“Invisible” implicit memory

Explicit memory recall is what we all think of as “remembering.” Explicit memory feels like “normal” memory. When we recall events through the explicit memory system, it feels, subjectively, like “I’m remembering something from my personal past experience.” For example, if I ask you “What did you do this morning?” you might tell me about getting woken up by the paper boy throwing the newspaper through your living room window at 5:30 a.m., and how you spent the next hour picking up broken glass, and you will feel like you are remembering something from your personal past. This conscious, autobiographical memory about your personal experiences is explicit memory.

Implicit memory is all memory phenomena that does not include the subjective experience of “I’m remembering something from my personal past experience.” Implicit memory content does not feel like “normal” memory. When the implicit memory systems are activated, our minds and brains recall memory material, but it does not feel, subjectively like explicit autobiographical memory. Since implicit memory does not feel like what we think of as memory, we usually do not have any awareness that we are remembering or being affected by past experience when memory material comes forward through one of the implicit memory systems. In fact, we sometimes refer to implicit memory as “invisible” memory, since it usually affects us without being “seen” by our conscious minds.

To give you more of an idea of what kind of phenomena I’m talking about, one of the most important and most common kinds of implicit memory is motor-skill memory. For example, you were not born with the ability to walk. You had to learn how to walk, and as you learned to walk your brain remembered the various motor skills involved. Every time you walk, your brain is remembering learned motor skills. Even though you have no conscious awareness of it, you are recalling and using implicit memory every time you walk, every time you ride a bike, every time you drive a car, and every time you type an e-mail. Another important and common kind of implicit memory is emotional memory.

There is a LOT of rigorous medical, scientific evidence proving the existence of implicit memory as separate from explicit memory. Some of the most easily understood data demonstrating the reality of implicit memory are observations from medical situations in which a particular neurological injury totally knocks out explicit memory while leaving a variety of implicit memory systems intact. For example, Dr. Oliver Sacks describes a carefully documented case study of a young man with complete loss of ability to lay down new explicit autobiographical memory due to a brain tumor that destroyed a part of his brain called the hippocampus. Within minutes after the actual event, Greg would lose every trace of explicit autobiographical memory for any personal experience – if you spoke with him for an hour, and then left briefly to use the restroom, when you returned five minutes later, he would have no conscious memory of ever having met you before. However, his implicit memory systems were still intact.

For example, he could learn new physical skills, such as typing or playing the guitar – even though he did not have any explicit autobiographical memories of his many practice sessions, if you put him in front of a typewriter he could type, and if you gave him a guitar he could play. He could learn new songs – even though he did not have any explicit memories of ever hearing the new songs before, if someone started humming the tune he could sing the rest of the song. And he could form new emotional associations – even though he did not have any explicit autobiographical memories of previous interactions with people on the staff, his face would light up when he met those who had been especially kind to him.

The relevant point with respect to our discussion is that the toxic content from unresolved trauma usually comes forward as various kinds of implicit memory. When something in the present triggers a traumatic memory, the unresolved content from the trauma, such as the distorted beliefs and emotions associated with the original painful experience, will come forward as “invisible” implicit memory that feels true and valid in the present. For example, if questions from a person’s boss trigger unresolved trauma from grade school, instead of having the explicit memory subjective experience of “I’m remembering the time when the teacher hit me with a ruler because I couldn’t answer his questions,” the person will just have the thoughts “I don’t know the answer, and now he’s going to hurt me,” he will feel intense anxiety, and he will perceive that these thoughts and emotions are true and valid in the present.

See chapter 2 for additional explanation, and more fascinating case study examples.

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