KRISTIN A DAVIS

Stephen F. Austin State University

Effects of Rhythmic Sound on a Visual Counting Task

This experiment examined interactions between visual and auditory sense modalities. Eighty participants performed a visual counting task accompanied by auditory noise, which was either slow (2 beats/s), medium (3 beats/s), fast (5 beats/s), or white noise (static). Attention to the auditory stimulus was manipulated to determine its effects on the expected cross-modal interactions. Test arrangements consisted of both asymmetrical and symmetrical configurations of 13 and 15 dots arranged in both near (1.27 cm) and far (5.08 cm) proximities, liesults indicated cross-modal effects for the medium sound rate so that response times were slower when attention to the auditory stimulus was given. This effect may be explained by interactions between saccadic eye movements, auditory stirn uli, and display configurations.

SENSORY INFORMATION CONVERGES IN THE BRAIN

to create a comple te percep t ion of the envi­ronment . Due to h u m a n reliance on vision, the

visual system has been studied in detail. However, the precise processes used by the brain to integrate visual input with the input from the o ther senses (i.e., o t h e r modes ) are no t well u n d e r s t o o d . Studying simple visual and auditory tasks and the ways in which the processing of these tasks interact can clarify the perceptual processes involved in cross-modal tasks.

Count ing is a basic process that usually relies on visual input , a l though information from other senses can also be used for count ing. C o m m o n count ing activities (e.g., count ing money) most often occur in an env i ronment where multiple sensory inputs are present . The influences that presumably extraneous sensory information exerts on the visual count ing process may help us to unders tand more complex cross-modal processing.

Quantification of objects has been proposed to occur through a variety of mental activities, which are often comprised of multiple cognitive steps. Lechelt (1971) showed that quantifying up to seven objects is almost automatic; he refers to this process as subitizing. More specifically, subitizing is defined as the imme­diate recognit ion of quantity that requires no pur­

poseful serial count ing for less than seven objects. Lechelt distinguished subitizing from two other types of mental activities, estimating and counting, that are used in de te rmin ing number . Estimating is multiple subitizing and adding to reach an approximate quan­tity. Count ing is the serial process of de te rmin ing precise quantities.

Research on the cognitive processes involved in serial count ing has suggested there are multiple steps in the count ing process. According to Lassaline and Logan (1993), any act of quantif icat ion requi res spatial indexing, mapp ing (to known numbers or quantit ies), and responding. Towse and Hitch (1997) proposed that the count ing process uses both visual part i t ioning and verbal labeling of objects, processes that are comparable to the processes described by Lassaline and Logan. Towse and Hitch assert that problems in count ing (e.g., an increase in errors or slow response times) may be due to the simultaneous performance of different cognitive processes.

In addit ion to the previously ment ioned cogni­tive processes involved in count ing , memory also appears to play an impor tant role in the count ing process. Lassaline and Logan (1993) d e t e r m i n e d that memory is necessary for count ing to take place because it plays a role in the th ree processes of

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SOUND RATE EFFECTS ON COUNTING • Davis

indexing, mapping, and responding. Towse and Hitch (1997) assert that the role of memory in counting is to facilitate counting each object only once. Inability to remember which items have been counted will hinder the process of accurate counting.

Other studies of counting have examined the more physical aspects of counting by studying physi­ological functions and behaviors linked with the visual system that might influence counting. Kowler and Steinman (1977) studied the use of saccades (rapid involuntary eye movements used in fixation) in visual counting tasks. The) found thai saccades aided the counting processes only when nonrepetitive objects were organized into distinct groups. However, when objects were in close proximity and highly similar, saccades hindered the counting process because they interfered with the kinesthetic methods of distin­guishing between the already counted objects and the objects that need to be counted. For objects placed far apart, the movement of the eyes offered a con­sciously detectable muscular sensation, which aided the counting process by allowing one to count the eye movements that occur. Consequently, Kowler and Steinman were able to show that the interaction between saccades and the spatial arrangements of stimuli is influential for counting.

