Memory Recall in Relation to the Morning and Evening Chronotype
Tracey A. Kent
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tkent@anselm.edu
Most people fall into one of two categories, those being a morning type or those being an evening type. People that fall into the morning chronotype typically rise earlier and are better able to function in the earlier hours of the day, while the evening chronotype rises later and performs better in the later hours of the day. The purpose of this study was to determine whether memory recall is affected when a morning or evening type is tested at different times of the day. All participants were asked to complete a questionnaire that deciphered whether they were a morning or evening type. After separating the two chronotypes, three evening and three morning types were asked to return in the morning, while the others were asked to return at night. Both groups were then given the same recall tests. After comparing the scores of the different groups, it was expected to find differences in the scores. It was expected that the morning types that were tested in the morning would have better recall than the morning types that were tested in the evening and the exact opposite for the evening types. It was also hypothesized that the amount of items recalled in list two would have dramatically decreased in comparison to list one and that the amount of items recalled in list three would dramatically increase due to a release of proactive interference. However, no significant results were found to support either hypothesis.Key Words: Morning Chronotype, Evening Chronotype, Memory Recall
Introduction
Research has shown that individual differences in a person’s circadian rhythm can have an effect on a person’s memory. The circadian rhythm in humans involves two processes, the first being the endogeogenous circadian pacemaker and the second is the sleep-wake cycle. These two processes usually work with each other but at times can be desynchronized, and it is believed that neither of these processes can account for rhythmic variations in cognitive performances independently of the other (Natale & Lorenzetti, 1997).
Within short-term memory, which is also classified, as working memory is what is known as a phonological loop. The phonological loop is responsible for the rehearsal and temporary storage of information (Terry, 2000). Another important function of the working memory is the visual spatial sketchpad that is accountable for the storage of visual images (Terry, 2000). In order to test the ability of short-term memory, distractor tasks are often used. It has been proposed by some that when rehearsal is prohibited or an individuals attention is changed to another topic that short-term forgetting is likely to occur (Tolan & Tehan, 1999). The purpose of distractor tasks is to determine the amount of time immediate memory can last throughout short delayed intervals (Terry, 2000). One such distraction task is the Brown-Peterson Distractor Task, which was described by both John Brown and Lloyd and Margaret Peterson. With the use of this distractor task, the individual if first presented with three items to be retained. Usually, if the individual is tested immediately after studying these words or letters, the amount of recall is often perfect (Terry, 2000). However, if a distractor task is performed, the amount of recall often decreases significantly, even with as little as nine seconds of distraction as described by Terry (2000).
Implications for the dramatic decrease in the amount of recall found when using distractor tasks could very well be due to proactive interference. Terry (2000) described proactive interference as the inability to fully retain new information due to the fact that the individual was presented with more than one list and therefore the items from previous lists interfere with the retention of current information. Evidence was found to support the idea of proactive interference with the use of the Brown-Peterson Distractor task. There are many trials throughout this distractor task, and the first trial was often found to be flawless after delays of fifteen seconds (Terry, 2000). This could be due to the fact that there was no previous material to interfere with the retention of the material presented in the first trial. However, as noted by Terry (2000) the decrease in recall does occur as the number of trials increase and trials that are conducted immediately following the previous trial can produce difficulties in recall. This is because the present material is interfered by the material retained from the previous trials.
Proactive interference is also more likely to occur when the trials all contain items belonging to the same semantic category (Terry, 2000). Forgetting often results when previous lists hold similar features to the present lists making it difficult to distinguish between the present and prior list of items (Tolan & Tehan, 1999). If however the category changes after a few trials to a new category the amount if retention will once again increase and this is known as the release from proactive interference.
Research has recently been conducted to suggest that an individual’s cognitive performance may have an effect on memory depending on whether or not the individual is a morning or evening type and what time of day they were asked to recall the information (Natale & Lorenzetti, 1997). A morning type can be distinguished as one who wakes up earlier in the day and falls asleep earlier in the evening. In contrast, an evening type is defined as one who rises later in the day and goes to sleep later in the evening. The morning type also shows less unpredictable sleep duration than the evening types (Song & Stough, 2000). It is also shown by Song and Stough (2000) that morning types memory efficiency decreases throughout the day while the evening types memory efficiency increases.
In Natale and Lorenzetti’s study the subjects were given a narrative test containing sixteen statements and were forewarned that a memory test will be given after the narrative was read. During the test the subjects were presented with forty-eight sentences and were asked to decipher which of the forty-eight sentences were present in the original narrative text. Natale and Lorenzetti found that morning types have better immediate recall in the morning, whereas evening types perform better in the evening (Natale & Lorenzetti, 1997).
