THE EFFECT OF PRESENTATION ON DEEPLY PROCESSED EXPLICIT MEMORY IN OLDER ADULTS

Felicia Elena Luz OropezaB.A., Stanford University, 2004

THESIS

Submitted in partial satisfaction of

the requirements for the degree of

MASTER OF ARTS

in

GENERAL PSYCHOLOGY

at

CALIFORNIA STATE UNIVERSITY, SACRAMENTO

SPRING

2012

THE EFFECT OF PRESENTATION ON DEEPLY PROCESSED EXPLICIT MEMORY IN OLDER ADULTS

A Thesis

by

Felicia Oropeza

Approved by:

__________________________________, Committee Chair

Dr. Kelly Cotter, Ph.D.

__________________________________, Second Reader

Dr. John Schaeuble, Ph.D.

__________________________________Third Reader

Dr. Emily Wickelgren, Ph.D.

ii

____________________________

Date

Student: Felicia Oropeza

I certify that this student has met the requirements for format contained in the University format

manual, and that this thesis is suitable for shelving in the Library and credit is to be awarded for

the thesis.

__________________________, Graduate Coordinator ___________________

Dr. Qin, Ph. D. Date

Department of Psychology

iii

Abstract

of

THE EFFECT OF PRESENTATION ON DEEPLY PROCESSED EXPLICIT MEMORY IN OLDER ADULTS

by

Felicia Oropeza

Statement of Problem

Is explicit memory test performance affected by thematically related and supraliminal presentation conditions?

Sources of Data

Forty eight individuals over the age of 55 were sampled from two senior communities, Ethel Hart MacLeod Senior Center and Swanston Community Center. Participants watched a series of 40 words on a computer monitor and then took a written exam that tested their explicit word recall.

Conclusions Reached

Main effects for relatedness and presentation were found for hits, or number of words correctly recalled. A higher number of words were correctly recalled in thematically related conditions than in non thematic conditions independent of presentation. Also participants produced a higher number of words in supraliminal presentation conditions, than in subliminal presentation conditions across relatedness conditions. There was a significant interaction of presentation and relatedness for hits where the number of words recalled in supraliminal thematic conditions was higher than that of subliminal non thematic conditions. For false positives, or the number of words written that were not presented in the word list, there was a main effect of presentation where participants produced more false positives in supraliminal presentation conditions than in subliminal presentation conditions. However, there was no main effect for relatedness showing no difference in false positives produced in thematic and non thematic relatedness conditions. Similarly, false positives did not show a significant interaction of presentation and relatedness.

_______________________, Committee Chair

Dr. Kelly Cotter, Ph.D.

_______________________

Date

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TABLE OF CONTENTSPage

Dedication................................................................................................................... vii

Acknowledgments......................................................................................................viii

List of Tables................................................................................................................ix

List of Figures............................................................................................................... x

Chapter

1. INTRODUCTION………………………………………………………………..1

Memory………………………………………………………………………..1

Explicit Memory………………………………………………………………2

Supraliminal and Subliminal Memory Processes……………………………..3

Levels of Processing………………………………………………………......4

Interaction of Levels of Processing and Timing of Presentation…………….5

The Present Study…………………………………………………………….6

2. METHOD………………………………………………………………………...8

Design...............................................................................................................8

Materials……………………………………………………………………...9

Word Generation……………………………………………………..9

Inter Rater Reliability………………………………………………...10

Final Word List Creation…………………………………………….10

v

Computer……………………………………………………………..12

Demographic Questionnaire………………………………………….12

Participants…………………………………………………………………..11

Procedure…………………………………………………………………….12

3. RESULTS………………………………………………………………………..14

Hits…………………………………………………………………………..14

False Positives………………………………………………………….........16

Covariates…………………………………………………………………...178

4. DISCUSSION…………………………………………………………………..18

Limitations and Strengths…………………………………………………...19

Further Directions…………….…………………………………………….20

References………………………………………………………………..................21

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Dedication

I would like to dedicate this thesis to my deceased maternal grandparents, Maria de la Luz Razo and Salvador Gomez who raised me and served as the inspiration for my topic on cognition and aging.

