The Effects of Cell Phone Conversations on the Attention and Memory of Bystanders

Abstract

The pervasive use of cell phones impacts many people-both cell phone users and bystanders exposed to conversations. This study examined the effects of overhearing a one-sided (cell phone) conversation versus a two-sided conversation on attention and memory. In our realistic design, participants were led to believe they were participating in a study examining the relationship between anagrams and reading comprehension. While the participant was completing an anagram task, the researcher left the room and participants overheard a scripted conversation, either two confederates talking with each other or one confederate talking on a cell phone. Upon the researcher's return, the participant took a recognition memory task with words from the conversation, and completed a questionnaire measuring the distracting nature of the conversation. Participants who overheard the one-sided conversation rated the conversation as significantly higher in distractibility than those who overheard the two-sided conversation. Also, participants in the one-sided condition scored higher on the recognition task. In particular they were more confident and accurate in their responses to words from the conversation than participants in the two-sided condition. However, participants' scores on the anagram task were not significantly different between conditions. As in real world situations, individual participants could pay varying amounts of attention to the conversation since they were not explicitly instructed to ignore it. Even though the conversation was irrelevant to the anagram task and contained less words and noise, one-sided conversations still impacted participants' self-reported distractibility and memory, thus showing people are more attentive to cell phone conversations than two-sided conversations. Cell phone conversations may be a common source of distraction causing negative consequences in workplace environments and other public places.

Full text

The Effects of Cell Phone Conversations on the Attention
and Memory of Bystanders
Veronica V. Galva
´
n
1
*, Rosa S. Vessal
1
, Matthew T. Golley
2¤
1 Department of Psychological Sciences, College of Arts and Sciences, University of San Diego, San Diego, California, United States of America, 2 Department of Liberal
Arts, D’Youville College, Buffalo, New York, United States of America
Abstract
The pervasive use of cell phones impacts many people–both cell phone users and bystanders exposed to conversations.
This study examined the effects of overhearing a one-sided (cell phone) conversation versus a two-sided conversation on
attention and memory. In our realistic design, participants were led to believe they were participating in a study examining
the relationship between anagrams and reading comprehension. While the participant was completing an anagram task,
the researcher left the room and participants overheard a scripted conversation, either two confederates talking with each
other or one confederate talking on a cell phone. Upon the researcher’s return, the participant took a recognition memory
task with words from the conversation, and completed a questionnaire measuring the distracting nature of the
conversation. Participants who overheard the one-sided conversation rated the conversation as significantly higher in
distractibility than those who overheard the two-sided conversation. Also, participants in the one-sided condition scored
higher on the recognition task. In particular they were more confident and accurate in their responses to words from the
conversation than participants in the two-sided condition. However, participants’ scores on the anagram task were not
significantly different between conditions. As in real world situations, individual participants could pay varying amounts of
attention to the conversation since they were not explicitly instructed to ignore it. Even though the conversation was
irrelevant to the anagram task and contained less words and noise, one-sided conversations still impacted participants’ self-
reported distractibility and memory, thus showing people are more attentive to cell phone conversations than two-sided
conversations. Cell phone conversations may be a common source of distraction causing negative consequences in
workplace environments and other public places.
Citation: Galva
´
n VV, Vessal RS, Golley MT (2013) The Effects of Cell Phone Conversations on the Attention and Memory of Bystanders. PLoS ONE 8(3): e58579.
doi:10.1371/journal.pone.0058579
Editor: Jan de Fockert, Goldsmiths, University of London, United Kingdom
Received August 8, 2012; Accepted February 6, 2013; Published March 13, 2013
Copyright: ß 2013 Galva
´
n et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reprod uction in any medium, provided the original author and source are credited.
Funding: V.V. Galva
´
n received a Faculty Research Grant from her institution, the University of San Diego. The funders had no role in study design, data collection
and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
* E-mail: vgalvan@sandiego.edu
¤ Current address: Clinical Psychology Program, Palo Alto University, Palo Alto, California, United States of America
Introduction
People spent an estimated 2.30 trillion minutes using their
wireless devices over the last year [1]. Cell phones, one subset of
these devices, are relied upon heavily for personal communication,
and are often used in public spaces [2]. Recent surveys indicate
that people are becoming more dependent on their cell phones.
Cell phones are increasingly replacing land lines and participants
described experiencing ‘‘a personal connection towards their cell
phone’’ [3]. People have reported feeling so emotionally attached
to their cell phones that they feel anxiety without their phones [4]
or feel they ‘‘can’t live without’’ them [5]. With more technological
capabilities, such as personal organizers and navigation devices,
people see the cell phone as an essential part of their everyday lives
and even feel that they have a ‘‘personal relationship’’ with their
phones [6]. Seventy-six percent of respondents also said their cell
phones were always on or on most of the time, and 24% felt they
had to answer their cell phones ‘‘even when it interrupts a meeting
or meal’’ [5]. With the increased presence and personal use of cell
phones, there is a greater likelihood that an individual will be
frequently impacted by cell phones because either they or someone
around them is using a cell phone.
Most cell phone research has focused on how using a cell phone
impacts the user. Much of the research has used a simulated
driving task to examine these effects and has found that drivers
using cell phones are slower to change speed or direction [7], and
are slower to brake and miss more red lights, regardless of whether
the device is held or ‘‘hands free’’ [8]. These cell phone effects are
strong enough that the chances of being in an accident are similar
to the risks of drunk driving [9,10] and the effects are not likely to
lessen with practice [11]. It is important to note that deficits
appear to be related to cognitive, and not motor, effects since
holding and dialing the phone were not significant factors [8].