Furthermore, there has been research conducted on the relationship between morningness-eveningness, time of day, speed of information processing, and intelligence. For example, Song and Stough (2000) gave participants a spatial subtest and it was found that those labeled as morning types performed poorly in the morning session and better in the late afternoon session and the evening types did the exact opposite. The subjects were also administered the Multidimensional Aptitude Battery IQ and the Inspection Time task, there were however no significant differences in the time of day the tests were given for the two types (Song & Stough, 2000).
Trockel, Barnes, and Egget (2000) researched college students and the effect of health variables on the students’ grade point average. Variables included in this study consisted of exercise, eat, and sleeping habits and also such variables as the individual’s time management and perceived stress. A questionnaire was randomly sent to 200 college students regarding such health related variables which literature has shown to be predictors of academic performance (Trockel, Barnes & Egget, 2000). After analyzing the questionnaires, the wake-up time of students seemed to account for the largest difference in grade point averages. Among the variables associated with lower grade point averages were “later weekday wake-up and later weekend wake-up times; later weekday and later weekend bedtimes; and greater number of hours of sleep on weekend nights” (Trockel, Barnes & Egget, 2000). Furthermore, it was found that weekday and weekend wake-up times particularly had the largest effect on a student’s grade point average.
Kelly, Kelly, and Clanton (2001) are few of many who have studied sleep. In their study they had three different categories of sleepers, which consisted of short sleepers: those who sleep less than 6 hours; average sleepers: those who sleep 7-8 hours; and long sleepers: individuals that sleep 9 or more hours (Kelly, Kelly & Clanton, 2001). Included in this study were 148 undergraduate students taking an introductory psychology class. Kelly, Kelly and Clanton (2001) asked the participants to complete a demographic data sheet and a questionnaire regarding the individuals average sleep length. The students were also asked to report their overall grade point average. After dividing the participants into the appropriate category of sleepers, it was found that students that were long sleepers had higher grade point averages than those classified as short sleepers, and the average sleepers were not significantly different than short or long sleepers (Kelly, Kelly, & Clanton 2001).
After conducting this research, it was expected to find differences in the number of items recalled between both the morning and evening types. It was hypothesized that morning individuals would have better memory recall in the morning whereas the evening types would have better recall in the evening. It was also hypothesized that memory recall would increase due to the release of proactive interference when there was a change in categories in both the morning and evening types regardless of when participants were tested.
Methods
Participants
The participants that were used in this study consisted of fifteen students at a small Catholic liberal arts college taking an introductory Psychology course. This study fulfilled a course requirement and the participants each received one credit for their participation. Among the fifteen participants were twelve females ranging in age from eighteen to twenty-two, and three males ranging from eighteen to twenty years of age.
Materials
The materials used in this study consisted of the Morningness-Eveningness Scale (Horne & Ostberg, 1976) and two self generated tests for auditory and visual recall. The morningness-eveningness scale (See Appendix B) is an evaluative instrument used to identify one’s typology. The determination of an individual’s circadian typology is based on a scale ranging from six to thirty-two, where the low scores indicate a greater degree of eveningness and the higher scores indicate a greater degree of morningness (Natale & Lorenzetti, 1997).
The second material used for this experiment was four different sets of pictures, where each set was made up of two pages (See Appendix C). Three of the sets contained pictures of furniture while the fourth category was comprised of articles of clothing. The first page of each set contained twenty pictures of furniture or articles of clothing, whereas the second page consisted of ten pictures from the previous page presented in a different order along with ten novel pictures. It is important to note that each picture was only present in one of each of the four sets.
Thirdly, there was an auditory component that also consisted of four different word lists (Appendix D). Three of the lists were comprised from the same semantic category, flowers while the fourth contained the names of twenty different types of vegetables. An answer sheet was provided for each of the lists and each answer sheet consisted of twenty words, ten that were present in one of the lists and ten novel words.