In addition to object proximity, the item arrange­ment can affect the counting process. For example, Noro (1980) studied the counting of black dots on a white screen using both symmetrical and randomly arranged patterns. The relation between number of dots and response time was examined. For random patterns, a linear relationship occurred: Increases in counting time directly related to increases in num­ber of dots for patterns containing four or more dots. Symmetrical arrangements did not produce this same linear relationship between number of dots and counting time. Noro also found that the number of saccades used for counting symmetrically arranged patterns was more variable than the number of saccades used for counting randomly arranged patterns. This finding suggests that physiological pro­cesses (eye movements) used in counting can be di­rectly affected by the arrangement of dots in a display.

The role of cognitive and physiological processes in visual counting raises questions concerning the influence of other sense modalities on the visual counting process. Although no studies have speci­fically investigated cross-modal interactions with counting, much research has been dedicated to study­ing the role of cross-modal interactions for all of the five senses. For example, researchers have investigated interactions between vision and touch, the influence of color on taste and smell, and the interactions

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between bright tones and colored words (see Goldstein, 1999). More relevant to the current study is the research concerning cross-modal interactions between vision and hearing. Bolia, D'Angelo, and McKinley (1999) found that when directional audi­tory and visual stimuli were congruent, the auditory stimuli enhanced visual processing by decreasing three-dimensional search times. Similarly, Lewis (1971) studied interference effects between auditory and visual stimuli in a visual recall task and found that directionally congruent auditory and visual stimuli enhanced recall, whereas incongruent audi­tory distracters interfered with recall of the visual stimuli. Other studies have shown that visual and auditory stimuli may provide differing influences in cross-modal tasks. For instance, an asymmetrical interactive relationship was found between auditory and visual stimuli for a categorization task (Ben-Artzi & Marks, 1995; Melara & O'Brien, 1987). More speci­fically, the visual stimuli in these studies were found to more strongly influence auditory perception than auditory stimuli influenced visual perception. How­ever, neither the Ben-Artzi and Marks (1995) study nor the Melara and O'Brien (1987) study provided an auditory reference for the perception tasks, and this deficit made the pitch placement (i.e., high or low) of the auditory stimuli more ambiguous relative to the physical/spatial placement (i.e., high or low) of the visual stimulus, which always had the monitor screen edges as a visual reference. In contrast, Wilkerson and Scharff (2000) implemented an audi­tory as well as visual reference for the cross-modal perception tasks. With a midpitch auditory tone reference prior to each trial, less asymmetry occurred between the classification of visual and auditory tasks, although there were still cross-modal interactions. These studies exemplify the interactive relationship of auditory and visual information and their influences on perception.

The current study was designed to determine how three rates of rhythmic sound (slow, medium, or fast) and a white noise (static) would affect counting of objects that are placed in near or far proximity, in both symmetrical and asymmetrical arrangements. Previous research has independently studied both proximity (Kowler & Steinman, 1977) and arrange­ment (Noro, 1980) but not the possible interactions between the two types of configurations. Further, no previous research has investigated cross-modal influ­ences on counting tasks.

Based on the assumption that a certain internal rhythm is inherent in the serial counting process, I expected more interference by rhythmic auditory sounds when compared to the interference created

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SOUND RATE EFFECTS ON COUNTING • Davis

FIGURE 1

Reduced-size sample displays. Actual stimuli were enlarged and presented individually on an Apple Color Plus 14" monitor when presented in the experiment.

(a) Far proximity, asymmetrical arrangement, 13 dots; (b) near proximity, asymmetrical arrangement, 15 dots; (c) near proximity, symmetrical arrangement, 13 dots;

(d) far proximity, symmetrical arrangement, 15 dots.

by a nonrhythmic sound (white noise). Furthermore, the rhythm rate was expected to interact with prox­imity and arrangement clue to the incongruity between internal counting speed (determined by spatial arrangement and proximity) and the exter­nal influence on counting speed (provided by the sound rates). Specifically, the external rhythm was expected to create interference when display arrange­ments predisposed an opposing internal counting rhythm. For example, a slow rhythmic sound was expected to increase response times for counting when dots were placed close together (for which eye movements were expected to occur more rapidly). Conversely, the fast rhythmic sound was expected to decrease response times for close dots, but cause increased response times when dots were far apart due to the interference between the expected slow eye movements and the fast rhythm.

