Why do primacy and recency effects occur

The serial position effect means that your memory is hindered for information that is presented in the middle of a series. We need to be aware of how our memory works in order to organize information in a manner that is most optimal for recall. Without knowledge of how we best remember information, we may use tactics such as repeating a list in the same order again and again, believing that repetition is enough for information to be committed to memory. Although individually, we can use tactics that try to counter the ways in which the serial position effect causes us to forget items in the middle of a series, we are often not able to control how information is presented to us.

It is usually up to people in leadership positions to decide how to present important information. This begins all the way in childhood, when teachers plan their classes. Teachers often have to try and squeeze large amounts of information in just a few classes and hope that their students are absorbing the information.

This makes awareness of the serial position effect vital for effective teaching. Teachers need to plan learning sessions that take advantage of the primacy effect and the recency effect, because cognitive memory biases are hard to overcome even if students are aware of them. Important information should be presented at the beginning and end of a class, presentation or lesson, in order to give people the best chance at remembering the most important aspects. The serial position effect is caused by two other memory recall biases called the primacy effect and the recency effect.

The primacy effect describes our tendency to better remember information at the beginning of a series. Items at the beginning of a series are stored in our long-term memory more easily because it takes less processing power for our brains to remember single items. As a series continues, our brains have to process groups of items, making the subsequent items harder to remember.

The recency effect describes our tendency to better remember information that was most recently told to us. It means that it is easier to remember the items at the end of a series. It is believed that the recency effect occurs because those items are stored in our short-term memory, which is only able to hold a small amount of information at a time.

It stores the information that was most recently told to us allowing us to quickly access it during recall. When combined, the primacy effect and the recency effect mean that our memory recall is better for both the items at the beginning and end of a series, but is poor for the items in the middle of a series. The serial position effect therefore provides evidence for the multi-store model of memory which suggests that information passes from a sensory register, to our short-term memory, to our long-term memory.

On a daily basis, we have to remember information that may be presented to us in series. Such instances can include remembering a grocery list, memorizing a phone number, or following instructions. Since we want to be able to remember important information, we need to be aware of how our memory works in order to improve recall.

Moreover, the serial position effect impacts more than day-to-day memory recall. It could also impact how we reflect on the past. When reflecting on a past event or experience, we may only remember the beginning and end of the event but be unsure about the details in the middle. Since the serial position effect has both small and large implications on our lives, it is essential that we understand how it affects our memories in order to devise strategies to help counter the fact that it makes it harder to remember information in the middle of a series.

Awareness of the serial position effect can also help us organize information that we are presenting to people. Since we know that they are more likely to remember the information presented at the beginning and end, we can ensure that we organize the most important information in those positions and include less relevant details in the middle.

The serial position effect negatively impacts our ability to remember information in the middle of a series. As mentioned, awareness of the serial position effect can also help us decide how to organize information. That can be information that we are presenting to others, to help them remember it, or it can be information that we are studying, to make us more likely to remember it when needed.

One way to use the serial position effect is to put the most important information at the beginning and end of a series of information. Another technique could be to mix up the serial position of items in a series. For example, imagine that you are trying to remember five facts about a particular phenomenon for an exam. Instead of studying the five facts in the same order repeatedly, you might want to write down the facts in a different order the second time you go through them.

That means that different items will be at the beginning, middle and end of the series, which gives you a better chance of remembering more items since more of them will have held a place at the beginning and end.

The serial position effect was first coined by German psychologist Hermann Ebbinghaus in , after he conducted a series of memory experiments on himself. In his book Memory: A Contribution to Experimental Psychology , Ebbinghaus outlines a series of free-recall experiments that he conducted on himself to examine whether the position of an item in a list affects how well it is remembered.

Ebbinghaus found that he could more easily remember the words that were at the beginning and end of the list compared to the words in the middle of the list.

Ebbinghaus realized that the position of an item in a list did impact how well it was remembered and named this cognitive function the serial position effect. He was the first to suggest that the serial position effect occurs because of a combination of the primacy effect and the recency effect. Most of the studies that provide evidence of the serial position effect are conducted on monolingual speakers. Jeewon Yoo and Margarita Kaushanskaya, PhD students with an interest in bilingualism and memory, wanted to examine whether bilingual individuals, were still impacted by the serial position effect in each language to the same degree.

