A study led by researchers at Edith Cowan University, published in the European Journal of Marketing, has analysed survey data from more than 800 Australian supermarket customers to understand what actually drives engagement with loyalty programs and how effectively those programs translate into genuine loyalty toward retailers. The findings paint a picture of consumer behaviour that is far more conditional, and far more skeptical, than the loyalty industry’s growth figures might suggest. Rather than a single factor determining whether shoppers embrace a loyalty program, the research identifies a convergence of psychological and practical conditions that must all be present before customers commit: trust in the retailer, mutual commitment between customer and retailer, perceived benefits, the temporal flexibility to wait for discounts, and the capacity to search for deals across multiple competing stores.

Professor Sanjit Roy, Professor of Marketing and Service Science at ECU’s School of Business and Law, argues that most consumers simply lack the time or inclination to perform the mental cost-benefit analysis that loyalty programs implicitly demand. When standing at a checkout, whether self-serve or staffed, the shopper is asked a deceptively simple question: do you want to scan your rewards card? Retailers understand this moment of friction and actively exploit it, prompting customers at the point of sale to reinforce the scanning habit until it becomes automatic. The problem, according to Roy, is that the arithmetic behind the habit rarely favors the customer. Under a typical scheme where one point is earned per dollar spent and 2,000 points yield a ten-dollar voucher, the return works out to a fraction of a percent of expenditure, a reward so modest that it invites a pointed question: is it worth surrendering detailed personal purchasing data when the resulting discounts and promotions are not even personalised to reflect that data?

This tension between what customers give and what they receive sits at the heart of the study’s conclusions. Loyalty programs are, in essence, data-exchange mechanisms. Customers provide retailers with an exhaustive record of their buying habits, brand preferences, spending patterns and household composition, and in return they receive modest discounts and occasional vouchers. The research suggests that customers have become increasingly aware of this asymmetry. They know they are a data point in a vast analytical machine, and unless the rewards feel meaningfully tailored to their individual circumstances, the perceived benefit of participation collapses, along with their engagement.

The study also reveals how economic circumstances shape whether loyalty programs can deliver their benefits at all. Dr Saalem Sadeque, Course Coordinator and Lecturer in Marketing at ECU, highlights the role of what the researchers describe as temporal price search strategy, the customer’s capability to wait for a predicted discount. A shopper who anticipates a future price reduction on a frequently purchased item may simply delay the purchase for a week or two and then buy in larger quantities, maximising the benefit of their accumulated loyalty. But this strategy requires a buffer of both time and money that many households do not possess. A parent who urgently needs nappies, or a family whose budget is too tight to purchase in bulk, cannot wait for the discount to arrive, and therefore misses out on the program’s benefits despite being genuinely loyal to the retailer. The program, in other words, rewards the financially flexible while leaving the most loyal yet constrained customers behind.

A parallel dynamic, the spatial price search strategy, further complicates the picture. Customers who have the ability and inclination to compare prices across multiple retailers engage with loyalty programs differently from those who shop out of convenience or habit. The research demonstrates that neither waiting capacity nor cross-store deal hunting alone determines engagement; rather, it is the combination of these practical strategies with the emotional and relational factors of trust, commitment and perceived benefit that produces sustained participation. Remove any one element from the equation and engagement falters.

The implications for retailers, particularly the major Australian supermarket chains like Coles and Woolworths, are substantial. Despite the ubiquity of their loyalty schemes, many customers simply do not engage with them, and the success or failure of any given program depends largely on that delicate combination of trust, commitment and perceived value. The stakes extend beyond marketing metrics. When customers fail to engage with loyalty programs, retailers lose visibility into purchasing patterns, which in turn creates uncertainty in cash flow projections. A program that generates lukewarm participation is thus not merely a missed marketing opportunity but a genuine operational liability, undermining the forecasting on which supply chains and pricing strategies depend.

The research lands at a politically sensitive moment for Australian grocery retail. The Australian Competition and Consumer Commission has recently advised supermarkets to be more transparent about their pricing, and the study’s authors echo and extend that call. Professor Roy contends that transparency about prices and business practices, exceptional customer service, and consistent brand messaging form the foundation on which loyalty must be built. A retailer that promises fresh fruit and vegetables, he notes, must actually deliver on that promise, because loyalty programs cannot compensate for a broken brand commitment. Perceived authenticity of the underlying relationship, in other words, precedes any loyalty scheme built on top of it.

Where the research offers its most constructive guidance is in the use of the data that loyalty programs collect. Rather than treating customer information as a resource for broad-brush promotional targeting, Roy argues that supermarkets should deploy it to establish a personalised dialogue with individual shoppers and to make loyalty benefits genuinely human-centric. This personalisation, he suggests, is not merely a feature enhancement but a precondition for trust. Customers already know their data is being harvested; what they lack is evidence that the harvest works in their favor. Demonstrating that a program remembers their preferences, anticipates their needs, and rewards them in ways that reflect their actual lives could transform the perceived exchange from extractive to reciprocal.