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ACKNOWLEDGMENTS

First and foremost, I would like to thank my parents for everything they have done for me. Since

preschool, my parents have impressed upon me the value of education and importance of using one’s

intellect to make a significant impact on the world; however small or big that may be. They gave me the

greatest gift that any parent could bestow on their child, individuation, by giving me the freedom to

explore my academic pursuits. My thesis topic availed me this golden opportunity to spread my wings

and fly. Special thanks to my mother’s extended family for their undying support of my educational

endeavors and contributions to my personal development throughout graduate school. During graduate

school, my grandmother passed away which was a major setback for our family, for she was the anchor

that held our family together. Amidst those trying times, my mom’s family taught me to rise above

hardships and to find my inner strength within to finish my degree. I would like to thank Dr. Kelly Cotter

for her patience, immense wisdom, alacrity, and generosity of time and effort towards helping me finish

my thesis. I would also like to thank Dr. John Schaeuble for helping me arrive at my thesis topic and for

assisting me with narrowing my thesis topic down to two variables. I would like to thank Dr. Wickelgren

for helping me with the Latin Square Experimental Design of my video presentations to eliminate bias. I

would like to thank Debbie Kircher for pacing me through the program and helping me see my own

beauty within. Finally, I would like to thank the two senior communities Swanston Community Center

and Ethel Hart MacLeod Senior Center, who graciously afforded me the opportunity to conduct my

experiment during their community events. For their patience and efforts to help me attain my degree, I

am grateful. My precious emblems, Belle, Lena, and Cha Cha have been my torches throughout the

entire writing process and they have seen it to completion providing constant companionship and support

when things seemed formidable and the end of the graduate school road seemed nowhere in sight.

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LIST OF TABLES

Page

[1.] Table 1 Descriptive Statistics for Hits and False

Positives………………….,,,,,,,,,,,,,,,,,,,,,,,,,167

ix

LIST OF FIGURES

Page

1. Figure 1 The Interaction of Presentation with Relatedness for Hits…………………… 156

2. Figure 2 The Main Effect of Presentation Time for False Positives…………………….187

x

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Chapter 1

INTRODUCTION

Dementia is a degenerative disease of the aging brain that impairs cognitive functioning

by attacking the central nervous system at the vascular and cellular levels (Whitehouse, Price,

Strubie, Clark, Coyle, & Delon, 1982). Although dementia impairs cognitive functioning in

many ways, profound and irreversible memory loss is its primary effect (Reed Group, 2009).

Because dementia is an increasingly prevalent age-related neural disease within senior

populations developing cognitive strategies for preventing memory loss is necessary for the

maintenance of quality of life and positive life orientations (Santacruz & Swagerty, 2001). I

focus on two potential memory-enhancing strategies in the present study: presentation of

information and processing of information. I examine these strategies as employed by older

adults who do not suffer from cognitive impairment, in hopes that what is learned in normal

aging populations can be beneficial for those at risk of developing dementia.

Memory

Memory, in its purest form, is the act of encoding, storing, and recalling a past event or

item of factual knowledge (The American Heritage Dictionary, 1985). Memory can be divided

into two forms: implicit and explicit (Graf & Schacter, 1985), both of which are affected by the

aging process (Light & Singh, 1987). Implicit memory is a memory task that depends on

cognitive processes occurring outside of one’s conscious awareness (Schacter, 1987). These

automatic processes can include stimuli-associate conditioning, social modeling, relearning and

practice effects, and priming (Schacter, 1987). Roediger and McDermott (1993) and Schacter

(1987) described implicit memory tasks as indirect or incidental, where there was no reference to

past exposure to information.

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In contrast, explicit memory tasks require the conscious recollection of an item directly

referenced by past experience (Graf & Schacter, 1985). When one performs well on an explicit

memory test, he or she has brought factual knowledge into awareness (Challis, 1996; Joyce,

Paller, McIsaac, & Kutas, 1998). Roediger and McDermott (1993) and Schacter (1987)

characterized explicit memory tests as tasks performed with intention, where participants are

instructed to recall or recognize stimuli they had previously seen.

In cross-sectional and longitudinal studies examining age-related memory, older

participants tend to score lower than younger participants on explicit memory tasks (Anooshian,

1997; Carroll, Byrne, & Kirsner, 1985; Ellis, Ellis, & Hosey, 1993; Greenbaum & Graf, 1989;

Lorsbach & Morris, 1991; Lorsbach & Worman, 1990; Naito, 1990; Parkin & Streete, 1988).

