Behavior is our medium

The focus should remain on human

This article is a tribute to Robert Fabricant, a thinker who deeply influenced me, not through direct mentorship, but via his inspiring lecture at IXDA 2009. In that talk, Fabricant revealed a simple yet powerful insight:

as designers, what we work with is behavior, shaping it, understanding it, and ultimately impacting lives.

His words have stayed with me over the years, guiding my journey as a designer and researcher in the fields of HCI and Interaction Design.

Time has passed. I’ve worked across various companies and projects, yet Fabricant’s phrase, “Behavior is our medium,” resonates now more than ever. Too often, those of us in design are consumed by efficiency metrics, conversions, and growth. You know the acronyms well: CAC, NPS, CSAT, LTV, ARPA, WAU, MAU, the endless race of numbers. It’s easy to get lost designing for what drives revenue or satisfies stakeholders. I understand; this is the reality of capitalism. I don’t view design purely from a ‘romantic’ perspective.

I believe good design must generate value and revenue, both for people and for the company. But that’s not the point I want to focus on in this article. Stay with me as we explore something deeper.

Behavior change

Behavior change, or behavior modification (Bandura, 1970), is a branch of behavioral science that draws on fields such as cognitive science, psychology, neuroscience, economics, and other social science disciplines to understand, influence, and alter human actions.

Defining behavior change is a complex task, as many researchers offer differing definitions. Here, however, I want to propose a different approach: to separate the term “behavior change” into two distinct parts.

First, we need to clarify what we mean by behavior. The Merriam-Webster Dictionary defines it as any observable action in response to stimuli, or the way in which something functions.

The notion of “change,” on the other hand, implies a shift in habits, attitudes, or routines. This definition should help us establish a common ground moving forward.

Over time, key thinkers such as Skinner (1932), Bandura (1970), Prochaska & DiClemente (1983) Kahneman & Tversky (1991) Fogg (2001), Thaler & Sunstein (2009), Fjeldsoe (2009), and Duckworth (2016) have shaped the field, highlighting behavior change as a pathway to better outcomes for individuals, society, and the planet.

Yet, while behavior can be studied objectively, it is inevitably influenced by subjective factors, personal perceptions, internal beliefs, and cultural norms. For instance, changing energy-use habits may depend on how people perceive cost savings (perception), why they care about sustainability (belief), and the cultural value placed on nature (context).

In HCI/IxD, even if it is not always explicitly acknowledged by practitioners, behavior is central to the user experience. We cannot discuss UX without addressing user behavior. When we design the UI or the information architecture of a digital product, we are inherently shaping behavior.

Although rooted in longstanding theory, behavior change in HCI and IxD is a relatively recent focus, especially when we consider that the commercial internet only began in the late 1990s, followed by the dot-com boom of the early 2000s. The application of behavior change in digital products remains an emerging area. As Rapp et al. (2023) point out, it is only in recent years that design has begun to seriously explore how technology can drive behavioral shifts, spurred by digital advances and a growing recognition of human factors in design.

Today, designers frequently employ behavior change techniques, evidence-based methods grounded in psychology and social science, as key components in interventions aimed at shaping user behavior. Yet, many of these efforts fail to produce meaningful or lasting change.

For instance, the use of game elements such as leaderboards, stars, points, and visual cues may capture users’ attention temporarily, but these techniques often do not sustain long-term engagement or behavioral impact. I don’t want to discourage designers. Rather, I believe we should embrace behavior change as a vital discipline within design.

Behavior should be treated as a design material, just as technology once became our material. If we use behavior thoughtfully, we can create better products. More than that, I believe there is a broader and more meaningful opportunity before us: to design for behavior. Not to make people addicted to products, but to help them grow as human beings, better parents, citizens, students, and professionals. Because if behavior is our medium, then design is our tool for empowerment.

Behavior as design material

Merriam-Webster defines material as the elements, constituents, or substances of which something is composed or can be made, or something (such as data) that may be worked into a more finished form.

In design, materiality refers to the qualities, affordances, and constraints of the substances or media through which designers give form to ideas. Traditionally, this included wood, metal, fabric, or plastic, tangible materials whose properties shape what is possible.

In HCI/IxD, materiality extends beyond the physical to include computation, code, data, time, and interaction patterns, each carrying its own “material” characteristics. As Wiberg (2017) explains, a material can be anything, physical or immaterial, that designers can shape to facilitate interaction between the user and the system. Similarly, Norby (2011, p. 4) argues that “for industrial and interaction designers, computational technology may be seen as materials that can be used to shape designs.” Historically, as Wiberg (2017, p. 6) emphasizes, “materiality has always been a central concern in interaction design, influencing how interactions are structured and experienced”.

A design material is any medium that designers manipulate to create form, meaning, and experience. To function as a design material, it should possess qualities that can be explored and appropriated, impose constraints that guide creativity, and enable expression in interaction. Researchers in HCI have argued that computation and interaction themselves are design materials because they actively shape what design outcomes can emerge.

