Proactive interference

Biological Parallel

Old learning interferes with new learning when systems are path-dependent. Salmon imprinted on natal stream odor at age 2-3 years show 80% homing accuracy, but fish forced to re-imprint on new streams at age 4+ show only 30% accuracy—old olfactory memories interfere with new. Honeybees trained on blue flower → nectar association for 50 trials, then switched to yellow → nectar, show 60% error rate initially versus 10% for naive bees. Migrating birds using traditional flyways for 3+ years show 70% navigation errors when forced to new routes versus 20% for first-year migrants. The pattern: strongly encoded early memories create proactive interference. Neural pathways strengthened by repetition compete with new pathways, making unlearning harder than initial learning.