However, older cohorts show equable performance to young adults on perceptual implicit tasks

(Light & Singh, 1987).

To understand potential compensatory mechanisms older adults can use to preserve

explicit memory, I analyzed the influence of two associative memory processes on explicit

memory test performance in aging adults: level of processing (shallow versus deep) and

awareness of presentation (subliminal versus supraliminal), described in detail below.

Explicit Memory

Explicit memory tests measure the conscious recollection of memory of previously

presented stimuli (Joyce et al., 1998). Explicit memory test stimuli can be presented visually,

pictorially, or aurally (Drury, Kinsella, & Ong, 2000). Recall and recognition are two main types

of explicit memory tests used by the research community. Free recall is a memory task that

depends on exerting cognitive resources to successfully retrieve a memory item. Performance on

a recall exam is a direct measurement of the conscious recollection of previously presented

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stimuli. This type of memory task relies on processing capacity, revealing the influence of

working memory and processing speed on retrieval (Craik, 1996; Whiting & Smith, 1997). Free

recall tests typically depend on effortful cognitive control and bottom up retrieval processes. I

chose to analyze free recall test performance as a measure of explicit memory processes in the

current study.

Recognition, on the other hand, is an explicit memory process that relies more on

automatic, top-down processes than processes required for recall tests. Performance on

recognition tests does not require the direct retrieval and generation of a memory trace, creating

less reliance on the use of cognitive strategies. Multiple-choice tests are one example of

recognition tests where performance is facilitated by the use of associative cues that assist

implicit retrieval of a memory trace. Thus, this type of test offers more environmental memory

support than is offered by free recall tests (Whiting & Smith, 1997). Recognition tests employ

different memory strategies from that of free recall tests, the measurement tool of the present

study.

A comparison of younger and older adults’ performance on implicit tests, such as word

stem completion, and explicit tests, such as word recognition, revealed lower test performance

for older adults on explicit memory tasks, but similar implicit memory performance across age

cohorts (Graf, 1992).

Supraliminal and Subliminal Memory Processes

As described above, explicit memory tests often involve asking participants to recall or

recognize information presented to them in a laboratory setting. The information can be

presented supraliminally (within one's conscious awareness) or subliminally (outside one's

ability to consciously perceive presented stimuli) in the study/encoding session. Supraliminal

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memory processes are driven by strong feelings of event recollection that enhance one’s ability

to visualize the scene (Aggleton & Brown, 1999; Gardiner, 1988; Gardiner & Java, 1990;

Gardiner & Java, 1991; Gardiner, Java & Richardson-Klavehn, 1996; Jacoby, 1991; Rajaram,

1993; Tulving, 1985; Wagner, Verfaeille, & Gabrieli, 1997; Yonelinas, 2002). Subliminal

processes depend upon feelings of familiarity that lack a concrete experience of an actual event

(Khilstrom, 1990; Khilstrom, 1996; Khilstrom, Barnhardt, & Tataryn, 1992a; Roediger &

McDermott, 1993; Szymanski & MacLeod, 1996; Toth, 1996).

The priming task is a classic methodology for studying subliminal processes. Age has

little effect on priming (Light & Singh, 1987). However, Englekamp and Wippich (1995)

demonstrate an age effect for conceptual priming, such that younger cohorts generally show

higher memory on implicit tests than older cohorts when presented with atypical stimuli at study.

Their study shows that younger cohorts tend to perform better than older cohorts in random

stimuli and subliminal presentation conditions while performing worse in moderate relatedness

conditions. Levels of processing may enhance performance in older cohorts on priming tests..

Levels of Processing

When presented stimuli within varying degrees of awareness, the brain can process

stimuli using deep or shallow processing. Deep encoding requires the utilization of meaning-

based encoding to activate associative memory network connections, while shallow processing

refers to the presentation of stimuli encoded at a rudimentary or physical level without the use of

semantic-level memory access (Craik & Lockhart, 1972). For example, deep processing is

applied during exposure to a word list consisting of items belonging to the same category, such

as Zoo Animals, because people form associations between the words. On the other hand,

shallow processing is utilized during exposure to randomly chosen words because there is no

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categorical link between the words. Craik and Lockhart (1972) showed that deep- or

semantically-processed stimuli had a higher chance of recall than shallow- or physically-

processed stimuli. This effect was found even when participants did not expect subsequent recall

or recognition tests.

