Reaction time and general intellectual ability: The ...

53
UNLV Retrospective Theses & Dissertations 1-1-1990 Reaction time and general intellectual ability: The effects of cues Reaction time and general intellectual ability: The effects of cues on the relationship on the relationship Nancy S Sirkin University of Nevada, Las Vegas Follow this and additional works at: https://digitalscholarship.unlv.edu/rtds Repository Citation Repository Citation Sirkin, Nancy S, "Reaction time and general intellectual ability: The effects of cues on the relationship" (1990). UNLV Retrospective Theses & Dissertations. 86. http://dx.doi.org/10.25669/4hfz-loqj This Thesis is protected by copyright and/or related rights. It has been brought to you by Digital Scholarship@UNLV with permission from the rights-holder(s). You are free to use this Thesis in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/ or on the work itself. This Thesis has been accepted for inclusion in UNLV Retrospective Theses & Dissertations by an authorized administrator of Digital Scholarship@UNLV. For more information, please contact [email protected].

Transcript of Reaction time and general intellectual ability: The ...

Page 1: Reaction time and general intellectual ability: The ...

UNLV Retrospective Theses & Dissertations

1-1-1990

Reaction time and general intellectual ability: The effects of cues Reaction time and general intellectual ability: The effects of cues

on the relationship on the relationship

Nancy S Sirkin University of Nevada, Las Vegas

Follow this and additional works at: https://digitalscholarship.unlv.edu/rtds

Repository Citation Repository Citation Sirkin, Nancy S, "Reaction time and general intellectual ability: The effects of cues on the relationship" (1990). UNLV Retrospective Theses & Dissertations. 86. http://dx.doi.org/10.25669/4hfz-loqj

This Thesis is protected by copyright and/or related rights. It has been brought to you by Digital Scholarship@UNLV with permission from the rights-holder(s). You are free to use this Thesis in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/or on the work itself. This Thesis has been accepted for inclusion in UNLV Retrospective Theses & Dissertations by an authorized administrator of Digital Scholarship@UNLV. For more information, please contact [email protected].

Page 2: Reaction time and general intellectual ability: The ...

INFORMATION TO USERS

The most advanced technology has been used to photograph and reproduce this manuscript from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer.

The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction.

In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion.

Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand corner and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book.

Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6" x 9" black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order.

U niversi ty Microfilms In te rn a t io n a l A Beil & Howell Inform ation C o m p a n y

3 0 0 N o r th Z e e d R o a d . A n n Arbor. Ml 4 8 1 0 6 - 1 3 4 6 USA 3 1 3 7 6 1 - 4 7 0 0 8 0 0 5 2 1 - 0 6 0 0

Page 3: Reaction time and general intellectual ability: The ...
Page 4: Reaction time and general intellectual ability: The ...

O rder N u m b er 1340597

R eaction tim e and general intellectual ability: The effects of cues on the relationship

Sirkin, Nancy S., M.A.University of Nevada, Las Vegas, 1990

Copyright ©1990 by Sirkin, Nancy S. All rights reserved.

UMI300 N. ZeebRd.Ann Arbor, MI 48106

Page 5: Reaction time and general intellectual ability: The ...
Page 6: Reaction time and general intellectual ability: The ...

REACTION TIME AND GENERAL

INTELLECTUAL ABILITY: THE EFFECTS OF CUES

ON THE RELATIONSHIP

ByNancy S. Sirkin

A thesis submitted in partial fulfillment of the requirements for the degree of

Master of Arts

in

Psychology

Department of Psychology University of Nevada, Las Vegas

May, 1990

Page 7: Reaction time and general intellectual ability: The ...

The thesis of Nancy S. Sirkin for the degree of Master of Arts in Psychology is approved.

irson, tTerry i.Knapp]Chairperson

Committee Member, [Joseph F. Raney]

Examining Committee Member, [Don Diener]

Graduate Faculty Representative, [Shirley Emerson]f

uGraduate Dean, [Ronald Smith]

University of Nevada Las Vegas, Nevada

May, 1990

Page 8: Reaction time and general intellectual ability: The ...

