Hoarding titmice predominantly use Familiarity, and not Recollection, when remembering cache locations

Area of Science:

• Cognitive neuroscience
• Animal behavior
• Comparative psychology

Background:

• Scatter-hoarding birds possess enlarged hippocampi, suggesting a role in spatial memory for cache retrieval.
• Cache retrieval can rely on Recollection (detailed recall) or Familiarity (general recognition).
• Previous research in rats indicated hippocampal involvement in Recollection but not Familiarity for olfactory memory.

Purpose of the Study:

• To test if food-hoarding birds, with larger hippocampi, primarily use Recollection for cache retrieval.
• To validate a novel method for constructing receiver operating characteristic (ROC) curves in humans.
• To apply this ROC curve method to analyze cache retrieval strategies in coal tits (Periparus ater).

Main Methods:

• Developed and validated a novel receiver operating characteristic (ROC) curve construction method in humans.
• Applied the ROC curve methodology to study cache retrieval in coal tits (Periparus ater).
• Analyzed memory performance in relation to retention intervals.

Main Results:

• Both humans and coal tits predominantly relied on Familiarity for cache retrieval.
• The contribution of Recollection was minimal and not significantly different from chance in birds.
• Memory performance in birds decreased as the time interval between caching and retrieval increased.

Conclusions:

• Food-hoarding birds, despite larger hippocampi, primarily use Familiarity for finding caches.
• The enlarged hippocampus may support associating cache contents and temporal context with locations, rather than spatial Recollection.
• Ecological pressures on Parids likely favor a Familiarity-based memory system for cache sites.