Bradshaw and Anderson (1982) showed the effect of elaboration and thematic-

relatedness on memory processes. Their study demonstrated higher memory performance in the

thematic conditions requiring the elaborate integration of memory traces and lower memory

performance in the conditions with minimal thematic relatedness yielding the integration of poor

memory traces. Similarly, levels of processing theory stipulates that performance is facilitated by

elaborately encoded or “deeply” processed stimuli and degraded by low-level encoding or

“shallow” level processing of stimuli. Hence, their study draws parallels between thematic

relatedness and levels of processing theory shedding light on the role of neural networks in the

creation of interconnected explicit memory traces seen in the present study (Bradshaw &

Anderson, 1982). In the current study, I adapted the methodology that used thematic relatedness

to operationally define levels of processing to fit my experimental model for studying explicit

memory performance.

Interaction of Levels of Processing and Timing of Presentation

A careful examination of presentation and levels of processing effects on explicit

memory is necessary for developing a comprehensive network model of consciousness and

meaning-based concept maps. Among the memory tasks available to researchers, the category

exemplar test is one of the most effective tools for studying the interaction of levels of

processing and exposure to subliminal and supraliminal stimuli (Mitchell & Bruss, 2003).

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Presenting target exemplars from taxonomic groups of animals and vegetables to the participants

resembles the methodology used in the present study.

Because category exemplar tests utilize both explicit and implicit memory processes, the

distinction between the cognitive resources that drive each process begin to blur (Srinivas &

Roediger, 1990). Thus, category exemplar tasks capture conceptual subliminal processes as well

as perceptual subliminal processes revealing the overlapping effects of conscious and

unconscious processes on memory trace formation. Monti et al. (1996) investigated how

category exemplar tasks rely on relatedness conditions to create and consolidate meaning-based

or deeply processed memory traces. He theorized that cognitive networks accomplish this task

when processing semantic supraliminally presented content. Although category exemplar tasks

are classically referred to as “implicit” memory tasks, its conceptual properties are sensitive to

effects of levels of processing at the supraliminal level (Monti et al., 1996). Hence, regardless of

whether category exemplar tests contain implicit or explicit memory components, these tests

may have more conceptually-driven effects on memory if coupled with deep levels of processing

conditions. Therefore, research provides evidence for the possible interaction of presentation of

stimuli by levels of processing. There remains a paucity of research that examines the direct

effects of semantically processed stimuli on category exemplar task performance in older adults.

In contrast to recent studies which examined the relationship between relatedness,

elaboration, and explicit memory, the current study analyzed the effect of presentation and

thematic relatedness on explicit memory of older adults (Bradshaw & Anderson, 1982).

The Present Study

In the present study, I examined how levels of processing (deep versus shallow) affects

explicit memory task performance when moderated by presentation type (subliminal versus

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supraliminal). I operationally defined deep levels of processing as the presentation of

thematically-related words from two thematic categories (Zoo Animals and Vegetables). I

defined shallow levels of processing as the presentation of randomly generated, non-thematically

related words. I defined supraliminal presentation as seeing a series of words for 2 seconds each.

Subliminal presentation was defined as seeing a series of words for .4 seconds each.

I expected to find main effects for both presentation and processing of stimuli. For the

main effect of presentation, I expected to see a higher number of supraliminally-presented words

recalled than subliminally-presented words. For the main effect of relatedness, I proposed that

memory for thematically-related words would be higher than memory for non-thematically-

related words. Specifically, I expected that thematically-related words would provide a semantic

(deep) form of processing that would facilitate memory performance across both supraliminal

and subliminal presentation conditions.

I also hypothesized that participants would have higher memory performance in

supraliminal-deep levels of processing conditions and lower performance in supraliminal-

shallow levels of processing conditions. I expected to see this interaction because meaningful,

related words shown for a longer amount of time on a computer screen tend to produce more

durable memory traces than random words presented for a shorter amount of time. The focusing

of one’s mind on semantic content should yield a compound effect on explicit memory

performance because supraliminal processes require the effortful application of cognitive

resources that spark neural network activation and parallel processing stream distribution.