Yoo and Kaushanskaya tested the serial position effect on 20 participants who were fluent in both Korean and English, with Korean being their native or primary language. Participants were presented with lists of 10, 15 and 20 items in both Korean and English and then were asked to recall as many words as possible, in no particular order.

Yoo and Kaushanskaya found that bilingual individuals are similarly impacted by the serial position effect in both their primary Korean and their secondary English language.

Options that are presented later tend to not be considered in the same way as the earlier options. In order to reduce survey bias arising from these two effects , the easiest thing you can do is to randomize the answer options.

From the graph below you can see where both effects occur. We tend to remember more the last words, especially when the length of the list increases. Use this list of random words to test out your memory. Try reading it out to someone nearby, and see which words they remember the best. When the list is read out, there will be a tendency to recall the later words better, the recency effect. To test out the primacy effect, show someone the list of words, and then remove the list and ask them to recall the words.

Since the list was presented to them in a visual manner, they saw the words rather than hearing them, the primacy effect is likely to be more apparent and the earlier words are likely to be remembered better. Check out the entire glossary list in a printable list.

In the study, brain activity associated with recognition of items in each of three separate positions in a six item list assumed to be representative of the single-item FOA, the multi-item region of direct access, and activated long-term memory was examined.

The imaging evidence was consistent with the three state account. Most importantly, like the previous studies exploring serial position effects at retrieval, the study found that recognition of the final item was faster, and accompanied by less medial temporal lobe MTL activation and more inferior temporal and left inferior parietal activation than recognition of items from elsewhere in the list.

Here, subjects were presented with five letter lists, with letters presented one at a time. After a short mask, a probe appeared containing two of the items, and subjects were asked which item came later in the list. In order to measure performance by serial position, trials were grouped by the serial position of the correct probe Muter, ; Hacker, ; Hockley, ; McElree and Dosher, When the correct judgment involved recognition of the item that had been presented in the final serial position, performance was faster and more accurate, and fMRI contrasts revealed reduced left hippocampal and left inferior frontal BA 45 activation, relative to trials for which the more recent of the probed items had not been in the final serial position.

The five imaging studies just reviewed provide evidence regarding the neural substrates of the behavioral recency effect. Moreover, by showing that retrieval of the final list item relies on a different set of neural processes e. It is noteworthy; however, that the studies comprising this work all involved highly similar testing procedures.

This is important because it is known that the magnitude of the behavioral recency effect varies substantially as a function of the particular task used to probe memory Oberauer, Item recognition and JOR tasks especially with verbal items tend to produce relatively exaggerated recency effects and attenuated primacy effects, in comparison to other memory tasks McElree and Dosher, Meanwhile, other tasks, such as immediate serial recall, tend to produce exaggerated primacy effects and attenuated recency effects Jahnke, , Accordingly, the present work examines whether the findings obtained from earlier imaging investigations of the serial position curve might be contingent on the specific task demands present in those studies, and not reflective of a general feature of item representation in the FOA.

In the judgment of primacy JOP task, subjects were asked to identify which of two test items had been presented earlier in the preceding list of items. By exploring the behavioral and neural correlates of JOP performance, and comparing them to the correlates of JOR performance, we hoped to achieve two objectives. First, we tested the prediction that representation in the FOA is not invariably tied to the last item in a list, but rather, that the FOA can be allocated flexibly according to task demands.

Specifically, we anticipated that JOR instructions would place a premium on retention of later items in the list, while JOP instructions would encourage participants to emphasize retention of earlier items within the FOA.

Behaviorally, we anticipated that this reallocation would impact the magnitude of the recency stronger in JOR and primacy stronger in JOP effects. In the brain, we anticipated that reallocation of the FOA would alter the pattern of activity produced by recognition of items from different serial positions.

We predict the pattern of less hippocampal activity for retrieval of recency items relative to other items will be seen in JOR but will not generalize to JOP.

Contrary to our predictions, evidence in favor of a single item FOA tied to the final item would emerge if both JOR and JOP revealed similar neural and behavioral correlates associated with retrieval of the final item. Although behavioral primacy effects were evident in prior studies, an emphasis on the relationship between recency and the FOA caused the neural correlates of primacy to be essentially overlooked.

For example, Nee and Jonides dissociated three different groupings for the six items in their lists the second and third item, the fourth and fifth items, and the sixth item. Indeed, there is at present little clarity regarding the memory or attentional state of the primacy item.