Dr Sadeque frames the ultimate recipe for success as a tailored, integrated strategy that aligns a loyalty program’s value proposition with trust building and relationship development. Retailers can cultivate customer commitment by conducting market research to ensure their values align with those of their customers, and by creating personalised offerings that improve perceived benefits, thereby increasing the likelihood of engagement. In an era of sophisticated digital marketing algorithms and ubiquitous discount codes, the study’s central message is paradoxically low-tech: loyalty is an emotional relationship before it is a points balance. Retailers that treat loyalty programs as data-collection instruments with discounts attached will continue to see lackluster engagement, while those that design programs delivering clear, consistent value and authentic emotional connection stand to convert transactional habit into durable, long-term customer relationships. In the end, as the study’s title suggests, the benefits of loyalty programs really are in the eye of the cardholder, and convincing cardholders that the benefits are real may be the hardest task the loyalty industry faces.

Retail stores frequently invest in elaborate in-aisle displays, essentially adding more merchandise in shoppers’ pathways, intending to catch their attention and encourage impulse buys. However, this new research introduces the concept of spatial crowding as a major factor undermining the efficacy of these displays. Spatial crowding occurs when shoppers perceive their physical freedom to move as restricted, a sensation that has been linked to purchase avoidance and overall shopping discomfort in behavioral science literature.

The investigation involved a congregation of methodologies, beginning with a longitudinal analysis of sales data within an aisle dedicated to household, baby, and pet products. Over a six-week interval, five mid-aisle display stands laden with additional merchandise were deployed, after which they were removed for a subsequent six-week period. Analysis of the data revealed an unexpected trend: weekly sales percentages tied to that aisle’s products increased following the removal of these mid-aisle stands, climbing from an average of 4.33% to 4.83% of the store’s total revenue.

To deepen their understanding, Streicher and his team conducted a secondary in-store observational experiment within the same aisle. They measured the frequency with which shoppers physically touched products — a behavior strongly correlated with eventual purchase decisions. Results demonstrated a sizable uptick in product interaction when mid-aisle displays were absent, with people using shopping carts engaging with products roughly 7.05 times more often without these displays than with them. Shoppers without carts exhibited a smaller increase of 3.81 times, suggesting that the negative effects of aisle crowding are amplified among cart users who need additional space to maneuver.

Complementing these findings, an online experimental simulation was performed with 200 participants. Subjects were asked to imagine themselves shopping with either a cart or a basket while viewing images of the store aisle configured both with and without the in-aisle displays. This simulation revealed that aisles filled with additional fixtures were consistently rated as significantly more crowded and restrictive, diminishing shoppers’ perceived control and comfort. This effect was notably more pronounced among those imagining cart shopping, underscoring how fixed physical objects restrict shopper movement and spatial freedom more for cart users than for basket shoppers.

The converging lines of empirical evidence suggest a fundamental tension in retail design between maximizing product exposure and preserving shopper comfort. While in-aisle displays aim to maximize visual merchandising, they inadvertently escalate spatial crowding, which can produce cognitive and physical discomfort that discourages purchasing. This effect seems most acute for cart users who require more maneuvering space and thus experience greater constraint.

One takeaway from this research is that retailers should be cautious about relying heavily on mid-aisle displays as a sales boost strategy. Instead, they could explore alternative approaches that enhance product visibility without encroaching too much on shoppers’ navigable space. For example, wall shelving, end-of-aisle displays, or digital interactive signage might better balance visibility with shopper mobility.

Moreover, the study sets the stage for follow-up research to investigate additional factors influencing the sales impact of in-aisle merchandise placements. Variables such as human crowding — when other shoppers populate aisles — promotional pricing, and seasonal shopping patterns might modulate or compound the observed negative effects. Understanding these contextual factors could further refine retail layout strategies and improve sales outcomes.

Further exploration might also consider the psychological dimensions of spatial crowding, detailing how such physical constraints translate into emotional responses like anxiety or frustration. These emotional states are likely mechanisms through which sales decrease, potentially mediated by reduced time spent browsing or impulse buying.

Streicher emphasizes the real-world importance of these findings, noting that “adding merchandise into store aisles can actually reduce overall sales by making the environment feel crowded and harder to navigate. Importantly, this negative effect is even stronger for shoppers using carts, as they experience greater spatial constraints and reduced control while shopping.” This insight challenges long-standing assumptions in retail marketing and underscores the complex interplay between physical environment, shopper behavior, and sales performance.

The implications extend beyond grocery stores to any retail space where movement and product interaction are critical components of the purchasing process. Designers and marketers alike might reconsider aisle clutter as a strategic choice, opting instead for layouts that foster openness, fluid navigation, and positive shopper experiences.

In conclusion, this comprehensive study uniquely combines empirical sales data, behavioral observations, and psychological experiments to illuminate the paradox of in-aisle displays: a tactic intended to increase shopper engagement can, under spatial constraints, suppress purchasing behaviors. Especially for cart users, the resultant feeling of crowding diminishes both perceived control and product interaction frequency, contributing to lower sales. Retailers should thus carefully evaluate their merchandising strategies, striving for configurations that maximize exposure while minimizing spatial discomfort.

Subject of Research: People

Article Title: When merchandise crowds the aisle and carts crowd the shopper: Joint effects on sales

News Publication Date: 22-Apr-2026

Web References: http://dx.doi.org/10.1371/journal.pone.0346492

References: Streicher MC (2026) When merchandise crowds the aisle and carts crowd the shopper: Joint effects on sales. PLoS One 21(4): e0346492.

Image Credits: Mathias C. Streicher, 2026, PLOS One, CC-BY 4.0

Keywords: spatial crowding, retail merchandising, shopper behavior, grocery stores, in-aisle displays, sales impact, shopping carts, consumer psychology, product interaction, retail layout