Many people place great stock in eyewitness testimony. If someone directly observed an event, they should be able to accurately describe what happened. Many people have been convicted of various crimes by eyewitness testimony. How accurate is the testimony of an eyewitness?
To demonstrate the accuracy of eyewitnesses, psychology teachers have done variations of a classroom demonstration. Psychologist Josh Gerow observed one such demonstration, when he was a graduate student. He had seated himself at the back of a psychology lecture hall with 600 students to listen to a speech on perception. Here is his account.
The professor entered the room through a side door and began his lecture. After a few minutes, the class settled down to taking notes and listening.
Suddenly, a student burst through the large doors at the rear of the lecture hall. I recognized him as the professor’s assistant, but no one else in the class knew who he was. I felt he overacted a bit as he stomped down the center aisle the lecture hall, screaming the foulest of obscenities. "Dr. X, you failed me for the last time, you *&%@#$ so-and-so. You’re going to pay for this!" The class was stunned. Everyone gasped as the student leaped over the lectern to grab the professor.
The student and the professor struggled briefly, and then — in clear view of everyone — there was a chrome-plated revolver! Down behind the lectern they fell. BANG! The sound of a gunshot filled the room. The students sat frozen in their seats. The graduate assistant raced out of the same side door the professor had entered just a few minutes earlier.
The professor lay sprawled out on the floor, moaning loudly.
Six hundred students sat stunned in their seats. At just the right dramatic moment, the professor drew himself back up to the lectern and in a calm voice said, "Now I want every one to take out a pencil and some paper and write down exactly what you saw."
Dr. Gerow didn’t read all of the 600 descriptions, but he did help to summarize the responses. The student was described as being anywhere between 5’4" and 6’3" tall and weighing between 155 and 235 pounds. Although there was some agreement, it would be very hard to come up with a single description of the "suspect" in the "shooting."
However, the most remarkable misperception had to do with the gun. Gerow had watched the professor before the lecture began.
As the professor took his place at the front of the class, he removed the pistol from his coat pocket and placed it on top of his notes. When the "crazed student" crashed into the classroom, the first thing the professor did was grab the gun and point it at the student, as he came charging down the center aisle. In fact, the student never had the gun in his hands! The professor had it all along. It was the professor who fired the shot that startled us all. Fewer than 20 students out of the 600 in the class reported seeing these events the way they actually occurred. The overwhelming majority of "witnesses" claimed it was the crazy student with the gun.
Some of you might be saying to yourself, "Although eyewitnesses may be inaccurate when they are emotionally aroused, they are probably reliable in day-to-day situations." Psychologist Elizabeth Loftus has found that memory can be changed by events that occur after the fact. In one of her studies, subjects viewed a film of one car colliding with another. After viewing the film, half of the subjects were asked, "How fast was the first car going when it hit the other?" The remaining subjects were asked, "How fast was the first car going when it smashed into the other?" The estimates of car speed were significantly higher for the car that "smashed into" the other car.
Merely by altering the questions, people will report things that were not even present. In 1978, Loftus showed subjects a series of slides depicting a Datsun approaching an intersection, turning right, and knocking down a pedestrian in the crosswalk. Half of the subjects saw the intersection with a yield sign, while the rest observed a stop sign. (Otherwise, the slides were identical.) In questions about the slides, half of each group of subjects we asked, "Did another car pass the Datsun while it was stopped at the stop sign?" The remainder of each group were asked, "Did another car pass the Datsun while it was stopped at the yield sign?"
All subjects were later shown a series of paired slides. They were asked to identify which slide they had seen previously. Researchers were interested in how subjects would respond to slides showing the Datsun at either the yield or stop sign. Of those who had been questioned with the opposite of what they had witnessed, 80% chose the sign consistent with the question — not consistent with what they had previously seen. In other words, if you had seen the slide with the stop sign and were asked the question with the yield sign, you would most likely pick the yield sign as what you saw!
How does this relate to you? I’m sure you have been in situations which your perception did not match what others say they saw. If you are typical, you probably assumed the others were mistaken in their perception. However, I want you to consider that you may have been mistaken — you may be part of that 80%. To this, some of you will get upset and declare, "I couldn’t be wrong. I saw it with my own eyes."
* Adapted from Josh R Gerow’s Psychology: An Introduction, Scott, Foresman & Company, 1995, pages 95, 268-271.
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