Date of Award

December 2020

Degree Type


Degree Name

Doctor of Philosophy (PhD)




Amy H. Criss


A unified memory model, Concurrent encoding and retrieval, REM, Scaffolded encoding

Subject Categories

Social and Behavioral Sciences


Repetitions are ubiquitous and are the foundation of episodic memory. As we investigate episodic memory in a laboratory setting and with, usually, a study-test design, we have inaccurately assumed encoding happens only at study and retrieval happens only at test. However, it’s entirely possible that encoding and retrieval happen simultaneously at both study, with explicit repetition, and test, with implicit repetition. The fallacy that encoding and retrieval are separate processes coincides with the unsatisfactory status of memory process model: there is no unified memory model. Most models of memory are models of retrieval tasks. Facing these two challenges, we proposed a model of scaffolded encoding. Building on previous modeling studies that include an updating mechanism (accumulating information in an old memory trace) for an old event and an adding mechanism (storing a new trace) for a new event, we presented a scaffolded encoding mechanism for a semi-old event. Scaffolding a new trace means a new trace is not encoded and stored from nothing. Instead, it is added to memory with already updated information from old memories. As a result, an exact repetition (an old event) leads to one single strong memory trace and a partial repetition (a semi-old event) is stored as a separate episode (new) with strengthened information (old). In this current project, we will present a thorough investigation implementing the scaffolded encoding mechanism within the retrieving effectively from memory model. Within this model, any study or test event can be identified as an old, new, or semi-old event, and then corresponding encoding process (updating, adding, or scaffolded encoding) takes place. Our model, unprecedentedly, successfully accounts for the hallmark findings that show effects of repetition, including list strength effect, output interference, proactive interference and proactive facilitation, from multiple retrieval tasks.


Open Access