Human perception isn't a passive video recording of reality, it's an active, constructive process shaped by biology, attention, expectations, past experiences, emotions, and even cultural or linguistic frameworks. This makes human perception inherently relative: the same objective event or stimulus can be interpreted, remembered, and recalled differently by different observers. Nowhere is this relativity more dramatically illustrated than when multiple eyewitnesses watch the exact same video footage, yet walk away describing strikingly different "realities."

The Illusion of Objective Seeing

We often assume "seeing is believing," and that shared visual input should produce shared understanding. But perception begins with selective filtering. The brain doesn't process every detail in a scene; it prioritises based on goals, attention, and prior knowledge.

Bottom-up processing handles raw sensory data (light hitting the retina).

Top-down processing overlays expectations, context, and meaning.

When these don't align perfectly, what one person "sees" diverges from another's. This isn't optical illusion, it's how the mind constructs reality.

Classic demonstrations highlight this:

In the famous "invisible gorilla" experiment (inattentional blindness), people counting basketball passes completely miss a person in a gorilla suit walking through the scene. Their focused attention blinds them to the obvious.

Change blindness shows similar failures: people fail to notice major alterations (like a person swapping identities mid-scene) if attention is elsewhere or disrupted briefly (e.g., by a cut or blink).

These phenomena directly apply to eyewitness scenarios. When people view a video of an event — say, a theft, altercation, or accident — their focus determines what registers. Someone scanning for threats notices different details than someone casually observing or distracted by conversation.

Why the Same Video Yields Different Realities

Several interlocking mechanisms explain eyewitness divergence:

1.Selective Attention and Inattentional/Change Blindness: Attention acts like a spotlight. In high-stakes or complex scenes, people tunnel-vision on one element (e.g., a weapon), missing peripheral details or even central changes. Studies show witnesses often fail to detect perpetrator swaps in videos if not intentionally tracking identity — leading to mistaken identifications.

2.Prior Expectations and Schemas: Brains fill gaps using mental templates ("schemas") from experience. If a scene fits a stereotype (e.g., "burglar" appearance), observers interpret ambiguously. Prejudices, biases, or cultural lenses amplify this — two viewers might "see" aggression or self-defence based on preconceptions.

3.Emotional and Stress Effects: Stress narrows focus (weapon focus effect: attention locks on a gun, blurring faces). High arousal can distort time perception or detail encoding, making recollections feel vivid but inaccurate.

4.Memory Reconstruction Over Replay: Memory isn't a tape — it's rebuilt each recall. Elizabeth Loftus's pioneering work shows post-event information (leading questions, discussions, media) contaminates memories via the misinformation effect. Witnesses incorporate suggestions unknowingly, creating confident but false details. Even video evidence can be reinterpreted through later narratives.

5.Slow-Motion Bias and Presentation Factors: Videos shown in slow motion make actions seem more intentional. Shaky footage heightens perceived intensity. Subtle differences in viewing conditions or repeated exposure alter interpretations.

Real-world examples abound: In high-profile cases (e.g., police incidents captured on bodycam), different observers — shaped by background, politics, or empathy — extract opposing narratives from identical footage. One sees justified force; another sees excessive violence. The video is objective; the perception is relative.

Implications for Justice and Everyday Life

Eyewitness testimony, once considered "gold standard" evidence, is now known to be fallible, contributing to many wrongful convictions (e.g., via DNA exonerations). Courts increasingly incorporate psychological science, favouring corroboration over sole reliance on memory.

Beyond law, this relativity underscores broader truths: arguments over "what happened" often stem from perceptual differences, not dishonesty. In relationships, politics, or history, people inhabit slightly different subjective realities.

Embracing Perceptual Relativity

Understanding this doesn't erode trust in perception, it refines it. Awareness of biases encourages humility: "This is what I saw, but it may not be the full picture." Tools like double-blind procedures, careful questioning, and cross-verification help align subjective views closer to objective truth.

In the end, human perception is relative not because reality is subjective, but because the mind is a masterful interpreter — filtering, constructing, and sometimes reinventing the world to make sense of it. When eyewitnesses watch the same video and see different realities, they're not wrong; they're human. The law has taken account of this in the theory of evidence.