Finally, when attention to the auditory stimulus was not explicitly instructed, interference effects were expected to decrease due to the ability to selectively

attend to visual information (i.e., participants might be able to "tune out" the auditory stimulus).

Method Participants

One hundred and two undergraduates partici­pated in this study. Participants were obtained through sign-up sheets in the psychology department and received course credit for participating. Each participant gave informed consent and received debriefing forms upon completion of the session.

Design This study was a 4 (sound rate: white, fast,

medium, slow) X 2 (attention instructions: attend, no attend) x 2 (proximity: near, far) x 2 (arrangement: symmetrical, asymmetrical) mixed factorial design. The within variables were proximity and arrange­ment. All participants were tested using both the near and far proximities in both the asymmetrical and sym­metrical arrangements. The between variables were

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S O U N D RATE EFFECTS ON C O U N T I N G • Davis

sound rate and a t tent ion instructions. Thus, each participant was tested with only one type of auditory stimulus, and the two groups for each type of audi­tory stimuli received different sets of instruction re­garding at tent ion to the auditory stimuli.

Apparatus and Stimulus The displays consisted of e i ther 13 or 15 black

dots that were vertical ovals with an approx imate length of 1.27 cm. Quant i t ies of 13 and 15 were chosen to prevent subitizing (which occurs when count ing quantities of seven or lower). All displays were c rea ted using the drawing function in B / C PowerLaboratory software for Macintosh (Chute & Westall, 1996).

The dot proximity (edge to edge) was ei ther near (1.27 cm) or far (5.08 cm) , and dots were displayed in both asymmetrical and symmetrical arrangements . I'he dots were placed on a white background that covered the ent ire viewing area on an Apple Color Plus 14" monitor. Figure 1 shows samples of experi­mental displays in the neat and far proximities, the asymmetrical and symmetrical arrangements , and the 13- and 15-dot configurations. For each of the four combinat ions of proximity and ar rangement , there were 10 trials for both the 13- and 15-dot displays. There were also 3 practice trials, for a total of 83 trials per participant.

The rhythmic sound rates were generated using a Lowers synthesizer, model V-120 (Victor Company, Tokyo), placed at the front of the testing room. The rhythmic sound consisted of an alternating drumbeat with cymbal, which was the most distinct rhythmic sound available on the synthesizer. Identical sounds were used for all rhythm condi t ions with only the speed of beats changed to create slow, medium, and fast rhy thms . In the slow rhythm cond i t i on , the sound rate was set at 1 beat per s, and was audible at a range of 44 dB SPL to 52 dB SPL corresponding to the front and back of the testing room. The medium sound rate was 3 beats per s with a range of 45 dB SPL to 52 dB SPL, and the fast sound rate was 5 beats per s ranging from 46 dB SPL to 54 dB SPL. The whi te noise (stat ic) was g e n e r a t e d with an off-frequency radio setting, and had a loudness range o f 5 8 d B B to 72 (IBB.

Procedure There were 10 participants per condit ion tested

in groups of 2 to 15 participants depend ing on avail­ability. Each participant was seated at a computer and was asked to sign an informed consent form before proceeding. For the groups requir ing at tention to the auditory stimuli, participants were instructed to

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listen for changes in the volume or rhythm of the aud i to ry s t imulus d u r i n g the session. T h e o t h e r groups were told only that a noise would be playing as they performed the counting task. No actual sound changes occurred in any of the sessions.

Presentation software (B /C PowerLaboratory for Macintosh) randomized the display order lor each participant. In addition, specific key-press instructions were used to counterbalance for handedness . Half the participants in each group were instructed to press the P but ton when they counted 13 dots and the Q button when they counted 15 dots. The o ther par­t ic ipants were ins t ruc ted to d o the oppos i t e bv pressing P for 15 and Q for 13.

All par t ic ipants were instructed to use only a visual counting method, and were explicitly instructed not to use kinesthetic behaviors (i.e., movements of their hands or the mouse) to aid them in the count­ing process. O the r than the difference in at tention instructions and the noise conditions, all participants p e r f o r m e d the same task and received ident ical instructions.

The auditory stimulus was started and partici­pants began the test by reading the instructions on the compute r screen. Participants were instructed to count the dots on the screen as quickly and accurately as possible and report their answers according to the key-press instructions they were given.