ABSTRACT

This study examined the relationship between reaction time (RT)

and intelligence. Fifteen female and nine male Caucasian

undergraduates and one black male undergraduate ranging in age from 19

to 38 served as subjects. The measure of intelligence was the

Otis-Quick Scoring Mental Ability Test. An Apple Macintosh personal

computer was used to present stimuli and measure reaction time. There

were four RT conditions; simple reaction time, and three complex

conditions in which no cue appeared, a correct cue, or an incorrect

cue appeared. A significant correlation was found between the correct

cue/no cue difference score (r=-.43, p < .05).

iii

Page 9: Reaction time and general intellectual ability: The ...

TABLE OF CONTENTS

Abstract............................................................ iii

List of Tables........................................................v

List of Figures......................................................vi

Introduction.......................................................... 1

Method............................................................... 11

Results.............................................................. 15

Discussion........................................................... 29

Appendix............................................................. 33

References........................................................... 39

iv

Page 10: Reaction time and general intellectual ability: The ...

List of Tables

Table 1. Parameters of RT Studies Correlated withIntelligence.......................................................4

Table 2. Mean of Mean Medians and Mean StandardDeviations for Reaction Time Conditions......................... 16

Table 3. Mean Number of Type of Errors forEach Reaction Time Condition.....................................19

Table 4. Correlation Coefficients of RT ConditionsWith Each Other.................................................. 20

Table 5. Correlation Coefficients Between the Otis and RT Means, Standard Deviations and DifferenceScores............................................................ 23

Table 6. Mean of Mean Medians and Mean StandardDeviations for Reaction Time Conditions......................... 26

Table 7. Correlation Coefficients Between the Otis and RT Means, Standard Deviations, and DifferenceScores............................................................ 28

Table 8. Comparison of Sirkin and Petrie Results................. 30Table 9. Mean of Median and Standard Deviation

for RT Conditions by Individual Fingers......................... 36Table 10. Mean Reaction Times, Standard

Deviations, and Mean Reaction Time Differencesfor Each Subject for Each Condition............................. 37

Table 11. Fastest Reaction Time for Each RTCondition for Each Subject.......................................38

v

Page 11: Reaction time and general intellectual ability: The ...

List of Figures

Figure 1. Apple Macintosh Plus Display Screen,Keyboard and Mouse............................................... 12

Figure 2. Mean of Mean Median Reaction Timesfor All RT Conditions............................................ 18

Figure 3. Frequency Distribution of ConvertedOtis "Gamma IQ" Scores for 25 Subjects.......................... 22

Figure 4. Frequency Distribution of ConvertedOtis "Gamma IQ" Scores for 25 Subjects.......................... 25

Figure 5. Mean of Mean Median Reaction Timesfor All RT Conditions............................................ 27

vi

Page 12: Reaction time and general intellectual ability: The ...

INTRODUCTION

During the past six decades many studies have been sought to

determine the relationship between Reaction Time (RT) and

intelligence. While studies have produced mixed results, Arthur J.

Jensen (1980, p. 104), a leader in the field, has stated that "The

first and most general conclusion we can draw with a great deal of

confidence is that measurements of RT parameters in a variety of

paradigms are indeed significantly related to scores on standard tests

of intelligence and other psychometric abilities."

Jensen is primarily referring to his own research (1979, 1980,

1981, 1987, 1989), in which he employed a task modelled after Roth

(1964). In Jensen's task, a subject sits in front of a panel with

eight green lights equidistant from each other and arranged in a

semi-circle. Eight pushbuttons corresponding to each of the green

lights are placed on the inner part of the semi-circle. The subject

rests one finger on a home button located in the center of the

semi-circle. When a light is illuminated, the subject moves his/her

finger from the home button to the pushbutton which corresponds to the

illuminated light. Subjects are presented with 1, 2, 4 or 8 stimulus

alternatives (0, 1, and 3 bits of information). In this task RT is

separated into two components. Decision time (referred to as RT by

Jensen) is the time between the onset of the stimulus and the release

of the home button, and movement time (MT) is the time required to

Page 13: Reaction time and general intellectual ability: The ...

