While audiences go to movies primarily for entertainment and amusement, cinema also serves as a social weather vane, indicating the general state of mind in a country or region. Look at the films produced during a particular period and you'll see many signs of what people were thinking, doing, and hoping -- often expressed in cloudy or indirect terms, but revealing and provocative all the same.
This is what makes ''A Dream, a Promise: Films of the Glasnost Era,'' now under way at Lincoln Center here, not just a motion-picture series but a major opportunity to gain new understanding of what may be the most remarkable era in Russian cultural life since the advent of Soviet rule.
Comprising more than 30 feature films as well as TV shows, cartoons, commercials, music videos, and other works, the exhibition clearly deserves its billing as the most comprehensive overview of the glasnost period -- from Mikhail Gorbachev's rise in the mid-1980s to the 1991 coup against him -- ever assembled in the United States.
Usually translated as ''openness,'' the Russian word glasnost took on international significance during the half-dozen years of Gorbachev's effort to bring new freedom and flexibility into Soviet culture. Along with perestroika (restructuring), it signaled a belated recognition that shackles on free expression -- a fact of life in the Soviet bloc throughout most of its history -- served less to foster social discipline than to block progress, stifle inventiveness, and suffocate new ideas.
Seizing on Gorbachev's initiative, his subordinates opened up cultural activity in unprecedented ways. This profoundly affected the nation's state-run film industry, which embarked on projects that would hitherto have been censored out of existence. Industry figures also started combing their vaults for movies that had been locked away for political reasons in earlier years.
As dramatic as this activity was, it remained under the control of a centralized bureaucracy that maintained its power until the Soviet Union's full disintegration. In program notes for the Lincoln Center series, curator Richard Pena rightly notes that glasnost-era filmmakers were not so much free of the authorities as in dialogue with their notions of how Soviet and Communist interests might best be served.
Pena also points out that glasnost was not limited to any single form of communication, but swept across the entire cultural field, sparking complicated new relationships between filmmakers and, say, rock musicians and visual artists -- including some who wished to probe politically embarrassing or socially unsavory aspects of modern Soviet life.
All of which made for a complex and fascinating epoch, reflected in a remarkable quantity of highly diverse films. Any attempt to arrange these in neat pigeonholes is bound to be somewhat arbitrary, but a few important categories can be usefully identified.
One is the group of banned movies that were withheld from exhibition before glasnost but later released to theaters, where they were often greeted with loud applause. An example is ''The Asthenic Syndrome,'' by Ukrainian director Kira Muratova, centering on a teacher whose sadness reflects the deep-rooted melancholy of society at large. Despite the somberness of its theme, its form resembles nothing so much as ''Slacker,'' a quirky American comedy made slightly after Muratova completed her film.
''Long Farewells,'' another banned film by Muratova, is less successful, imperfectly mixing Chekhovian drama with New Wave stylistics. More socially and cinematically striking are ''Repentance,'' by Georgian director Tenghiz Abuladze, a surrealistic fable about a deceased dictator who won't stay buried; and ''Commissar,'' by Aleksandr Askoldov, about a government official whose affection for new-found Jewish friends leads to a scathing realization of anti-Semitism in recent Soviet history.
Another category in glasnost-era cinema is the small but important group of films that were exported to the West with notable success on the art-theater or home-video circuits. ''Commissar'' is one of these, as is Pavel Lounguine's jazzy ''Taxi Blues,'' a neon-tinted melodrama about a down-and-out musician and a misanthropic cab driver who exploits him. Also worth special mention is ''Little Vera,'' by Vassily Pichul, about a high-spirited young woman whose adventures represent everything the strait-laced Soviet authorities did their best to discourage.
Still another category is the avant-garde cinema. ''The Asthenic Syndrome'' might be counted in this group, along with almost anything by Alexander Sokurov, one of the boldest figures in world film today. ''The Second Circle,'' more accessible than some of his later works, focuses on a young man who visits Siberia to bury his deceased father, only to face a series of unexpected obstacles. ''Moscow Elegy,'' an offbeat documentary, continues Sokurov's interest in the symbolism of funerals with a multifaceted look at opera singer Feodor Chaliapin's life and death. ''Interpretation of Dreams,'' by Ukrainian filmmaker A. Zagdansky, explores the collective Soviet unconscious through old movie images and passages by Sigmund Freud, himself a banned author in the USSR until glasnost liberated his writings.
Along with more conventional pictures, these and other experimental films vividly illustrate the imaginative energies set loose when glasnost launched its long-overdue revivification of Soviet cultural life. Lincoln Center is doing a favor for both East and West by showcasing such a generous selection of carefully chosen works.
* Curated by Richard Pena and Soviet film specialist Alla Verlotsky, ''A Dream, a Promise'' continues at the Walter Reade Theater through May 5, accompanied by an exhibition of Ukrainian art and two symposiums: one on filmmaking of the glasnost era, the other on current cinema in the former Soviet Union.