feedback-design

# Feedback Design

Feedback is how software communicates with users. Good feedback creates anticipation, confirms actions, and guides recovery.

## Evidence Tiers

```
[Research]   — Peer-reviewed studies, controlled experiments
[Expert]     — Nielsen Norman Group, recognized UX authorities
[Case Study] — Documented examples from major products
[Convention] — Industry practice, limited formal validation

Multiple tags = stronger evidence: [Research][Expert]
Mixed findings noted as: [Research — Mixed]
```

---

## Response Time Thresholds

**[Research][Expert]** Jakob Nielsen, based on Miller (1968), established response time limits in *Usability Engineering* (1993):

| Threshold | User Perception |
|-----------|-----------------|
| **0.1 sec** | Feels instantaneous — direct manipulation illusion |
| **1.0 sec** | Noticeable delay — user stays focused but notices wait |
| **10 sec** | Attention limit — user needs progress indicator or will leave |

These thresholds are based on human perceptual abilities and remain foundational in interaction design.

**Source:** [Nielsen Norman Group - Response Times](https://www.nngroup.com/articles/response-times-3-important-limits/)

---

## Progress Indicators

**[Research]** Dopamine research (Schultz, Sapolsky) shows the brain releases dopamine during *anticipation* of reward, not after. Progress indicators work because they create anticipation.

### Pattern: Progress Over Spinners

**Weak feedback:**
```
Loading...
```

**Strong feedback:**
```
Uploading photo 3 of 7...
████████░░░░░░░░ 47%
```

Progress creates anticipation. Spinners create uncertainty.

---

## Skeleton Screens

**[Research — Mixed Results]** Skeleton screen research shows inconsistent findings:

- Mejtoft et al. (2018) found skeleton screens scored higher on perceived speed
- Viget's study (136 participants) found skeleton screens **performed worse** than spinners — users took longer and evaluated wait time more negatively

**When skeletons may help:**
- F