2

depress the pushbutton which corresponded to the stimulus

alternative. Independent measures for RT and MT and their correlates

with a standard test of intelligence are obtained.

Jensen considered the following parameters the most important in

RT research as they are found to significantly correlate with

intelligence; the intercept and slope of the regression of median RT

on bits, the mean of the standard deviation (SD) of RT for each level

of task complexity, the slope of the SD of RT on bits, the mean median

movement time (MT), and the SD of MT.

The intercept has been found to be the most easily influenced of

the parameters by variations in experimental procedures and

apparatus. Intraindividual variability in RT as measured by the

standard deviation of an individual's RT over repeated trials appears

to be most thoroughly related to levels of intelligence. A negative

correlation between intraindividual variability in RT and IQ has been

found within all levels of intelligence ranging from university

students to the severely retarded. These parameters have been found

to be negatively correlated with g. G refers to a general ability

factor with the basic idea being that the level of a person's

intelligence is directly related to the speed of neuronal conduction

produced. Assessments of mental abilities have been found to be

intercorrelated despite differences in theory or differences in the

tests themselves and g has been found to account for a significant

source of the variance among these assessments. Jensen (1980b)

cautions that an individual's median RT varies from day-to-day for

complex RT and that the parameters which show the highest correlations

Page 14: Reaction time and general intellectual ability: The ...

3

to IQ, have the lowest day to day reliability. Simple RT tends to

remain stable on a day-to-day basis.

Reaction Time and 10 Studies Briefly Reviewed

A comprehensive list of frequently examined parameters in RT-IQ

research is presented in Table 1. Several of these studies warrant

further discussion.

In the earliest of Jensen's studies, he and Munro (1979) examined

39 ninth grade girls using the Raven's Standard Progressive Matrices

(SPM) as the measure of intelligence. A linear relationship of RT to

bits (amount of information) for individuals was found. MT was found

to vary slightly in relation to the amount of information presented.

Jensen & Munro (1979) expected that the slope of regression of RT on

bits would show the highest correlation with Raven scores. To their

dismay, the correlation between Raven scores and the slope of

regression of RT on bits was nonsignificant -.30 (p=.06). A

nonsignificant correlation was also found for mean SD of MT, (+.07)

and for the slope of regression of MT on bits (r = +.05). Significant

negative correlations were found for mean median RT -.39 (p < .02);

mean SD of RT, -.31 (p < .05); and mean median MT, -.43 (p < .01).

Jensen & Munro (1979) hypothesized that the different correlations

found for mean SD of RT and the mean SD of MT reflect different

components of information processing capacity.

Vernon (1983) has conducted the most comprehensive,

methodologically sound study of RT and IQ relationships to date. He

used five tests of speed-of-processing with 100 university students to

examine a variety of information-processing variables. These included

Page 15: Reaction time and general intellectual ability: The ...

4

Table 1

Parameters of RT Studies Correlated with Intelligence

Author(s)Mean

Median RTMean

SD of RTRT

SlopeRT

Intercept

Jensen and Munro (1979) -.39* -.31* -.30 _Bockrath (1980) -.42** — — —Smith and Stanley (1980) .20 .15 — .05Gay (1981)Jensen, Schafer, and Crinella

-.13 -.24* -.14 -.07

(1981) -.13 -.44 — —Vernon (1981) -.24* -.32* -.23* -.16*Carlson and Jensen (1982) -.54 -.71** -.20 —Nettlebeck and Kirby (1983) Sen, Jensen, Sen, and Arora

— -.66** -.56** -.40**

(1983) -.43** — — —Small, Raney, and Knapp (1985) -.34 -.18 .02 -.38*Petrie (1986) — -.42* — —Small, Raney, and Knapp (1987) -.44 — — —

* E < .05.** £ < .01.Partially based on Table 1 of Petrie (1986).

Page 16: Reaction time and general intellectual ability: The ...

5

speed of encoding, short-term memory scanning and efficiency of

short-term memory storage and processing, long-term memory retrieval,

and simple and choice reaction time or decision making speed. He also

compared the intercorrelation that existed among the tasks and the

multiple R's collectively produced by their parameters to measures of

intelligence. The Wechsler Adult Intelligence Scale (WAIS) and the

Raven Advanced Progression Matrices were employed as the measures of

intelligence.

