On the fifth floor, children were playing creative games: on the seventh, a mariachi band was playing "Cucurucucu Paloma," and over in once corner of the East Building of the National Gallery, S. Dillon Ripley and J. Carter Brown were playing a private game that one observer called "museum polities."

At a reception to open the two-day colloquium on "Play and Inventiveness," sponsored by 10 government, research and educational organizations and held at the National Gallery, the scene was the kind of cheerful jumble that is usually associated with both playfulness and creativity. There was serious academic work-for example, a talk by psychologist Erik Erikson on Einstein's childhood-but there was a prevailing atmosphere of playfulness.

Organized play began as soon as the guests entered, with the name tags they were to wear during the reception. Each guest was given a piece of construction paper on which to write his or her name, and then invited to attach any number of identifying labels (which ranged from "Candy Lady" and "Social Butterfly" to "Rat Racer" and "Superstar") for further details.

Lynda Robb chose to identify herself as "Donwnhome" and "Nearsighted," which nobody present was prepared to deny, while J. Carter Brown chose two tags which might have been accurate but seemed somehow incomplete: "Happy Face" and "Paper Shuffler," S. Dillon Ripley displayed a healthy self-esteem with "Hero," "Great Wizard" and "Mind Machine."

Funny hats were worn by many of the children, who also wrote peoms about ideas and imagination, built intricate machines to symbolize the working of their minds, improvised brief ballets to the rhythms of people's names, conducted interviews, wrote recipes for such concoctions as happiness and generally behaved in a bright, well-behaved manner. Some of the adults joined in the spirit of the children's games, while others sipped margaritas or sangria, munched tacos and enjoyed two of Washington's most spectacular views from the east and south balconies of the East Building's seventh floor.

Erik and Joan Erikson smiled benignly on the turbulence of activities around them but preserved their adult identities as befits a couple in their late 70s-though Mrs. Erikson was heard to remark that "learning never stops, even when you're crowding 80."

Each of the Eriksons spoke on turn at the colloquium's opening lectures, Mr.s Erikson leading off with a discussion of the early stages of a child's development. Creativity is the natural heritage of all humans, she said. "I don't believe in talent-in fact, the word originally and specifically referred to money . . . and the idea obstructs the development of creativity in such a large majority of people."

Her husband devoted his lecture to Einstein, who "started lief with some seeming deficiencies but ended as one of the geniuses of our time." He attributed the range and flexibility of Einstein's mind, in part, to "a certain lasting childishness" and noted that the boy's parents were worried for many years about what seemed to be symptoms of retardation. He warned that if children are tested in should be in "a whole broad range of children's capacities." CAPTION: Picture, Erik and Joan Erikson, by James M. Thresher-The Washington Post