Today we will continue the story of how our brain works, why we remember and forget certain things, and whether these events are related to the situation around us. Cognitive Bias Codex: We reduce events and lists to their key elements.

Suffix effect

People often have to recall a series of items in order, such as a phone number. When the list of items is heard (as opposed to read silently), people usually are very good at remembering the final list item. However, if the list is followed by an irrelevant item (the suffix), recall of the final item is substantially impaired. This impairment is called the suffix effect. The suffix has to be perceived as speech in order for it to have a large effect on memory performance. If the suffix is a pure tone, there is no impairment. Although the suffix has to be speech, it does not have to be a word. In general, the suffix will have a larger effect the more acoustically similar it is to the list items. One reason that the suffix effect has attracted a lot of attention is that recall is impaired even when the suffix is expected and even when the suffix is the same item (usually the digit 0) on every trial. The best explanation is that when the suffix is perceptually grouped with the list items, it functionally increases the list length. So, rather than trying to recall a 9-item list, you are in effect recalling a 10-item list. In general, the longer the list, the worse performance is, so any increase (whether from 6 to 7 items, or 7 to 8 items) cna result in reduced accuracy (see Neath & Surprenant, 2003).

Serial position effect

Serial-position effect is the tendency of a person to recall the first and last items in a series best, and the middle items worst. The term was coined by Hermann Ebbinghaus through studies he performed on himself, and refers to the finding that recall accuracy varies as a function of an item’s position within a study list. When asked to recall a list of items in any order (free recall), people tend to begin recall with the end of the list, recalling those items best (the recency effect). Among earlier list items, the first few items are recalled more frequently than the middle items (the primacy effect). One suggested reason for the primacy effect is that the initial items presented are most effectively stored in long-term memory because of the greater amount of processing devoted to them. (The first list item can be rehearsed by itself; the second must be rehearsed along with the first, the third along with the first and second, and so on.) The primacy effect is reduced when items are presented quickly and is enhanced when presented slowly (factors that reduce and enhance processing of each item and thus permanent storage). Longer presentation lists have been found to reduce the primacy effect. One theorised reason for the recency effect is that these items are still present in working memory when recall is solicited. Items that benefit from neither (the middle items) are recalled most poorly. An additional explanation for the recency effect is related to temporal context: if tested immediately after rehearsal, the current temporal context can serve as a retrieval cue, which would predict more recent items to have a higher likelihood of recall than items that were studied in a different temporal context (earlier in the list). The recency effect is reduced when an interfering task is given. Intervening tasks involve working memory, as the distractor activity, if exceeding 15 to 30 seconds in duration, can cancel out the recency effect. Additionally, if recall comes immediately after the test, the recency effect is consistent regardless of the length of the studied list, or presentation rate. Amnesiacs with poor ability to form permanent long-term memories do not show a primacy effect, but do show a recency effect if recall comes immediately after study. People with Alzheimer’s disease exhibit a reduced primacy effect but do not produce a recency effect in recall.

Part-list cueing effect

The modulation of part-list cues on long-term memory has been well-documented, whereas its impact on working memory remains largely unknown. The current study recruited a working memory part-list cuing paradigm to investigate how re-exposing part-list items affected item representation in working memory, and more specifically, whether the cuing effect was modulated by the task presentation mode. Our results showed that when the part-list re-exposure and no-part-list re-exposure trials were presented in separate blocks, using the re-exposed items as retrieval cues (part-list cue condition) significantly impaired recognition speed, accuracy and elevated judgement criteria (Experiment 1a), whereas merely relearning the re-exposed items (part-list relearning condition) has no such effect (Experiment 1b). When the part-list cue trials are randomly interleaved with the no-part-list cue trials, recognition accuracy was significantly lower in the part-list cue condition, whereas the recognition speed and judgement criteria were not significantly different under the two conditions (Experiment 2). These results indicate that re-exposing subsets of previously memorized items as retrieval cues can reduce the strength of other representations in working memory. Moreover, the effect of part-list cues in working memory is affected by task presentation mode. The mechanisms of part-list cuing within working memory were discussed.

