Authors: Stephanie Hofland and Rebekah A. Dieter
Faculty Author:Dr. Sherri B. Lantinga
Institution: Dordt College
Abstract Go to: [Introduction] [Methods] [Results] [Discussion] [References] Memory can be powerfully triggered by smell. In this study, smell was tested as a cue or trigger related to cue-dependent and state-dependent memory for recalling information from a short reading passage. College-age participants were divided into three groups in which a third were given lemon-scented paper at encoding and retrieval, one third were given lemon-scented paper just at encoding, and another third were given non-scented paper. The results of a memory recognition test, taken twenty-four hours after reading the passage, showed no significant difference between the groups. Implications for memory theories are discussed. This study showed that using a lemon smell while reading did not improve one's memory of that reading.
Introduction Go to: [Abstract] [Methods] [Results] [Discussion] [References] Memories link people to their past and thus help them remember what they have experienced. Society is shaped by memories since many social, political, emotional, and physiological experiences are dependent on memories. These memories can be retrieved in a number of ways. For instance, a word, a sight, a sound, or even a smell can create a state in which a memory is recalled. Although psychology has not delved extensively into the issue of sensation and memory, psychologists recognize that all memories are a result of sensory input (Murdock, 1967). Psychologists are beginning to see that sensory input can trigger memory retrieval (Eich, 1980).
Sight is the most often-studied sense connected to memory. Experiments have demonstrated that visual imaging makes learning more rapid and accurate than learning done without visual images (Simon, 1972). Other senses besides sight have also been tested. Cann and Ross (1989) did a study using photographs and smell in which they discovered that having a smell at encoding and retrieval increased the number of photographs participants recognized. Schab (1990) found that memory of a list of words increased when smell was part of the encoding and retrieval environments. For example, in one of his studies he used a chocolate smell at encoding and retrieval of a list of antonyms and found that the smell significantly increased recall of the list compared to those who had the smell just at encoding or not at all. A smell's effectiveness as a memory trigger varied based on the type of smell. For example, when a pleasant odor was used, goal levels, amount of work, and use of effective strategies in cognitive tasks increased among subjects (Baron, 1990). However, unpleasant odors increased frustration and decreased memory scores (Rotton, 1983).
Smell is a powerful trigger of memory. There are two theories which relate to the idea of using smell to enhance memory. The first theory is cue-dependent memory (Schacter, 1996), which states that when a cue is present at the time of memory encoding, it triggers the memory if it is presented again at the time of retrieval (Godden & Baddely, 1975). In cue-dependent memory a smell can act as a cue to recall memories that were formed when that smell was previously presented. For example, smelling cinnamon can remind one of Christmas at Grandma's house, or the smell of old oranges can remind one of the elementary school cafeteria. Scent cues have been effectively used to enhance memory recall especially when they are subtle and constant (Eich, 1980; Murdock, 1967; Schab, 1990).
A second theory also dealing with smell as a memory enhancer is called state-dependent memory. State-dependent memory theory suggests that information is recalled better when encoding and retrievel of the information happen under the same circumstances (Godden & Baddely, 1975). Godden and Baddely (1975) found, in their experiment concerning state-dependent memory, that those who learned a list of words underwater recalled those words better underwater. For this reason, students who study in the same room they will be tested in tend to have increased test scores (Wilhite, 1991). The pairing of smell (which is part of a setting) with a memory increases the potential for memory retrieval (Westman, Westman, & Orellana, 1996).
Smell can powerfully trigger memories which may include childhood experiences or more recent incidences (Engen, 1991; Laird, 1935; Schab, 1990; Westman et al., 1996). The bond between a memory and an associated smell can be so strong that, when either the smell or the memory are presented, the other is recalled (Engen, 1991). Schab (1991) found that smell is as memorable as information formed from other senses.
The physiology of smell influences the present study since smell can trigger a physiological state in the brain on which memory may be dependent (Myers, 1995). Odors are processed in the mid-brain, whereas auditory and visual senses are processed in the cortex of the brain (Almagor, 1990). Odors are often not easily named or described, but are often remembered and labeled in association with certain events and situations because of how they are processed (Engen, 1991). When people smell scents, a chemical triggers an olfactory epithelial cell (a smelling cell in the nose or mouth area) to operate (Myers, 1995). A chemical can trigger a mental state on which a memory may be dependent. Part of the theory behind aroma therapy, in which scents are believed heal relatively minor psychological problems, is on the idea that a smell can triggering a mental state (Engen, 1991). As a result of research on aroma therapy, lemon oil was chosen for the present study since lemon smell has been found to promote "concentration and awareness" ("Lemon," 1997, p. 2).
