1. Jakob’s Law:
Definition: Users expect your site or product to behave similarly to other products they already use.
Implication: Familiar design patterns and common interface conventions reduce the user’s cognitive load, as people form mental models based on their past experiences with other websites and apps. Staying consistent with established norms helps new users learn your interface more quickly.

2. Fitts’s Law:
Definition: The time required to move a pointer to a target (e.g., a button) is a function of the target’s distance and size.
Implication: Larger and closer targets are easier and faster to click or tap. Buttons that are frequently used should be positioned centrally and made sufficiently large to speed up interaction and reduce friction.

3. Hick’s Law (Hick-Hyman Law):
Definition: The time it takes to make a decision increases with the number and complexity of choices.
Implication: Reducing the number of options, simplifying decision-making steps, and breaking complex tasks into smaller chunks helps users make quicker, more confident decisions. Less is often more when it comes to menu options or form fields.

4. Miller’s Law:
Definition: The average person’s working memory can hold about 7 ± 2 items at once.
Implication: Complex information or lists should be broken down into manageable groups or “chunks.” This can mean grouping navigation items, using progressive disclosure, or employing concise messaging to prevent cognitive overload.

5. Tesler’s Law (Law of Conservation of Complexity):
Definition: Every application has an inherent amount of complexity that cannot be removed, only shifted.
Implication: As a designer, you can simplify the user interface, but you cannot eliminate complexity entirely—some of it will need to be managed by the system or the user. The goal is to handle as much complexity under the hood as possible, leaving users with a simpler, cleaner experience.

6. Aesthetic-Usability Effect:
Definition: Users perceive more aesthetically pleasing designs as easier to use, even if that’s not objectively the case.
Implication: Good visual design and aesthetics improve perceived usability, encourage user trust, and can make users more tolerant of minor usability issues. A balance of both form and function is essential.

7. Peak-End Rule:
Definition: People judge an experience mainly by how they felt at its most intense point (peak) and at its end, rather than by its entirety.
Implication: Optimize your users’ journey so that the “peak”—their most memorable moment—and the end of the experience are positive. For example, ensure the checkout process in an e-commerce app is smooth and the confirmation screen is delightful.

8. Von Restorff Effect (Isolation Effect):
Definition: When multiple similar stimuli are presented, the one that differs is more likely to be remembered.
Implication: Emphasize important elements—like primary calls-to-action—by making them stand out visually. Unique color contrasts, bold typography, or distinct placement can help guide user attention.

9. Doherty Threshold:
Definition: Productivity, performance, and user satisfaction improve when system response times are less than 400 milliseconds.
Implication: Users are more engaged and feel more in control when interaction feedback is nearly instantaneous. If the task involves longer processing times, providing a meaningful loading state or progress indicator helps maintain engagement.

10. Pareto Principle (80/20 Rule):
Definition: Roughly 80% of outcomes come from 20% of causes.
Implication: Identify the 20% of features or functions that your users value most and focus on optimizing those to deliver the greatest impact on overall satisfaction and efficiency.

11. Occam’s Razor:
Definition: Among competing designs or solutions that achieve the same result, the simplest one is usually the best.
Implication: Avoid unnecessary complexity. By stripping away extraneous features and clutter, you produce interfaces that are easier to use and understand.

12. Zeigarnik Effect:
Definition: People remember uncompleted or interrupted tasks better than completed ones.
Implication: If certain actions need to be completed across multiple sessions or steps, providing clear progress markers or saving partial work can motivate users to return and finish what they started. Progress bars, checklists, and reminders can take advantage of this effect.