UMass study finds adding symbols to license plates does not increase recall

By Patrick Hoff

Flickr/Corey O'Connor

A new study completed by memory experts at the University of Massachusetts states that adding non-alphanumeric symbols to license plates in Massachusetts would not make the plates easier to remember for adults than the current license plates that contain only letters and numbers.

Cognitive psychologists and memory experts Caren Rotello and Andrew Cohen teamed up to investigate the issue, which was brought up last year in Massachusetts Senate bill S-2299, which proposed a change to state license plates that called for non-alphanumeric symbols,  such as stars or circles. The Legislature never took a vote on the bill.

“We found that whether the license plate contained a symbol or not didn’t matter when people tried to remember details,” Rotello said in a press release. “There was no overall benefit to license plates with symbols in our study. Like others, we intuitively had thought symbols might be better recalled, but that wasn’t the case, at least with adults.”

Study participants between the ages of 18 and 70 were recruited using Amazon’s Mechanical Turk service, the release stated. Data from 619 adults was analyzed as well as two additional examinations with over 300 adults each.

The study asked the adults to look at a photograph of a license plate for one, two or three seconds. The photos varied between four alphanumeric characters and a symbol, five characters with no symbol to control for length, and six characters, which is the current design of license plates. Another variable to the test was looking at the photographs backwards to mimic seeing a license plate in a rearview mirror.

After the photographs, participants were asked to watch a 15- or 30-second video simulating sitting in a car with the radio on, the release stated. After the video, subjects were asked to type three digits on a keyboard and to remember the license plate number and color of the car they had seen.

The results of the study, the release said, showed that adding symbols to the alphanumeric characters of license plates did not increase the memorability of the license plate. Viewing it backwards reduced memory for the plate overall, and the non-alphanumeric cognition was equally impaired. Gender and age were effects that researchers looked into when examining the results, but nothing substantial “popped out,” Rotello said in the release. She added, however, that these subgroups may not have been large enough to see effects.

“We think it’s important to get this information out now, when there appears to be renewed interest in making these changes,” Rotello said in the release. “There’s a huge amount of money at stake and it has such clear policy implications. There may be other more effective designs, or other changes we can make to license plates to improve people’s ability to recall them, but adding symbols isn’t the answer.”

She and colleagues plan to conduct a future study about the recall effect of non-alphanumeric symbols on license plates in children, using both plates with and without symbols in testing.

Rotello added in the release: “We were a little surprised that there’s really nothing there. There’s just no benefit at all to this particular design.”

Patrick Hoff can be reached at [email protected]