuration. The shift was not designed to accommodate dogs, but hard floors and owners living on a higher plane were essential prerequisites.

Third, Japan imported from the west the idea that dogs need not be simply utilitarian working animals. Disney movies featuring lovable indoor dogs such as “Peter Pan” (1953), “Lady and the Tramp” (1955), and “101 Dalmatians” (1961) boosted the popularity of cocker spaniels and Dalmatians in particular.

However, the most important factor that opened Japanese homes to dogs was a decline in the fertility rate, which dropped from four children per woman to two between 1950 and 1975, and then fell to 1.36 in 2000, where it has more or less remained.

Large families abruptly went out of fashion, leaving a vacuum that has been filled by dogs (and cats, which, because of their unobtrusive size and habits, have met with less resistance indoors).

The Japanese dog breeds that were kept outdoors have been replaced by small, indoor-friendly western breeds that serve as child-substitutes: toy poodles, Maltese, Shih Tzus and the like.

Demand for canine companionship has created its own supply of supporting products and services. Rental houses and apartments, which once uniformly forbade dogs, now have more liberal policies. Trimming salons, organic dog food and veterinarians specialising in geriatric canines have become part of the landscape.

In deference to ancient custom, owners still wipe their dogs’ paws before allowing them into their houses after walks. But this ritual observation of the boundary between the outside world and the inner sanctum of the home is a small detail compared to the deeper changes reflected in letting dogs into houses.

When dogs lived outdoors, it was common practice for the male head of the household to drop his suit or work clothes on the tatami mat for his waiting wife to fold and put away.

It is not just dogs that have been promoted to a better place in daily life.

This article was written by Stephen Givens for Nikkei Asia.