What are the availability heuristic and the anchoring bias?

Availability: you judge how likely something is by how easily examples come to mind. Anchoring: an initial number drags your estimate toward it.

• Availability heuristic (Verfügbarkeitsheuristik) — you estimate the frequency or probability of something by how easily instances spring to mind. Vivid, recent, or heavily-reported events feel more common than they are. People overestimate plane-crash or shark-attack risk because those events are memorable, not because they're frequent.
• Anchoring bias (Ankereffekt) — the first number you encounter ("the anchor") biases your subsequent estimate toward it, even when it's arbitrary. Ask someone whether a population is more or less than 50 million and their guess clusters near 50 million; ask "more or less than 500 million" and it jumps — same target, different anchor.

Both are mental shortcuts that misfire: availability lets ease of recall stand in for actual frequency, and anchoring lets an arbitrary starting point contaminate a reasoned estimate.

Tip: Availability = "if I can think of it easily, it must be common." Anchoring = "the first figure I heard quietly sets my whole range." Both replace data with a shortcut.