Instead, it appears that impairment of visual attention leads to
cognitive impairments such that drivers ‘see’ less [12] and
remember fewer objects they directly looked at while driving [13].
While most research on cell phones has focused on drivers,
more recent research has shown pedestrians are also affected by
their cell phone usage. Pedestrians talking on cell phones have
impaired visual attention while crossing the street [14,15,16] to
such an extent that most pedestrians on cell phones did not see a
clown riding on a unicycle nearby [17].
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Cell phone use can clearly have a negative impact on the user’s
cognition particularly when the user is driving or crossing streets
on foot. A question worth considering is whether there is any
impact on bystanders who overhear cell phone conversations,
since there are possibly millions of bystanders to the millions of cell
phone conversations that take place yearly. Surveys have shown
that 82% of respondents are annoyed by others’ cell phone use in
public [5] and that the level of annoyance depends on the public
location [18]. However, only a few studies have experimentally
addressed the effects of cell phone conversations that are
overheard by bystanders. Monk and colleagues questioned
bystanders who overheard either a one-sided or two-sided
conversation at a bus stop or on a train [19,20]. Participants
found one-sided conversations more noticeable and intrusive. This
difference was not due to the presence of a cell phone since both
versions of the one-sided conversation (a person using a cell phone
or a person who spoke in a normal tone with a partner who
whispered) were viewed unfavorably [20]. Unfortunately, Monk
and colleagues were limited by the transportation authorities to
only five questions, and thus were unable to examine other issues
about the different types of conversations.
The only study thus far to examine the cognitive effects of one-
sided conversations on bystanders is a study by Emberson,
Lupyan, Goldstein, and Spivey [21]. In this well-controlled study,
participants were asked to ignore sixty seconds of speech that
occurred while they completed verbal tasks and motor tasks.
Participants were told they would hear speech from the computer
speakers and were asked to focus their attention on the computer
tasks. In the within-subject design, participants overheard different
types of auditory distractions (one-sided, two-sided, monologue,
and silence) over thirty-two verbal and motor trials. When
compared to the silent baseline, participants were more distracted
by overhearing a one-sided conversation than hearing either a
monologue or two-sided conversations. In a follow-up study,
Emberson and colleagues filtered the conversations, making the
speech incomprehensible. Unlike their first study, they found no
significant differences when comparing the monologue, two-sided
and one-sided conversations to the silent condition. The research-
ers concluded cell phone conversations are more distracting than a
typical dialogue because the content of a cell phone conversation is
less predictable [21].
Our study tests the cognitive effects of one-sided conversation
and serves as a bridge between research done in a well-controlled
laboratory setting and a completely naturalistic setting. We were
able, with the help of confederates, to have a realistic situation in a
controlled environment. In contrast to Emberson et al. [21],
participants were exposed to the conversation in a more natural
context; i.e. they were not informed that a conversation would take
place; they only heard one conversation one time and, more
importantly, were not aware that the conversation was part of the
study. The current study’s realistic context allows it to be more
generalizable to real-world situations in which people overhear a
conversation. In addition, participants were asked to work on an
attention task which they were told would impact their participa-
tion in the study, encouraging the participants to perform well on
the task. By using a laboratory setting, we were able to control
where the participant and confederates sat, the number of people
in the room, and outside distractors. The laboratory setting also
allowed us to test cognitive effects of overhearing the cell phone
conversation.
In our experimental paradigm, participants were led to believe
they were participating in a study examining the relationship
between anagrams and reading comprehension. While the
participant was completing an anagram task, the researcher left
the room under the pretext of needing to make more copies. The
participant overheard confederate(s) engaged in either a one-sided
or two-sided conversation while the researcher was out of the
room. After the researcher returned, she explained that the
purpose of the study was to see how a conversation affected a
person. The participant took a recognition test, assessing their
memory for words from the conversation, and completed a
questionnaire regarding the distractibility of the conversation.
Based on abundant experimental and survey research showing the
distracting nature of cell phones, we predicted one-sided
conversations would be more distracting than two-sided conver-
sations because of the unpredictable nature of a one-sided
conversation. It was hypothesized that participants exposed to
the one-sided conversation would be more distracted by it and
would thus make more mistakes on the anagram task, but perform
better on the memory task.
Methods
Ethics Statement
This study and consent process received approval from the
University of San Diego’s Institutional Review Board. Participants
provided their written consent to participate in this study. All
participants were 18 years of age or older.
Participants
Participants were 164 undergraduate students taking an
Introduction to Psychology class at the University of San Diego.
Fifteen participants guessed the purpose of the study and their data
was not analyzed. Of the remaining 149 participants, 110 were
female and 39 were male, with a mean age of 18.48 years
(SD = .778, range = 18–21; one participant declined to list age).
The ethnicities of the 149 participants were: 117 Caucasian, 15
Asian-American, 14 Hispanic, and 2 African American, and 1
Pacific Islander. Participants were recruited from the Psychology
Department’s participant pool. Introductory Psychology students
were required to either earn five research participation credits or
perform alternative assignments. This study counted for two
credits.