Thus, a further aim of the present work was elucidation of characteristics of primacy effects and also their relationship to the status of representation in WM. A final objective in the current work was to investigate the role of the hippocampus and surrounding MTL in WM. Historically, the MTL has not been implicated in WM, in large part because damage to the MTL is associated with profound long-term memory deficits but typically leaves short-term memory intact Squire and Schacter, Most neuroimaging studies of short-term and WM have, consistent with earlier neuropsychological findings, failed to elicit activation of the MTL Wager and Smith, ; Owen et al.

Recent studies probing the hippocampus in the retrieval period of JOR and item recognition tasks Talmi et al. Through serial position contrasts examining a variety of items on the serial position curve i. In sum, there are competing accounts of the structure of WM. While recent papers argue that a single item recency effect is indicative of a single item FOA, this phenomenon has only been examined for a narrow set of tasks.

Here, the generalizability of recency effects and their neural correlates is revisited in order to inform the use of the recency effect as a marker of the FOA. Of primary interest to the current paper are the following questions: Are the magnitudes of primacy and recency effects dependent on task-demands?

And, do primacy and recency effects have consistent neural signatures across tasks? These questions are probed in two parallel experiments, one behavioral and one using fMRI, and the results are discussed as they inform the structure of WM and conceptions of the relationship between WM and the FOA. All subjects received course credit for participation. Each trial was initiated by the subject's key press and then followed the same sequence: ms fixation, five items presented sequentially for ms each, ms mask, and a 3-second probe, which included two items from the trial Figure 1.

The probe remained on the screen for 3 s, regardless of whether the subject responded. Figure 1. Schematic of the tasks from Experiments 1 and 2. The JOR and JOP tasks employed identical timing and stimuli but differed in whether participants were instructions to report the later or earlier of the two items in the probe. Trial sequences were constructed prior to the experiment in order to control the serial position of the correct and incorrect probes.

The two items contained in each probe were counterbalanced so that in half of trials the correct answer was on presented on the right side of the screen and half the trials it was on the left side of the screen.

Tasks were constructed so that each of the four possible correct serial positions was probed as the correct response 24 times, resulting in 96 trials per task, and the serial position of the incorrect probe was also balanced.

Trials were blocked by task so that subjects would not be required to rapidly switch task-demands between trials. Task order was counterbalanced across subjects. Within each task block of 96 trials, the order of trials probing different serial positions was randomized, as was the identity of the letters presented in each serial position. In an attempt to encourage verbal phonological coding, and to discourage simple perceptual matching of the encoded and probed items, capital letters were used for item presentation while lowercase letters were used for retrieval probes.

In each task, subjects completed 5 practice trials, followed by 96 actual trials. Each task block lasted roughly 15 min each trial was 6. To supplement the NHSTs, effect size estimates were calculated using partial eta-squared. Behavioral measures included both accuracy and reaction times, but reaction time on correct trials was the main outcome of interest for examining serial position dynamics.

Serial position analyses proceeded with two separate methodologies for defining primacy and recency trials and calculating primacy and recency effects.

Serial position analysis, method 1: primacy and recency assigned according to the position of the correct response. Here, primacy and recency trials were defined by whether the earliest or latest possible correct response was included in the probe.

In JOR, primacy trials were trials where the correct response was item 2 1—2 probes , middle trials were trials where the correct response was item 3 or 4 1—3, 1—4, 2—3, 2—4, and 3—4 probes , and recency trials were trials where the correct response was item 5 1—5, 2—5, 3—5, and 4—5 probes.

In JOP, primacy trials were trials where the correct response was item 1 1—2, 1—3, 1—4, and 1—5 probes , middle trials were trials where the correct response was item 2 or 3 2—3, 2—4, 2—5, 3—4, and 3—5 probes , and recency trials were trials where the correct response was item 4 4—5 probes. In both JOR and JOP, separately, primacy effects were calculated as a percent change with the following procedure: 1 reaction times on middle trials were averaged; 2 the average of the reaction times for primacy trials was subtracted from this average; 3 the resulting difference was divided by the average of the middle items; and 4 the result was multiplied by Recency effects were calculated with the following, analogous, procedure: 1 reaction times for middle trials were averaged; 2 the average of the reaction times for recency trials was subtracted from this average; 3 the result was divided by the average of the middle trials, and 4 the result was multiplied by Serial position analysis, method 2: primacy and recency assigned according to whether the first or last items are included in the probe.

