J Health Behav Med Hist 2025-16.
Introducing the Striver: Completing the Zoo in Our Brain
Robert C. van de Graaf, MD, director
MEDTCC Institute for Health, Behaviour, Medicine and its History, The Netherlands.
Abstract
Human behaviour is guided by multiple evolutionary motivational systems that have shaped our species over millennia. In the original Zoo in Our Brain model, five metaphorical animals were used to represent these core drivers: the Comfort Seeker, the Belonger, the Creature of Habit, the Explorer, and the Meaning Maker. Over time, however, one central motive proved difficult to place: the drive for ambition, influence, and social recognition. This follow-up paper introduces the Striver as the sixth animal, completing the motivational landscape. We explore its evolutionary foundations, its role within the broader system, and its dynamic interactions with the other animals. By making ambition explicit, the Striver allows us to understand a crucial dimension of human motivation that often operates just below the surface.
Expanding the Zoo
The Zoo in Our Brain model was developed to bring clarity to the complex web of human motivation through an accessible evolutionary psychological metaphor. Each “animal” represents a cluster of motivational tendencies that have emerged to solve adaptive challenges throughout human history.
The original five animals [Van de Graaf, 2025] are:
- the Comfort Seeker, oriented towards safety and physiological stability;
- the Belonger, focused on social bonding and group cohesion;
- the Creature of Habit, which supports efficient, automatic functioning;
- the Explorer, driven by curiosity and novelty seeking; and
- the Meaning Maker, which creates narratives, purpose, and shared frameworks of understanding.
Together, these five forces provide a remarkably coherent map of human behavioural tendencies. Yet one recurring theme remained insufficiently represented: our drive to strive—to compete, to rise in status, to achieve, and to leave a mark. These ambitions have played a decisive role in human evolution and cultural development. Recognising their distinct motivational character led to the articulation of a sixth animal: the Striver.
Expanding the Zoo
The Zoo in Our Brain model was developed to bring clarity to the complex web of human motivation through an accessible evolutionary metaphor. Each “animal” represents a cluster of motivational tendencies that have emerged to solve adaptive challenges throughout human history.
The original five animals are:
- the Comfort Seeker, oriented towards safety and physiological stability;
- the Belonger, focused on social bonding and group cohesion;
- the Creature of Habit, which supports efficient, automatic functioning;
- the Explorer, driven by curiosity and novelty seeking; and
- the Meaning Maker, which creates narratives, purpose, and shared frameworks of understanding.
Together, these five forces provide a remarkably coherent map of human behavioural tendencies. Yet one recurring theme remained insufficiently represented: our drive to strive—to compete, to rise in status, to achieve, and to leave a mark. These ambitions have played a decisive role in human evolution and cultural development. Recognising their distinct motivational character led to the articulation of a sixth animal: the Striver.
The Evolutionary Logic of the Striver
Ambition is not a modern invention; it is a deep evolutionary force. In early human societies, social status and influence determined access to resources, mates, and protection. Individuals who successfully navigated social hierarchies were more likely to survive and reproduce. Over time, this selective pressure shaped neural systems associated with competitive behaviour, reputation management, and long-term strategic thinking.
The Striver embodies these motivational systems. It represents the impulse to achieve, influence, and be recognised—not merely for personal gratification, but as a means of securing one’s position within complex social structures. Human ambition operates across multiple domains: material success, intellectual achievement, artistic creation, leadership, and moral influence. In each case, the Striver provides energy and direction for outward impact.
A Conceptual Map of the Six Animals
The expanded Zoo can be understood in terms of two functional clusters.
The basic drives—the Comfort Seeker, the Creature of Habit, and the Belonger—form the evolutionary foundation of human motivation. These systems ensure stability, safety, and social integration. They are shared, in various forms, with many other social mammals and underpin much of our daily behavioural repertoire.
The higher drives—the Explorer, the Meaning Maker, and the Striver—build on these foundations. They enable distinctively human capacities: exploration and innovation, the creation of meaning and culture, and the pursuit of status and achievement. These higher systems allow individuals to transcend immediate circumstances, imagine alternatives, and shape their environment and social world in unprecedented ways.
Importantly, these systems do not function independently. They form a dynamic network of interacting motivational forces. Sometimes these interactions are harmonious, as when ambition aligns with social bonds and shared meaning. At other times, tensions arise—for example, when the drive to strive collides with the need for rest, or when exploratory impulses disrupt established habits. It is this dynamic interplay, rather than any single system in isolation, that shapes the diversity and complexity of human behaviour.
The Striver in Relation to Other Animals
Within this motivational network, the Striver occupies a distinctive position. It connects deeply human capacities for planning and imagination with social hierarchies and cultural systems of recognition. Its interactions with the other animals illuminate many familiar psychological patterns:
- Striver and Comfort Seeker: A perennial tension between ambition and rest. Unchecked striving can override recovery needs; excessive comfort can suppress ambition.
- Striver and Belonger: Ambition unfolds in social contexts. Striving can strengthen group identity through leadership and contribution, but can also generate competition and social strain.
- Striver and Creature of Habit: Habits provide the stable routines that sustain ambition over time, but rigid patterns can inhibit growth and change.
- Striver and Explorer: Exploration fuels innovation and reputation, yet unbridled novelty seeking can scatter ambition and dilute focus.
- Striver and Meaning Maker: When ambition is integrated with purpose, it becomes a constructive force for cultural and personal development; when disconnected, it risks becoming shallow or self-serving.
These interactions reveal why the Striver is indispensable to a complete picture of human motivation. It acts as both a catalyst and a destabiliser—driving progress while generating tensions that must be managed by the whole motivational system.
Towards a More Complete Motivational Landscape
By introducing the Striver, the Zoo in Our Brain model reaches greater conceptual completeness. The six animals together represent a balanced set of evolutionary motives that underlie human behaviour:
- three foundational systems that secure safety, stability, and belonging, and
- three higher systems that enable exploration, meaning making, and striving.
Understanding human behaviour through this lens highlights that no single driver is inherently positive or negative. Each can be adaptive or maladaptive depending on context and its relation to the others. Ambition, in particular, has often been treated as either a virtue or a vice, depending on cultural framing. The Zoo model instead treats it as a neutral but powerful evolutionary force—one that must be integrated rather than ignored.
Conclusion
The addition of the Striver enriches the Zoo in Our Brain framework by illuminating a central dimension of human motivation: the desire to achieve, influence, and be recognised. This drive has deep evolutionary roots and plays a pivotal role in shaping human culture, social structures, and individual life courses.
By viewing ambition as one of six interacting motivational forces, rather than as a standalone trait, we gain a clearer and more balanced perspective on human behaviour. The Zoo model does not prescribe solutions; it offers a conceptual map for understanding the dynamic tensions that animate our inner world. With the Striver in place, that map becomes more complete.
References
Van de Graaf RC. The Zoo in Our Brain: An Evolutionary Psychology Framework for Understanding and Coaching Human Behaviour. J Health Behav Med Hist 2025-9.