Serial memory processing

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Serial memory processing is the act of attending to and processing one item at a time. This is usually contrasted against parallel memory processing, which is the act of attending to and processing all items simultaneously.

Contents

In short-term memory tasks, participants are given a set of items (e.g. letters, digits) one at a time and then, after varying periods of delay, are asked for recall of the items. As well, participants could be asked whether a specific target item was present in their original set. The serial order of items and the relationships between them can have varying effects on the item's speed and accuracy of recall. [1]

Overview

Serial memory processing uses internal representations of the memory set in order to compare them to a target stimulus or item that is being presented. These internal representations are then compared to the target stimulus, one at a time. Reaction time increases linearly with the set size, where the more items in the memory set, the longer it will take to compare. [2]

Graph showing Self-Terminating Search.jpg
Self-Terminating Search
Graph Showing Exhaustive Search.jpg
Exhaustive Search
Hypothetical slopes for positive and negative trials

Serial memory processing can be either self-terminating or exhaustive. Self-terminating implies that comparisons stop abruptly as soon as the target is found, and then the response is generated. [1] Evidence for this method is found in reaction time studies. If the reaction time slope for a positive trial (where the target was present in the memory set) is about half of the slope for a negative trial (where the target was not present in the memory set) this demonstrates self-terminating processing. This is because, on average, participants (on positive trials) will stop comparisons about halfway through when they find the target match but participants (on negative trials) will need to compare until the end when no target match is found. [3] On the other hand, exhaustive implies that comparisons continue until the entire set is compared and then a response is generated. [1] Evidence for this method is also found in reaction time studies. In this case, the reaction time slope is equal for both positive and negative trials, as comparisons are made to the end in both cases. [2] Participants may process some serial memory sets using the self-terminating method and in other cases use the exhaustive method, there is no clear distinction between which method is better to use. [1]

Characteristics of processing

Primacy and recency effects

In serial memory processing, Primacy effect and Recency effect effects for accuracy of recall are commonly found. These effects are found for both visual [4] and auditory [5] stimuli in memory tasks. This means that of the many items in a memory set during serial memory processing, the first item and the last seem to be recalled faster and more accurately than the other items. These effects may exist if recall errors are due to serial position. It is theorized that items are mistaken for other items from a nearby position in the memory set (e.g. the 5th item is mistaken for the 4th item or the 6th item). Since there are more nearby serial positions to middle items in a set, there are therefore more opportunities for mixing-up items. On the other hand, there are very few serial positions nearby to the first and last position, and therefore these positions may be remembered more accurately (or mistaken less). The first and last position may be less error-prone positions and more easily recalled. [6]

This graph, recreated from Nairne (1992), demonstrates the primacy and recency effects for recall of serial order. These effects are consistent regardless of memory set length Graph of the Primacy-Recency Effects.jpeg
This graph, recreated from Nairne (1992), demonstrates the primacy and recency effects for recall of serial order. These effects are consistent regardless of memory set length

The suffix effect is an effect that removes the recency effect by adding in a meaningless item at the end of the original memory set. The belief is that this meaningless item will be remembered instead of the second-to-last item which was originally remembered due to the recency effect. However, the suffix effect varies based on the similarity of the item to the set. For visual stimuli, adding in the meaningless item, whether or not it is visually similar to the original memory set, will remove the recency effect. For auditory stimuli, adding in the meaningless item will only remove the recency effect if it is phonologically similar. Adding an item that is phonologically different (e.g. A, Q) will not have this effect. [7]

Stimuli grouping effects

Items in a serial memory can be presented in ways that promote grouping amongst the items. Individuals can group a set of items spatially and temporally based on their characteristics of presentation. [4]

Spatial grouping refers to the items in the original memory set being grouped by their spatial characteristics. An example of this would be presenting the first three items in the top right corner, and the remaining three items in the bottom left corner. These items are now grouped into two groups of three based on their spatial attributes. It has been found that the longer the spatial pathways from item to item, the slower the recall time and the lower the accuracy of recall. Therefore, item's that have a small spatial pathway between them, are remembered better and faster. In this case, the fourth item would be remembered less easily, because the spatial pathway from the top right corner (where the third item was) to the bottom left corner (where the fourth item will be) is longer than most. [4]

Temporal grouping refers to the items in the original memory set being grouped by their temporal characteristics. An example of this would be presenting the first three items simultaneously, then waiting five seconds, and then presenting the remaining three items. These items are now grouped into two groups of three based on their temporal attributes. It has been found that when item's are grouped temporally, the accuracy of recall is higher than when they are not. As well, there is evidence that participants may create their own temporal groupings. In a memory task where items were not temporally grouped, the reaction times of recall for the 1st, 4th and 7th (out of 9) items were significantly faster. This finding shows evidence that participants may be creating their own temporal group of three, since the first item of each group (the 1st, 4th and 7th) are recalled faster than the rest of the items in their "group". [4]