A second method of condition assignment involved consideration of the serial position of both the correct and incorrect probe. Here, primacy and recency were defined according to whether the primacy item 1st or recency item 5th was contained in the probe as either the correct or incorrect response. This method provides a more direct comparison of primacy and recency across the two task types and takes advantage of the fact that the probes comprise the same exact serial positions in both tasks.

Within each task, trials were averaged into four types: 1 primacy trials for which probes included the first item from the list, but not the last 1—2, 1—3, and 1—4 trials ; 2 recency trials for which probes included the last item from the list but not the first 5—4, 5—3, and 5—2 trials ; 3 middle trials for which the probe contained neither the first not the last item 2—3, 2—4, and 3—4 trials , and 4 1—5 trials that contained both the primacy and recency items.

In JOP and JOP, separately, the magnitude of the primacy effect was calculated by subtracting the reaction time on correct primacy trials from the reaction time on correct middle trials, dividing this value by the reaction time on correct middle trials, and then multiplying the product by The magnitude of the recency effect was calculated by subtracting the reaction time on correct recency trials from the reaction time on correct middle trials, dividing this value by the reaction time on correct middle trials, and then multiplying the product by Figure 2.

These analyses confirm performance differences associated with the serial position of the correct response, and the interaction of task and serial position found in the reaction time data suggests that serial position dynamics are not identical across tasks see Figure 2. In fact, in JOR there was no significant primacy effect [e. Crucial to the aims of the present paper was whether the presence and magnitude of primacy and recency effects varied across task-demands. Primacy and recency effects, calculated using method 1 were entered into a 2 by 2 repeated measures ANOVA examining the interaction between task-demand JOR, JOP and effect-type recency effect, primacy effect with the size of the primacy or recency effect as the dependent variable.

Figure 3. Error bars represent the standard error of the mean. Method 1 divides trials by the serial position of the correct probe item, and primacy and recency trials were defined by whether the earliest or latest possible correct response was the correct answer in the probe. Here, trials are divided by considering both items in the probe, and primacy and recency item trials are trials that include the earliest primacy or latest recency item. A series of paired comparisons exploring the significant interaction revealed that in JOR there was a significant primacy effect [i.

In JOP there was a highly significant primacy effect [i. The magnitude of the primacy and recency effects were calculated within each task, this time using method 2, and the results were entered into a 2 by 2 repeated measures ANOVA examining the interaction between task-demand JOR, JOP and effect-type recency effect, primacy effect. In order to evaluate primacy and recency effects and their comparative size in different task contexts, primacy and recency effects were examined as a function of task-demand JOR, JOP.

Primacy and recency effects were calculated both according to whether the earliest or latest potential correct response was the correct response in the probe, and as a function of whether the earliest or most recent item was contained in the probe either as the correct or incorrect response. Instead, both methods of calculating primacy and recency effects revealed that the comparative size of these effects differed between JOR and JOP.

Importantly, this pattern of results demonstrates an impact of task-demand on the size of primacy and recency effects, even when the two tasks possess identical stimulus presentations and basic response requirements. Indeed, these tasks shared every feature except for the requirement to identify the earlier or later of the two items presented in the probe.

Arguably, tasks differing in more extensive ways would also produce differential serial position effects although not necessarily in a single direction or additive fashion. This experiment demonstrated behavioral evidence that the size of primacy and recency effects are dependent upon task conditions, and this finding is important in that it informs discussion of alternative views of the inherent structure of states within WM.

Still, Experiment 1 focuses on behavioral indices alone and leaves under-determined whether these retrieval advantages come about from the same or different cognitive and neural processes.

For example, it might be the case that the recency effect could arises from one cognitive process e. Moreover, the prior fMRI literature explores the neural underpinnings of a recency effect, but does not examine primacy effects, or compare the neural markers of primacy and recency effects. Thus, in a second experiment, fMRI was used to explore the neural correlates of both recency and primacy effects, and to examine whether these neural correlates are stable across task JOR, JOP.

The length of the ITI varied from 2 to 16 s, with a mean of 6. The same trial randomization was used for all subjects in order to take advantage of the Optseq2 optimizations. Subjects were scanned using a Siemens Skyra 3-Tesla scanner equipped with a 16 channel phased array head coil.

