Despite efforts to portray themselves to the outside world as united behind Ayatollah Ruhollah Khomeini, the men and women holding 50 Americans hostage appear characterized by indecision, tensions and intense rivalry.

Journalists, diplomats and other outsiders who have approached the hostages' captors since the Nov. 4 occupation of the U.S. Embassy are convinced that various rival groups are nearly paralyzed by a lack of strong leadership.

Decisions large and small routinely are referred to a central committee -- which may number as many as 50 members -- under the guise of democracy.

But the haggling, rigid, unsmiling captors are so jealous of each other that colored string is used in various corridors and rooms of embassy buildings to delineate the territory apportioned to different groups.

One student reported there are now so many checkpoints inside the 27-acre compound that it takes as long as one hour to move from one end to the other.

Some visitors have detected as many as five different groups, including some members of the Revolutionary Guards, Khomeini's elite troops. But the captors have succeeded in keeping secret their exact indentities. One school of thought argues that most belong to a fundamentalist group called the Phalange, which originated among middle-class students of Tehran bazaar merchant families.

Aside from students drawn from Tehran universities, the captors' ranks also include theological students from the holy city of Qom. That group is considered the only one literally fitting the description they all claim -- "students following Khomeini's line."

Some sources suggest the Qom students were brought to provide a loyalist core for Khomeini after the initial assult at the embassy.

Outsiders' suggestions that leftists or communists are involved in the embassy occupation have not been confirmed.

Often cited as evidence of leftist involvement is the captors' diligence in publishing purported official American documents said to have been found in the embassy.

Mardom, the official organ of the pro-Moscow Tudeh Communist Party, has called for all documents to be published.

Buttressing assertions of leftist influence are the captors' political vocabulary, punitive attitude toward the hostages and general inflexibility.

Analysts noted, however, that these techniques have become common practice in hostage seizures by many different political groups, and they are loath to draw any definitive conclusions. Indeed, most observers believe the dominant theme in this case is thoroughly Islamic fundamentalism.

The degree of religious fervor does appear to vary among various captors. For example, some, possibly leftist, women are willing to shake hands with male visitors, while others refuse in keeping with their more orthodox Islamic beliefs.

If the outside world is kept in the dark about the captors' identities, various Iranian public figures claim to know which groups are involved, although they have refused so far to provide any detailed accounting.

Abol Hassan Bani-Sadr, now the fiance minister, has recounted how the students telephoned him to announce their embassy takeover plans. A friend answered the telephone and did not bother to tell him.

"Fate," Bani-Sadr said. He has expressed deep-seated opposition to the embassy takeover, repeatedly and publicly calling it a misguided adventure. "I knew them and could have talked them out of it," he mused.

His efforts to do that have been notable failures so far.

On the surface the captors still demand the unconditional return of Shah Mohammad Reza Pahlavi as their price for freeing the hostages.

But gradually over the weeks their single-theme approach has been eroded. Khomeini himself first suggested a trial for hostages deemed quilty of spying, a stratagem which could lead to show trial and immediate expulsion of the diplomats.

Similarly, the students this week have gone along with Khomeini's endoresement of a grand-jury-like board of international inquiry into the shah's alleged crimes. If convened, this could serve a similar face-saving purpose.

The captors also accepted his approval for "independent international observers" to visit the hostages, a request hitherto refused out of hand.

Such unwonted accommodation contrasts with bitter-end arguments condemning compromise on grounds that Iran has already so angered the United States that returning the hostages without the shah's extradition will only mean Tehran's doom.

The captors have established their repeated contempt for the theoretically ruling Revolutionary Council, which on various occasions has sought to work out a face-saving formula.

In the past five weeks the students have become the major political force in Iran, second only to Khomeini himself. But the politics of ultimate radicalization they are pursuing may contain the seeds of their own destruction.

Like everyone else in revolutionary Iran, they are undergoing a political apprenticeship after the void left by the shah's authoritarian reign.

Judging from their progress in ferreting out incriminating official American documents -- after initially sophomoric efforts to pass off walkie-talkies and metal detectors as spy gear -- they may have learned more than now meets the eye.