Imagine walking into a store late in the day to buy a T-shirt. You find a sparsely stocked display with visible gaps between the few remaining items. This physical arrangement might prompt a split-second evaluation. The missing inventory could suggest the shirts are popular, or it might imply that earlier shoppers picked through the stack and left only the undesirable ones behind.
Retailers invest heavily in determining exactly where and how products are displayed. Previous research shows that when store management intentionally spaces products apart, the merchandise often appears more aesthetically pleasing and premium. However, in busy physical stores, spacing is frequently created by the customers themselves as they remove items from shelves.
A research team set out to investigate how this specific type of customer-induced spacing influences the people who browse the aisles later. Hao Liu of Shandong University of Finance and Economics and his colleagues published their findings in the Journal of Business Research. The study reveals that visible gaps between leftover products consistently reduce purchase intentions.
The Leftover Effect
The researchers conducted a field study in a convenience store to observe real-world purchasing behavior. They focused on a display of homemade bread, observing shoppers across four consecutive days during peak hours. The team alternated the presentation of the bread daily.
On two days, the leftover bread was arranged with visible gaps between the items. On the other two days, the bread was arranged tightly together with no gaps. Throughout the study, staff promptly restocked any items sold to keep stock levels consistent. Staff recorded the purchasing decisions of more than 200 customers.
The results from the field observation showed a clear pattern. Shoppers were significantly less likely to purchase the target bread when it was displayed with gaps compared to when it was arranged tightly together.
Testing the Chain of Events
To understand the psychological process driving this behavior, the researchers designed a series of online experiments. They presented hundreds of participants with images of retail shelves featuring different products, such as cookies and T-shirts. Participants were randomly assigned to view items displayed with unequal gaps, equal gaps, or no gaps at all.
The visual experiments confirmed that product spacing lowered the desire to buy. Interestingly, it did not matter whether the gaps were uniform and neat or irregular and uneven. The mere presence of empty space between the items was enough to trigger a negative response.
The researchers mapped out the sequence of mental steps that leads to this drop in sales. First, consumers notice the gaps and make a specific inference. They assume the items on the shelf are leftovers that previous shoppers examined and rejected.
This initial assumption leads directly to a secondary judgment. Shoppers begin to perceive the remaining items as deficient in some way, assuming they must be of lower quality or defective. This perception of deficiency ultimately drives down the intention to make a purchase.
The study also ruled out several alternative explanations for the drop in sales. The researchers measured participants’ perceptions of store aesthetics, their fear of contamination from items touched by others, and their judgments of the store’s service quality. None of these factors explained the drop in purchase intention as clearly as the chain of events involving leftover assumptions and perceived product deficiency.
Conditions That Protect Sales
The research team identified two specific scenarios where the negative impact of product spacing disappears. The first involves the reputation of the brand being sold. Brand reputation often serves as a mental shortcut that consumers use to judge quality when they are uncertain.
In one experiment, the researchers presented participants with images of spaced-out clothing. They told one group the clothes were from a brand with an “A-level” reputation, while another group was told the brand had an “E-level” reputation. A third group received no brand information.
For the low-reputation brand and the unknown brand, the gaps on the shelf triggered the usual chain of negative assumptions. However, for the high-reputation brand, the spacing had no effect on purchase intent. The researchers interpret this as evidence that a strong brand reputation acts as a buffer. It reassures consumers about the quality of the item, preventing them from assuming the leftovers are defective.
The Role of Product Standardization
The second scenario involves the nature of the product itself. Some items are highly standardized, meaning every unit is virtually identical. Other items are more prone to inconsistencies in manufacturing, materials, or durability. The researchers refer to this concept as product variance.
To test this, the team asked participants to evaluate coffee cups displayed on a shelf. They informed half of the participants that the cups were subject to strict quality control, resulting in identical thickness and stability across every unit. They told the other half that the cups exhibited batch-to-batch variations, with some being fragile or uneven.
When the participants believed the cups varied in quality, the gaps on the shelf significantly lowered their willingness to buy. They assumed previous shoppers had picked out the good ones. When the participants believed the cups were standardized, the gaps on the shelf did not affect their purchasing decisions.
Managing Retail Layouts
The findings outline a few practical realities for managing physical retail spaces. Maintaining tightly packed displays by continuously front-facing merchandise can prevent consumers from making negative assumptions about the remaining inventory. In stores where constant shelf reorganization is not feasible due to staffing limits, retailers can rely on visual signage indicating high brand reputation to help offset the leftover effect.
Retailers can also use these insights to prioritize their labor. Because low-variance, standardized products are largely immune to the negative effects of shelf gaps, store managers can spend less time reorganizing those specific aisles. Instead, staff efforts to close product gaps can be redirected toward categories where quality is known to vary, as those items are most susceptible to lost sales when left scattered on a shelf.
