Garold Stasser

Garold Stasser is a social psychologist whose experiments show how groups can overlook information that only some members possess. In the account of collective problem solving, his research supplies a precise explanation for a recurring failure: a group may contain more relevant knowledge than it actually brings to bear, because discussion favors what everyone already knows and can force new evidence into an existing picture.

The Hidden-Information Experiment

Stasser studied a group of eight people asked to rate the performance of thirty-two psychology students. Each member received two relevant pieces of information about the students, such as grades and test scores. Two members received two additional pieces, such as classroom performance, and one member received another two. The group therefore held six useful pieces of information altogether, but only two were shared by everyone.

The ratings relied almost entirely on those common facts. Information held by only some members was treated as unimportant or unreliable, even though it could have enriched the group’s judgment. The experiment exposed a gap between information available to a group and information it actually uses: pooling people in one discussion does not automatically pool what they know.

How Discussion Protects the Familiar

Stasser also found that unstructured, free-flowing conversations tend to spend the most time on information everyone already knows. The pattern is paradoxical: the facts most likely to be repeated are not necessarily the ones that add the most to the group’s understanding. Shared information is easy to recognize and discuss; less familiar contributions have fewer opportunities to shape the conversation.

Even when new information is presented and heard, it may have little effect. Participants can reinterpret a message to fit what they already believe, or modify it until it agrees with the group’s prior picture. This makes unusual information especially vulnerable: precisely because it departs from expectations, it may be discounted instead of prompting a revision. Stasser’s findings therefore distinguish mere exposure to evidence from actually incorporating it into judgment.

Significance for Collective Decisions

The work is used to explain why groups need more than access to diverse information. In the discussion of a NASA decision-making team, the group’s tendency to begin with a conclusion and reinterpret later evidence in its favor is presented as a related danger. Stasser’s research provides a concrete model of the process: shared facts dominate deliberation, while knowledge held by fewer people can be sidelined or misread. Better group judgment depends on creating conditions in which distinctive information can be voiced and taken seriously, rather than assuming that discussion alone will make a group wiser.

The broader point is not that every uncommon contribution is correct, but that a group cannot assess information it has effectively screened out. Stasser’s experiments show how collective intelligence can fail inside a room full of relevant knowledge: the weakness lies not only in what members know, but in the discussion’s capacity to let that knowledge alter the result.