Types Of Memory: Short Term Memory

New theory

After significant research, a new theory has been proposed that states that there are possibly up to 5 different types of isolatable memory systems (Markowitsch, 1995). These systems consist of Procedural, perceptual-representation, working, semantic, and episodic. Each of these systems involves the acquisition, representation, and retrieval of a different kind of learning or skill. These different systems are also believed to have specialized subsystems. The concept of different isolatable memory systems discloses the question of the reason for how and why they came into existence. Complex systems don’t just come into existence by chance, they must have evolved to their current and present state due to specific evolutionary pressures in the past.

Research has found that there is a significant relationship between decision making, retrieval processes, and memory systems (Klein et al, 2000). When someone makes a decision, there must be a system in place to sort through the information they’re looking for. The more information an organism can encode, the harder it becomes to identify relevant information quickly. This is why evolution has managed to develop a match between stored information, and the mechanism that retrieves and requires it (Nadel, 1994). First, there is a problem in an organism's environment in which they must make a decision rule to solve. The content needed that is appropriate for that decision varies between different kinds of problems. This is why different memory systems have come into existence. Some decisions may only require one type of system, whereas other more intense and important tasks could be relying on multiple different memory systems.

Episodic Memory

At the moment, there is significant research regarding the episodic memory system. Episodic memories are memories of autobiographical events; they include contextual information regarding who was there and what specifically happened. In animals, this could include where a food item was hidden or what happened when a predator tried to attack them. These memories can also include memories of smell and taste; the memory is literally like a sensory “episode.” This type of memory has been shown to occur not only in humans but also in birds and rodents (Crystal, 2010). This brings into question whether this is due to convergent evolution or if it’s simply just a fundamental ancestral trait of both mammalian and avian species.

The hippocampus and prefrontal cortex, which are the primary brain structures involved in the processing of episodic memory, are found across all mammalian and avian species. Mammals specifically have a circuit that uses these structures to encode a memory. At the moment there is little information known about the circuit in birds, but they do at least have the structures that have the ability to perform a similar function (Allen and Fortin, 2013). Based on this evidence, researchers have hypothesized that humans share an ancestral episodic memory system with all other mammals and most likely birds.

One of the most important aspects of Episodic memory is future planning or in the context of episodic memory, “the ability to stimulate plausible future events or scenarios”(Allen and Fortin, 2013). Another important feature of this type of memory is the ability to understand social relationships in a group. This memory system can allow organisms to remember things like who has been cooperative or aggressive. Because so many species have the capacity for episodic memory, it is assumed that it has notable advantages. There is further research necessary to fully understand the link between episodic memory and fitness.

Episodic Memory and Semantic Memory Systems combined

In the context of trait judgment, research has proven that episodic memory and semantic memory work together to conclude accurate judgments (Klein et al, 2002). Semantic memory is a type of long-term memory used to recall factual information. Because social interactions require very fast decisions, these immediate decisions can be made easier when the answers have already been “precomputed.”