Recency effect

The recency effect is dependent upon short-term memory. This type of memory, also known as active or primary memory, is the ability to hold a relatively small amount of memory in the mind for a brief period of time. This information is held and kept active for use, but it is not manipulated. Briefly storing a phone number someone just recited to you for long enough to dial it is a good example of short-term memory. Short-term memory is limited in terms of both capacity and duration. Most information in short-term memory only lasts between 15 and 30 seconds without active maintenance or rehearsal. Approximately four pieces of information can be held in short-term memory for a brief period. Perhaps not surprisingly, delaying recall after hearing a list of items has a dramatic impact on the recency effect. A very long delay between learning items and recalling will often completely eliminate this effect. In other words, the recency effect may occur because you are able to easily remember those items that are still being briefly stored in your short-term memory. If you do not rehearse that information, however, it will quickly be lost and fade from memory.

Primacy effect

The primacy effect, in psychology and sociology, is a cognitive bias that results in a subject recalling primary information presented better than information presented later on. For example, a subject who reads a sufficiently long list of words is more likely to remember words toward the beginning than words in the middle. Many researchers tried to explain this phenomenon through free recall [null tests]. Coluccia, Gamboz, and Brandimonte (2011) explain free recall as participants try to remember information without any prompting. In some experiments in the late 20th century it was noted that participants who knew that they were going to be tested on a list presented to them would rehearse items: as items were presented, the participants would repeat those items to themselves and as new items were presented, the participants would continue to rehearse previous items along with the newer items. It was demonstrated that the primacy effect had a greater influence on recall when there was more time between presentation of items so that participants would have a greater chance to rehearse previous (prime) items. Overt rehearsal was a technique that was meant to test participants’ rehearsal patterns. In an experiment using this technique, participants were asked to recite out loud the items that come to mind. In this way, the experimenter was able to see that participants would repeat earlier items more than items in the middle of the list, thus rehearsing them more frequently and having a better recall of the prime items than the middle items later on. In another experiment, by Brodie and Murdock, the recency effect was found to be partially responsible for the primacy effect. In their experiment, they also used the overt-rehearsal technique and found that in addition to rehearsing earlier items more than later items, participants were rehearsing earlier items later on in the list. In this way, earlier items were closer to the test period by way of rehearsal and could be partially explained by the recency effect. In 2013, a study showed that primacy effect is also prominent in decision making based on experience in a repeated-choice paradigm, a learning process also known as operant conditioning. The authors showed that importance attached to the value of the first reward on subsequent behaviour, a phenomenon they denoted as outcome primacy. In another study, participants received one of two sentences. For example, one may be given “Steve is smart, diligent, critical, impulsive, and jealous.” and the other “Steve is jealous, impulsive, critical, diligent, and smart.” These two sentences contain the same information. The first one suggests positive trait at the beginning while the second one has negative traits. Researchers found that the subjects evaluated Steve more positively when given the first sentence, compared with the second one.

Memory inhibition

In psychology, memory inhibition is the ability not to remember irrelevant information. Memory inhibition is a critical component of an effective memory system. For example, imagine if, when a person tried to remember where he had parked his car, every place he had ever parked his car came to mind; this would not be beneficial. In order to remember something, therefore, it is essential not only to activate the relevant information, but also to inhibit irrelevant information.