Materials
Demographics. The demographics contained questions
about age, gender, ethnicity, and primary spoken language. It
also contained four questions about reading interests and word
puzzles to maintain the perception that the study was about the
relationship between anagram performance and reading compre-
hension.
Anagrams. Anagrams were used as an attention measure
since the participant attempted to complete them while the
conversation was taking place. Two types of scrambled words were
used: easy anagrams, where first and last letters were in the correct
position so that only middle letters are scrambled (e.g., hosue = -
house), and hard anagrams, where all of the letters were scrambled
(e.g. suohe = house). This procedure was based on the methodol-
ogy of Foley, Foley, Wilder, and Rusch [22]. The two levels of
anagram difficulty have resulted in measureable differences in
performance, such as in the time it takes to solve easy versus hard
anagrams [23]. There were 15 easy anagrams and 15 hard
anagrams. Words varied in length from 4–7 letters. The easy and
hard categories had equal numbers of 4–7 letter words. In addition
the average meaningfulness (easy = 6.66, hard = 6.61), imageability
(easy = 6.18, hard = 6.36) and concreteness (easy = 6.08,
hard = 6.46) were similar across the easy and hard categories
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according to the word ratings from Paivio, Yuille, and Madigan
[24] and Fear [25].
Conversation. The conversation was a scripted conversation
that lasted approximately seven minutes and covered three topics:
a birthday party for dad, shopping for furniture, and meeting a
date at the shopping mall. A one-sided conversation was
conducted by a confederate talking on the cell phone; whereas
two-sided conversations were carried out by two confederates
speaking to each other. Confederates read the conversation off of a
computer screen during the study. Each speaker said 506 words.
Words that were tested on the recognition test only came from the
conversation uttered by the speaker seated next to the participant.
In both the one-sided and two-sided conversations, the confeder-
ate sitting next to the participant read from the same role in the
script. None of the words on the recognition tests were repeated by
the second speaker so that the participant only heard the
recognition words one time, even if he/she overheard a two-sided
conversation.
Manipulation Check. Participants answered the following
three questions to determine if they knew the purpose of the study:
‘‘What do you think the purpose of this study is?’’, ‘‘Do you have
any questions about this study?’’ and ‘‘Do you think there is any
other purpose to the study? If yes, please describe fully.’’
Recognition Test. A recognition test was used to assess
memory. This test took place approximately four minutes after the
conversation ended. It consisted of seventy words from five
categories. Participants were tested on their ability to discriminate
(1) actual words from the conversation, (2) related words (same
category as actual words), but not part of the conversation, and (3)
other categories with varying relatedness to the conversation topic.
Relatedness to the conversation topic was operationally defined as
the number of words from that category that appeared in the
conversation. For example, no words from the ‘beach’ category
occurred during the conversation. In contrast, 10 words, such as
‘‘potatoes,’’ that fit into the food category appeared in the
conversation. There were also six conversation words in the
‘school’ category and zero conversation words in the ‘household
items’ category. None of these conversation food words appeared
in the recognition test; for example ‘‘potatoes’’ did not appear in
the recognition test, but a new word ‘‘salad’’ did. Mistakes were
tracked to see if participants were more likely to make false alarms
for food words as opposed to beach words. This procedure was
meant to assess not only how many conversation words filter into
the participant’s memory, but also what type of content was
‘picked up’ by the participant. During the recognition test, one
word was shown on the computer screen at a time, and
participants were asked to determine whether each word was
part of the conversation they had just heard. To respond, the
participant was asked to choose their confidence level on a scale of
1–6, from ‘‘definitely not’’ to ‘‘definitely yes.’’ Responses included:
definitely not, probably not, maybe not, maybe yes, probably yes,
and definitely yes.
Distractibility Scale. A seven item self-report questionnaire
was administered on the distracting nature of the scripted
conversation. The questionnaire was adapted from Monk et al.
[19] and asked participants to rate how they felt while the
conversation was taking place. It included the following state-
ments: ‘‘I was surprised that the conversation was going on’’, ‘‘The
conversation was noticeable’’, ‘‘I found myself listening to the
conversation’’, ‘‘Did you believe that the conversation was real?’’,
‘‘The conversation was distracting’’, ‘‘I found the volume of the
conversation annoying’’, and ‘‘I found the content of the
conversation annoying.’’ The answers were on a seven point
Likert scale which ranged from strongly disagree to strongly agree.
Post-Experiment Interview. At the end of the study,
participants were asked about their thoughts regarding the study
(‘‘what were you thinking/feeling/considering doing?’’), whether
they were able to look at all the anagrams, and whether they were
able to hear both sides of the one-sided conversation. They were
also asked whether they had heard talk on campus about this
particular study and were asked again about the purpose of the
study.
Procedure
Subjects were randomly assigned to one of three conditions:
(1) two-sided conversation – participant heard both sides of a
conversation taking place between two confederates.
(2) one-sided/cell phone conversation – participant heard one
side of a cell phone conversation taking place between a
confederate and the researcher who was not in the room.
(3) one-sided conversation with silent confederate – participant
heard one side of a cell phone conversation, but there was also
a second, silent, confederate present. This condition was used
to determine if any differences between condition 1 and 2
were due to the different number of people in the room. It was
thought that if the silent confederate appeared to ignore the
conversation, the participant might also, making the results
more similar to a two-sided conversation.
