Hierarchical searching in episodic memory

An analysis of free-recall datasets from two independent experiments allows to identify two anomalous instances of non-monotonicity in free recall: a maximum in the dependence of the inter-response intervals on the serial-position lags, and a minimum in the rate of contiguous recall near the beginning of the recall process. Both effects, it is argued, may stem from a hierarchical search protocol in the space of memories. An elementary random-walk model on binary strings is used to test this hypothesis.