Modality effect

Modality can refer to a number of characteristics of the presented study material. However, this term is usually used to describe the improved recall of the final items of a list when that list is presented verbally in comparison with a visual representation. The effect is seen in free recall (recall of list items in any given order), serial recall (recall of list items in the order of study), short-term sentence recall (recall specific words from sentences with similar meanings) and paired associate recall (recall of a pair from presentation of one of its members). For paired associates, the effect is limited to an increased probability of recall for the final 2 or 3 pairs studied. In free recall and serial recall, the modality effect is seen as simply an exaggerated recency effect in tests where presentation is auditory. In short-term sentence recall studies, emphasis is placed on words in a distractor-word list when requesting information from the remembered sentence. This demonstrates the modality effect can be more than auditory or visual. Some studies use the term modality to refer to a general difference in performance based upon the mode of presentation. For example, Gibbons demonstrated modality effects in an experiment by making participants count either beeping sounds or visually presented dots. The to-be-remembered number was derived from the number of dots or beeps counted. In memory experiments, the modality effect is an example of source clustering, which refers to the tendency of items presented in the same modality to be grouped together during recall. Within-list manipulations of modality affect recall probability, order of recall, and grouping. Bennet Murdock used a basic free recall paradigm, with different types of lists, mixing auditorally and visually presented words. The results he obtained showed that modality improved recency but did not affect recall for the pre-recency items. This effect was seen to be slightly larger when the items for study were presented more rapidly. However, with mixed list presentations (lists presented both auditorally and visually in a single study period) the superiority of auditory study is seen in all serial positions, not just in recency. Murdock interprets this as evidence for separate short term stores for visual and auditory memory. Glenberg showed that the modality effect is also prevalent in long term memory, showing that to-be-remembered word pairs that are separated by distractor activity are better recalled if presented auditorally vs. visually. By using techniques similar to Murdock’s free recall paradigm, plus the addition of varied amounts of distraction time (filled with counting backwards), Glenberg showed that the modality effect is not affected by a disruptive task and therefore is theoretically not restricted to short term memory. In his book about teaching Mathematics, Craig Barton refers to the Modality Effect, arguing that students learn better when images or narrations are presented alongside verbal narration, as opposed to being presented with on screen text. This is because the text would be initially processed as an image, adding to the work already being done by the brain in processing the other image. In contrast, the narration is dealt with by the ‘Phonological Loop’ while the ‘Visuospatial Sketchpad’ deals separately with the original image and hence both pieces of information can be processed simultaneously. Teachers can hence seek to avoid overloading students’ working memories by not using slides containing many images and text at the same time. Several terms have been used to refer to the modality effect on recency. Crowder and Morton refer to it as PAS, or precategorical acoustic store. This and other similar terms (echoic memory, phonological loop) are used to explain a specialized short-term memory system store for phonological information.

Serial recall effect

For serial recall, the modality effect is seen in an increased memory span for auditorally presented lists. Memory span is defined as the maximum number of items that participants correctly recall in 50% of trials. Typically, studies find these to be seven digits, six letters and five words. In a study done by Drewnowski and Murdock, a visual list of English words was found to have an immediate recall of 4.82 words while an auditory representation of this same list led to a memory span of 5.36, a statistically significant variance.

Duration neglect

Duration neglect is the psychological observation that people’s judgments of the unpleasantness of painful experiences depend very little on the duration of those experiences. Multiple experiments have found that these judgments tend to be affected by two factors: the peak (when the experience was the most painful) and how quickly the pain diminishes. If it diminishes more slowly, the experience is judged to be more painful. Hence, the term “peak–end rule” describes this process of evaluation. Duration neglect is a specific form of the more general extension neglect. In one study, Daniel Kahneman and Barbara Fredrickson showed subjects pleasant or aversive film clips. When reviewing the clips mentally at a later time, subjects did not appear to take the length of the stimuli into account, instead judging them as if they were only a series of affective “snapshots”. In another demonstration, Kahneman and Fredrickson with other collaborators had subjects place their hands in painfully cold water. Under one set of instructions, they had to keep their hand in the water for an additional 30 seconds as the water was slowly heated to a warmer but still uncomfortably cold level, and under another set of instructions they were to remove their hand immediately. Otherwise, both experiences were the same. Most subjects chose to repeat the longer experience. Subjects apparently judged the experience according to the peak–end rule (in other words, according to its worst and final moments only), paying little attention to duration. Duration neglect can be observed in medicine, as it may lead patients to be inaccurate when judging whether their symptoms are improving with treatment.

List-length effect

The list-length effect refers to the phenomenon of people remembering only a small percentage of items from a list – however as the list gets longer a greater number of items are actually remembered. For instance, when a person goes grocery shopping and forgets their list they tend to remember only a few items. But this happens whether it is a short list or a long list. If a person has a long list they are more likely to remember a larger percentage of the items because the list was longer than if they tried to remember a short list.

