It’s about 11 in the morning, and I’m already thinking about lunch. I’m at my desk in my downtown office, so I have lots of options. I could go to that new sandwich place around the corner, where I know they make a great turkey club. Or I could walk up the street and get one of those big salads, which would be satisfying and healthy. Or I could just run downstairs to the snack bar and grab a yogurt and some pretzels. It’s a tough decision.
It’s also a common decision, one that many of us confront every day. Our choices have implications, not only for how much we enjoy lunch today, but also for longer term goals like fitness and health. But how do we choose? What are the basic cognitive processes that lead from initial hunger pang to this soup or that sandwich?
Memory may play a key role. After all, sorting through our lunch options is basically an act of remembering lots of past experiences. How was that tuna fish sandwich from the deli? Was it pleasurable and filling? Skimpy? Did the clam chowder live up to its reputation, or was it disappointing? And so forth. The answers are our memories, but how reliable are they? Are they good guides to today’s lunch decision and overall good nutrition?
These are among the questions that Stanford University psychological scientist Emily Garbinsky and her colleagues have been exploring in some recent experiments. They wanted to know if certain tricks of memory might bias our food decisions in healthy or unhealthy ways. Here’s the scientists’ reasoning:
The simple fact is that most of our eating experiences are boring and repetitive, sort of like my default to pretzels and yogurt. These meals, such as they are, are not rich and memorable events that we store away and cherish in their every detail. How many of your weekday lunches do you remember at all? As a result of this repetitive, tedious munching, it’s very easy for our final memory—that last satiating bite—to trump memories of all of the earlier, identical bites, including the first.
This is known, in the field’s jargon, as the “recency effect.” Garbinsky suspected that the final moment of enjoyment has a disproportionate influence on whether and when we will choose a particular sandwich or dessert again. Specifically, she speculated that the more satiated we are at the end of lunch, the less we will recall enjoying the lunch—and the less likely we will be opt for that same lunch again soon. So portion size might influence satiety, which in turn might shape lunches of the future.
At least that’s the theory, which they tested by asking a group of students to eat some crackers. Not exactly a savory lunch, but fine for the sake of the study. Some ate just five crackers, while others ate 15. The idea was that those who ate 15 crackers would come closer to being satiated. The next day, some students of each group were prompted either to recall their last cracker, or their first. They were all then asked when they would like more crackers. The scientists wanted to see which memories made them more or less eager for more crackers.
The findings were clear. As reported in an article to appear in the journal Psychological Science, the snackers’ memories for the final cracker—and the moment of greatest satiety—interfered with their memories of the first crackers. These final memories were what influenced their desire for more. What’s more, portion mattered: Those who ate a large portion recalled much less enjoyment, compared to those who ate a small portion. Being full diminished their memory of the last bite, and thus the entire meal, causing them to tire of crackers for longer.
The scientists ran a couple more variations on this experiment, to expand and clarify the results. Taken together, the studies show that enjoyment at the end of a meal—not the beginning—determines how much time will pass until that particular food appeals again. This is because we really don’t remember the rest of the meal, which tends to blur together.
The findings show what a crucial role memory plays in our decisions about what and when to eat next, and they could have practical implications for all those pondering lunch across the country. Portion sizes in the U.S. have been steadily increasing since the 1980s, clearly an unhealthy trend. Big portions not only make us eat more, they decrease our average enjoyment of that food. But those who sell us our lunches should also pay attention. If our last memory of the deli is one of being stuffed and uncomfortable, that memory may keep us from going back there for a while. After all, we have lots of other options.
Follow Wray Herbert’s writing about psychological science in The Huffington Post and on Twitter at @wrayherbert.