What is Aphantasia? What is SDAM?
1. Aphantasia
1-1. Definition (in brief)
Refers to a state in which there is no (or significantly limited) experience of
intentional (voluntary)mental imagery while awake.For more details, click here.
1-2. Quoted from the glossary
⬛️ Aphantasia
Aphantasia is a state in which the subjective experience of mental imagery does not occur or is significantly limited.
Specific examples can be found here: My inner world with Aphantasia and SDAM
It was named by Adam Zeman and others in 2015. The most well-known state is the absence of visual mental imagery, meaning one does not—or has a very faint experience of—"calling to mind" landscapes or people's faces when closing one's eyes. Note that this is not limited to vision; there are cases where imagery experience is limited across multiple sensory modalities (sensory modes/sensory aspects), such as auditory, tactile, olfactory, gustatory, and kinesthetic.
On the other hand, other mental representations such as concepts and propositions function normally, so there is no difficulty in handling knowledge or concepts like "what kind of fruit an apple is," even if one cannot visualize an apple in one's mind. Aphantasia is generally understood not as a disease or disorder, but as a form of individual difference or diversity in mental imagery.
1-3. Personal notes
The explanation by Wikipedia is here.
Mental imagery, in brief, refers to "subjective experiences similar to perception that occur in consciousness without external stimuli, separate from perception caused by actual sensations (external stimuli)." (Note: As I have never experienced mental imagery myself, I am writing this as a conjecture based on conceptual understanding.)
In many cases, visual mental imagery is what is discussed.
In my case, since I likely do not experience mental imagery even in dreams, it may not be limited to "no intentional (voluntary) mental imagery experience while awake," but rather a general "absence of mental imagery experience."
According to the views of major researchers, at this time, Aphantasia itself is understood not as a disorder or disease, but as a form of individual difference or diversity.
⇒ Claude's log (PDF version | Image version)
2. SDAM (Severely Deficient Autobiographical Memory)
2-1. Definition (in brief)
Refers to a state in which there is no (or significantly limited) re-experiencing of autobiographical memory throughout one's life.
For more details, click here.
2-2. Quoted from the glossary
⬛️ SDAM (Severely Deficient Autobiographical Memory)
SDAM stands for "Severely Deficient Autobiographical Memory," a condition in which episodic autobiographical memory—the ability to subjectively re-experience events from one's past—is either absent or severely limited throughout one's life.
For specific examples, see here: My Inner World with Aphantasia and SDAM
It was proposed by Palombo et al. in 2015. It is clearly distinguished from acquired memory impairment caused by brain injury or neurological disease and is positioned as a lifelong condition. The characteristic of SDAM is that even if one knows the facts of past events, one does not recall them with the accompanying scenes, sensations, or emotions of that time. For example, while one may remember the fact of "where I went on a trip last year," one does not mentally recreate the sights or feelings of that moment. Semantic autobiographical memory, such as "where I lived" or "what I was doing," is often relatively preserved. Additionally, research has reported that people with aphantasia have a relatively high rate of co-occurring SDAM.
2-3. Personal Notes
An explanation by Dr. Levine, who named SDAM, can be found here.
Autobiographical memory refers to the totality of an individual's past experiences, episodes, and semantic knowledge about the self. It refers to memory that is not merely a list of past events, but has an aspect of being structured as a story and is deeply involved in the formation of self-identity. (Note: As I have never re-experienced autobiographical memory myself, I am writing this as a conjecture based on a conceptual understanding.)
Semantic memory (such as the meaning of events and knowledge) is often relatively preserved in many cases.
While it is known to often co-occur with aphantasia, the two are independent concepts and do not necessarily always co-occur.
According to the views of major researchers, at this time, SDAM itself is not understood as a disorder or disease, but as a form of individual difference or diversity.
⇒ Claude's log (PDF version | Image version)
3. My Case
I have written down my "inner world" as someone who has congenital aphantasia (no experience of mental imagery throughout life) and SDAM (no re-experience of autobiographical memory throughout life).