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Chapter 2

METHOD

Design

With a 2x2x4 mixed repeated-measures factorial design, described in detail below, I

examined the nature of semantic facilitation on explicit memory for words presented at the

conscious and the unconscious perceptual level. I showed each participant a series of forty words

flashed on a computer screen and later asked participants to recall the words. The two within-

subjects independent variables were thematic association of words and presentation of stimuli.

The between-groups independent variable was order or presentation. Explicit memory recall test

performance was my dependent variable.

The first within-subjects independent variable was thematic association/level of

processing. Thematic association referred to how easily participants could form associations with

presented words (thus affecting their memory for those words), and was comprised of two levels:

a thematically-related word condition (deep processing) and a non-thematic word condition

(shallow processing). The thematically-related word condition was a list of ten words related to

the same category, either Zoo Animals (e.g., zebra) or Vegetables (e.g., broccoli). The non-

thematic word condition was a list of ten randomly generated words that had no relation to each

other (e.g., skirt, motorcycle).

The second within-subjects independent variable, presentation of stimuli, referred to how

long participants saw words flashed on the computer screen. This variable had two levels: the

supraliminal condition and the subliminal condition. In the supraliminal condition, participants

were exposed to words for 2 seconds each. This presentation time was long enough for

participants to read and understand the word, thus processing it completely (Moore, 1982;

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Whiting, 1997). Words were presented for .4 seconds each in the subliminal condition. This

presentation time was long enough for participants to detect a word, but not long enough to

consciously process it (Moore, 1982; Khilstrom, 1987).

Video presentation was the only between-subjects variable used in this study. It consisted

of four levels in order to control for potential order effects. Each video started with a

supraliminal phase in order to prevent the participant from thinking that there were no words

presented in the video. To control for the order effect of presenting supraliminal conditions first

in all video presentations, I used a partial Latin-Square to counterbalance the sequence of phases

within each video presentation. This method of counterbalancing ensured that the thematic and

non-thematic words were presented in every possible order (first, second, third, fourth). For

example, order one consisted of supraliminal thematic words presented in phase 1, subliminal

non thematic words presented in phase 2, supraliminal non-thematic words presented in phase 3,

and subliminal thematic words presented in phase 4. In contrast, in order two supraliminal non

thematic words appeared in phase 1, subliminal thematic words appeared in phase 2,

supraliminal thematic words appeared in phase 3, and subliminal non thematic words appeared in

phase 4. Thus, the presentation conditions were counterbalanced across the four different videos.

A total of forty words were presented in each video.

Materials

Word Generation. To create the vegetable word list I randomly selected 41 Vegetable

words from the following website: http://www.gardenology.org/wiki/List_of_vegetables. To

create the zoo animal word list I randomly selected 26 Zoo Animal words from the following

website: http://www.catalandictionary.org/wordnets/eng/ZooAnimalList.htm. To create the non-

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thematic word list I randomly generated 24 words from the following website:

http://coyotecult.com/tools/randomwordgenerator.php.

Inter-rater Reliability. The relatedness of a word to a category could affect the speed

and accuracy by which a participant could retrieve the word from memory, thus assisting in the

formation of cognitive associations (Anderson, 1980). Therefore, I wanted to make sure that one

word list did not contain words that were more related to the theme than the other word list. To

check the equivalence of thematic-relatedness of the words in the two thematic word lists, I

collected inter-rater reliability data on the degree of relatedness of each word to its specific

category.

Ten friends and family members below the age of 55 participated as raters. They were

asked to rate how much each word from the vegetable list was related to the theme of vegetables,

and how much each word from the zoo animals list was related to the theme of zoo animals.

Relatedness ratings were collected only for thematic words.

I also collected inter-rater reliability data on the commonness of each word in everyday

usage because the commonness of a word could also increase the accuracy of recall (Deese,

1960; Gregg, Montgomery, & Castano, 1980; Hall, 1954; Matthews, 1966; May, Cuddy, &

Norton, 1979; May & Tryk, 1970; Postman, 1970; Sumby, 1963; Tulving & Patkau, 1962;

Whiting & Smith, 1997). The commonness inter-rater questionnaire asked raters to rate how

commonly words are used in everyday speech. Commonness ratings were collected for thematic

and non-thematic words. Upon completion of the word rating procedure, I rewarded the raters

with $5.00 Target gift cards.

