Microinteractions improve the usability of a GUI in several ways:

1. Feedback: Microinteractions provide instant feedback, confirming user actions and reducing uncertainty.

2. Guidance: They guide users through interactions, helping them understand what's happening and what's expected.

3. Contextualization: Microinteractions provide context to user actions, making the interface feel more dynamic and responsive.

4. Engagement: Microinteractions create an engaging experience, making users more likely to interact with the GUI.

5. Error prevention: Microinteractions can prevent errors by providing subtle cues or warnings.

6. Clarification: They clarify complex interactions, making them feel more straightforward.

7. Delight: Microinteractions can add delight and personality to the GUI, enhancing the overall user experience.

8. Learning: Microinteractions help users learn how to interact with the GUI through subtle cues and feedback.

9. Responsiveness: Microinteractions create a sense of responsiveness, making the GUI feel more alive and interactive.

10. Polish: Microinteractions add a level of polish and attention to detail, enhancing the overall quality of the GUI.

By incorporating microinteractions, GUI designers can create a more engaging, intuitive, and user-friendly interface that delights and assists users.