Designing with the Mind in Mind

1. Our perception is biased by experience, context, and goals

What we perceive is not an accurate reflection of our environment. It is biased by at least three factors: past experience, current context, and future goals.

Experience shapes perception. Our brains interpret sensory input based on prior experiences, leading to phenomena like:

• Perceptual priming: We more easily recognize objects we've recently seen
• Mental frames: We fill in missing details based on familiar patterns
• Habituation: We become less sensitive to repeated stimuli

Context influences interpretation. The same sensory input can be perceived differently depending on:

• Surrounding visual elements
• Auditory cues
• Cultural context
• Emotional state

Goals direct attention. Our current objectives act as a filter, causing us to:

• Notice goal-relevant information more readily
• Overlook unrelated details, even if they're obvious (inattentional blindness)
• Interpret ambiguous stimuli in ways that align with our goals

2. Vision is optimized for structure and contrast, not absolute brightness

Our vision is optimized to detect contrasts (edges), not absolute brightness.

Edge detection is key. The visual system is highly attuned to:

• Boundaries between light and dark areas
• Changes in color or texture
• Shapes and outlines of objects

Relative differences matter more than absolutes. This explains visual illusions where:

• The same shade of gray appears lighter or darker depending on its surroundings
• We can recognize objects in various lighting conditions

Color perception is complex. Our ability to distinguish colors depends on:

• The size of the colored area
• The background and surrounding colors
• The overall illumination level

These principles have important implications for user interface design:

• Use contrast to draw attention to important elements
• Be mindful of color combinations, especially for users with color vision deficiencies
• Ensure that information isn't solely conveyed through subtle color differences

3. Peripheral vision is poor but serves important functions

Our peripheral vision is roughly equivalent to looking through a frosted shower door, and yet you enjoy the illusion of seeing the periphery clearly.

Foveal vs. peripheral vision. The human visual field has:

• A small area of high acuity (fovea) at the center
• A much larger area of low resolution in the periphery

Despite this limitation, peripheral vision serves crucial functions:

1. Guiding eye movements to interesting areas
2. Detecting motion and potential threats
3. Providing context and a sense of spatial awareness

Implications for interface design:

• Important information should be placed near the center of the visual field
• Use motion or contrast in the periphery to draw attention when necessary
• Don't rely on fine details being noticed in peripheral areas
• Consider how information is distributed across the entire display

4. Reading is an unnatural skill that can be disrupted easily

Reading is an artificial skill that we learn by systematic instruction and practice, like playing a violin, juggling, or reading music.

Reading is a learned skill. Unlike spoken language, humans didn't evolve to read naturally:

• It requires explicit training and practice
• The brain repurposes existing neural circuits for this task

The reading process is complex. It involves:

• Rapid eye movements (saccades) between fixation points
• Recognition of letter shapes and word forms
• Integration with language processing areas of the brain

Many factors can disrupt reading:

• Unfamiliar vocabulary or jargon
• Poor typography or layout
• Low contrast between text and background
• Distracting visual elements

To support efficient reading in interfaces:

• Use clear, familiar language
• Ensure good contrast and legibility
• Organize text with clear hierarchies and structure
• Minimize unnecessary text and visual clutter

5. Attention and memory have severe limitations

Short-term memory covers situations in which information is retained for intervals ranging from a fraction of a second to a few minutes. Long-term memory covers situations in which information is retained over longer periods (e.g., hours, days, years, even lifetimes).

Working memory is limited. Humans can typically hold:

• Only 3-5 items in working memory at once
• Information for just a few seconds without rehearsal

Long-term memory is vast but imperfect. It is:

• Susceptible to distortion and false memories
• Strongly influenced by emotions and repetition
• More focused on general patterns than specific details

Implications for interface design:

• Break complex tasks into smaller steps
• Provide clear, persistent information about system state
• Use recognition rather than recall where possible
• Offer external memory aids (e.g., history lists, saved preferences)
• Design for interruptions and task resumption

6. We prefer familiar paths and struggle with novel actions

Learning from experience and performing well-learned actions are easy largely because they don't require constant awareness or focused attention and because they can occur in parallel.

Automatic vs. controlled processing. Human cognition operates in two modes:

• Automatic (System 1): Fast, effortless, unconscious
• Controlled (System 2): Slow, effortful, conscious

Familiarity breeds efficiency. Well-practiced actions become automatic, allowing for:

• Faster execution
• Lower cognitive load
• Ability to multitask

Novel actions are challenging. They require:

• More conscious attention
• Greater mental effort
• Slower execution and higher error rates

To support users, interfaces should:

• Leverage familiar patterns and conventions
• Provide clear paths for common tasks
• Offer guidance for novel or complex actions
• Allow for gradual learning and increasing efficiency

7. Decision-making is rarely rational and easily influenced

Economists often assume that decision making is rational and stable, but research indicates that human decision making is rarely so.

Cognitive biases affect decisions. Common biases include:

• Loss aversion: We fear losses more than we value equivalent gains
• Framing effects: How choices are presented influences our decisions
• Availability heuristic: We overestimate the probability of events we can easily recall

Emotions play a significant role. Decisions are often driven by:

• Gut feelings and intuitions
• Immediate emotional responses
• Subconscious associations

Context shapes choices. Decisions are influenced by:

• Recent experiences and priming
• Social pressure and norms
• Environmental factors (e.g., time pressure, cognitive load)

Implications for interface design:

• Be aware of how information presentation can bias decisions
• Provide clear, objective information to support rational choices
• Consider the emotional aspects of user experience
• Offer tools to compare options and analyze trade-offs

8. Hand-eye coordination follows predictable laws

The larger your target on a screen and the nearer it is to your starting point, the faster you can point to it.

Fitts' Law governs pointing tasks. It states that:

• Larger targets are easier and faster to hit
• Closer targets are easier and faster to hit
• The relationship is logarithmic, not linear

The Steering Law applies to path-following tasks. It predicts that:

• Wider paths are easier to navigate
• Shorter paths are easier to navigate

These laws have important implications for interface design:

• Make frequently used controls larger and/or closer to common starting points
• Provide ample space between clickable elements to prevent errors
• Consider the trade-offs between menu designs (e.g., linear vs. radial)
• Optimize gestures and drag-and-drop interactions based on these principles

9. Responsive systems must meet specific time requirements

To be perceived by users as responsive, interactive software must follow these guidelines: Acknowledge user actions instantly, even if returning that the answer will take time; preserve users' perception of cause and effect.

Human perception has inherent time constraints. Key thresholds include:

• 0.1 seconds: Limit for perceived instantaneous response
• 1 second: Maximum delay before users feel interrupted
• 10 seconds: Limit of focused attention without feedback

Responsiveness is crucial for user satisfaction. It involves:

• Providing immediate feedback for actions
• Keeping users informed about system state
• Allowing for task interruption and resumption

Strategies for improving perceived responsiveness:

• Use visual indicators for system status (e.g., progress bars, spinners)
• Prioritize the display of critical information
• Perform background processing and preloading when possible
• Break long operations into smaller, interruptible steps

By aligning system behavior with human perceptual and cognitive limitations, designers can create interfaces that feel more natural, efficient, and satisfying to use.

Last updated: February 4, 2025