Other errors

There are other errors that exist in serial memory tasks based on the item's characteristics. Serial position errors have been discussed earlier, in relation to the primacy and recency effect. These errors have been found to be independent from other errors, such as acoustic errors. Acoustic errors result from items that are phonologically similar. An example of this would be recalling "B" as opposed to the actual item "P". These items are phonologically similar and can cause acoustic errors. These are related to the suffix effect as well, which found that the rececny effect was only removed when phonologically similar stimuli were used. [8] As well, other variables of verbal stimuli have been found to cause acoustic errors. Examples of these variables are word length, word frequency and lexicality. These interact to cause acoustic errors in serial memory tasks by adding in acoustic confusability amongst the items. [9]

Processing in atypical individuals

It has been found that when mental age is equated, there is no difference in performance on serial memory tasks for children with autism. This is an important finding as serial memory processing is a cognitive ability that may not be related to other cognitive abilities that are hindered by autism spectrum disorders. [10]

Neuro-perspective

Serial memory processing has been studied neurologically, and certain brain regions have been found to be associated to this processing. There is evidence that both the prefrontal cortex and the hippocampal region are related to serial memory processing. This is because lesions in these areas tend to be related to impaired ability in remembering serial order. These brain regions can have impairments on memory for temporal order. Lesions on the medial prefrontal cortex shows total memory loss for the temporal order of spatial locations (this was tested by ability on a maze task). On the other hand, lesions in the hippocampal regions showed delayed memory loss. The participants remembered for a short time the temporal order of spatial locations; those memory declined thereafter. [11] Rat studies have shown that lesions in the prefrontal cortex cause an inability to remember the 2nd of two items in a set. As well, the rats showed increased corticosterone while experiencing stress during a serial memory task. On the other hand, rat studies have also shown that lesions in the hippocampal regions cause an inability to remember the 1st of two items. Furthermore, these rats do not show an increase in their corticosterone while experiencing stress, demonstrating differing effects for differing brain regions. As well it shows that the different brain regions differentially activate corticosterone, a hormone related to memory effects. [12]

Generally, it has been found that the left hemisphere is better at serial processing and serial memory comparisons than the right hemisphere. These processes may be more related to the lateralization of left hemispheric functions rather than right hemispheric ones. [13]

Associated models

One popular model that has been used to organize serial memory processing is the ACT-R. ACT-R model is Adaptive Control of Thought-Rational. This cognitive architecture has been used to help hierarchically organize serial memory. This model separates declarative memory and production memory into separate functions. During serial memory processing, declarative memory works to encode the physical positions of the items in the original memory set. As well, the production memory works to help organize the later recall of the items in the memory set. The ACT-R is a limited-capacity model meaning that there is a limited amount of activation available to use for processing. This limited-capacity helps to explain the linear relationship between time of recall and size of memory set. According to the ACT-R, the longer the original memory set, the longer the recall because the amount of available activation is being divided amongst more items now. [14] More evidence exists for the ACT-R modeling serial memory processing. It has been found that the ACT-R models the serial position error [6] nearly perfectly. It produces the same primacy and recency effects found in earlier studies. [14] As well, the ACT-R has been found to model acoustic errors [8] nearly perfectly. It demonstrates the same findings of phonologically similar and different items found in earlier studies. [14]

Another model of serial memory processing is the model for item recognition. This model helps to explain how items in the memory set are compared to the target item. It explains the processes that go into the response decision of whether the target item was present in the original memory set of items. Firstly, this model states that after the target item, being compared to the memory set, is presented, it is then encoded into the brain. The next step is to complete serial comparisons based on the mental representation of the memory items and the target item. These comparisons are completed serially, in order, and are affected by the size of the original memory set. Where the longer the original memory set of items, the longer it will take to complete the comparisons. While comparisons are being done, there is a binary decision being made for each comparison. This decision is either positive or negative, depending on whether the target item matches the representation of an item in the memory set. After each comparison, and individual decision, is completed, the responses are organized and finally expressed. This model demonstrates the relationships between lengths of memory set and longer recall time. As well, this model focuses on exhaustive processing, where all comparisons are made, regardless of whether a positive response was found. [3]

It has been found that confusability in the items in the memory set can affect item recognition. Auditory and phonological confusability in the memory set is associated with increased encoding time. As well, visual confusability in the memory set is associated with increased comparison time. It is shown that the modality of the items can affect different processes in item recognition. [15]

See also

Related Research Articles

Short-term memory is the capacity for holding a small amount of information in an active, readily available state for a short interval. For example, short-term memory holds a phone number that has just been recited. The duration of short-term memory is estimated to be on the order of seconds. The commonly cited capacity of 7 items, found in Miller's Law, has been superseded by 4±1 items. In contrast, long-term memory holds information indefinitely.