Vernon suggested that individual differences in intelligence, to a

certain degree, may be the result of differences in the speed or

efficiency that individuals perform the aforementioned information

processing variables. Multiple regression analysis indicated an

obvious relationship between the cognitive tests used in Vernon's

study and measures of intelligence. Speed and a consistency of

response highly correlated with each other and appeared to be jointly

related to an individual's information processing capability.

Small, Raney, and Knapp (1985) replicated portions of Vernon's

(1983) study. Twenty-eight university students were administered the

WAIS-R as well as completing the Jensen RT task. Small, et al (1985)

found that RT increased as a function of bits as Vernon (1983) did in

his study. RT parameters were found to be negatively correlated with

WAIS subscales. However, the majority of significant correlations

were with the performance scales of the WAIS. The only general RT

parameter significantly correlated to full scale WAIS scores was RT

intercept, -.38 (p < .05).

In a related study, Small, Raney, and Knapp (1987) compared

Page 17: Reaction time and general intellectual ability: The ...

6

Jensen's RT task to one similar in concept, yet easier to administer.

This task was similar to that of Stanley and Smith (1980), and is

referred to as the Keyboard task. In the Keyboard task subjects sat

at a portable computer with their index and middle finger of their

right hand on two adjacent keys on the bottom row of the Keyboard.

The same was done with the left hand on the left side of the

Keyboard. Each finger corresponded to an outlined rectangular block

on the screen. Following an auditory warning signal, a dot appeared

tinder one of the rectangular blocks. Subjects were instructed to

press the corresponding key. Subjects were the same as those used in

the previously discussed Small, Raney, and Knapp (1985) study. They

found a correlation of r=.87 between the Jensen median decision time

and the Keyboard RT for the single RT condition and a correlation of

r=.75 between the four light median decision time and Keyboard RT for

choice RT. For simple and choice RT, Small, et al (1987) found

noticeable similarities between the Keyboard task and the Jensen task

in relation to Verbal IQ, Performance IQ, and Full Scale IQ.

Jensen's task has been criticized for a possible spatial factor

which may effect choice RT's and be shared with some measures of

intelligence (Longstreth, 1984). Also Jensen's task has been

criticized for methodological issues of counter-balancing, visual

attention effects, and response bias. The Keyboard task requires more

precise motor responses and decision and movement time are not

separated. The rationale behind the Keyboard task and combining

decision and movement time is that the time used to program

differential motor responses may increase the predictive capacity of

Page 18: Reaction time and general intellectual ability: The ...

7

the reaction task.

Petrie (1986) assessed differential reaction time and general

intellectual ability; however, she employed the Keyboard task

developed by Raney and Knapp to assess RT. Petrie (1986) used a four

choice RT task (termed Child task) and an eight choice task (termed

Adult task) with 42 university students. Level of intelligence was

measured by the Otis-Quick Scoring Mental Ability Test.

Petrie (1986) found that as the complexity of the task increased

so did the mean median RT and standard deviation scores. All subjects

had higher RT scores on the Adult RT task than the Child RT task, and

the two were significantly correlated, .63 (p < .05). Of the various

RT parameters examined, only the mean SD of the four choice RT task

was found to be significantly correlated with IQ, -.42 (p < .01).

Petrie's findings offered only limited support for a significant

relationship between RT and intelligence. She suggested this may be

due to the fact that previous studies have employed intelligence

measures which incorporated verbal and performance measures. The Otis

is strictly a verbal measure of intelligence.

The Effects of Cues Briefly Reviewed

Previous studies focusing on the relationship between RT and

intelligence have manipulated the complexity of stimuli through

increasing the number of stimulus alternatives. There are other ways

of introducing complexity, however. One is through the use of cues to

indicate which stimulus alternative the subject should prepare to

respond to.

Research has recently begun to examine the effects of cues on

Page 19: Reaction time and general intellectual ability: The ...

