Chapter 14
MEMORY MECHANISMS
Learning and memory are intrinsically interrelated.
One cannot profit from prior experiences if these experiences have been forgotten.
The distinction between studies of memory and studies of learning poses a fundamental question:
While both learning and memory involve the retention of information, they focus on different stages of information processing.
STAGES OF INFORMATION PROCESSING
For experiences to influence behavior in the future, three essential processes must occur: ASR
Acquisition: Information must be acquired and encoded into NS.
“input” or acquisition stage.
Storage: Once encoded, the information must be stored for future use.
storage or “retention” stage.
Retrieval: Information must be retrieved from storage when needed.
retrieval stage.
DIFFERENCES IN FOCUS
Studies of learning primarily focus on the acquisition stage, where acquisition varies while retention and retrieval stages remain constant.
In contrast, studies of memory maintain a constant acquisition stage while manipulating the retrieval and retention stages.
DELAYED MATCHING-TO-SAMPLE PROCEDURE
Memory procedures require meticulous controls to ensure behavior is attributed to past experiences and not confounding variables.
The Delayed Matching-to-Sample (DMTS) procedure consists of the following steps:
A sample stimulus is presented for a specific period of time.
The sample stimulus is then removed for a certain duration.
A multiple-choice memory test follows, where the organism must select the previously presented sample to receive reinforcement.
DMTS can be creatively adapted to study memory across various types of events, including:
Visual stimuli
Auditory stimuli
Temporal stimuli
Numerical stimuli
Spatial stimuli
The DMTS procedure has been successfully utilized to study memory in a wide spectrum of species, including but not limited to:
Pigeons
Rats
Dolphins
Monkeys
Humans
TRAINING ON SIMULTANEOUS MATCHING-TO-SAMPLE
Before applying DMTS, organisms are trained using the Simultaneous Matching-to-Sample (SMTS) procedure.
This training ensures that each stimulus appears equally in terms of being a sample, as well as correct and incorrect alternatives across spatial positions during trials.
TYPES OF MEMORY
There are three principal types of memory that warrant detailed study based on the nature of information being remembered:
Episodic Memory:
Refers to memory for specific episodes or events.
In humans, it involves conscious awareness and the retrieval efforts of personal experiences.
Semantic Memory:
Concerns memory for basic declarative information, such as facts.
While it involves conscious awareness, it often does not include memories of when or where the information was learned.
Procedural Memory:
Characterized by automatic recall of habits and skills.
Humans may not always be consciously aware of these memories.
Pavlovian and instrumental conditioning are key methods to form procedural memories.
Instances involving procedural memory include S-S, S-R, and R-O associations.
The textbook takes a stance that animal memory must also account for conscious feelings, with research demonstrating that animals can remember the what, when, and where of stimuli and events,
WORKING MEMORY AND REFERENCE MEMORY
The Delayed Matching-to-Sample is the standard methodology in memory research, necessitating different memory types for success:
Working Memory:
Refers to memory related to trial-specific information.
It is essential for responding accurately during the current trial but not applicable for subsequent trials.
Reference Memory:
Concerns the aspects of a task that remain constant across trials.
General rules of the DMTS task are stable, although stimuli and correct responses differ each trial.
MEMORY TRACE VS. ACTIVE MEMORY PROCESSES
A fundamental question in memory study is whether it involves creating a neural stimulus trace.
The trace theory posits that a neural trace is established during stimulus presentation, promoting remembering, while it automatically decays post-stimulus removal, leading to forgetting.
The strength of this trace at the time of testing is believed to dictate the accuracy of choice behavior.
Early data provided substantial support for trace theory; however, as researchers adopted more sophisticated approaches, they began to question it.
They suggested that more complex processes might be necessary to account for the intricacies of memory performance.
EMPIRICAL EVIDENCE AGAINST TRACE THEORY
Considerable evidence indicates the insufficiency of trace theory, illustrated by two examples:
Cued retention intervals can influence working memory performance.
Directed forgetting demonstrates that memory processes can be activated or deactivated on an item-specific basis.
