In 2016, we shared an interesting study on how food arrangement can be used to nudge us towards healthier choices: How To Make People Prefer A Dry Salad Over A Tasty Cheeseburger.

The study demonstrated that choice for healthy foods can be increased by simply displaying them on the left side of their lesser healthy counterparts. For example, displaying the salads on the left page of a restaurant menu, and the burgers on the right page, will lead significantly more patrons to order the former. In similar vein, supermarkets whose shelfs display healthier options to the left side will bear a similar positive influence on our health.

Will a few design tricks put a stop to the epidemic of obesity? Likely not – but as goes for many small adjustments in our daily lives: they compound and make a substantial difference in the long run. Now, a new study has been published that further explores under what circumstances the healthy left effect is likely to arise.

Why your brain expects healthy options to be placed on the left

Where does this left-side bias come from? As it turns out, our brain likes to intuitively place objects and concepts on a horizontal left to right scale. We do this with many things: ranging from tangible properties such as size (small goes to the left, large to the right) all the way to complex abstractions such as one’s political affiliations.

Similarly, our brain appears to connect ‘healthy’ to the left. This falls in line with similar findings on the physical associations, in particular ‘lightness’, which is allocated to the left both in terms of colors (lighter colors to the left or darker ones) and light weight (lighter objects to the left of heavier ones). This explains why healthy options, which can be interpreted as light in a both literal and figurative sense, end up in the same corner of our mind.

Does the healthy left effect always work?

A matter of hunger Recently, a new team of scientists set out to further dissect the healthy left effect. They crafted various restaurant menus, again alternating the placement of healthy and unhealthy options. During the experiment, respondents were simply asked to order the food of their preference.

However, this time, the healthy left nudge showed only a marginally significant effect. It shined through, but wasn’t as crystal clear as in the previous study.

What happened? After more closely examining the data, the researchers discovered one key variable that caused the healthy left effect to arise: hunger. Restaurant visitors that were hungry and ordered the food for instant consumption were particularly susceptible to the effect of left-sided placement, swaying them towards healthier alternatives then they otherwise would have chosen.

Alternatively, patrons that ordered the food for later consumption were not influenced by the menu design. However, this particular group of people were already more likely to order healthy options, whereas the hungry patrons are more attracted to unhealthy foods by default.

The nudge shows its strongest effects at our weakest moments

This study illustrates an interesting principle of nudging: the effects of a nudge are not universally shared, but dependent upon the mindset and characteristics of the individuals who are being nudged. This particularly nudge – influencing choice by food arrangement – appears to only affect those who are most susceptible to the allure of unhealthy foods. This is actually a promising result, because there is a lot less to be gained from a health-focused nudge that would only affect those who wear Fitbits, never miss their 10,000 daily steps and religiously count their calories.