People default to additive strategies when problem-solving, even if subtracting is more efficient

April 7, 2021
Changing the way you look at a problem can generate better solutions. (AP Photo/Ron Schwane)

Changing the way you look at a problem can generate better solutions. (AP Photo/Ron Schwane)

When presented with an opportunity to change or improve something, adults are more likely to rely on addition to correct a problem, instead of subtracting from it, a team of researchers determined in the first study to analyze additive and subtractive cognitive processes.

A paper published Wednesday in Nature investigated why people don't readily think of subtractive solutions to problems. Co-authors Gabrielle Adams, an assistant professor at the University of Virginia, and Benjamin Converse, an associate professor at the university, told The Academic Times that when participants in their experiments were asked to transform a block structure, for example, they were more inclined to add more blocks than to subtract blocks. 

The researchers explained that people first ask themselves what they can add and rarely ask themselves what they might subtract when confronted with a situation where they can change or improve something. Because of this, they may be missing out on a whole category of changes they could potentially make.

"This research really helps us generate the distinction between additive and subtractive ideas and shows that people don't think of them," Adams said. "What we're trying to do is identify the fact that people are potentially missing out on an entire class of solutions because they fall prey to this way of thinking."

In a series of experiments, the authors first observed the rate at which people changed objects by adding or subtracting. They hypothesized that a variety of stimuli would cause additive ideas to come to mind first when adults were faced with simple problems. If the participants were presented with a general object, situation or idea and instructed to transform it in some way, the authors expected that the first question the participants would ask themselves would be, "What can I add?"

The participants were only likely to consider the strategy to subtract components if they thought harder about the problem, had longer time to consider it and could give the problem their undivided attention, the researchers theorized. 

"Transforming an object, idea or situation in a novel way begins as an act of imagination, a process of searching the environment and one's store of knowledge for possible changes," the authors said in the paper. "The cognitive science of problem-solving describes iterative processes of imagining and evaluating actions and outcomes to determine whether they would produce an improved state."

In one task, participants were asked to change a series of digital grid patterns to be symmetrical. They could toggle the color of any box by clicking on it, and it took the same amount of effort to subtract marks from the side that had a greater number of colored boxes as it did to add marks to the side with fewer colored boxes. But only 20% of the participants favored the subtraction approach.

The researchers also examined data from a previous survey that asked for improvement ideas by the incoming president of a university. Of the survey responses that were categorized as either additive or subtractive, only 11% were subtractive, such as removing an existing regulation, practice or program. Similar low rates of subtraction were found among participants who were prompted to transform block structures, essays and itineraries in other tasks.

"Our experiments showed that the identification of advantageous subtractive changes depends on the presence of cues that prompt subtractive search, on the number of opportunities one has to recognize the shortcomings of an additive default and on the situational availability of cognitive resources," the authors said in the paper.

Rates of subtraction were lower than rates of addition across a range of goals given to the participants, including to "improve," "enable" and "arrange" different stimuli. Going a step further, one task gave participants a puzzle in which subtracting was objectively the correct answer, Converse said, and the researchers compared participants doing this task while distracted or not. 

"Under those distracting conditions, we would expect people to use whatever quick and easy answer comes to mind. And in this case, the prediction was that [it] would be the additive answer, and that's what we found," Converse said.

To address this type of thinking and get people to consider other problem-solving strategies beyond addition, the authors suggested increasing their attention, time and effort; decreasing distractions in their environment; or reframing the problem to help them think of new solutions.

"If you want to encourage people to at least consider subtraction, you either have to slow them down, help them develop more solutions or give them undivided attention," Converse said. "Subtractive solutions aren't necessarily harder to think of once they're presented to you. … The problem is, it's sort of hidden deeper in mind, and you have to work a little harder to access it."

The authors recommended that future research on this topic explore the notion that people think of both additive and subtractive strategies but disproportionately employ, or prefer, additive ones. This study also primarily recruited American adults, and the authors noted that cultural differences may play a role in results, suggesting the need for a more diverse sample in further studies.

"The tendency to overlook subtraction may be implicated in a variety of costly modern trends, including overburdened minds and schedules, increasing red tape in institutions and humanity's encroachment on the safe operating conditions for life on Earth," the authors said. "If people default to adequate additive transformations — without considering comparable (and sometimes superior) subtractive alternatives — they may be missing opportunities to make their lives more fulfilling, their institutions more effective and their planet more liveable."

The study, "People systematically overlook subtractive changes," published April 7 in Nature, was authored by Gabrielle Adams, Benjamin Converse, Andrew Hales and Leidy Klotz, University of Virginia.

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