Procedures
The participants in this study were first given a consent form (Appendix A) that included a brief description of the study. All participants signed the consent form and were then given the Morningness-Eveningness Scale to fill out. After the questionnaire was filled out they were individually scored and separated into two groups: those characterized as morning types and those characterized as evening types. There were a total of seven morning types and eight evening types. These groups were then further divided into two randomly assigned testing groups and were asked to return to either a morning session (8:30 AM) or an evening session (7:00 PM). The morning session consisted of three morning types and three evening types and the evening session was made up of four morning types and five evening types. Both sessions were administered the same memory recall tests. The participants were first tested on visual memory. The participants were instructed to study the first set of twenty pictures of furniture for thirty seconds. When the time was up, the participants then turned to a blank piece of paper and were instructed to count backwards by three’s. After the distraction task was completed the participants were then instructed to turn to the next page that also contained twenty pictures of furniture. Furthermore, the participants were told to circle the pieces of furniture they recalled seeing from the previous page of furniture. This process was then repeated for the next set of pictures containing new pieces of furniture. The third set of pictures the participants were instructed to look at were articles of clothing. Once again, the participants studied the pictures for thirty seconds, followed by the distraction task. After completion of that set of pictures the participants then were instructed to once again look at more pieces of furniture and continue the process as previously stated. The next step was then to move onto the auditory portion of memory recall.
In order to test auditory memory recall the participants were instructed to listen as the administrator read a list containing twenty different types of flowers, where one word was read per second. After listening to the whole list the participants were then instructed to once again count backwards by three’s and then check off on the provided answer sheet the words they recalled. This was again repeated for the second list of words. The third list of words consisted of names of vegetables and they repeated the same process and then once again returned to a new list of flowers. The whole process required approximately fifteen minutes of the participants’ time. The participants were then given their debriefing statement (See Appendix E) along with their credit slip.
Results
A 2 x 2 factorial analysis of variance was used to compute the results of this study. It examined the differences between the circadian typology (morningness vs. eveningness), the time of day the memory recall test was taken (morning vs. evening), on the dependent variable, the number of correct words recalled.
First, the circadian typology was determined and there were a total of six morning types and nine evening types. Secondly, the morning and evening types were furthered divided into two testing groups. There were a total of three morning types and three evening types tested at 8:30 in the morning. The mean number of items recalled in this testing session was almost equal for both groups, showing that there were no significant differences between the two groups. The evening session, which was held at 7:30 PM consisted of four morning types and five evening types and the amount of items recalled for both types were too similar to account for any differences.
There was also no significant differences between the number of items recalled in the second trial and the number of items recalled in the third trial showing that there were no significant effects of proactive interference or the release of proactive interference. There were no significant differences in the means for both the morning and evening types in the number of items recalled in trials two and three.
Discussion
The fact that there was no significance found between the circadian typology and the amount of items recalled and that there was no significant differences between the second and third trials to support proactive interference and the release of proactive interference could be due to many factors. Among these factors can include the size of the subject pool, and the use of self-generated testing materials.
Originally, there were a total of twenty-six participants that joined the study, however not all showed up. On the first morning session a total of thirteen participants were told to report, however only two participants did. In order to account for that loss all the participants were left voicemails reminding them to attend a session and another morning session was scheduled, to which four participants attended. There were a total of thirteen participants asked to attend the evening session and of the thirteen, nine showed up. There were a total of fifteen participants, six morning types and nine evening types. The size of the subject pool was not large enough to determine differences between the groups and there also was not an equal amount of morning and evening types. The lack of participants resulted in even smaller subgroups when the subjects were divided into two different testing sessions. There were a total of three morning types and three evening types in the morning session and four morning types and five evening types in the evening session. These numbers were not large enough to find any significant differences.
Among other discrepancies found in the method of this study, the fact that there was no significance found could be due in part to the self- generated materials used. First of all, the pictures used in the visual portion of the memory recall task may have not been clear enough. The pictures may have been too dark therefore making certain items indistinguishable. Another factor could be that the categories chosen may not have had distinct subcategories making it difficult to retain. For instance, within the furniture category were pictures of many beds, armoires, chairs, tables, and ottomans, among a few other items. The participants however only had thirty seconds to study the twenty items and then had to try to recall these items which was quite difficult due to the fact that there many new pictures of furniture that were significantly similar to the previous pieces but differed in miniscule ways making it difficult to distinguish those differences.
The effect of word size could have also played a significant role in this study. In the auditory component of the memory recall test, there were list of flowers that contained as little as three letters per word, to as many as thirteen letters per word. It has been shown that the longer the length of the word the decreased amount of items is to be retained (Coltheart, 1999). This would therefore result in a decrease of the amount of total words recalled if there were a significant amount of longer length words present in any one of the lists. In order to obtain significant results in a study of this kind it is important that the above problems are corrected and therefore future research in this area could in fact produce significant results.
Relevant Links (examples)
Saint Anselm College
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