It's a rare college student who will raise a hand in the classroom and say to the instructor, "Could you please repeat that? I don't understand."
More common are groups of students who, when asked if they understand material just covered, sit and stare back, neither nodding nor shaking their heads.
Faculty members tend to take no response as an affirmative, pass out tests, then find out who actually understood the material only after scoring the tests.
And with some classrooms seating several hundred students, knowing who gets it and who doesn't is as challenging for the professor as getting them all to show up.
But faculty at Purdue University think they're on to something that could answer the challenge.
Clickers-hand-held feedback devices-allow students to provide anonymous feedback and faculty to evaluate the comprehension level of their class in seconds.
The interactive system uses a radio-frequency receiver installed in the classroom. Up to 1,000 students can simultaneously send feedback.
Responses are instantly tabulated and converted to histograms that can be projected on a screen for everyone to see.
Students know right away whether they are in the majority or minority of those who grasp the material. And they never have to raise their hands and risk embarrassment to find out.
"They are a great learning tool for the students," said Harry Morrison, a chemistry professor. "It allows me to stop the class periodically and probe their comprehension of the material I have just gone over. I know right away if there's a significant number of confused students."
What started two years ago as a pilot program with devices used in six Purdue classrooms has grown to more than 200 classrooms wired for the technology.
The university's initial program used clickers that transmitted an infrared signal, like that used for TV remote controls. So if something got in the way, the transmission wasn't received and the student had to try again.
A best case allowed 80 clickers to work with a single receiver. So a class of 400 required that five receivers be installed.
And with other technology firms offering similar products, some packaged with textbooks, without standardization, students in the same classroom could be using different clickers.
"That just wasn't efficient," said Ed Evans, director of information technology at Purdue, the department that selected the system to be used.
So Purdue began shopping around for a better clicker.
The school now uses clickers that work off radio frequency, which is not dependent on line-of-sight technology.
Students pay $16 for a clicker that can be used in any classroom wired for the technology.
The school has licensed the technology from Texas-based e-Instruction Corp., which has about 800 universities around the world using its clickers, including Indiana University at Bloomington and IUPUI.
But the West Lafayette campus is the first to standardize the technology with the intent of deploying the system campuswide, said Darren Ward, vice president of business development at e-Instruction.
"We're seeing an increase in use of this new technology, which some get behind more quickly than others," Ward said. "Purdue is on the cutting edge."
This semester, 43 instructors have chosen to use the clickers. But those numbers are expected to increase dramatically as word of mouth spreads that the system improves attendance, engages students and better prepares them for exams.
"The nice thing about it is, it's anonymous," said Brian Geddes, who used the clicker for a couple of semesters before graduating this past May.
Not thrilled with the idea of having to buy a remote control on top of a book he didn't want to buy, Geddes quickly grasped how it could help.
"Once I was using it, I quickly took advantage of it. It allowed me to focus more on the material. I knew what I didn't know."
Geddes was also involved in gathering research on the clickers to determine if there is a correlation between performance and clicker use.
About 800 students using the clickers in five classrooms were surveyed three times during the spring 2005 semester. Students also provided information about their learning styles, whether they enjoy school, and feedback on their instructors.
Student's grade point average and SAT scores were included in the data.
Wanting to know if using the clicker aids learning of high-, moderate- and low-ability students, Erina MacGeorge, a communication professor leading the research, said a correlation is likely going to be strongest between clicker use and the moderate-ability students.
"Students in the mid-range, with 3.0 GPA and 1000-1200 SAT scores, seem to be most affected positively," said MacGeorge, who has a doctorate in speech communication and has done research on interpersonal communications and quantitative-research methods.
But, she cautioned, the findings are preliminary because she has only looked at the first of the three surveys.
"If the trend continues through the other two survey points, we will know [whom] we really need to focus on," she said.
Which lines up nicely with why professors say they use this tool, MacGeorge said. "They're not worried about the A students."
David Elmore, a physics professor, is using the devices for the third semester in two sections of a class with 150 students each.
Elmore gives short quizzes in class. His students respond to multiple-choice options with the clickers and subsequent discussions are tailored from the histogram results.
Other professors use clickers to take attendance, dole out participation points, and go over material that will be on tests.
"I use it to show me what they're understanding," Elmore said. "But what's really important is, it engages students much better than if we just lecture to them."