From this perspective, materiality is a central component for interaction designers. However, beyond computational materials, there is a growing recognition that behavior itself can be considered a design material. Behavior includes both system behavior — how a digital or physical system acts and responds, and user behavior — how people act within or in response to the system. As Cooper (2007) emphasized, systems must respond appropriately to user actions, making behavior a cornerstone of design.

This is where the materiality of behavior reveals its unique complexity. Unlike wood or code, human behavior is inherently unpredictable and contextual. It carries its own agency, is shaped by emotions, and is influenced by several external factors.

Designing with behavior, therefore, is a dynamic and relational practice: the designer carefully sculpts the system’s behavior with the intention of influencing, guiding, or facilitating certain user actions, while recognizing that the outcome is always a co-creation, a dialogue between the system’s rules and the user’s unpredictable will.

Behavior has distinct qualities such as timing, rhythm, predictability, and adaptability. It also constrains what is possible, as the way a system behaves defines which actions become meaningful for the user. Moreover, behavior is expressive: a robot moving slowly and smoothly communicates friendliness, whereas abrupt and jerky movement communicates aggression. Unlike static materials, behavior unfolds over time, meaning designers sculpt temporal patterns as deliberately as physical form.

A practical example of this dynamic is Duolingo’s “streak.” The designed system behaves as a visual counter that increments daily and resets to zero if a lesson is missed, directly seeking to shape user behavior by fostering a daily learning habit. This visual cue leverages psychological principles such as loss aversion and the satisfaction of maintaining progress to promote consistency. It exemplifies behavior as a material: the designer is intentionally shaping the properties of human motivation to “sculpt” a desired routine.

Ultimately, interaction design is less about static objects and more about how things and people behave toward one another. In this sense, behavior is not a byproduct but the very substance of interaction design. It is a design material because it carries properties, constraints, and expressive potential that designers can intentionally shape, just like wood, metal, or code.

The focus should remain on Human

Design, technology, and computing are ultimately about people. Design is created by people, for people, and with people, not the other way around. Yet so much of what we build today fails to support what truly matters to individuals. Why, in an age of intelligent systems and smart computing, are we still primarily designing for task completion and efficiency? Why is interaction design so often stuck in a mindset of consumption?

We should be designing for transformation to make interactions between people and technology smoother, more meaningful, and more human. This could mean creating systems that foster deep focus instead of constant interruption, that support memory augmentation rather than replacement, or that facilitate genuine connection.

Technology should not be a cage. It should be a set of wings.

Instead, we too often create systems that trap users in loops of distraction and consumption. Look around: technology has made us faster and more efficient, yes. But it has also made many of us more anxious, disconnected, and dependent. For countless users, hours are lost to social media feeds instead of invested in rich, real-world interaction. We are outsourcing cognition, offloading memory, letting machines think for us. That is not an empowering future; it is a cage.

As designers, our focus must remain on humans. We carry the responsibility to design for both human needs and business needs, balancing them while always grounding our work in human well-being as a non-negotiable foundation.

As interaction designers, we have a responsibility to use technology to empower, not to confine. And yet, look at us now: we are becoming trapped, uncertain, drifting. The algorithm is leading; we have forgotten that it is we who must define how the algorithm interacts with humans, not the other way around.

Designing for behavior change

Although there is a wide range of techniques and methods available for designing behavior change, many designers still lack the skills to apply them effectively. First, when approaching behavioral science in design, or behavior design, designers often encounter significant challenges. For some, behavior change feels “too scientific,” requiring a foundation of knowledge they may not yet possess. Moreover, behavior itself is complex, making it difficult to translate theory into practice.

Second, many designers rely heavily on pre-defined tools such as cognitive biases or behavior design pattern libraries, but struggle to develop their own understanding or creative approach to behavior change. Finally, despite the existence of influential models such as the Fogg Behavior Model, the Hook Model, and the COM-B Model, the field still lacks well-defined heuristics and design techniques that can be consistently applied in practice. As a result, applying these frameworks in real-world projects remains a major challenge for designers.

Although designing for behavior change is challenging, when we as designers consciously treat behavior as a design material, we open the door to creating a deeper and more lasting impact on both people and the planet. Designing products and services that guide people toward positive outcomes requires a solid understanding of human behavior.

As Niedderer et al. (2018, p. 10) point out, “designing for behavior change is not a new concept; it’s well-rooted in design practice.” Since the late 19th century, and throughout the 20th century, thinkers like Papanek (1971) and McDonough (2002) have explored how design can influence human choices and actions.

More recently, this conversation has expanded into the domain of interaction design, where scholars such as Fogg (2001), Lockton (2005), Lilley (2009), and Niedderer et al. (2018) have advanced the field by exploring how digital products can be intentionally crafted to shape user behavior in meaningful ways.

Traditionally, design was closely associated with the creation of physical objects or visual communication. From a linguistic perspective, the verb to design implies crafting something with purpose and intention. As McDonough (1992) stated, design is the first signal of human intention. Every product we encounter in the world carries with it the intentions, whether conscious or not, of the designer or team that created it (Nzongo, 2022).

