Say you’re on a date at a restaurant.
You and the person you’re with are talking. You’re enjoying the conversation and don’t want to break eye contact, but also want to take a sip of your wine. So you reach out for the glass, but you do it carefully, because if you reach too far and knock the glass over, that cabernet will end up on your date’s lap.
When confronted with a situation like this, you’re using visual working memory, a term that refers to the system your brain uses to maintain visual information for ongoing tasks. Your mental picture of where the wine is as you reach out is maintained by visual working memory.
A pair of Drexel researchers recently tested how visual working memory works in situations where there may a penalty for some fuzziness in that memory, such as reaching too far and knocking over the wine in our scenario. And what they found was that our mind subconsciously plays it safe for us, making sure to avoid mistakes that could cost or even hurt us.
Rachel Lerch, a Drexel University graduate student, and Chris Sims, PhD, an assistant professor in the University’s College of Arts and Sciences, published a paper on their experiments, “Decision Theory, Motor Planning and Visual Memory: Deciding Where to Reach When Memory Errors are Costly,” in Experimental Brain Research.
“We demonstrated that the brain is capable of very sophisticated decision-making that happens at an unconscious level, even for extremely simple tasks,” Sims explained. “When we act on the basis of our memories, we need to take into account the uncertainty of our memory in order to avoid costly mistakes, and our research shows this happens in a nearly optimal way.”
Lerch and Sims’ experiments played out like a horizontal game of pin the tail on the donkey that, instead of a paper donkey, used a projector table that briefly displayed target-shaped dots of light on its surface. After the targets disappeared, the participants were asked to point to the spot on the table where they remembered them being.
If they pointed to the exact location of the target, they got 10 cents. But to add a cost-of-error to the experiment, a participant could be penalized. In one phase of the experiment, they were penalized 20 cents if they pointed beyond where the target had appeared (called overshooting). In another phase, the script was flipped and they’d be penalized if they pointed at an area in front of the target (undershooting).
A second experiment applied the same rules, but initially displayed three targets that were then removed — challenging participants to remember more.
When the experiments were finished, it was clear that the experiment using three targets was much more difficult. The average payouts in the single-target experiment doubled those in the three-target experiment.
It was determined that subjects “significantly shifted their mean aim location away from the penalty region,” in each experiment, especially during the harder three-target trial.
But that could have been evidence of a person’s mind lying to them — biasing them into thinking a target was closer or farther away from the penalty area.
So, to see if the participants could genuinely determine relative distance, a third experiment was brought in. In this experiment, a target was displayed on the projector table before disappearing. Then, another stimulus of light appeared and the participant had to say whether the stimulus was closer or farther away from the original displayed target.
The results of that experiment pointed to participants regularly remembering the distances properly, thus eliminating the possibility of memory bias.
So with the possibility of the brain lying being ruled out, it appeared that the participants’ behaviors during the target-pointing experiments were influenced subconsciously — their brains remembered where the target was and steered their location pointing toward the safe areas.
“Participants over- or undershot based on how uncertain their memory was,” Lerch said. “This suggests a decision strategy that was influenced after exposure to the task rather than just by a beforehand judgment call to bias their aim away from penalty regions.”
Lerch and Sims’ experiment demonstrated that, when faced with costly decisions, our minds are less concerned with exactitudes and more with being safe.
“This suggests that the ‘bigger picture’ goal for the brain is to concern itself not with perfection but, rather, with minimizing errors that would interfere with the achievement of its goals,” Lerch said.
With lessons learned from their experiments, Lerch and Sims hope to develop training methods that would enhance visual working memory for complex tasks that could involve life-or-death situation.
“In many cases, memory errors are harmless, but in other cases the consequences for error can be quite serious,” Sims said. “For example, surgeons rely on visual working memory in guiding their hands during delicate operations. The military would also like to train soldiers to have good visual working memory, since they need to be able to orient themselves to maps in an unfamiliar environment. This research has important real world applications.”
Media interested in speaking with Sims and Lerch should contact Frank Otto at 215.571.4244 or fmo26@drexel.edu.