Final Word List Creation. To create lists of equivalent length (10 words) for each

condition (thematically-related and non-thematically-related), I entered the participants’ ratings

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into a spreadsheet. Next, I eliminated some words from the original lists by sorting the word lists

(Zoo Animals, Vegetables, non-thematic) from the highest to lowest mean commonness rating.

Then I chose every other two words descending from the highest to lowest mean commonness

rating until I obtained 10 words for each thematic list (Zoo Animals, Vegetables) and 20 words

for the non-thematic word lists. These 20 words were divided into two lists of ten words each

using the ABBA sorting sequence.

When the final word lists were created, I calculated the variability between the two

thematic word lists on relatedness and the variability between the two thematic and the two non-

thematic lists on commonness. T-tests revealed no significant differences between Zoo Animal

words (Μ = 4.09, SD = .54) and Vegetable words (M = 3.71, SD = .76) on relatedness to their

respective thematic category; t (38) = 1.73, p = .09. In other words, Zoo Animal words and

Vegetable words had the same degree of relatedness to their respective theme. T-tests also

showed no significant differences between thematic (M = 3.49, SD = .63) and non-thematic

words (M = 3.34, SD = 1.03) on commonness; t (38) = .70, p = .48. Thus, both thematic and non-

thematic words were considered equivalent on commonness.

Upon completion of the word list generation procedure I had four lists of 10 words. These

lists were capped at 10 words each because the average older adult has a working memory

capacity of 4 (+/- 2) items (Bo, Borza & Seidler, 2009). I chose to increase the size of the word

list from four words to ten words because I wanted to avoid any potential ceiling effects (Miller,

1956).

Finally, to randomly sort the words within the four lists for the video presentation

conditions, I used the following website: http://textmechanic.com/Sort-Text-Lines.html, which

generated random orders for each ten word list.

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Computer. Words were presented to participants on an ASUS gaming laptop computer

running Microsoft Movie Maker for Windows 7 Home Premium operating system.

Demographic Questionnaire. Before administering the computerized portion of the

procedure I collected the following demographic information: gender, educational status,

occupation ethnicity, and religion. Age information was not collected because my entire

participant pool consisted of older adults and I did not want the sensitivity of the age question to

deter them from participating in my study.

Participants

I sent letters to fourteen different agencies within the Sacramento Valley region and

called ten agencies. I recruited forty-eight older adults over the age of 55 from the following

agencies: Senior Center at Elk Grove, Mission Oaks/Swanston Community Center in

Carmichael, and Ethel Hart Senior Center. Of the twelve participants who gave a response to the

gender question on the demographic questionnaire, three participants were male and nine

participants were female. Four out of 48 participants “Completed High School,” 11 “Went to

college but did not finish,” 12 “Finished some graduate school or higher”, and 2 ”Earned a

doctorate degree.” Almost half of the participants were “Caucasian” (n = 23), 4 were “Hispanic,”

1 was of “Asian American” descent, 2 were “African American,” and 18 did not indicate their

ethnicity. Out of 45 participants whothat responded to the Religion question, 12 were

“Catholic”, 13 were “Christian,” 5 were “Spiritual,” 1 was “Mormon,” 1 was “Episcopalian,” 3

were “Atheist,” 3 were “New Age,” 2 were “Baptist,” and 5 participants reported “Other” to

signify that they were of a religious affiliation other than what was presented.. Three participants

out of 48 did not respond.

Procedure

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I received ethical approval to recruit participants from the Human Subjects Committee in

the Department of Psychology with minimal risk in Spring 2011. Next, I pilot-tested the

procedure with four individuals who did not meet the study’s criteria for participation to make

sure the testing protocols ran smoothly. There were no problems with the procedure.

To prepare for the experiment, I made arrangements with the activity coordinators from

each agency listed above to secure a room and a specific time to run my study. Before the day of

the experiment, I randomly assigned the participants to one of four video conditions. On test day,

I greeted each participant individually, showed the participant to his or her seat in front of the

laptop, and led the participant through the informed consent procedure. Next, I handed

participants an informed consent form to sign and return back to me. I then provided the

participants with a demographic questionnaire that asked participants to reveal their gender,

education status, occupation, religion, and ethnicity.

Before starting the video presentation, I instructed the participant to not touch any key on

the keyboard or touchpad because the screen ran by itself. Next, I started the video assigned to

the participant. Within each video, the supraliminal condition had one thematic phase and one

non-thematic phase. The subliminal condition also had one thematic phase and one non-thematic

phase. The order was counterbalanced, as described above.