Participants were led to believe they were participating in a
study examining the relationship between the ability to unscram-
ble anagrams and reading comprehension. Trained confederates
also appeared to be participating in the same study for research
credits. For the two-sided conversation (Condition 1) and the one-
sided conversation with silent confederate (Condition 3), two
confederates showed up for the study; while one confederate
showed up for the one-sided conversation (Condition 2). One
participant was tested at a time.
The researcher indicated where each participant should sit. The
room in which the experiment took place had three desks adjacent
to each other, each with its own desktop computer. The desks were
separated by a two-inch wide partial partition that extended
approximately three feet from the wall and was five and a half feet
high; the partition extended seven inches past the edge of the
desks. The participant sat closest to the door and the confederates
sat in the seats next to the participant, separated by the partition.
The participant and the confederates always sat in the same seats
so that the participant sat next to the confederate saying the half of
the conversation that all participants would hear. This seating
arrangement minimized differences between the volume of the
words overheard that would be later tested on in the recognition
task.
After seating the participant and confederate(s) and adminis-
tering the informed consent, the researcher described the study as
investigating the relationship between anagrams and reading
comprehension. The researcher explained that the results of the
anagram task would be used to determine which group each
participant would be placed in for the reading comprehension
portion of the study, thus imparting some consequences on the
participant’s anagram performance. The researcher gave the
participant a copy of the anagrams to unscramble. The researcher
then pretended to realize that the other anagram copies were bad
copies in which half the anagrams were not printed. The
researcher showed the participant and confederate(s) the bad
copies, apologized, and explained that he/she needed to leave the
room to make more copies of the anagrams for the other subject(s)
(the confederate(s)). The researcher instructed the participant to go
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ahead and complete the anagrams since they were only part of the
‘pre-experiment’, and that the researcher would pick up the
participant’s anagram answer sheet upon the researcher’s return.
After the researcher left the room, the confederate either received
a phone call from the researcher or engaged in a conversation with
the other confederate. For one-sided conversations, the cell phone
was placed out of view on the desk and was answered after the first
vibration. During the one-sided conversations, the confederate sat
next to the participant and read from the script. For the two-sided
conversations, only the confederate sitting next to the participant
said the words that were later included in the recognition task.
Upon the researcher’s return, the participant was given the
manipulation check in which they were asked to write down what
they thought was the purpose of the study. The confederates were
then excused and the participant was given a surprise recognition
memory test on the computer using MediaLab (Empirisoft).
Finally, the participant was asked a series of questions regarding
the distracting nature of the conversation (whether it was loud,
annoying, believable, etc.) on a Likert scale of 1–7, and were
interviewed about their thoughts regarding the study. The
participant was then debriefed, asked to maintain confidentiality
regarding the study, and thanked for their time.
Results
Participants’ data were not analyzed if the participant guessed
the purpose of the study (n = 15). This left 60 participants who
overheard the two-sided conversation, 56 who overheard the one-
sided conversation, and 33 participants who overheard the one-
sided conversation with a silent confederate. A three-way analysis
of variance (ANOVA) showed that the one-sided and one-sided
with silent confederate conditions were not significantly different
from each other on either the attention or memory tests (see
Recognition test and d’) so these two conditions were combined,
leaving 60 participants who overheard the two-sided conversation,
and 89 who overheard the one-sided conversation. A Chi-square
test comparing participants in the three conditions revealed that
participants in the three conditions were not significantly different
in regards to gender, ethnicity, and primary spoken language
(Table 1) or age (Table 2). A second Chi-square test comparing
participants in the combined one-sided group versus the two-sided
group also showed that participants were not significantly different
in their demographic characteristics (Tables 3 and 4).
Distractibility Scale
A Cronbach’s alpha was used to determine whether the seven
statements of the distractibility scale were measuring the same
concept. The distractibility scale had a Cronbach’s alpha of.752.
The item measuring the believability of the conversation had a
corrected item-total correlation of.072. Since the believability was
not related to the distractibility of the conversation, it was dropped
from further distractibility analysis. Believability was significantly
different between groups (one-sided, M = 6.31, SD = 1.21; two-
sided, M = 5.71, SD = 1.93; F(1) = 5.102; p = .025. However,
further analyses revealed that believability was not related to
performance on either the anagram or recognition task, or to any
performance differences between the one-sided and two-sided
conditions. The Cronbach’s alpha for the remaining six questions
on the distractibility scale was.796.
An overall distractibility score was calculated for each partic-
ipant by summing each participant’s responses to the remaining
six items of the distractibility scale. An independent sample t-test
indicated participants exposed to the one-sided conversation
reported more distraction (M = 28.517, SD = 5.872) than those
exposed to the two-sided conversation (M = 22.700, SD = 7.797;
t(102.682) = 4.915, p ,.001). A comparison between conditions
indicated that the distractibility scale did not meet Levene’s test of
Table 1. Demographic information for participants in the
one-sided, two-sided, and one-sided with silent confederate
conditions.
Conversation Type
one-sided two-sided one-sided silent
N%N%N %
Gender Female 45 80.4 43 71.7 22 66.7
Male 11 19.6 17 28.3 11 33.3
Ethnicity White 46 82.1 47 78.3 24 72.7
Hispanic 4 7.1 6 10.0 4 12.1
Asian 5 8.9 6 10.0 4 12.1
Pacific
Islander
1 1.8 0 0.0 0 0.0
African
American
0 0.0 1 1.7 1 3.0
First
Language
English 52 92.9 54 9.0 29 87.9
Other 4 7.1 6 1.0 4 12.1
doi:10.1371/journal.pone.0058579.t001
Table 2. Average age for participants in the one-sided, two-
sided, and one-sided with silent confederate conditions.
