Probe trials, explained

The probe is the moment of truth. Take the platform away and watch where the animal searches. It's memory, made visible.

How to score it

• Time in the target quadrant (chance is 25 percent).
• Platform crossings.
• Time close to where the platform used to be.
• Proximity: average distance to that spot.

Proximity measures are often more sensitive than quadrant time because they give credit for near-misses.

When to run it

A probe 24 h after training tests long-term memory. Probes during training show how learning builds up.