Memory is the persistence of learning over time, through the encoding, storage, and retrieval of information.

Psychologists use memory models to think about how our brain forms and retrieves memories. Information-processing models involve three processes: encoding, storage, and retrieval.

The three processing stages in the Atkinson and Shiffrin classic three-stage model of memory are sensory memory, short-term memory, and long-term memory.

More recent research has updated this model to include two additional concepts: (1) working memory, to stress the active processing occurring in the second memory stage, and (2) automatic processing, to address the processing of information outside of conscious awareness.

Implicit (nondeclarative) memories are our unconscious memories of skills and classically conditioned associations. They happen without our awareness, through automatic processing.

Explicit (declarative) memories are our conscious memories of general knowledge, facts, and experiences. They form through effortful processing.

In addition to skills and classically conditioned associations, we automatically process incidental information about space, time, and frequency. Our two-track mind works efficiently with the parallel processing of different subtasks.

Sensory memory feeds some information into working memory for active processing there.

An iconic memory is a very brief (a few tenths of a second) picture-image memory of a scene; an echoic memory is a three- or four-second sensory memory of a sound.

Short-term memory capacity is about seven items, give or take two, but this information disappears from memory quickly without rehearsal.

Our working-memory capacity for active processing varies, depending on age and other factors.

Effective effortful processing strategies include chunking and mnemonics.

Such strategies help us remember new information because we then focus our attention and make a conscious effort to remember.

Massed practice, or cramming, results in poorer long-term recall than encoding that is spread over time. Psychologists call this result of distributed practice the spacing effect. The testing effect is the finding that consciously retrieving, rather than simply rereading, information enhances memory.

If new information is not meaningful, it will be difficult to process. We can avoid some encoding errors by thinking about what we have learned and translating it into personally meaningful terms.

We have an unlimited capacity for storing information permanently in long-term memory.

Memories are not stored intact in the brain in single specific spots. Many parts of the brain interact as we encode, store, and retrieve memories.

The frontal lobes and hippocampus are parts of the brain network dedicated to explicit memory formation.

Many brain regions send information to the frontal lobes for processing. The hippocampus registers and temporarily holds elements of explicit memories (which are either semantic or episodic) before moving them for storage elsewhere (memory consolidation).

The cerebellum and basal ganglia are parts of the brain network dedicated to implicit memory formation. The cerebellum is important for storing classically conditioned memories.

The basal ganglia are involved in motor movement and help form procedural memories for skills.

Emotional arousal causes an outpouring of stress hormones, which lead to activity in the brain’s memory-forming areas. Significantly stressful events can trigger very clear flashbulb memories.

Long-term potentiation (LTP) appears to be the neural process for learning and memory. It involves an increase in a synapse’s firing potential as neurons become more efficient and more connections between neurons develop.

Psychologists assess memory by studying evidence of it in the recall, recognition, and relearning of information:

Retrieval cues, such as context and mood, are information bits linked with the original encoded memory. These cues activate associations that help us retrieve memories; this process may occur without our awareness, as it does in priming.

Returning to the same physical context or emotional state (mood congruency) in which we formed a memory can help us retrieve it.

The serial position effect accounts for our tendency to recall best the last items (which may still be in working memory) and the first items (which we’ve spent more time rehearsing) in a list.

Normal forgetting can happen because we have never encoded information (encoding failure); because the physical trace has decayed (storage decay); or because we cannot retrieve what we have encoded and stored (retrieval failure).

Retrieval problems may result from proactive (forward-acting) interference, when prior learning interferes with recall of new information, or from retroactive (backward-acting) interference, when new learning disrupts recall of old information.

Freud believed that motivated forgetting occurs, but researchers have found little evidence of repression.

Memories can be continually revised when retrieved, a process memory researchers call reconsolidation.

Misinformation (exposure to misleading information) and imagination effects corrupt our stored memories of what actually happened.

Source amnesia leads to faulty memories of how, when, or where we learned something, and may help explain déjà vu.

False memories feel like real memories and can be persistent but are usually limited to the gist (the general idea) of the event.

Incest and abuse happen more than was once supposed. But unless the victim was a child too young to remember, such traumas are usually remembered vividly, not repressed.

Psychologists agree that (1) sexual abuse happens; (2) injustice happens; (3) forgetting happens; (4) recovered memories are common; (5) memories of events that happened before age 4 are unreliable; (6) memories “recovered” under hypnosis are especially unreliable; and (7) memories, whether real or false, can be emotionally upsetting.

Children’s eyewitness descriptions are subject to the same memory influences that distort adult reports. If questioned soon after an event in neutral words they understand, children can accurately recall events and people involved in them.

Memory research findings suggest the following strategies for improving memory: Study repeatedly, make the material meaningful, activate retrieval cues, use mnemonic devices, minimize proactive and retroactive interference, sleep more, and test yourself to be sure you can retrieve, as well as recognize, material.