Conversation Type
one-sided two-sided one-sided silent
m (SD) m (SD) m (SD)
Age 18.4 (0.71) 18.5 (0.79) 18.6 (0.87)
doi:10.1371/journal.pone.0058579.t002
Table 3. Demographic information for participants in the
one-sided and two-sided conditions.
Conversation Type
one-sided two-sided
N%N%
Gender Female 67 75.3 43 71.7
Male 22 24.7 17 28.3
Ethnicity White 70 78.7 47 78.3
Hispanic 8 9.0 6 10.0
Asian 9 12.5 6 10.0
Pacific Islander 1 1.4 0 0.0
African American 1 1.4 1 1.7
First Language English 81 91.0 54 9.0
Other 8 9.0 6 1.0
doi:10.1371/journal.pone.0058579.t003
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equality of variances (F = 5.566 and p = .020) and therefore, we
adjusted the degrees of freedom from 147 to 102.682.
A multivariate analysis of variance (MANOVA) compared the
responses between conditions to the individual questions on the
distractibility scale (Figure 1). Participants who overheard the one-
sided conversation were more surprised that the conversation took
place (p,.0001), and rated the conversation as more noticeable
(p,.0001), and distracting (p = .037) than those who overheard the
two-sided conversation. They were also more likely to rate the
content (p = .020) and volume (p = .005) of the conversation as
annoying.
Anagram Data
The number of anagrams that were solved correctly and
incorrectly was tallied. Incorrect anagrams included responses in
which participants crossed out or erased their answers as well as
wrong answers. Paired-samples t-test revealed that participants
correctly solved more easy anagrams (M = 12.557, SD = 2.613)
than hard anagrams (M = 5.826, SD = 3.106; t(148) = 26.150,
p,.001; Figure 2). There was a significant difference between the
total number of anagrams that females (M = 19.000, SD: 4.195)
and males (M = 16.641, SD: 5.932) correctly solved;
t(52.10) = 2 2.289, p = .026 (Figure 3). The number of anagrams
solved correctly did not meet Levene’s test of equality of variances
(F = 6.854 and p = .01) and therefore, we adjusted the degrees of
freedom from 147 to 52.10. However, there were no significant
differences between the two-sided and one-sided conversations in
regards to number of anagrams solved correctly or incorrectly. In
addition, the number of easy versus hard anagrams that were
solved correctly also did not vary by condition (one-sided easy/
hard anagrams: 12.43/6.11; two-sided easy/hard: 12.75/5.4) as
revealed by a 262 ANOVA (anagram type6conversation type).
Recognition Test and d’
For the recognition task, participants’ responses were measured
in terms of d’, a formula that takes into account each participant’s
ability to correctly discriminate stimuli amongst novel distractors
[26]. d’ takes into account ‘‘hits’’ (correct identifications of
repeated words), ‘‘misses’’ (failures to identify repeated words),
‘‘correct rejections’’ (correct identifications of novel words), and
‘‘false alarms’’ (mistakenly identifying a novel word as a repeated
Table 4. Average age for participants in the one-sided and
two-sided conditions.
Conversation Type
one-sided two-sided
m (SD) m (SD)
Age 18.5 (0.77) 18.5 (.79)
doi:10.1371/journal.pone.0058579.t004
Figure 1. Average responses to distractibility scale. Participants’ averaged responses to statements on the distractibility scale. For example,
responses to the statement ‘‘While the conversation was taking place, the conversation was noticeable’’ could range from 1, ‘‘not at all noticeable,’’ to
7, ‘‘very noticeable.’’ A response of 4 indicated ‘‘neither noticeable nor not noticeable.’’
doi:10.1371/journal.pone.0058579.g001
Figure 2. Average number of correct easy and hard anagrams.
The average number of easy and hard anagrams that each participant
completed correctly, regardless of which conversation they overheard.
doi:10.1371/journal.pone.0058579.g002
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word). The formula is d’ = Z(hit rate) 2 Z(false alarm rate). Hit
rate = hits/(hits+misses). False alarm rate = false alarms/(false
alarms+correct rejections). In cases where the response rate was
0, the response was converted to 1/(2N) where N = the number of
trials [27].
A three way ANOVA comparison of the d’ for the on-sided
condition versus the two-sided condition and one-sided condition
with silent confederate revealed a main effect for conversation
type. (one-sided conversation, M = .65, SD = .56; two-sided
conversation, M = .31 SD = .48; and one-sided with silent confed-
erate, M = .57, SD = .69; F(2) = 5.487, p = .005). Post hoc tests
revealed that one-sided condition vs. one-sided with silent
confederate condition were not significantly different from each
other, p = .521. However, the one-sided condition was significantly
different from the two-sided condition, p = .002, and the one-sided
condition with silent confederate was also significantly different
from the two sided condition, p = .038. Since the one-sided
condition and the one-sided condition with silent confederate were
not significantly different from each other but both of these groups
were significantly different from the two-sided group, we collapsed
the data for the one-sided group with the one-sided with silent
confederate group.