The video presentation lasted for 3.99 minutes. After the video was complete, I

administered the free recall exam by giving the participant a pen and piece of lined 8.5 x11 white

printer paper with the following instructions at the top of the page: “Please write as many words

as you can remember from the presentation you just saw. You have as much time as you want to

complete this form.” Next, I told participants that they could take as much time as they needed to

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complete the test while I was out of the room. After the exam was complete, I debriefed the

participant and gave the participant $5 gift card to Walmart.

Chapter 3

RESULTS

Using two mixed repeated measures ANOVAs, I examined differences between the

thematic and presentation conditions on recall (see Table 1). The first dependent variable, the

number of “hits,” represented the number of words the participant wrote down on the recall

task that were presented in the video presentation (i.e., correctly-recalled words). The second

dependent variable, number of false positives, was the number of words that the participant

wrote down on the recall task that were not presented in the video presentation.

Hits

The between subjects variable, order, did not show a significant main effect for hits, F (3,

44) = 2.18, p = .10, partial η2 = .13, indicating that order of presentation had no effect on

correct recall for presented words. The first within-subjects variable, timing of presentation,

showed a significant main effect for hits F (1, 44) = 220.90, p < .001, partial η2 = .83, such that

supraliminal presentation conditions yielded a higher number of hits than subliminal

presentation conditions, as predicted (see Table 1).

The second independent variable, thematic-relatedness, also showed a significant main

effect for hits, F (1, 44) = 100.37 p < .001, partial η2 = .70, such that thematic conditions

produced significantly more hits than non thematic conditions. However, this main effect was

qualified by a significant interaction where the number of hits in thematic conditions was

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higher in supraliminal presentation conditions than in subliminal presentation conditions, F

(1,44) = 109.13, p < .001, partial η2 = .71, see Figure 1.

Thematic Non Thematic0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

4.104

1.146

0.1460

The Interaction of Presentation and Thematic Re-latedness

SupraliminalSubliminal

Relatedness

Performance

Presentation

Figure 1. This graph shows the significant interaction of presentation and thematic relatedness

for number of hits. Thematic supraliminal conditions yielded higher performance than non

thematic subliminal conditions.

The pairwise comparisons for the number of hits for supraliminal presentation conditions

showed significant mean differences between thematic and non thematic conditions such that

the number of hits in thematic conditions was significantly higher than the number on hits in

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non-thematic conditions during supraliminal presentation conditions. However, the pairwise

comparisons for the number of hits in subliminal presentation conditions did not show

significant differences between the two thematic variables.

Note: N=48 participants were randomly assigned to one of four presentation videos.

False Positives

The between subjects variable, order, did not show a significant main effect for false

positives F (3, 44) = .60, p = .62, partial η2 = .04, revealing no effect of video order

presentation on the number of written responses that were not on the word list. Presentation

showed a statistically significant main effect for false positives F (1, 44) = 10.05, p < .001,

partial η2 = .19 such that there were more false positives produced in supraliminal presentation

conditions than in subliminal presentation conditions (see Table 1).

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Table 1.

Descriptive Statistics for Hits and False Positives

Hits False Positives

Independent Variable Effects M SD M SD

     

Thematic 2.13 .13 0.10 0.04

Non-thematic 0.57 0.11 0.13 0.05

Supraliminal 2.63 0.17 0.22 0.06

Subliminal 0.07 0.05 0.01 0.01

Relatedness*Presentation        

Supraliminal Thematic 4.10 0.23 0.21 0.07

Subliminal Thematic .15 0.09 0.00 0.00

Supraliminal Nonthematic 1.15 0.2 0.23 0.09

Subliminal Nonthematic 0.00 0.00 0.02 0.02

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However, thematic relatedness did not show a main effect for false positives, F (1, 44)

= .19, p = .67, partial η2 = .00. Similarly, there was no statistically significant interaction of

presentation and thematic-relatedness, F (1, 44) = .00 p = 1.00, partial η2 = .00. See Figure 2

for the main effect of presentation time on false positives.

Thematic Non Thematic0

0.05

0.1

0.15

0.2

0.25

0.208

0.229

0

0.021

The Main Effect of Presentation for False Posi-tives

Su;raliminal

Relatedness

Performance

Presentation

Figure 2. Main effect of presentation time on false positives. This graph does not show a

significant interaction of thematic relatedness with presentation for number of false

positives.

