URC

The Effect of the Olfactory Sense and Handedness on Memory

Ajleeta Sangtani

Southview High School, Sylvania, Ohio


Abstract

The project focused on creating engrams, or neural connections, to effectively retrieve information and find the connection between handedness and memory. The project consisted of seventy-five mixed gender and handedness ninth grade students who studied material for forty-two minutes and took a test two weeks later, each time with a scent or lack thereof, depending on the condition. Results for the olfactory sense part and handedness supported the null hypotheses (R = 0.027, p =.14). Although scores were low overall, results possibly suggested that the scent had a positive effect during study time but not during testing time; further research will need to confirm this.

Introduction

People often remember an event better when they have a scent associated with it. For example, the smell of a blueberry pie might remind one person of his/her grandmother, who made blueberry pies. Because humans use their olfactory sense for abstract memory, or events, it is possible that they can use their olfactory sense for semantic memory, or fact recall, as well. The intention of this project was to find out whether the olfactory sense allows for better fact recollection, which could aid students with recall.

Students often struggle with semantic memory in school. They find it difficult to remember information they previously studied. And they often have difficulty either registering information or retrieving it (Thorne, 2008). Because the olfactory sense would connect the two memories together by linking the current and previous smell, the student might find it easier to retrieve the information. An easier way for students to study and then retrieve information would help students perform better on tests due to improved recall memory.

Humans store information by encoding it (Myers, 2007; Human Memory, 2005). Encoding, an active process, requires selective attention. When a person pays attention to certain information, it is stored and then can be later retrieved. Encoding includes three levels of depth. Structural encoding, which is the physical structure of the stimuli, is the lowest level, storing the least information. Phonemic encoding, which focuses on word sounds, is the intermediate level. Semantic encoding, which focuses on word meanings, is the deep level. Encoding also includes elaboration, which is the association of a memory with other information, such as sounds, scents, and sights. Elaboration was important for this particular experiment, because it deals with scents and memory (Human Memory, 2005).

Once a memory is stored, it first enters a short-term stage from which it is either discarded or put into long-term storage so it can be retrieved. The human memory process is similar to that of a computer. The memory first enters the short-term memory stage, which can typically only hold seven items and stays there for twenty to thirty seconds, without rehearsal. Then, if the memory is not needed, it is discarded. If it is necessary or well rehearsed, the memory is moved to long-term memory stage (Human Memory, 2005; Myers, 2007). In short-term memory, the memory is discarded after a while, but in long term memory the brain creates a link between the memory and surroundings, called a conditioned response. This allows a memory to be retrieved by matching. When a person forgets information, it is the result of one of three things: the brain either failed to encode the information, the information was discarded, or the information is inaccessible (Myers, 2007; Thorne, 2008). Uncoded information is inaccessible because it was never entered into the brain in the first place. When people believe they will no longer need information, it is often discarded (Thorne, 2008). Inaccessible memory results from lack of sufficient data, so this is the focus of the project.

The olfactory sense is a chemical sense and therefore works similarly to the taste sense. The olfactory sense is made up of the olfactory epithelium and the olfactory nerve. The epithelium, located at the top of the olfactory sense, has three types of cells, the olfactory receptor cells, the supporting cells, and the basal cells. The supporting cells produce mucus, olfactory receptor cells (neurons) record scents, and basal cells become new receptor cells when needed (Kruszelnicki, 2003). The receptor cells bond to G proteins, activating Adenylyl cylclase that recognizes and stores one thousand smells per receptor. The receptor cells make up three percent of the total genes. In addition, when odor molecules touch the receptor cells they signal the olfactory nerve, which signals the amygdala, hypothalamus, hippocampus, and the olfactory cortex (Myers, 2007).

The scent used for this project was roses. Roses have a strong smell, which makes them easier to identify and recognize. Furthermore, roses are thought of as a “sweet” smell, which helps with perceptions. Because some people learn by “perceptual learning”--remembering based on their perception of the memory, roses will work well (Human Memory, 2005). Furthermore, roses are a common smell; the more a scent is smelled, the easier it is to recognize. Finally, because flowers in general are common, the smell will be easily remembered. People who smell one type of scent, such as spice scents or floral scents, can distinguish any scent in the category.

The memory part of the brain shares parts with the olfactory part of the brain, resulting in a connection between memory and the olfactory sense (Witze, 2006). Therefore, olfaction allows the retrieval of some memories.