There was a significant effect of conversation type on d’
(Figure 4). An independent samples t-test revealed that participants
exposed to a one-sided conversation had a larger d’ score on the
recognition test (M = .616, SD = .608) than those who overheard a
two-sided conversation (M = .311, SD = .481); t(147) = 3.256,
p = .001. We initially restricted data analysis to only those
participants who rated the conversation as moderately or highly
believable (believability . = 4, then believability . = 5, etc), but
the significance values on the recognition test did not change to
any notable degree. A univariate ANOVA revealed no interaction
between gender and conversation type. We analyzed the
individual components that are factored into d’ and found no
significant differences between conversation types on false alarms
made to the five word categories on the recognition task. However,
participants who overheard the one-sided conversation correctly
identified more words from the conversation, i.e. made more
‘‘hits’’, (M = 4.47, SD = 2.216) than those who overheard the two-
sided conversation (M = 3.75, SD = 1.819); t(147) = 2.092,
p = .038.
Recognition Test and Confidence Ratings
The confidence levels for different types of responses were
compared. Participants were more confident in their correct
rejections (M = 2.058, SD = .428) than their misses (M = 1.960,
SD = .545; paired samples t-test; t(148) = 2.993; p = .003;
Figure 5A), but there were no significant differences between
one-sided and two-sided conditions in regards to correct rejections
or misses. In contrast, participants who overheard the one-sided
conversation were more significantly more confidant in their ‘hits’
(M = 1.877, SD = .545) than participants who overheard the two-
sided conversation (M = 1.687, SD = .495; t(142) = 2.13, p = .035;
Figure 5B).
The accuracy for each type of confidence rating was also
calculated: 1) definitely (definitely yes and definitely not), 2)
probably (probably yes and probably not), and 3) maybe (maybe
yes and maybe not)(Figure 5C1 and 5C2). A multivariate anova
(MANOVA) revealed a significant difference for accuracy of
‘‘probably’’ ratings of words from the conversation (one-sided
conversation: M = 46.18, SD = 33.94; two-sided conversation:
M = 31.96, SD = 32.14; F(1) = 4.649, p = .033).
Discussion
We hypothesized that the self-report questionnaire, anagram
task, and recognition task would reveal that participants who
overheard the one-sided conversation would be more distracted
than participants who overheard the two-sided conversation. As
predicted, participants exposed to the one-sided conversation did
report being more distracted by the conversation than those who
overheard the two-sided conversation. In addition, those who
overheard the one-sided conversation had a more accurate
performance on the recognition task, and were more confident
and accurate in their responses to words from the conversation.
Although participants completed more easy than hard anagrams,
and females performed better on the anagram task than males,
there were no significant differences between the different
conversation conditions on the anagram task.
Figure 3. Average number of correct and incorrect anagram
responses by gender. The average number of easy and hard
anagrams that males and females answered correctly, regardless of
which conversation they overheard.
doi:10.1371/journal.pone.0058579.g003
Figure 4. Average d’ for each conversation type. The average d’
score for participants who overheard a one-sided versus two-sided
conversation.
doi:10.1371/journal.pone.0058579.g004
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Several components of the distractibility questionnaire were
significantly different between the two conditions. Participants
who overheard the one-sided conversation rated the conversation
as more noticeable, and distracting. They were also more surprised
that the conversation took place than participants in the two-sided
condition. Participants who overheard the one-sided conversation
were also more likely to rate the content and volume of the
conversation as annoying than those who overheard the two-sided
conversation. These results are in agreement with those of Monk
et al. [19,20]. Their participants rated the one-sided conversation
as more noticeable and intrusive, and were more likely to find
themselves listening to it. One important note is that Monk’s
participants found the volume more annoying even though the
researchers controlled for volume level of the conversation [19].
The annoyance that participants who overheard the one-sided
conversation felt is consistent with surveys that have shown people
are annoyed by other’s cell phone use in public [5,18]. This
annoyance may be caused by the ‘‘blurring of the distinction
between the public and the private sphere’’ [28]. For example,
people typically have personal, not business, conversations while
they use cell phones in public [2]. Bystanders who are exposed to
these personal conversations may not have much control over the
situation, thereby increasing their levels of annoyance and
frustration. Research has shown that bystanders in situations
where they are not free to leave (for example, waiting for or using
public transportation) often find cell phone conversations annoy-
ing [18,19]. Other research investigating the effects of lack of
control have shown that lack of perceived control can, in turn, lead
to an increase in stress responses [29,30].
In regards to results of the anagram task, females have been
shown to perform better than males on anagrams tasks [31], and
it’s not surprising that participants would complete more easy than
hard anagrams. However, we did expect to see a difference in
anagram performance between conditions and did not. Emberson
et al. [21] observed significant differences between the silent
condition and one-sided conversation, but not between the two-
sided conversation and silence, on their choice reaction and motor
tracking tasks. It is interesting to note that Emberson et al. did not
report any differences across attentional measures (verbal or
motor) between their one-sided and two-sided groups. Since
previous research did not reveal differences between conversation
types on their primary attention tasks, we concluded that perhaps
a different task that allows more attentional resources to be paid to
distractors might reveal attentional differences. Lavie [32] has
suggested, with support from many studies [33], that distractors
have a larger impact on an easy task versus a harder task. The
reason is that less attentional resources are used in the easy task,
leaving participants free to be distracted by irrelevant stimuli. Not
only does task load affect performance on the primary task, but it
also affects memory for the irrelevant distractors [34]. Memory for
unattended distractors is greater on tasks with low loads. We had
equal number of easy and hard anagrams. In the easy anagrams,
the first and last letters were in the correct position so that the
middle letters were scrambled; in the hard anagrams, all of the
letters were scrambled. Perhaps a future study using a greater
number of easy anagrams would reveal differences between
conditions on our paradigm.