Numerous studies have tested people's ability to remember smells (e.g. White & Treisman, 1997), but few have used smell to enhance memory recognition (Murdock, 1967). Schab (1990) has done studies which directly tested the effects of having the same ambient odor at the time of encoding and retrieval on memory. In Schab's study, an ambient odor that had little meaning to the context of the information was paired with the information and showed significant improvement in recall ability. Memory of word lists and other simple memory tasks have been tested in this way, but would the memory used in reading comprehension produce different results? What would happen if the smell used at encoding and retrieval was known to promote memory? Based on previous studies, if smell can be used as a memory trigger, then having a smell at encoding and retrieval of information was expected to result in better memory retrieval than having either the smell only at encoding or no smell present.
Methods Go to: [Abstract] [Introduction] [Results] [Discussion] [References] Participants
The participants were 21 male and 31 female undergraduate students taking a lower level psychology class, with a mean age of 20.25 years. They voluntarily signed up for the experiment and in turn received extra-credit towards their course grade for their participation.
Materials
The two smell conditions used the essential oil of lemon, which was a smell unrelated to the reading selection. A drop of this oil was placed in the upper left-hand corner of the informed consent, the short story, the short essay sheet, and the questions on the story. The story participants read was a narrative essay, "Rudeness at the Movies," of approximately 1200 words (Wine, 1995). The short essay sheet asked participants to write about their worst theater experience. A 20-question multiple-choice test was developed based on the details of this story which included questions about what characters wore, said, and did. A demographic questionnaire was also given which included questions about age, gender, GPA (grade point average), reading ability, amount of sleep, and the smell in the room. Participants were seated in cubicles in which they could not see the other participants but could see the experimenter. The room in which the experiment was conducted was a new study room and smelled of new carpet.
Procedure
The participants were randomly assigned to either the smell at encoding and retrieval, the smell only at encoding, or the no smell condition. They were made to believe that they were in a study about theater environments. Participants were randomly assigned into the three groups with a maximum of 15 people per session per testing time, given an identification number, and taken into a large room. The conditions were tested simultaneously in separate areas of the same room, approximately 8 feet apart. The informed consent form and the short story were placed in the cubicles. Those in both smell conditions had a drop of oil put on their papers ahead of time so the oil was dry and not overpowering. The participants were told to take a seat in the cubicle with the corresponding number to the number they had been given at the door and were asked not to touch the material until given further instruction. They were then told to complete the informed consent form, which said that the study was about theater environments, and asked to look up from their cubicles upon completion of the informed consent form. Then participants were given ten minutes to read "Rudeness at the Movies." Next they were given three minutes to write a short essay about their worst theater experience, as part of the cover story (the information from this essay was not analyzed). The participants returned 24 hours later to the same testing room and cubicles to answer 20 multiple-choice questions based on the story. They were given seven minutes to complete these questions on which lemon oil was placed for only the smell at encoding and retrieval condition. Then a demographic questionnaire was given without any oil on it since the questionnaire had no connection to using smell as a memory cue. After the questionnaire, the participants were debriefed.
Results Go to: [Abstract] [Introduction] [Methods] [Discussion] [References] The effects of a smell at the encoding and retrieval of information on memory recognition were tested. Specifically, would those having a lemon smell at encoding and retrieval have higher memory scores than those who had the smell only at encoding or those who did not receive a smell? Differences were expected between the groups because having a smell at both encoding and retrieval of information would act as a memory trigger or cue and result in increased memory scores.
At the conclusion of the testing period in the experiment, participants were asked, as a manipulation check, if they noticed any unusual smell in the room. The results of the manipulation check were as anticipated, F (2, 49), = 17.78, p < .05. A post hoc Tukey test revealed that participants in the no-smell condition were significantly less likely to report noticing a smell (5.60%) than those in the smell only at encoding (76.60%) or those in the smell at encoding and retrieval (70.60%) conditions, with no significant difference between the latter two conditions. Two participants in the control group complained of having a cold; however, since they were in the control group, their data was kept. In the matter of scoring the 20 multiple-choice questions about a short narrative story, the results were recorded as a percent correct. The percentage correct ranged from 40.00% to 85.00% with a mean of 55.19%.
The results of a one-way ANOVA showed that the scent did not influence memory scores. Those with the smell at encoding and retrieval (M = 56.18) showed no significant difference from those who either had the smell just at encoding (M = 55.00) or those in the control group (M = 54.44), F (2, 49) = .11, ns. Smell, as a cue, did not significantly increase memory scores.
A number of exploratory tests were conducted which included the possible interaction between gender, memory, and smell. Gender was suspected to influence test scores as a result of differences in sensitivity to smell between men and women (Baron, 1988; Douek, 1974). Women were expected to score higher on the memory test as a result of their greater sensitivity to smell. However, after a further look using a factorial ANOVA, no significant interaction between gender and condition was found, F (2, 46) = .35, ns. Other exploratory analyses indicated that GPA, amount of sleep, reading concentration, and age, as covariates, did not influence test results.