CUED RETENTION INTERVALS
A study by Wasserman, Grosch, & Nevin (1982) utilized two colors as sample and test stimuli with retention intervals of 1 and 5 seconds:
In the experimental group, two angled lines overlay on the sample to indicate the retention interval duration (1- or 5-second).
A control group was conditioned without correlated cues.
Results indicated that cued retention intervals influenced memory performance, confirming that cues can enhance performance at shorter intervals, yet could be detrimental at longer intervals.
A follow-up experiment utilizing miscuing aimed to explore the reasons behind these effects.
MISCUED RETENTION INTERVALS
Miscuing revealed that incorrect cues diminished memory performance during shorter retention intervals but surprisingly improved performance at longer intervals.
Pigeons exhibited greater motivation to remember when informed about an impending test compared to information about a test scheduled for later.
This suggests that memory can be modulated by motivation levels.
DIRECTED FORGETTING AND REHEARSAL
Directed forgetting research shows working memory processes can be modified item-by-item.
It is posited that humans utilize rehearsal techniques to avoid memory loss, which could exceed simple memory trace mechanisms.
To investigate if rehearsing occurs within animals, the directed forgetting paradigm is applied:
Participants receive cues to remember or forget after exposure to the sample stimulus.
Remember cues are given before the memory test, while forget cues precede trials without a memory test.
A critical aspect of testing is if forget cues adversely impact rehearsal:
When comparing performances after forget cues and remember cues, lower memory post-forget suggested item control over rehearsal processes.
A study by Kaiser, Sherburne, & Zentall (1997) demonstrated that pigeons exhibited lower memory on trials preceded by forget cues compared to those preceded by remember cues, indicating that memory performance involves more than mere trace strength.
RETROSPECTIVE VS. PROSPECTIVE MEMORY
Understanding working memory as an active rather than passive process leads to questions regarding what organisms retain during retention intervals to facilitate accurate responses.
Prospective Memory:
Involves actively maintaining a representation of anticipated future stimuli or responses.
Retrospective Memory:
Concerns memory of previously encountered stimuli or events.
The distinction between these forms of working memory is crucial, enabling organisms to prepare for future actions and avoid repeating actions that are already completed.
DISTINGUISHING BETWEEN RETROSPECTIVE & PROSPECTIVE MEMORY
Potential contents of working memory may depend on whether the relation involved is symbolic rather than identity-based.
An experimental study by Honig & Wasserman (1981) demonstrated this distinction using pigeons within various memory tasks involving both prospective and retrospective cues.
Results showed a stronger prospective memory for food or no food compared to retrospective memory concerning the recognition of one of two colors.
SOURCES OF MEMORY FAILURE
Forgetting indicates that something was learned and encoded but then becomes inaccessible.
This phenomenon is challenging to exhibit empirically because outright forgetting rarely explains memory failures.
Alternative explanations for memory failure include:
Original learning may not have taken place.
Ineffective retrieval of stored information may occur.
Several competing memories may complicate the retrieval process.
RETRIEVAL FAILURE
A primary contributor to memory failure is the inability to retrieve previously learned information.
Retrieval Cues:
Are stimuli that were present during the original learning and can aid in recalling the target information when retrieving.
These cues can revive responding after various events including extinction, latent inhibition, overshadowing, and blocking.
In these instances, the stored information is not erased but rather unrecoverable.
INTERFERENCE EFFECTS
Information occurring before or after a target event is a common cause of memory failure, categorized into two types of interference:
Proactive Interference:
Involves stimuli presented prior to the target event.
Often arises from closely spaced trials, leading to excessive recall of prior trials.
Retroactive Interference:
Involves stimuli presented after the target event.
Results from presenting additional stimuli during the retention interval, leading to failure in retrieving the correct target information.
SUMMARY
Learning and memory are interconnected processes:
Learning prioritize the acquisition stage, while memory emphasizes storage and retrieval.
Reference memory involves aspects of tasks that are consistent across trials, while working memory pertains to temporary retention of task-relevant information.
Memory encompasses both retrospective elements that look back on past experiences and prospective elements that prepare for future actions.
Memory failures arise mainly due to proactive and retroactive interference and inadequate retrieval cues.