In previous years, scientists proved a connection between abstract memory and the olfactory sense. In a phenomenon called the “Proust phenomenon,” people have the ability to remember events long past with a simple scent connected to the memory (Kruszelnicki, 2003). The Proust phenomenon proves definite connection between memory and the olfactory sense. Research also showed that humans have the ability to store scents for long periods of time along with the memories that are associated with the smell, a process called “conditioned response” (Jehl, Royet, & Holley, 1995). This relationship further supports the connection between recognition and the olfactory sense. Also, the amygdala and hippocampus are part of the limbic system, which deals with memories. However, the hippocampus deals with episodic memories, while the amygdala deals with semantic memories (Tulving & Markowitsch, 1998). Furthermore, scientists proved that odor recognition is stronger under bilateral conditions. This means that humans can smell better with both nostrils than they can with just one (Bromley & Doty, 1995). Furthermore, the olfactory sense proved to be stronger than both the sight and sound senses. This research is significant because it explores the ideal conditions of testing that will be most effective.

Handedness also plays a large part on memory. Research showed that each hand is controlled by opposite hemispheres, so the left hand is controlled by the right hemisphere and the right hand by the left. Handedness also determines which hemisphere of the person will be stronger. Right-handed people have stronger left brains, so they can encode memories easier; the left brain enforces encoding. Left-handed people have stronger right brains, so they can retrieve memories better because retrieval is enforced by the right brain. Ambidextrous people tend to have the best memory, because both sides of their brain are strong, and therefore they can retrieve and encode well (Annett, 1970). Functions of the olfactory sense is also located on the right side of the brain, so it is hypothesized that students who are ambidextrous will perform the best on the memory tests, followed by students who are left-handed.

Factors that could affect the project include age and gender. Age proved not to be a significant factor in this experiment, because people between the ages of eleven and eighteen can recall, identify, and recognize a scent equally. Also, only people over the age of sixty-five have a weakened sense of smell. Because all the subjects were between the ages of eleven and eighteen, this was not a factor in the project ( Murphy, Nordin & Acosta, 1997). Gender proved, however, to be a significant factor in the project; females have a better memory than males. Women are able to recognize odors quicker and more accurately than males, therefore giving females an unfair advantage in the experiment (Lehrner & Lumeng, 1993). To solve this problem, males and females were first taken as a divided group and then as a complete group.

Hypotheses

The purpose of this experiment was to find better conditions for students to study so that they might recall more information and perform better on tests, therefore improving test scores. If the olfactory sense can help a person recall information that is difficult to access, then this will address one of the problems currently faced by memory retrieval. The first hypothesis was that use of the olfactory sense would improve recall. The second hypothesis was that ambidextrous students would perform the best on the memory tests. The rationale was that the olfactory sense and memory are connected, and therefore recall should improve because the previously inaccessible information will be accessible. Because students find difficulty retrieving information partially because of their inability to have enough previous information, the smells should provide a connection in order to retrieve information. Furthermore, students who are ambidextrous will be able to encode and retrieve the information and scents better than the other students, and therefore they would perform better.

Materials and Methods

For this project, seventy-five ninth grade students of mixed gender, race, and handedness. The students were enrolled in ninth grade Physical Science, periods one to three.

For the control condition, the students were placed in their normal classroom, and they studied material from their textbook as they always do. Then, about a week later, the students were tested on the material.

For the first experimental condition, the students were placed in their normal classroom and studied with a rose scented plug-in. Then, about a week later, they were tested on the material without the scent.

For the second experimental condition, the students were placed in their normal classroom and they studied material from their textbook, as in the control condition. When they took the test, a rose scent was used.

For the final experimental condition, students studied the material and then took the corresponding test, with the scent both times.

There were approximately 25 students in each group, and all seventy-three students participated in all four conditions but at different times and with different chapters. The testing format was the same.

Students were then asked to fill out a form asking them about their handedness in ten activities. A scale that determined the handedness of the student analyzed the results.

The rest of data, with the test scores of each student in each condition, was analyzed by STATGRAPHICS.

Results

Phase 1

The average test scores for each of the three groups can be found below in Table 1. To evaluate the test results comparing the control and the three experimental groups, an ANOVA test was used. Results showed no statistical significance for experiment 3, F(3,266) = 1.79, p = .1489. Because the p-value is greater than the alpha level of .05, the experimenter must accept the null hypothesis.

Table 1 Average Test Scores

 

Count

Average

Standard deviation

CONTROL

73

37.6301

8.23864

EXPERIMENT 1

69

40.2029

7.04519

EXPERIMENT 2

56

37.7143

7.99253

Experimental 3

72

37.4861

8.7998

Total

270

38.2667

8.09396

However, a multiple range test showed that experiment 1, the scent only during studying, was significantly better than experiment 3, scent during studying and testing, with a difference of 2.716. Comparisons between the other groups were insignificant, as shown in Table 2.

