Explicit & Implicit memory

Explicit memory (declarative memory) is a type of long-term memory which can be intentionally and consciously recalled. It's divided up into two main categories, being: episodic (personal events) and semantic (facts) memories.

Explicit memory involves conscious recollection, such as remembering the time of an appointment or recollecting an event from years ago.

Implicit memory is sometimes referred to as unconscious memory or automatic memory. Implicit memory uses past experiences to remember things without thinking about them.

One of the most common forms of implicit memory is procedural memory, which helps people perform certain tasks without conscious awareness of these previous experiences.

Evidence for implicit memory arises from priming, a process whereby subjects are measured by how they have improved their performance on tasks for which they've been subconsciously prepared. It can also be measured by looking at skill learning - gradual improvement of performance with practice that generalises to a range of test stimuli. It can be measured by looking at sensorimotor skills and perceptual skills.

Milner & Corkin (skill learning): Patient HM able to learn a mirror tracing task and rotary pursuit. He had to be told instructions on how to perform the task each time because he had no recollection of doing it before. It was one of the earliest demonstrations that amnesia is a selective memory deficit, not just an inability to transfer information from STM to LTM.

Priming is an implicit memory effect in which exposing to one stimulus influences the response to another stimulus. Priming can occur following perceptual, semantic, or conceptual stimulus repetition. For example, if a person reads a list of words including the word "table", and is later asked to complete a word starting with "tab", the probability that they will answer "table" is greater than if they weren't primed.

Warrington & Weiskrantz (1968): priming data from amnesic patients. Encoding phase - patients shown lists of words, e.g elephant, radio, telephone etc. Retrieval phase - patients peformed poor on explicit memory recall tests. However, word-stem completion tasks show evidence of implicit learning. Participants were faster completing words when they have seen them previously compared to ones that they hadn't.

Serial reaction time task (Nissen & Bullemer, 1987): On each trial, a light goes on and participants are told to press the corresponding button. Unknown to the subject, the sequence is governed by a hidden rule (D is always followed by C). Subjects became sensitive to the presence of the sequence even when they deny knowing that there even was a sequence.

Is infant learning implicit? Infants habituating to stimuli are probably not aware of the memories they're forming.