The first three trials were practice trials. After each of the practice trials, the correct answer was dis­played. A blank screen followed each display (includ­ing the practice trials), which provided an oppor tu­nity for participants to ask questions between trials and allowed for self-paced testing by the participants. All stimulus displays were presented to the partici­pant until a key press was made, then response time was recorded. No response times were recorded for the pract ice trials. Average total testing t ime was approximately 12 min.

After comple t ing the visual count ing task, the groups that were instructed to at tend to the sound were asked to complete a written repor t describing any changes they detected in the sound dur ing the session. For both volume and rhythm rate, partici­pants were asked to report the detect ion of changes and the n u m b e r of changes that may have occurred (luring the session.

Results Of the 102 participants tested, 80 part icipants '

data were used in analysis. Data from 16 participants were el iminated due to high er ror rates (over 10% error) to eliminate participants who did not follow instructions (e.g., randomly answered without per-

ESEARCH 10.3 ..:'.. Kio-107/ ISSN 1089-4136).

S O U N D RATK EFFECTS ON C O U N T I N G • Davis

FIGURE 2

Mean response times (in seconds) and standard error bars for each sound type (fast, medium, slow, white) in both the attending and nonattending conditions. Whereas

the attention conditions are always slower, this is only significant for the medium sound rate.

•o C O o 0) U) 0)

E i-d) co c o Q. (/) CD

• Attention

No Attend

White Fast Medium

Sound Type

Slow

forming the c o u n t i n g task). An addi t ional 6 par­t ic ipants were r andomly e l i m i n a t e d to make 10 participants per sound group for each instruction type because the part icipant distr ibution was markedly skewed between condi t ions . Response times were sor ted by proximity (nea r and far) , a r r a n g e m e n t (asymmetrical and symmetrical), and n u m b e r of dots (13 and 15) for each participant, and the medians of each condit ion were de termined; medians were used to eliminate outliers from individual condit ions for each participant. Then the medians within each prox­imity and a r r a n g e m e n t for the 13-dot and 15-dot condit ions were averaged together for each partici­

pant . These means of the medians were analyzed using a 4 (sound type) x 2 (attention instructions) x 2 (proximity) x 2 (arrangements) mixed analysis of variance.

Two significant main effects and several inter­a c t i o n s were fo u n d . Nea r -p rox imi ty (1.27 cm) configurations (M= 6.1 s) required significantly more time to count than the far (5.OS cm) configurations (Af = 5.9 s), F(l, 72) = 4.97, p< .05. Instructions to attend to the auditory stimulus (.\/= 6.4 s) significantlv increased response times as compared to condit ions in which at tent ion was not specified (M= 5.6 s), /•"(!, 72) =7.12, / ;< . ( ) ! .

Standard Error of the Meai for Both Attend

Sound type

White (static)

Fast (5 beats/s)

Med (3 beats/s)

Slow (1 beats/s)

Attent

Asymmetrical

Far

.449

.585

.541

.302

Near

.449

.566

.682

.488

TABLE 1

is for Each Sound Type in Each Display Type ng and Nonattending Conditions

ion

Symmetrical

Far

.397

.563

.637

.469

Near

.397

.499

.705

.488

Asy

Far

.261

.459

.258

.467

No attention

nmetrical

Near

.397

.713

.194

.517

Symmetrical

Far

.524

.459

.192

.459

Near

.343

.488

.265

.518

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Sol M) R A H h i I l-cis o \ C O I M I M . Davis

FIGURE 3

Graph of the mean response times (in seconds) for each sound type for each configuration type in both the attending and nonattending conditions.

For each configuration condition, the medium sound rate conditions showed significantly slower counting times when attention to the auditory stimulus was instructed.

In contrast, not attending showed significant decreases in counting time for the medium sound rate. (See Table 1 for standard error values for each condition.)