Misinformation effect

The misinformation effect occurs when a person’s recall of episodic memories becomes less accurate because of post-event information. The misinformation effect has been studied since the mid-1970s. Elizabeth Loftus is one of the most influential researchers in the field. The misinformation effect is an example of retroactive interference which occurs when information presented later interferes with the ability to retain previously encoded information. Individuals have also been shown to be susceptible to incorporating misleading information into their memory when it is presented within a question. Essentially, the new information that a person receives works backward in time to distort memory of the original event. One mechanism through which the misinformation effect occurs is source misattribution, in which the false information given after the event becomes incorporated into people’s memory of the actual event. The misinformation effect also appears to stem from memory impairment, meaning that post-event misinformation makes it harder for people to remember the event. The misinformation reflects two of the cardinal sins of memory: suggestibility, the influence of others’ expectations on our memory; and misattribution, information attributed to an incorrect source. Research on the misinformation effect has uncovered concerns about the permanence and reliability of memory. Understanding the misinformation effect is also important given its implications for the accuracy of eyewitness testimony, as there are many chances for misinformation to be incorporated into witnesses’ memories through conversations with other witnesses, police questioning, and court appearances.

Leveling and sharpening

Leveling and sharpening are two functions that are automatic and exist within memory. Sharpening is usually the way people remember small details in the retelling of stories they have experienced or are retelling those stories. Leveling is when people keep out parts of stories and try to tone those stories down so that some parts are excluded. Therefore, it makes it easier to fill in the memory gaps that exist. According to a study conducted by psychologists in 1945 leveling and sharpening is involved in the retelling of stories. A person retelling the story about Noah’s Ark might do it in the following way: “There was a world filled with sin, where God could not find one virtuous man but one, Noah. God descended to him and said: “This sinful world is coming to an end. You must build a giant vessel for me so that only the most virtuous specimen can survive.” Noah tried to warn mankind, but all they did was mock him and his project of building a colossal boat. They went on as usual: They murdered, stole, embezzled and acted in all other sorts of wicked behavior. A pair of each of the finest animals in the world came to Noah and his boat. The animals traveled in one row. Noah said to his peers “This is a divine sign! You must come with me on my boat because something terrible will happen”. But no one believed him. So the whole of humanity, except Noah’s family, was drowned in a giant flooding that God had summoned. And all animals except one couple of every species drowned as well. For months Noah sailed the seas. One day when he was removing the covering of the ark, he noticed how the water no longer seemed as deep. The ark eventually landed on firm soil, and from there a new mankind and animal kingdom arose.” This retelling of the story of Noah’s ark includes sharpening. Vivid details are retroactively added in the storytelling. Noah’s interaction with the rest of the mankind and its explicit portrayal as wicked is not included in the Bible. This version also includes leveling. Events in the original story are excluded and altered. According to the Bible, Noah sent out birds from his boat to try to discover if there was land. First he sent a raven, which kept returning home to the ark and then again flying out into the sea. When the raven no longer returned, he sent a dove which returned with an olive leaf. In the story given here it is portrayed as if God summoned a flood from nowhere, instead of first making it rain as it is described in the Bible.

Peak-end rule

The peak–end rule is a psychological heuristic in which people judge an experience largely based on how they felt at its peak (i.e., its most intense point) and at its end, rather than based on the total sum or average of every moment of the experience. The effect occurs regardless of whether the experience is pleasant or unpleasant. According to the heuristic, other information aside from that of the peak and end of the experience is not lost, but it is not used. This includes net pleasantness or unpleasantness and how long the experience lasted. The peak–end rule is thereby a specific form of the more general extension neglect and duration neglect. The peak–end rule is an elaboration on the snapshot model of remembered utility proposed by Barbara Fredrickson and Daniel Kahneman. This model dictates that an event is not judged by the entirety of an experience, but by prototypical moments (or snapshots) as a result of the representativeness heuristic. The remembered value of snapshots dominates the actual value of an experience. Fredrickson and Kahneman theorized that these snapshots are actually the average of the most affectively intense moment of an experience and the feeling experienced at the end. The effects of the duration of an experience upon retrospective evaluation are extremely slight. Fredrickson and Kahneman labeled this phenomenon duration neglect. The peak–end rule is applicable only when an experience has definite beginning and end periods. Enjoy new knowledge and learn more about how our brains work!