In 1937, he applied to work with Wilder Penfield at the Montreal Neurological Institute, researching the effect of brain surgery and injury on human brain function.

In 1942, Hebb moved to Orange Park, Florida to once again work with Karl Lashley at the Yerkes National Primate Research Center. Here, studying primate behavior, Hebb developed emotional tests for chimpanzees.

He returned to McGill University to become a professor of psychology in 1947 and was made chairman of the department in 1948. Here he once again worked with Penfield, but this time through his students (including Brenda Milner), who extended his earlier work with Penfield on the human brain.

Hebb's 1949 book The Organization of Behavior: A Neuropsychological Theory put forward what he called his "neuropsychological postulate," the assumption that cognitive processes like perception and learning can be understood in terms of the connections between assemblies of neurons. Hebb's thesis was that behavior is to be understood entirely in terms of brain function.

Hebb is considered one of the fathers of neural network theory, which is central to artificial intelligence research. Hebb's networks called "cell assemblies" were connected in ways that control the responses to various stimuli.

Hebbian assemblies of neurons are a model for memory often called "Hebbian learning." He described his "neuropsychological postulate" as this assumption:

When an axon of cell A is near enough to excite cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A's efficiency, as one of the cells firing B, is increased.

Hebb, D. O. (1949). The Organization of Behavior: A Neuropsychological Theory. New York: Wiley and Sons, p.62

This assumption is often paraphrased as "Neurons that fire together wire together," or simply "Fire together, Wire together."

The Experience Recorder and Reproducer (ERR) model of information philosophy is built on Hebb's assumption as the basis of the Recorder stage, where the Reproducer depends on this extension of Hebb's insight.

Neurons that have been wired together in the past will fire together in the future (reproducing all or part of relevant past experiences).

Ours is not the first such suggestion. Giulio Tononi and colleagues wrote this in the Publications of the National Academy of Sciences in 2008, and referenced two earlier suggestions from the 1990's.

Consider neurons that are coactivated during learning tasks and become more strongly connected, in line with Hebbian principles (fire together, wire together). After learning, the same neurons show an increase in correlated firing when they are spontaneously active, both in quiet wakefulness and during sleep (wire together, fire together)

A BOLD window into brain waves. PNAS October 14, 2008 105 (41) 15641-15642

Our ERR mind model grows out of the biological question of what sort of "mind" would provide the greatest survival value for the lowest (or the first) organisms that evolved mind-like capabilities.

We propose that a minimal primitive mind would need only to "play back" past experiences that resemble any part of current experience. Remembering past experiences has obvious relevance (survival value) for an organism. But beyond survival value, the ERR touches on the philosophical problem of "meaning." We suggest the epistemological "meaning" of information perceived may be found in the past experiences that are reproduced by the ERR.

The ERR model is a memory model for long-term potentiation stored in neocortical synapses. Short-term (working) memory must have a much faster storage mechanism. While long-term storage is slow, we shall see that ERR retrieval is just as fast, and it does not fade as does short-term, working memory. For all we know, traces of all past experiences may be present in a mind. Consider Marcel Proust's Madeleines

We propose that the ERR reproduces the entire complex of the original sensations experienced, together with the emotional response to the original experience (pleasure, pain, fear, etc.). Playback of past experiences may be stimulated by anything in the current experience that resembles something in the past experiences, in the five dimensions of the senses (sound, sight, touch, smell and taste).

The ERR model stands in contrast to the popular cognitive science or “computational” model of a mind as a digital computer with a "central processor" or even many "parallel processors." No algorithms or stored programs are needed for the ERR model. There is nothing comparable to the addresses and data buses used to stored and retrieve information in a digital computer.

The ERR is entirely an analog model of mind.