The United States Constitution bars Congress from abridging freedom of speech. But at a U.S. Senate Judiciary Committee hearing this week, some speakers said free speech is not being protected enough at American colleges. Zachary Wood is a student at Williams College in Massachusetts. Wood heads a group called Uncomfortable Learning. The group’s aim, he told the committee, is to invite speakers whose opinions are unpopular and troubling to college students. Two years ago, Wood, who is African American, invited a speaker who had written about the results of blacks on intelligence tests. Some people described the speaker’s writings as racist. Wood said the school’s president canceled the speech, and he says that was wrong. Students, he said, should have a right to hear the speaker, and express objections to the speaker’s comments directly to him.