8

reaction time. Some studies have examined the effect of a previous

stimulus (S1) on a second stimulus (S2) in relation to alternation

and repetition effects. When a stimulus is the same as the preceding

stimulus, there is a tendency for subjects to respond faster. This is

known as a repetition effect. Alternation effects occur when the

response to a stimulus is faster when the stimulus preceding it was

different. It is possible that the positive effects of a valid cue

and the negative effects of an invalid cue are a result of category

repetition and category alternation respectively.

Cues must be identified or categorized and it is unlikely that

subjects can just ignore a cue in order not to respond if they are to

benefit from the cue. Responding to a cue may require subjects to

inhibit their selection or execution to a response associated to the

cue's category or identity. Inhibition of the response may carry over

to the next trial resulting in an increase in RT for valid cue trials

in relation to RT on invalid cue trials. An increase in RT due to

category repetition will have a positive non-informative effect and RT

inhibition will have a negative non-informative effect in cueing

experiments.

Harvey (1980) examined the effects of non-informative attributes

of cues upon RT. He suggested that under some conditions the effects

of response inhibition can override any positive non-informative

effects of category repetition. He employed high and low stimulus

categories in both auditory and visual modalities which were varied

across experimental conditions. In Experiment I Harvey (1980) looked

at category relation and modality combination effects. For category

Page 20: Reaction time and general intellectual ability: The ...

9

relation effects, even though S1 contained no information about the

S2 category, subjects did not ignore S.̂ suggesting subjects are

not able to ignore irrelevant information. Additionally, there was

found a negative non-informative effect of the cues. Harvey (1980)

interprets these results as support for a carryover of response

inhibition from to S2 when it arrived.

An effect was also found for modality combination. RT was as fast

to an auditory S2 whether it followed a visual or auditory S^.

However, RT to a visual S2 was faster when it followed an auditory

than a visual S^. This finding suggests that auditory cues

capture attention more automatically and are more alerting than visual

cues. In his second experiment, Harvey (1980) further examined

category relation and modality combination effects finding similar

results to his first study.

Other studies involving cues have focused on the relationship

between detection, focus of attention and the structure of the visual

system. Posner, Snyder, and Davidson (1980) examined the relationship

between orienting and detecting processes with the task of reports in

the presence of a visual signal. Orienting is the direction in which

attention is pointed and detecting is the contact between the input

signal and the attentional system so that an arbitrary response can be

made to it. Posner, et al (1980) found that knowledge about the

location of where a stimulus will occur affects the efficiency of

detection. In addition, depending on whether a general set is

maintained over trials or a precue is provided on each trial will

influence the kind of effect found. Therefore, knowing where a

Page 21: Reaction time and general intellectual ability: The ...

10

stimulus will occur yields benefits when used actively (cued) but not

when used to maintain a general set (blocked). They suggested, based

on their results, that there is an interaction between the structure

of the visual system and the structure of the attentional system.

Detecting occurred more quickly when subjects were provided with cues

allowing them to carry out the act of orienting. It followed then,

that orienting would be either parallel to or precede detecting.

Hypothesis

It has been shown that higher IQ subjects tend to have shorter

RT's in comparison to lower IQ subjects as condition complexity

increases, where condition complexity is a matter of increased number

of stimulus alternatives. Based on this finding, it would be a

reasonable assumption that higher IQ subjects would better utilize

provided stimulus alternative information than lower IQ subjects. The

current study focused on the relationship between reaction time and

intelligence but with an additional dimension of complexity. Subjects

received cues, either correct or incorrect, or no cue as to which

stimulus alternative they were to respond to. The Keyboard task, as

developed by Raney and Knapp, was employed to assess RT. It was

hypothesized that higher IQ subjects will utilize both the incorrect

and correct cues provided to them more efficiently and thus have

shorter RT's under both conditions than lower IQ subjects.

Page 22: Reaction time and general intellectual ability: The ...

METHOD

Subjects. Fifteen female and nine male Caucasian subjects and one

black male subject were solicited from undergraduate students in

Abnormal Psychology and History of Psychology classes. Participants

received extra course credit for their involvement.