•o c o %

0)

E i-Q) CO C

o Q. </> d)

cc

-A— Attention

- o — No Attend

-r 1 1 r-

W F M S

Asymmetrical Far

W F M S

Symmetrical Far

T 1 1 1 1 —

W F M S

Asymmetrical Near

F M S

Symmetrical Near

Sound Type

A significant interaction occurred between sound rate and attention, F(3, 72) = 2.83, p < .05. Tukey's HSD post hoc analysis revealed that response times increased for the medium-level sound regardless of configuration when participants were instructed to attend to the auditory stimuli, but attention led to no significant differences for the other sound rates (see Figure 2). This is contrary to the hypothesis that attention would cause increased interference for all sound types. An interaction between arrangement and proximity was also obtained, F( 1, 72) = 4.93, /; < .05. Response times lor the asymmetrical arrange­ment were more affected by dot proximity than were the response limes lor the symmetrical arrangement. Specifically, Tukey's HSD post hoc analysis showed that for the asymmetrical arrangement, near-proxim-itv response times were significantly slower than the

far-proximity response times for that arrangement, whereas proximity did not affect the response times for the symmetrical arrangement.

Finally, a significant four-way interaction was also obtained, F(3, 72) = 2.83, p < .05. Figure 3 shows a plot of means for each condition, and the standard errors for each condition are presented in Table 1. Response times were longer for the medium sound rate when participants were instructed to attend to the sound. Tukey's HSD post hoc analysis showed that this result is exaggerated within the near-proximity, asymmetrical-arrangement conditions and the far-proximity, symmetrical-arrangement conditions. When attention to the auditory stimulus was not specified, the medium sound rate was significantly associated with the shortest response times of all the sound types. In addition, there was a tendency for

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SOUND RATE EFFECTS ON COUNTING • Davis

the variance for medium sound rate conditions with­out attention instructions to be smaller than all other conditions. As seen in Figure 3, attention to the audi­tory stimuli for the slow and fast sound rates appear to show slight increases in response times; however, these increases were not significant. In general, the white noise conditions were least affected by atten­tion to the auditory stimuli.

Of the groups instructed to attend to the sound, all but 2 participants reported change(s) in either rhythm or volume despite the fact that no actual changes occurred.

Discussion The results of this study indicate that a cross-

modal interaction occurred between the auditory and visual stimuli, although much of the effect was dependent on attention to the auditory stimulus. Further, the dot configurations of the displays created individual effects on counting as well as interactive effects between the different configuration types.

In support of past research (Kowler 8c Steinman, 1977), the near-proximity configurations produced longer counting times for all conditions. Further inspection of the interaction between proximity and arrangement suggests that this proximity effect is driven by the large difference between response times for the near and far proximities in the asymmetrical but not the symmetrical arrangement. An arrange­ment effect was also found by Noro (1980); however, in his study, the dot proximity within the arrange­ments was not manipulated. The results of the present study show that proximity has an influence on count­ing time, and that the asymmetrical arrangements are more strongly affected by the proximity of the objects to be counted.

More specifically, the asymmetrical arrangement in the near-proximity condition produced the long­est counting times. This result is most likely due to saccadic interference that is known to occur in close-proximity arrangements of similar objects (Kowler & Steinman, 1977) coupled with greater difficulty counting asymmetrical configurations when the number of dots is greater than four (Noro, 1980). However, saccadic interference cannot be firmly established in the current study because saccades were not measured.

Based on the studies of Kowler and Steinman (1977) and Noro (1980), the shortest response times should have been for the symmetrical arrangement in the far proximity. Contrary to these expectations, however, the best response times were seen for the asymmetrical arrangements in the far-proximity configuration. This effect could be due to counting

106 PsiCm Copyright 2003 by Psi Chi. The

strategy. Some participants commented that count­ing the symmetrical patterns was easier when a group­ing strategy was implemented (e.g., the dots are grouped and then added), whereas counting the asymmetrical configurations was not aided by this strategy. Perhaps the estimating strategy is actually less time efficient than the serial counting strategy. A group-and-add strategy may have been used in Noro's study in which the asymmetrical configuration showed an increase in counting times as the number of dots increased, but the same trend was not seen in the symmetrical arrangements.

Attention to the auditory stimuli produced increases in counting time. Because the groups who received no instruction to attend did not need to retain any information about the auditory stimuli, they could easily ignore the noise in much the same way that a person would ignore the radio while read­ing. For the groups that were told to attend to the sound, they had to divide their attention between listening and visual counting. Thus, it is not surpris­ing that the necessity of simultaneously performing two tasks hindered one or both processes. Towse and Hitch (1997) also found that performing multiple cognitive tasks created detriments in at least one of the tasks.