Working memory is a cognitive system with a limited capacity that can hold information temporarily. It is important for reasoning and the guidance of decision-making and behavior. Working memory is often used synonymously with short-term memory, but some theorists consider the two forms of memory distinct, assuming that working memory allows for the manipulation of stored information, whereas short-term memory only refers to the short-term storage of information. Working memory is a theoretical concept central to cognitive psychology, neuropsychology, and neuroscience.

Recall in memory refers to the mental process of retrieval of information from the past. Along with encoding and storage, it is one of the three core processes of memory. There are three main types of recall: free recall, cued recall and serial recall. Psychologists test these forms of recall as a way to study the memory processes of humans and animals. Two main theories of the process of recall are the two-stage theory and the theory of encoding specificity.

<span class="mw-page-title-main">Spatial memory</span> Memory about ones environment and spatial orientation

In cognitive psychology and neuroscience, spatial memory is a form of memory responsible for the recording and recovery of information needed to plan a course to a location and to recall the location of an object or the occurrence of an event. Spatial memory is necessary for orientation in space. Spatial memory can also be divided into egocentric and allocentric spatial memory. A person's spatial memory is required to navigate around a familiar city. A rat's spatial memory is needed to learn the location of food at the end of a maze. In both humans and animals, spatial memories are summarized as a cognitive map.

Baddeley's model of working memory is a model of human memory proposed by Alan Baddeley and Graham Hitch in 1974, in an attempt to present a more accurate model of primary memory. Working memory splits primary memory into multiple components, rather than considering it to be a single, unified construct.

<span class="mw-page-title-main">Visual memory</span> Ability to process visual and spatial information

Visual memory describes the relationship between perceptual processing and the encoding, storage and retrieval of the resulting neural representations. Visual memory occurs over a broad time range spanning from eye movements to years in order to visually navigate to a previously visited location. Visual memory is a form of memory which preserves some characteristics of our senses pertaining to visual experience. We are able to place in memory visual information which resembles objects, places, animals or people in a mental image. The experience of visual memory is also referred to as the mind's eye through which we can retrieve from our memory a mental image of original objects, places, animals or people. Visual memory is one of several cognitive systems, which are all interconnected parts that combine to form the human memory. Types of palinopsia, the persistence or recurrence of a visual image after the stimulus has been removed, is a dysfunction of visual memory.

Explicit memory is one of the two main types of long-term human memory, the other of which is implicit memory. Explicit memory is the conscious, intentional recollection of factual information, previous experiences, and concepts. This type of memory is dependent upon three processes: acquisition, consolidation, and retrieval. Explicit memory can be divided into two categories: episodic memory, which stores specific personal experiences, and semantic memory, which stores factual information. Explicit memory requires gradual learning, with multiple presentations of a stimulus and response.

The Levels of Processing model, created by Fergus I. M. Craik and Robert S. Lockhart in 1972, describes memory recall of stimuli as a function of the depth of mental processing. Deeper levels of analysis produce more elaborate, longer-lasting, and stronger memory traces than shallow levels of analysis. Depth of processing falls on a shallow to deep continuum. Shallow processing leads to a fragile memory trace that is susceptible to rapid decay. Conversely, deep processing results in a more durable memory trace.

Tip of the tongue is the phenomenon of failing to retrieve a word or term from memory, combined with partial recall and the feeling that retrieval is imminent. The phenomenon's name comes from the saying, "It's on the tip of my tongue." The tip of the tongue phenomenon reveals that lexical access occurs in stages.

Memory has the ability to encode, store and recall information. Memories give an organism the capability to learn and adapt from previous experiences as well as build relationships. Encoding allows a perceived item of use or interest to be converted into a construct that can be stored within the brain and recalled later from long-term memory. Working memory stores information for immediate use or manipulation which is aided through hooking onto previously archived items already present in the long-term memory of an individual.

Free recall is a common task in the psychological study of memory. In this task, participants study a list of items on each trial, and then are prompted to recall the items in any order. Items are usually presented one at a time for a short duration, and can be any of a number of nameable materials, although traditionally, words from a larger set are chosen. The recall period typically lasts a few minutes, and can involve spoken or written recall. The standard test involves the recall period starting immediately after the final list item; this can be referred to as immediate free recall (IFR) to distinguish it from delayed free recall (DFR). In delayed free recall, there is a short distraction period between the final list item and the start of the recall period. Both IFR and DFR have been used to test certain effects that appear during recall tests, such as the primacy effect and recency effect.

