There are some who might scoff at it, but I’m always a bit charmed to meet someone who puts their fingers and thumbs in the classic “L” and “reversed L” formations to differentiate between left and right. And although I usually don’t need to do this, it seems to be a relatable enough experience to at least spawn a TikTok trend.
The ability to remember your left from your right is very important to cognitive psychologists, although the reasons are admittedly not always very exciting. Pragmatically, if you want to design an experiment where pressing a right-side button means something different from its left-side counterpart, you’ll obviously want your participants to remember the difference between left and right. But of course, since this isn’t always intuitive, researchers must factor in the possibility that at least some people will mix up their right and left during an experiment. (*Cue TikTok audio.*)
A common practice to account for this is to just counterbalance the assignments of the two buttons: half of your participants do the experiment with the right button meaning one thing and the left meaning the opposite, and the other half do the same experiment with the assignments reversed. If the likelihood of recruiting someone who easily mixes up their left and right is more or less random, then the noise that they add to your data should ultimately wash out in the average across the whole sample. And indeed, researchers often find no effects of button assignment, thereby allowing them to focus on the mental processes they’re more deeply interested in.
But what about situations where button assignment does have a discernible effect? This is where it gets interesting, and it also brings us to the featured article, “The interaction of study sequence presentation mode and response assignment reveals the effects of multiple computational systems on an immediate visual recognition task” by Arnold L. Glass (pictured below), Tingtao Wang, and Allyson Fu, published in Attention, Perception & Psychophysics.
To better understand the potential for button-assignment to influence broader cognitive processes, the authors leveraged different elements that go into the design of simple memory experiments. Participants had a fairly straightforward task: They studied a string of digits in sequence (meaning they saw each digit one at a time) and had to indicate whether a given test digit was the same or different from any of the digits they studied by pressing one of two adjacent buttons.
I’m going to focus on just the response time data, but the full paper also has very interesting data about error rates. First, the authors examined whether the ordinal position of an item within the sequence (i.e., whether it was first, second, third, etc.) would influence response times, with the idea being that different response time patterns will be indicative of different cognitive strategies.
Previous work by this group has suggested two possible strategies that could come into play. Specifically, assigning the right button to mean same seems to trigger a strategy based on holistic judgments of recency to guide participants’ responses. On the other hand (no pun intended?), assigning the right button to mean different led participants to invoke a more systematic retrieval strategy, in which they mentally scanned their memory of the string, one digit at a time, as indicated by slower response times for digits in later ordinal positions.
Based on this previous work, the authors believed that this pattern, and therefore the systematic retrieval strategy that underlies it, would also occur in the current study. In other words, if response times slow down for digits that were encountered in later ordinal positions, this would suggest that participants were using a systematic retrieval strategy. If this pattern only emerges under certain button assignment conditions, then use of this strategy would additionally depend on what each button is meant to represent in terms of a behavioral response.
And indeed, there was a linear relationship between response time and ordinal position of, where people were slower to make their responses for items that were seen later in the study string. Importantly, this linear relationship was only observed when the right button meant different, and not when it meant same, suggesting that participants were indeed using different memory strategies that were triggered by what behavioral response was assigned to the left and right buttons.
What about when the other potential strategy, where assigning the right button to mean same potentially triggers participants to rely on a more holistic approach? Adding to the intrigue of their results, the authors found diverging patterns of response times when the right button was assigned to mean same, depending on whether the digit sequences were presented a single central location or at different locations moving from the left to the right sides of the display.
For these data, there was virtually no effect of an item’s ordinal position, but only for a left-to-right presentation style. This is indeed in line with a strategy of holistic evaluations of how recently an item was encountered and again suggests that different strategies are triggered by different button assignment. What’s particularly intriguing is what happened when the string was presented centrally.
Surprisingly, there was a linear relationship between response time and ordinal position that was opposite to what was seen when the right button meant different: response times were slower for earlier items instead of later ones. When averaged across button meaning assignments, as is often done during data analysis, these different but opposing linear trends would cancel out and falsely suggest that button assignment has no effect on memory strategies!
Altogether, these response time data indicate that there are multiple cognitive strategies in play during even “simple” memory studies, and the ways that these cognitive strategies are deployed can be decided by even subtle or seemingly inconsequential details, like how to use the right vs left buttons. What’s more, the two strategies described in the paper might also be involved in other capacities besides just memory. As the authors detail in the full report, spatial navigation research suggests that people often use similar strategies that are differentiated by holistic vs. systematic approaches. These paired strategies between memory and navigation have also been linked to distinct neural systems, with systematic strategies involving more activity from the caudate nucleus, while holistic strategies are more tied to the hippocampus, a typical brain area to study in memory research.
These data patterns are pretty nuanced, but they could have some broad implications for cognitive research. First, on a practical level, they serve as a reminder to researchers to always scrutinize the possibility that even the most seemingly inconsequential elements of an experiment’s design, like button assignment, could have an impact on their data. In terms of broader discoveries, the implication that these subtle influences could invoke not just different mental strategies, but also different brain networks, suggests that some of the longest-running mysteries in neuroscience could potentially be solved by examining other areas of the brain. And as you can imagine, these are distinctions that are a little harder to figure out than right vs. left.
Featured Psychonomic Society article
Glass, A.L., Wang, T. & Fu, A. (2025). The interaction of study sequence presentation mode and response assignment reveals the effects of multiple computational systems on an immediate visual recognition task. Attention, Perception & Psychophysics, 87, 952–967. https://doi.org/10.3758/s13414-025-03032-7