In this study, participants who overheard the one-sided
conversation performed better on the recognition memory task
than those who overheard the two-sided conversation, indicating
that they remembered more words that were said in the
conversation. The one-sided condition’s better memory for the
conversation occurred despite an experimental design in which
participants were not asked to focus on the stimuli of interest. In
memory studies, the researcher typically knows that the partici-
pants attended to the stimuli; for example, the participant is asked
to study the stimuli or there is only one set of stimuli (e.g., [35]).
Even in covert memory studies, participants are often asked to rate
the stimulus on a particular dimension (e.g., [36]). However, in this
study, whether or not participants paid attention to the stimulus
was a decision that was left to each participant. Many participants
said that they tried to ignore the stimulus. This type of design likely
minimized differences between the two conversation conditions.
Thus, our paradigm may have attenuated overall memory
Figure 5. Re cogn itio n Test a nd Confidenc e Ratings. 5A.
Confidence levels for correct rejections and misses, regardless of which
conversation participants overheard. 5B. Confidence levels for hits for
participants who overheard a one-sided versus two-sided conversation.
5C. The accuracy of different types of confidence ratings (definitely,
probably, maybe) on the recognition test. Responses are shown for
participants who overheard one-sided versus two-sided conversations.
5C1. Accuracy of responses to repeated words. 5C2. Accuracy of
responses to novel words.
doi:10.1371/journal.pone.0058579.g005
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performance, yet exposed unique, intrusive, "attention grabbing"
aspects of a one-sided cell phone conversation.
Many studies have examined performance regarding unattend-
ed stimuli (e.g., [37,38,39]). The responses to the unattended
conversation in this study were stronger than those in some studies
[34,39,40]. However, it is difficult to compare our results with
these studies since their stimuli were very brief, 170 to 500 ms, and
participants were instructed to attend to the target stimuli and
ignore distractors. Another factor that may have improved
performance in our study is that the stimuli were in two different
modalities, visually-presented anagrams and auditory distractors.
According to multiple resources theory [41], performance on tasks
with simultaneously-presented stimuli from multiple modalities
shows less decrement than competing stimuli from the same
modality. This occurs because the multimodal stimuli are using
different attentional resources, and thus are not competing for the
same resources. It could be that the visually-presented anagrams
did not use the same attentional resources as the conversation and
thus made it easier for participants to process the conversation.
Perhaps the primary reason we found differences in d’ perfor-
mance is that participants chose to attend to the conversation
despite the researcher telling them that their performance on the
anagram task would impact their participation in the rest of the
study and that their answer sheet would be picked up upon the
researcher’s return. Lavie notes that this may also be a factor in
studies which do explicitly ask their participants to ignore
irrelevant stimuli: ‘‘According to the load model, the allocation
of attention is an automatic process in the sense that it cannot be
simply withheld at will because of the instruction to ignore task-
irrelevant objects’’ [34]. In our study, every participant attempted
the anagrams, and many participants appeared to pay some
attention to the conversation during the anagram task based on
their performance on the memory task. This study adds to the
body of research by suggesting that overhearing a cell phone
conversation competes for attentional resources that may have
otherwise been devoted to other tasks.
There were also significant differences between conditions in the
accuracy of high confidence responses on the recognition test.
Participants in the one-sided condition were more likely to be
correct when they said that words were ‘‘probably’’ part of (or not
part of) the conversation. When participants were unsure about a
word’s presence in the conversation and chose ‘‘maybe’’, there
were no significant differences between groups. Hoffman et al.
[38] have suggested that memory studies may have missed the
retention of unattended stimuli. They argue that the retention of
unattended stimuli is detectable if the confidence ratings for ‘‘no’’
responses (i.e., the participant says the word is not a repeated
word) are studied. They found that ‘‘no’’ responses to unattended
stimuli (misses) were less confident compared to ‘‘no’’ responses to
novel stimuli (correct rejections). Our comparison of confidence
levels for misses and correct rejections (mistakes versus correct
responses) revealed results similar to Hoffman et al.; participants
were more confident in their correct rejections than their misses.
In addition, participants who overheard the one-sided conversa-
tion were more confident in their ‘hits’ and their moderately high
(‘probably’) confidence responses were more accurate than those
in the two-sided condition. The stronger confidence ratings and
accuracy of the one-sided group could be due to some of the
factors that may have improved d’ performance in our study:
longer stimuli, different stimuli modalities, and participants
choosing to pay attention to the conversation.
The main strength of the current study is its realistic design.
Participants were led to believe that the conversation was not part
of the study. Similar to cell phone conversations in natural settings,
the conversations in our study had an element of surprise and
bystanders to the conversation decided themselves whether or not
to attend to the conversation. When people are distracted by a
conversation while working on a task, they are not usually warned
a conversation will take place. Moreover, if participants had been
asked to ignore the conversation, it might lessen the generaliz-
ability of the study. The current study is also unique in several
other regards. First, the participants heard the conversation only
one time as people would in naturalistic settings. Second,
participants were tested on two cognitive abilities, attention to
the anagram task during the conversation and memory for the
conversation after it ended.