Apparatus. The Otis-Quick Scoring Mental Ability Test, Gamma

Test: Form Fm, was used to measure general intellectual ability. The

Otis is a verbal test of knowledge and mental skill acquired by an

individual. It is a group administered, time limited test, which is

hand scored and contains 80 items which address vocabulary, analogies,

similarities, antonyms, and arithmetic reasoning. Using the

Spearman-Brown formula, split-half reliability has shown the Otis to

have reliability coefficients between .88 and .92 (Otis, 1954).

An Apple Macintosh Plus personal computer was used to present

stimuli and to measure response latency (see Figure 1). This

apparatus included a display screen where the subject viewed the

stimuli. In front of the screen was a keyboard similar to a

typewriter keyboard. A limited number of keys were employed for

subject responding to the RT stimuli.

Procedure. The Otis was administered to subjects during their

regular class period. Testing procedures were in accordance with the

instructions in the Otis manual (Otis, 1954). The tests were hand

scored by the experimenter twice to ensure accuracy. The raw scores

Page 23: Reaction time and general intellectual ability: The ...

(D irplay Screen)

mi mi

nn nno o o o o o o oCMditina am.IV

12

(Monitor)

(Mouse)

(Keyboard)

x - Subjects* finger positions fo r RT task

FIGURE 1. Apple Macintosh Plus display screen, keyboard and mouse.

Displayed on the screens are what the subject sees at the start of

each trial. Subject presses corresponding key when one of the dots

goes solid black. Experimenter presses the mouse control to start each trial.

Page 24: Reaction time and general intellectual ability: The ...

13

were then changed into IQ equivalents according to the procedure in

the Otis manual (Otis, 1954).

The RT task was administered individually with each subject

receiving the same instructions prior to starting the RT task (see

Appendix A). During the instructions each of the four conditions was

modelled for the subject, and followed by 10 practice trials for each

of the conditions.

Subjects were seated in front of the computer using the bottom row

of keys. Specifically, subjects placed their fingers on the eight

keys closest to each of the shift keys. Each key corresponded to a

solid black rectangular box on the screen (see Figure 1). An RT trial

began with one or eight outlined dots showing under the rectangles

(see Figure 1) followed by the sounding of a tone indicating the trial

had begun. Between one and four seconds later one of the outlined

dots went solid black. It was the subjects' task to press the key

corresponding to the blackened dot as quickly as possible. In the

simple RT condition only one outlined dot appeared on the screen, thus

clearly indicating which key subjects would need to press.

For the three complex RT conditions, subjects were presented with

eight stimulus alternatives. Each complex RT condition differed in

the cueing information provided the subject. In the first eight

choice RT condition (no cue) subjects received no cue as to which

outlined dot would blacken. In the second eight choice RT condition

(correct cue) subjects were presented with a correct cue which

identified the specific stimulus alternative which would blacken. For

the third eight choice RT condition (incorrect cue) an incorrect cue

Page 25: Reaction time and general intellectual ability: The ...

14

was presented to subjects. In other words, the cue signalled that one

stimulus alternative would blacken when in actuality a different

stimulus alternative would blacken. For the latter two conditions,

where a cue was given, the cue was a quick dark flash which occurred

in the center of a stimulus alternative. The four RT conditions were

randomly presented to subjects and the experimenter initiated each

trial by pressing the mouse control. Trials were presented at a

steady pace.

Subjects completed a minimum of 160 trials. For each condition,

the simple RT condition and the three complex RT conditions, there

were 40 trials. If subjects made an error, they were given feedback

on the type of error made and the trial was repeated at another time

during the program run. There were three types of errors subjects

could make: first, button errors in which subjects depressed the wrong

button, second, anticipatory errors, whereby subjects responded prior

to the presentation of the stimulus alternative, third, delayed

errors, in which subjects waited too long to respond.

Although subjects were informed they could request a break at

anytime, no subjects asked. Subjects received a 15 to 30 second rest

period at the halfway mark (80 trials) at which time demographic data

was gathered by the experimenter. The experimenter inquired about

age, typing skills, video game play time, and left/right hand

preference.

Page 26: Reaction time and general intellectual ability: The ...