On inspection of the interaction between sound rate and attention, the significant attention effects were seen for the medium sound rate only. The medium sound rate conditions led to the fastest response times when no attention was given to the auditory stimuli, but they showed tin- slowest response times for all conditions in which the auditory stimuli were attended. This effect may be explained by the timing of the saccadic eye movements as the eyes move from item to item within a display. Saccades themselves last 20 to 100 ins, whereas the fixations between them require approximately 200 ms (Matlin & Foley, 1997). The physiological constraints of these saccadic movements allow for a maximum of three to four fixations within 1 s. Thus for the fast (5 beats per s) and white noise (static) conditions, the sound rates were inconsistent with any naturally occurring saccadic eye movements. If participants voluntarily matched the slow rate (1 beatpei s), then they would have slowed their counting times, which was contra­dictory to testing instructions. However, the medium sound rate (3 beats per s) approximately corre­sponded to the normal number of saccadic move­ments per second in a scanning task (3 to 4 per s).

For the medium sound rate conditions in which no attention was instructed, the response times may have reached an optimal speed because the sound rate and the rate of saccadic eye movements were able

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SOUND RATE EFFECTS ON COUNTING • Davis

to become synchronized. The neural mechanisms that control the rate of saccades may have been influenced by the external rhythm (sound rate), thereby con­tributing to the synchronicity of the eye movements and the sound rate. Alternately, during the medium sound rate condit ions in which at tent ion was instructed, there was a need to perform two differ­ent tasks in which the stimuli induced behaviors that occurred at similar rhythms or frequency of occur­rence. This requirement may have caused increased counting times due to a greater interference between the tasks. Because both tasks required the same rhythm of behavior occurrence, attending to both auditory and visual stimuli may have required more effort to keep the two tasks separated.

In conclusion, the sound rates did not uniformly interfere with visual counting. Although the medium sound rate did produce some of the expected inter­ference effects, the effects were influenced by attention and display configuration. The effect for the medium sound rate (3 beats per s), which is presumably created by the physiological correlation between eye movements and attention to the audi­tory stimulus, suggests neural interactions between high-level processes (attention and counting) and low-level processes (eye movements).

Other high-level processes are likely to influence the perceptual processing for the tasks in this study. One example would be memory, as proposed by Towse and Hitch (1997) and Lassaline and Logan (1993). In addition, the possibility that grouping strategies were used when counting the symmetrical arrangements could mean that, for these displays, the serial counting process was not measured. The use of grouping strategies may decrease the need for memory in a counting task (much like chunking in a recall task), thereby changing the cognitive processes used. Thus, a grouping strategy may influence the role of memory in counting. Further, this alternate strategy for counting may have affected accuracy by exchanging speed for increased accuracy. In the cur­rent study, accuracy was not analyzed and excessively inaccurate data were discarded, therefore any effects on accuracy by possible alternate counting strategies could not be determined.

Future research could inspect the cognitive counting processes between arrangement types in more detail prior to inspecting the cross-modal influences. The possibility of variable counting strat­egies used for different display types needs to be clarified before further investigation of the cross-modal influences on these strategies is conducted. In addition, the possible interaction between high-and low-level processing found in this study indicates

that other high-level processes are likely to be influential for counting. Exploration of these possible influences on counting may lead to better research when examining the cross-modal influences on counting.

Finally, changes in the stimuli could produce different results than were obtained in this study. Using different types of sound (e.g., changes in pitch or volume, or in length and type of pulse) could change the perception of the auditory stimulus, thereby producing different interaction effects. The characteristics of the visual stimulus could be manipu­lated as well. For example, displays containing differ­ent object types could change the effects of object proximity seen in the current study. As noted by Kowler and Steinman (1977), saccadic interference in near-proximity configurations was increased by the object similarity within a display. Therefore, chang­ing the objects in the display would likely influence the effects of dot proximity on a counting task.

Further research into the cross-modal effects on counting is needed to fully elucidate the influences that may occur during the task. This type of percep­tual-cognitive information is required to more fully understand the ways the human brain functions in a multisensory environment.

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