Table 2 Multiple Range Tests

Method: 95.0 percent LSD

Contrast

Sig.

Difference

+/- Limits

CONTROL - EXPERIMENT 1

 

-2.57276

2.66402

CONTROL - EXPERIMENT 2

 

-0.0841487

2.81851

CONTROL - Experimental 3

 

0.144026

2.63534

EXPERIMENT 1 - EXPERIMENT 2

 

2.48861

2.85375

EXPERIMENT 1 - Experimental 3

*

2.71679

2.673

EXPERIMENT 2 - Experimental 3

 

0.228175

2.82699

* denotes a statistically significant difference.

Phase 2

In a comparison of handedness to memory, a simple regression test was used. The absolute value of the handedness was used in comparison with the test scores, with the lowest handedness scores being more ambidextrous, and higher scores more single-handed, both right and left. Results showed a correlation of only 0.08, and the graph was scattered. The correlation was not strong enough, so the null hypothesis was accepted that handedness showed no implications for memory. Figure 1 shows the results.

Figure 1: Test scores vs. handedness score

Conclusion and Discussion

Phase I

The experiment supported the null hypothesis that the rose scent would have no effect on memory. The experiment one group, the group that had a scent during studying but not during testing, performed the best out of the four groups, significantly better than the experiment three group that had a scent both times. This may be because the scent only had a positive effect on studying but not testing. The scent might only prove to be helpful during encoding but not during retrieval. An application of this would be having a scent during class when students are encoding the information, but not when they take the test. The experiment suggested that if teachers do use a scent, they should use it during study time. More tests should be conducted to understand the effect of the scent on studying. Perhaps the scent has a positive effect while studying, by relaxing the students, but serves only as a distraction while taking the test. Therefore, further research could study the effect of scent on encoding specifically and focus on why scents would be beneficial to encoding but not retrieval.

The experiments could have possible errors. Because each class conducted a different experiment during each test, the scent might have lingered in the room for the following classes, therefore having an effect on their scores. Furthermore, the scores in the experiment were low, possibly suggesting that the low grades were due to other factors. The experiment was as controlled as possible, but other factors such as the teacher inadvertently commenting on the scent might have caused scores to be different.

Phase II

The experiment supported the null hypothesis that handedness has no effect on memory. This may be because the experimenter had an unequal amount of left-handed, ambidextrous, and right-handed people. Furthermore, the grades were low, averaging only seventy-five percent, which is below average according to the Southview scale. This suggests that either the tests were too hard or the material was not properly taught. However, even with these circumstances, some variance was expected. The experiment strongly suggested that handedness had no effect on memory.

References

Annett, M. (1970). A classification of hand preference by association analysis. British Journal of Psychology 61:303-321.

Bromley, S. M., & Doty, R. L. (1995). Odor recognition memory is better under bilateral than unilateral test conditions [Electronic version]. Cortex, 31 (1), 25-40.

Human Memory. (2005). Retrieved September 6, 2008, from Intelegen Inc. Web site: http://www.web-us.com/memory/human_memory.htm

Jehl, C., Royet, J. P., & Holley, A. (1995). Odor discrimination and recognition memory as a function of familiarization [Electronic version]. Perception and Psychophysics, 57 (7),1002-1011,

Kruszelnicki, K. S. (2003). Smell and memory. Great moments in Science. Retrieved July 1,2008 from http://www.abc.net.au/science/k2/moments/s313347.htm .

Lehrner, J. P., & Lumeng, J. C. (1993). Gender differences in long- term recognition memory: verbal versus sensory influences and the consistency of label use [Electronic version]. Chemical Senses. 18 (1), 17-26.

Murphy, C., Nordin, S., & Acosta, L (1997). Odor learning, recall, and recognition memory in young and elderly adults. Olfactory Sense 11, 126-37.

Myers, D. G. (2007). Memory. Psychology: Eighth Edition. New York: Woolworth Productions.

Thorne, G. (2008). What are some problems students have with memory? Center for Development and Learning. Retrieved May 15, 2008 from http://www.cdl.org/resource-library/articles/memory_pt2.php .

Tulving, E., & Markowitsch, H.,J. (1998). Episodic and declarative memory: role of the hippocampus. Memory. 8, 198-204.

Witze, A. (2006). Scientists finding direct links between smell, brain, and its emotions. World Of Scents. Retrieved May 15, 2008 from http://worldofscents.com/News/Scientists.htm

 


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