Graffiti Writers Sort Themselves Across the City Like Competing Species

On the walls of Ghent, Belgium, graffiti is not a random splatter of urban noise. It is a finely sorted landscape in which different kinds of graffiti writers appear to avoid one another, occupying different street segments in patterns that ecologists would recognize instantly as the signature of competition. A new study published in the American Journal of Criminal Justice by K Kuralarasan of Ghent University, Wim Bernasco of the University of Amsterdam and the Netherlands Institute for the Study of Crime and Law Enforcement, and Christophe Vandeviver of Ghent University, shows that graffiti types with contrasting levels of visual complexity cluster apart from each other across the city’s streets. The finding extends a criminological idea known as spot theory, and it does so by borrowing one of the most powerful analytical tools from community ecology: the null model of species co-occurrence.

Spot theory, formulated by Jeff Ferrell and Randall Weide, holds that graffiti writers seek out visible locations, or spots, where their work will be seen by the largest possible audience. Visibility is the currency of the graffiti world. A tag placed where no one passes earns the writer nothing, while a piece on a prominent wall broadcasts skill and reputation across an entire neighborhood. Earlier research by the same team, published in Crime & Delinquency in 2024, demonstrated that writers choose locations that optimize exposure. But that work treated visibility as an absolute quantity, a property of a place measured in the number of eyes that might pass by. The new study asks a subtler question: does the graffiti already present at a location shape where new graffiti of different types appears?

The researchers frame the answer in terms of contested resources. In the graffiti economy, two resources matter enormously: visible urban surface on which to write, and the attention of the audiences who move through the street. Both are finite. A wall covered in elaborate masterpieces offers little unclaimed space, and a street saturated with tags may offer a different kind of signal about who dominates the visual field. If writers of different graffiti types compete for these resources, then types that demand similar surfaces and similar audiences should tend to exclude one another from the same street segments, while types with different demands might coexist. This is precisely the logic ecologists use when they ask whether two species compete for the same food, nesting sites, or territory.

To test this idea, the team needed data of unusual granularity. They turned to systematic social observation, a method in which trained observers record features of the environment directly, in situ, rather than relying on police records or self-reports. Across 1,640 street segments in Ghent, the researchers documented 13,097 individual graffiti instances. Street segments, the short stretches of street between two intersections, are the standard micro-geographic unit in crime-and-place research, a field that has shown since landmark work by David Weisburd and colleagues that crime concentrates intensely at very small spatial scales. Classifying each instance by type, the researchers distinguished masterpieces, the large, elaborate, visually complex productions that require time, skill and planning; tags, the quick, simple signatures of a writer’s name; and intermediate forms that blend features of both.

The central analytical question was whether these types co-occur on the same street segments more or less often than chance would predict. Measuring that requires a benchmark, and the researchers constructed one using a Fixed-Fixed null model, an approach canonized in ecology by Nicholas Gotelli. Under this model, the total number of graffiti instances of each type is held fixed, as is the total number of instances per street segment, and the types are redistributed randomly across segments. The observed pattern is then compared against this spatially indifferent baseline. If graffiti types were simply drawn to the same visible, graffiti-friendly places, their co-presence under the null model should match reality. Any significant departure indicates that something beyond raw attractiveness of place is sorting the types.

To quantify co-presence, the team used the Morisita-Horn Index, a similarity measure developed by Horn in 1966 for comparing the overlap of species distributions between samples. The index takes the count distributions of two graffiti types across all street segments, normalizes and log-transforms them, and produces a value reflecting how similarly the two types are distributed in space. A high value means the two types rise and fall together across the city; a low value means they occupy different territories. Comparing the observed Morisita-Horn values for each pair of graffiti types with the distribution of values generated by the Fixed-Fixed null model yields a statistical test of spatial segregation that is robust to the uneven baseline attractiveness of different streets.

The results were unambiguous. All three pairs of graffiti types showed significantly lower co-presence than expected under spatial indifference. Masterpieces and tags, the two visually most contrasting types, were separated most strongly; tags and intermediate forms, which resemble each other most closely, were separated least. In other words, the more two graffiti types differ in visual complexity, the less likely they are to share the same street segment. This gradient is exactly what a competition-based explanation predicts. Writers of visually similar work compete less directly with each other, because their demands on surface and audience attention overlap less, so they can tolerate closer proximity. Writers of maximally different work, by contrast, appear to avoid one another’s territories.

The authors interpret this pattern as evidence that graffiti location choice depends not only on visible places but also on the competitive visual composition of those places. A writer contemplating where to paint is not merely scanning for a wall with foot traffic; the writer is reading what is already there. A street dominated by tags may signal to a masterpiece writer that the local visual field is occupied by a different register of work, while a segment already hosting elaborate pieces may be unattractive or unproductive for a tagger seeking quick, high-turnover exposure. The title of the study, borrowed from economist Robert Frank’s 1985 book Choosing the Right Pond, captures the idea: people seek status not in absolute terms but relative to the company they keep, and graffiti writers, it seems, choose their ponds with care.

The theoretical payoff is an extension of spot theory from absolute exposure to relative visual positioning. Where the original formulation asked whether a location is visible enough, the extended version asks whether a location’s existing visual content leaves room, literally and symbolically, for a particular kind of work. This reframing connects graffiti research to broader themes in the criminology of place, including the law of crime concentration and the role of place managers, and it resonates with classic territorial studies of graffiti, such as Ley and Cybriwsky’s 1974 work in Philadelphia, which showed that writers mark neighborhoods as their own. It also echoes ecological concepts like niche overlap and competitive displacement, concepts the authors cite alongside studies of ungulate communities and elk-deer-cattle resource partitioning, underscoring how deeply the analogy between graffiti writers and competing species runs.

The study’s practical implications reach into urban policy and crime prevention. If different graffiti types occupy different micro-locations for competitive reasons, then interventions such as murals, which previous research has suggested can deter graffiti, may work differently depending on the type of graffiti they displace and the visual composition of the surrounding streets. Rapid removal strategies, which aim to deny writers the audience feedback that sustains the practice, might be targeted more effectively at the segments where particular types cluster. The authors have also made a replication package, including the data and full code, publicly available, reflecting a growing emphasis on transparency in quantitative criminology. For now, the image that lingers is one of an unexpected kinship: the tagger and the muralist of Ghent, sorting themselves block by block, behave less like vandals scattering at random and more like species partitioning a habitat, each carving out a visual niche in the crowded ecology of the city street.

Subject of Research: Spatial segregation of graffiti types by visual complexity across urban street segments

Article Title: Choosing the Right Pond: Spatial Clustering of Street Graffiti by Visual Complexity

Article References: Choosing the Right Pond: Spatial Clustering of Street Graffiti by Visual Complexity. (n.d.). https://doi.org/10.1007/s12103-026-09958-4

Image Credits: AI Generated

DOI: 10.1007/s12103-026-09958-4

Keywords: graffiti, spot theory, visual complexity, criminology of place, street segments, Morisita-Horn Index, null model, systematic social observation, Ghent, competition, urban ecology, location choice