A possible limitation of this study may be the difference in
number of words overheard in the two types of conversations.
Compared to the two-sided conversation, those who overheard the
one-sided conversation heard only half of the words. It’s possible
that participants who overheard the one-sided conversation
performed better on the recognition task because of experimental
confounds. Participants in the one-sided condition heard less noise
and had less information to remember, and possibly the
confederates spoke louder during the one-sided conversation than
the two-sided conversation. We did not control for the difference
in sound and word count which may have contributed to the
differences in distraction. Nevertheless, in Emberson et al. [21],
the participants in the one-sided conversation performed worse
than those in the two-sided conversation when both groups were
compared to the silent condition. The poorer performance of their
one-sided group occurred even though this group was exposed to
42% less words and noise. They attributed the poor performance
of the one-sided group to the unpredictability of the one-sided
conversation’s content, and not the difference in amount of speech
overheard. Emberson et al.’s [21] hypothesis was supported by
results in a follow-up study in which performance did not differ
between groups when conversation content was filtered out, even
though the two-sided group was exposed to almost twice as much
noise. Compared to predictable noises, unpredictable noises
appear to be better distractors because they caused slower reaction
times. However, when participants were given instructions to pay
attention to the sounds, all participants had slower reaction times.
Participants were able to tune out the predictable better than they
could random sounds [42]. In our study, the one-sided cell phone
conversation, with the missing content, could be described as
unpredictable. This supports previous research findings that one-
sided conversations are less predictable because they are missing
content [21].
Although the volume for each conversation type was not
recorded, attempts were made to ensure that each participant was
tested under similar conditions. For example, in order to reduce
between-subject volume differences, only the confederate sitting
next to the participant said the words that were tested on the
recognition task. While participants in the one-sided conversation
were more likely to rate the volume as annoying, the average
rating for the one-sided conversation was 4.35 on a scale of 1 to 7,
midway between a score of 4, neither distracting nor not
distracting and 5, slightly distracting. Thus it seems that the
volume of the one-sided conversation was only mildly annoying.
It’s possible that participants rated the volume of the one-sided
conversation as more annoying even though there were no volume
differences between the conversations. Prior research has shown
that participants can rate the volume of one-sided conversations as
more annoying even when volume is controlled [19].
Although, we did not record volume levels for the conversations
described in this study, we have completed a follow-up study in
which volume was recorded for 54 participants (n = 27 one-sided;
Cell Phone vs. Normal Conversation Distraction
PLOS ONE | www.plosone.org 8 March 2013 | Volume 8 | Issue 3 | e58579

27 two-sided). The conversation in the follow-up study was not
identical to the one described in this paper, but was centered on
the same list of words and was thus tested with the same
recognition test. Although, there were no significant differences in
volume between the two groups (one-sided volume = 55.09dB;
two-sided volume = 54.38dB), the d’ for the 1 one-sided conver-
sation was significantly greater than the d’ for the two sided
conversation (p = .028). Since both studies were conducted using
the same procedure in the same room, and d’ was significantly
different despite equal volume levels in the follow-up study, we
have reason to think volume probably played a negligible role in
this study.
It is likely that cell phone conversations would impact a
bystander’s cognition. Monk and colleagues [20] theorize that
people have a tendency to want to complete information that is
missing in order to make it understandable. Similarly, Hughes,
Vachon, and Jones [43] believe that people attempt to process and
integrate peripheral information (even if it’s to be ignored), and
when it is not possible to process and integrate, attention is
captured. Thus, it is expected that a one-sided cellphone
conversation would negatively impact a bystander’s cognitive
processing. Emberson and colleagues [21] demonstrated that
unpredictable content, but not unpredictable noise, negatively
affect performance. They also explored whether errors were due to
participants’ attempts to fill in the missing conversation during the
silent periods of the one-sided conversation. Participants made
more errors when the one-sided speaker began speaking after a
period of silence, in comparison with periods of silence and two-
sided conversations. Emberson et al [21] reason that bystanders to
cell phone conversation, unlike those exposed to dialogues, do not
know what turn the conversation will take when the cellphone user
speaks again after a silence. Attempting to process the conversa-
tion without the context provided by the prior speaker increases
the cognitive processing that a bystander must use.
This study is the first to have observed cognitive effects of cell
phone conversations on bystanders in a realistic context.
Participants rated the cell phone conversation as more distracting
and were more likely to remember content from the conversation,
even though they were working on another task and were unaware
that the conversation was part of the study. These results have
implications for workplace environments, transportation hubs and
other public areas. Future studies should explore how attention
and cognitive effects of cell phone use vary as a function of
conversation volume and content. Additionally, it will be
important to determine what types of tasks are subject to
performance impairments by overheard cell phone conversations.
Acknowledgments
The authors wish to thank A. Wray and A. Koenig for feedback on
experimental design, C. N. Smith for advice on d’, N. Goldschmeid for
statistical advice, and P. W. Vanderklish for insightful feedback on the
manuscript. The authors also wish to than k a large group of
undergraduates for help in designing and administering the study, and
also analyzing data.
Author Contributions
Edited manuscript: MTG. Conceived and designed the experiments:
VVG. Performed the experiments: VVG MTG RSV. Analyzed the data:
RSV MTG VVG. Wrote the paper: VVG RSV.
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