<span class="mw-page-title-main">Negative priming</span> Initial stimulus inhibits response to subsequent stimulus

Negative priming is an implicit memory effect in which prior exposure to a stimulus unfavorably influences the response to the same stimulus. It falls under the category of priming, which refers to the change in the response towards a stimulus due to a subconscious memory effect. Negative priming describes the slow and error-prone reaction to a stimulus that is previously ignored. For example, a subject may be imagined trying to pick a red pen from a pen holder. The red pen becomes the target of attention, so the subject responds by moving their hand towards it. At this time, they mentally block out all other pens as distractors to aid in closing in on just the red pen. After repeatedly picking the red pen over the others, switching to the blue pen results in a momentary delay picking the pen out. The slow reaction due to the change of the distractor stimulus to target stimulus is called the negative priming effect.

Selective amnesia is a type of amnesia in which the sufferer loses only certain parts of their memory. Common elements that may be forgotten are relationships, where they live, and certain special abilities and talents.

Echoic memory is the sensory memory that registers specific to auditory information (sounds). Once an auditory stimulus is heard, it is stored in memory so that it can be processed and understood. Unlike most visual memory, where a person can choose how long to view the stimulus and can reassess it repeatedly, auditory stimuli are usually transient and cannot be reassessed. Since echoic memories are heard once, they are stored for slightly longer periods of time than iconic memories. Auditory stimuli are received by the ear one at a time before they can be processed and understood.

The modality effect is a term used in experimental psychology, most often in the fields dealing with memory and learning, to refer to how learner performance depends on the presentation mode of studied items.

Retrospective memory is the memory of people, words, and events encountered or experienced in the past. It includes all other types of memory including episodic, semantic and procedural. It can be either implicit or explicit. In contrast, prospective memory involves remembering something or remembering to do something after a delay, such as buying groceries on the way home from work. However, it is very closely linked to retrospective memory, since certain aspects of retrospective memory are required for prospective memory.

There is evidence suggesting that different processes are involved in remembering something versus knowing whether it is familiar. It appears that "remembering" and "knowing" represent relatively different characteristics of memory as well as reflect different ways of using memory.

Recognition memory, a subcategory of declarative memory, is the ability to recognize previously encountered events, objects, or people. When the previously experienced event is reexperienced, this environmental content is matched to stored memory representations, eliciting matching signals. As first established by psychology experiments in the 1970s, recognition memory for pictures is quite remarkable: humans can remember thousands of images at high accuracy after seeing each only once and only for a few seconds.

Auditory spatial attention is a specific form of attention, involving the focusing of auditory perception to a location in space.

Difference due to memory (Dm) indexes differences in neural activity during the study phase of an experiment for items that subsequently are remembered compared to items that are later forgotten. It is mainly discussed as an event-related potential (ERP) effect that appears in studies employing a subsequent memory paradigm, in which ERPs are recorded when a participant is studying a list of materials and trials are sorted as a function of whether they go on to be remembered or not in the test phase. For meaningful study material, such as words or line drawings, items that are subsequently remembered typically elicit a more positive waveform during the study phase. This difference typically occurs in the range of 400–800 milliseconds (ms) and is generally greatest over centro-parietal recording sites, although these characteristics are modulated by many factors.

References

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  5. ↑ Avons, S. E. (1998). Serial report and item recognition of novel visual patterns. British Journal of Psychology, 89(1).
  6. 1 2 Nairne, J. S. (1992). The loss of positional certainty in long-term memory.Psychological Science, 3(3).
  7. ↑ Parmentier, F. B., Tremblay, S., & Jones, D. M. (2004). Exploring the suffix effect in serial visuospatial short-term memory. Psychonomic Bulletin and Review, 11(2).
  8. 1 2 Bjork, E. L., & Healy, A. F. (1974). Short-term order and item retention. Journal of Verbal Learning and Verbal Behavior, 13(1).
  9. ↑ Burgess, N., & Hitch, G. H. (1999). Memory for serial order: A network model of the phonological loop and its timing. Psychological Review, 106(3).
  10. ↑ Prior, M. R., & Chen, C. S. (1976). Short-term and serial memory in autistic, retarded, and normal children. Journal of Autism and Childhood Schizophrenia, 6(2).
  11. ↑ Chauveau, F., et al. (2009). The hippocampus and prefrontal cortex are differentially involved in serial memory retrieval in non-stress and stress conditions. Neurobiology of Learning and Memory, 91(1).
  12. ↑ Chiba, A., Kesner, R., & Reynolds, A. (1994). Memory for spatial location as a function of temporal lag in rats: Role of hippocampus and medial prefrontal cortex. Behavioral and Neural Biology 61(1).
  13. ↑ O'Boyle, M. W., & Hellige, J. B. (1982). Hemispheric asymmetry, early visual processes, and serial memory comparison. Brain and Cognition, 1(1).
  14. 1 2 3 Anderson, J. R., & Matessa, M. (1997). A production system theory of serial memory. Psychological Review, 104(4).
  15. ↑ Connor, J. M. (1972). Serial and parallel encoding processes in memory and visual search. Journal of Experimental Psychology, 96(2).
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