As a practitioner, I see design as a powerful and flexible tool that can be approached from multiple angles to support and influence behavior change through thoughtfully crafted products and experiences. Design isn’t just about form or function; it’s about shaping interactions, decisions, and ultimately, outcomes.

Niedderer et al. (2018, p. 11) capture this well when they state, “The capacity of a designer lies in creating change through design by transforming the existing situation into a preferred one.” In this sense, design becomes a form of intentional intervention, an opportunity to shift the current state of things toward something better, whether that means encouraging more sustainable habits, improving well-being, or supporting meaningful social change.

Design for behavior change represents the next frontier in design.

We must adopt a broader perspective, as Norman (1984) did when connecting design to behavior, emphasizing that artifacts are created to facilitate actions through their physical, symbolic, or social functions. From this viewpoint, design inherently drives transformation, shaping attitudes and behaviors.

Niedderer et al. (2018, p. 9) highlight this transformative power, arguing that design has shaped modern society and continues to influence behavior in profound ways. Forcato (2015, p. 78) reinforces this perspective, noting that “design has always influenced behavior, whether intentionally or not.”

Designing for behavior change isn’t just an idealistic goal; it’s a necessity. As Fabricant points out, behavior is our medium, and we should be using it to empower individuals and transform our communities. If behavior is the medium, then design is the tool for shaping it. By applying behavior change techniques and social theory, we have the potential to design digital products that go far beyond surface-level aesthetics. I truly believe we can and should create tools that support deeper, more meaningful change.

Designing for fitness habits

In this project, I applied principles from social psychology and behavioral science to design a fitness app focused on fostering long-term well-being, not just logging workouts. The goal was to create a system that supports intrinsic motivation and sustainable habit formation.

The design leverages two interconnected features: progressive self-monitoring and a meaningful achievements system, grounded in a cohesive theoretical framework.

Fostering intrinsic motivation through self-monitoring and identity

At the core of the design lies the principle of self-monitoring, a key technique in the persuasive systems design (PSD) model. The app enables users to track their performance and compare progress against personal goals.

This continuous feedback loop is crucial for sustaining motivation. According to self-determination theory (SDT) (Deci & Ryan, 1985), such feedback fosters positive emotions like satisfaction and pride as users observe their own improvement, directly strengthening their sense of competence, a fundamental pillar of intrinsic motivation.

To strengthen this connection, the app incorporates a 3D avatar as a virtual representation of the user. This feature leverages the proteus effect, a psychological phenomenon in which individuals unconsciously begin to align their behavior with the identity of their avatar. This “imagined self” acts as a powerful, internalized motivator, reinforcing commitment by allowing users to visualize their future, healthier selves.

Reinforcing progress with a theory-driven reward system

The motivation generated through self-monitoring is further reinforced by a carefully designed achievements system. While badges act as external rewards, their true power lies in their ability to validate effort and signify mastery. This aligns with expectancy theory (Behling & Starke, 1973), which suggests that motivation is driven by the belief that effort leads to success — badges make this “success” tangible.

Additionally, the system operates on the principles of positive reinforcement (Skinner, 1938), where desirable behaviors, such as consistent training, are followed by a rewarding outcome. The ultimate aim, however, is to guide users from external reinforcement toward internal satisfaction. By visualizing achievements, the system strengthens the user’s sense of competence, thereby continuing to support the intrinsic motivation emphasized in self-determination theory (SDT).

This project exemplifies how interaction designers can move beyond surface-level aesthetics to create products that facilitate meaningful, positive change. By consciously applying behavior change principles using self-monitoring to build competence, an avatar to support identity, and achievements to reinforce progress, we can create tools that empower users and support their long-term well-being. It is a practical demonstration of using behavior as a design material with intention and responsibility.

Read more about the project details at this link.

Conclusion

We can’t limit ourselves to designing only for task completion or task success. This approach is becoming outdated. It’s time to look toward a new horizon and embrace behavior as a design material.

As intelligent systems (AI) become increasingly prevalent, understanding human behavior is no longer optional; it is essential. Our responsibility as practitioners grows: we are not only shaping how these systems behave, but also influencing the behaviors humans develop when interacting with them. As designers, we must acknowledge this impact.

Every screen, every system, and every micro-interaction represents an opportunity to shape behavior. In essence, we are already designing behavior. The critical question, then, is not whether we influence behavior, but what kind of behavior we are enabling and with what intention.

Designing for behavior change is not about control; it is about care. It requires using our tools, research, empathy, theory, and craft to act responsibly and intentionally. As we move further into an age of AI and autonomous systems, the choices we make today will shape the habits, values, and actions of tomorrow.

Let’s choose to design for good. Let’s choose to design for change. Because when we design for behavior, we’re not just designing experiences — we’re shaping futures.

Behavior is our medium was originally published in UX Collective on Medium, where people are continuing the conversation by highlighting and responding to this story.

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