Covariates

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Finally, I examined the covariates, “Gender” and “Highest Education Achieved”, because

they were categorical variables with ordinal levels. However, I found no significant

relationships among the covariates.

Chapter 4

DISCUSSION

The results confirmed my hypothesis that older adults would produce a higher number of

correctly recalled words in supraliminal presentation and thematically related conditions and a

lower number of correctly recalled words in supraliminal presentation and non thematically

related conditions. This main result was consistent with the previous literature on how levels of

processing strengthened the effect of supraliminally presented stimuli on category exemplar

test performance (Bradshaw & Anderson, 1982). Additionally, performance on the free recall

exam was higher in thematic relatedness conditions than in non thematic conditions. This

finding resembles the results of the Craik and Lockhart (1972) study which shows the positive

effect of deep levels of processing on explicit memory. Similarly, performance on the recall

test was higher in supraliminal conditions than in subliminal conditions coinciding with Monti

et al.’s (1996) study showing how conceptually-driven aspects of memory tasks could mediate

the engagement of supraliminal processes; thereby, enhancing explicit memory test

performance. Notably, older adults produced more words on the recall exam that were not

presented in the video supraliminal presentation conditions than in subliminal conditions but

there was no difference in thematic and non thematic conditions. Supraliminality and the

application of cognitive effort seemed to have more of an effect on incorrect guessing than

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meaning-based memory processes such as levels of processing. Possibly, levels of processing

produces more accurate memory trace formations as a result of efficient neural network

activation whereas, conscious cognitive exertion of resources may be more useful in situations

that require the generation of ideas without the need for the accurate retrieval of exact memory

traces.

Limitations and Strengths

The elegance of this study’s design increases the strength of its internal validity. Because

the recall test was administered immediately after the study condition, the small time gap

between study and test increased the measurement’s accuracy for memory of the presented

words. The Latin-Square partial counterbalancing measure did not eliminate all bias; however,

it ensured that all relatedness and presentation conditions were viewed by each participant.

Equivalence of word lists’ variances also enhanced the strength of the present study.

The small sample size of forty-eight participants limited the power of my study by

increasing the risk of Type I error. Because I pooled my sample from a population within two

senior communities in the outlying areas of Sacramento, the sample was not representative of

the entire population of individuals over fifty-five years of age. I obtained the sample using a

convenience sample instead of using a random sample so I did not assume a normal

distribution of performance scores. Because I did not collect a random sample, the economic,

educational, and health characteristics unique to the senior communities sampled may have

biased the results in favor of individuals with high cognitive functioning and healthy lifestyles.

The sample also consisted of a disproportionate number of females compared to males.

Therefore, its limited generalizability to the universe of moderately healthy functioning older

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adults decreased its external validity and application to real world situations that would include

older low functioning individuals as well. If I were to replicate this study, I would restrict the

number of words to twenty because the current forty word list intimidated many participants

when they realized that the next exercise was an exam of the words presented on the screen.

Additionally, I would also set a time limit for the exam to reduce the bias of some participants

remembering more words than others simply because they had more time to remember the

words. I would increase my sample size to 100 participants and would allot more time to

participant recruitment increasing the number of letters sent out to senior centers within the

Sacramento region. I would include a Telephone Interview Questionnaire for Cognitive Status

to obtain a more accurate picture of the cognitive functioning status of the participant pool. I

would include in the questionnaire a question on “Age.” With the information on cognitive

status and “Age”, I could analyze the relationship between Age, cognitive functioning, risk for

dementia, and the age group’s test performance.

Future Directions

To further analyze the relationship between relatedness and presentation, one might want

to incorporate elements from human-computer interface psychology literature to produce

websites that will facilitate the engagement of older adults. Websites designed with age-

relevant meaning-based contextual cues can assist the recall of older adults by activating

associative frameworks within their cognitive substrates. This may have important

applications in the design of educational curricula in senior centers. For example, teachers

could use computers to present seniors with supraliminally-timed reading exercises that consist

of related material sparking, consolidation of short term memories and association formations

within cognitive networks. The results from this study may assist those older adults with a

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genetic history of Alzheimer’s disease because knowing how to facilitate recall could provide

older adults with a buffer against memory loss.

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