Discussion Go to: [Abstract] [Introduction] [Methods] [Results] [References] The purpose of the study was to see if using a smell as a memory cue, by having the smell present at encoding and retrieval of the information, would increase memory scores as opposed to having the smell only at encoding or not having the smell present. The results did not give significant evidence that the lemon smell was an effective memory cue in this memory context.
The present study followed the suggestion of Eich (1980) who said that further research could focus on the effects of smell as a cue. Unfortunately, essential oil of lemon is not an effective memory cue or effective in evoking state-dependent memory in the present study's context. The results did not support the theory of cue-dependent memory since having the lemon smell as a cue did not increase the memory scores in comparison to those who did not have the smell or those who just had the smell at encoding (Schacter, 1996).
State-dependent memory was the second theory looked at in this experiment. This more physiologically-based theory involves creating an environment which is the same at both encoding and retrieval of information (Godden & Baddely, 1975). State-dependent memory theory was also not supported by the present study. Although smell does produce a physiological state, this study did not show the state to have a significant impact on memory (Godden & Baddely, 1975). Non-significant results are not uncommon in state-dependent memory which is the result of a created physiological state (Eich, 1980). In his research using psychoactive drugs to induce state-dependent memory, Eich found that only drugs which acted on, rather than outside, the central nervous system were effective in producing state-dependent memory. The activation location may explain why smell was not effective in producing state-dependent memory since olfactory epithelial cells fall outside of the central nervous system.
Other possible reasons that this study did not generate significant results include the length of time between encoding and retrieval. The possibility exists that having a prolonged interval between encoding and retrieval might increase the impact of smell on memory. The small number of participants (N = 52) is another possible reason for the lack of significant results.
A smell as a cue in cue-dependent memory did not significantly increase memory scores in this study possibly because of the type of memory which was tested. In a study similar to the present one, Schab (1990) successfully used smell as a memory cue in recalling a list of words rather than recognizing details of a passage of reading.
One question raised as a result of this experiment is the possible effects that other smells may have on memory. For example, if participants were given a smell other than lemon, would that smell effect them differently? If the smell was related to the material being learned, would the memory increase? Another question concerns the type of memory and learning taking place. Would a smell cue be more effective in conceptual or emotional memory than in memory for factual details of a story? A final unanswered question is whether participants' ability to recognize the smell had a negative or positive effect on their memory scores.
This study encountered a couple of limitations. One limitation was that all the conditions were tested in the same room at the same time and, even though there was distance between the conditions, the smell was difficult to control. Some participants in the control group may have been unconsciously affected by the smell. Another limitation is the fact that only one type of smell and one type of memory was tested.
Research on smell as a memory trigger is important to our society since our culture puts increasing importance on the amount of knowledge retained. The aroma therapy industry has brought smell to the foreground of research. People using or interested in aroma therapy will benefit in knowing that, although lemon may be effective in promoting concentration and awareness, it was not effective in this study in increasing memory recognition ("Lemon," 1997).
Questions which may be explored in future research include those of gender, and concentration of smell and types of smell. Would smell have a stronger impact on men than women because it tends to be more subtle to men? Would varying concentrations of smell make a difference on its effectiveness as a memory cue? Or would the type of smell make a difference in smell's ability to trigger cue or state-dependent memory? Could a different type of information such as spatial, emotional, or conceptual learning be remembered better when paired with a smell than when not paired with a smell? Would lengthening the time between encoding and retrieval of the information result in significant differences between those who had the smell at encoding and retrieval and those who did not?
Smells saturate the air every day, often without people even noticing them. These smells give information about the world, both past and present, some pleasing and others offensive. Sometimes smells are paired with memories in such a way that smells increase memory. However, smell did not seem to increase memory in the present study. This finding is valuable in the age of increasing intrigue in the area of learning because researchers are continually looking for ways in which memory can be aided (Godden & Baddely, 1975).
References Go to: [Abstract] [Introduction] [Methods] [Results] [Discussion] Almagor, U. (1990). Some thoughts on common scents. Journal of the Theory of Social Behavior, 20, 181-195.
Baron, R. (1988). Perfume as a tactic of impression management in social and organizational settings. In S. Van Toller & G. H. Dodd (Eds.), Perfumery: The psychology and biology of fragrance. (pp. 91-104). New York, NY: Chapman & Hall.
Baron, R. (1990). Environmentally induced positive affect: Its impact on self-efficacy, task performance, negotiation, and conflict. Journal of Applied Social Psychology, 20, 368-384.
Cann, A. & Ross, D. A. (1989). Olfactory stimuli as context cues in human memory. American Journal of Psychology, 102, 91-102.
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