Stimuli were projected onto a visual display in the magnet's bore and viewed by the subject through a mirror above his or her eyes. Subjects responded with a handheld response box, and the experiment onset was synchronized with scanner activity through a trigger system. Thirty-four 3 mm oblique axial slices with 2. A total of 6 functional runs were collected with three runs for each task. Each run was roughly 7 min and included whole-brain acquisitions i.

Each participant completed 20 practice trials prior to functional data collection. Each of the 6 functional runs was composed of 32 task trials, and subjects completed 96 total trials of each task. The order of the tasks was counterbalanced, so that half of the subjects began the session with JOR and the other half began with JOP.

Subjects completed 3 runs of one task, were given a brief break, and were then briefed about the change in task. Before the second task began, subjects were reminded about the nature of the new task requirements and were probed to make sure they understood the change in task-demand. Data underwent the follow preprocessing steps prior to statistical analysis.

Individual slice time-series were shifted to compensate for interleaved collection of slices, and both functional and structural images were re-sampled from oblique to cardinal coordinates. A despiking procedure was used to reduce the impact of artifactual outliers on the dataset. Both structural and functional data were aligned through a procedure that registered each of the functional volumes to the 4th volume of the first functional run using a 6-parameter affine motion-correction algorithm, and then aligned all functional acquisitions to the individual subject's high-resolution structural image.

Spatial smoothing was applied to functional images with a 6-mm full-width half-maximum Gaussian kernel. Signal was also percentized using the mean value of each run so that beta weights could be interpreted as percent signal change. For group analyses, structural data were converted into a normalized template available through afni and in Talairach space.

Analyses were implemented using a general linear model GLM approach. Models included regressors of non-interest for the six motion parameters resulting from the motion correction step, as well as for the cubic polynomial trends in the run-wise data.

To model multiple task events, separate regressors were entered for the encoding-maintenance phase the interval from presentation of the first item through the end of the mask , retrieval phase including 8 separate regressors for each correct serial position in each task , and for extended baseline periods associated with the ITI specifically, the final 4 s of ITIs exceeding 10 s were modeled in order to establish an optimal estimate of baseline activity.

Retrieval events were modeled using a single parameter gamma-variate function approximating the shape of the canonical hemodynamic response. Encoding-maintenance regressors were modeled using a one parameter block stimulus of duration 3. The ITI was modeled as a block period of 4 s with no convolution.

In serial position comparisons, regressors were entered for the retrieval phase and ITI periods exceeding 10 s. Main analyses included 8 separate retrieval period regressors based on the serial position of the correct response and divided by task i.

Follow-up analyses based on method 2 i. Individual subject data were analyzed with a subject-specific fixed-effects model, and contrasts of interest were submitted to a second-level random effects group analysis. Correction to a FWE rate of 0. For both the encoding and retrieval phase data, this correction resulted in several very large clusters containing multiple local maxima. Behavioral analyses were consistent with those performed in Experiment 1. Serial position analyses focused on reaction time in order to focus on how differences in retrieval speed may be considered differences in memory state, and due high accuracy which corresponded to very few errors per condition.

Method 1. Again, primacy and recency effects were calculated using method 1 and the resulting indices were compared across JOR and JOP to test whether the items with the quickest retrieval speed and arguably the most heightened memory state were consistent across task.

Therefore, like Experiment 1 the magnitude of serial position effects was task-dependent, indicating that the size of the retrieval advantage for primacy or recency items shifted with task instructions.

Method 2. Separate analyses probed activation patterns during two segments of the task: 1 the encoding-maintenance period, which included item presentation and the mask between encoding and retrieval, and 2 the retrieval period, based on the moment at which the test probe was shown.

Tables listing the outcomes of the full set of imaging contrasts are provided in the Supplemental Materials. The encoding-maintenance period of the both JOR and JOP were marked by significant positive activations when compared to the ITI in several regions, including: bilateral premotor cortices, extending through lateral portions of BA 6 and 4, the left supplementary motor area SMA including medial regions of BA 6 extending down to BA 32 in the dorsal anterior cingulate cortex, and bilateral activations in the posterior parietal lobe that extended through the superior and inferior parietal lobes BA 7 and 40 via the intraparietal sulcus.

Areas showing higher activation for the ITI relative to the encoding-maintenance period i. Nearly identical patterns of activation were found for encoding-maintenance across tasks, and in fact, not a single cluster of activation reached significance in a direct comparison of encoding-maintenance activity during JOR vs.

The retrieval period was also investigated in comparison to the ITI, separately for each task, and between tasks.