RESULTS

The results from four subjects were excluded from the analyses.

One subject did not follow the instructions given for the Otis-Quick

Scoring Mental Ability Test which resulted in his/her bypassing an

entire page of the Otis. Therefore, an accurate measure of IQ was not

possible. A second subject had a larger simple RT than complex RT (no

cue) which might indicate they did not fully understand the task

requirements or failed to attend to the task. Finally two subjects'

data were excluded from the analyses because of age. These two

subjects were 16 and 20 years older than the oldest subject included

in the analyses. Subjects ranged in age from 19 to 38 years with a

mean age of 24.6 years.

There were more female than male subjects, 15 and 10,

respectively. All but two subjects were right handed. There were 18

subjects who had typing skills as opposed to seven subjects without

such skills. In connection with video game play, 18 subjects claimed

to be experienced in video game play, while seven stated they had no

experience.

Reaction Time

The Macintosh personal computer measures time in 1/60 seconds. In

order to facilitate comparisons with other research, this measurement

was converted to milliseconds. Table 2 presents the mean of mean

medians and the mean SD for the simple and complex RT conditions

Page 27: Reaction time and general intellectual ability: The ...

16

Table 2

Mean of Mean Medians and Mean Standard

Deviations for Reaction Time Conditions

RT ConditionMean of

Mean of Medians*Mean

Standard Deviations

Simplex 299.27 6.17

Complex 523.81 33.6

Correct Cue 433.48 35.15

Incorrect Cue 541.51 38.6

* All units are in milliseconds.

Page 28: Reaction time and general intellectual ability: The ...

17

collapsed across fingers; these data are plotted in Figure 2. The

results for individual fingers may be found in Appendix B. The mean

of mean medians for the simple RT condition was 299.27 msecs and the

SD was 6.17, while for the complex RT condition the mean of mean

medians was 523.81 msecs and the SD was 33.6. For the correct cue RT

condition the mean of mean medians was 433.48 and the SD was 35.15,

while for the incorrect cue RT condition the mean of mean medians was

541.51 and the SD was 39.6. It was found that as the complexity of

the RT condition increased from a simple to a complex RT condition, so

did the mean of mean medians RT and SD.

Individual subjects' mean RT's, SD's, and mean RT differences for

each condition are presented in Appendix C. It was found that 7 out

of the 25 subjects had shorter mean RT's under the incorrect cue

condition when compared to the complex no cue condition. When

subjects' fastest RT scores (see Appendix D) were examined, 11 out of

the 25 subjects' incorrect cue RT scores were shorter than or equal to

their no cue complex RT scores.

Errors

Subjects could make three kinds of errors. The error rates for

each type of error and for each RT condition are listed in Table 3.

The most common error made was button errors, i.e., pressing the wrong

key. The least number of button errors were in the simple RT

condition. The largest number of button errors were in the incorrect

cue condition.

RT Intercorrelations

Table 4 lists the correlation coefficients found among the mean

Page 29: Reaction time and general intellectual ability: The ...

Reaction Tim

e in

Msec

18

700

600

500

400

300

200

100

CC IC

FIGURE 2 . Mean of Mean of Median Reaction Tines for all RT conditions.

Page 30: Reaction time and general intellectual ability: The ...

19

Table 3

Mean Number and Tvoe of Errors for Each

Reaction Time Condition

RT Conditions 1 2 3

Simple .48 .08 .76

Complex 5.16 .12 .12

Correct Cue 3.64 .12 .08

Incorrect Cue 8.12 .36 .16

1 = Button errors.

2 = Anticipatory errors.

3 = Errors due to delayed responses.

Page 31: Reaction time and general intellectual ability: The ...

Tabl

e20

**

Page 32: Reaction time and general intellectual ability: The ...

21

median scores and standard deviations for each of the RT conditions.

The Pearson Product Moment Correlation was employed for the

correlation analyses. The different measures of RT were significantly

intercorrelated.

Otis 10

Figure 3 presents the distribution of the Otis IQ scores. The

Otis is normed for a mean of 100. The converted IQ scores ranged from

102 to 127. The mean IQ for subjects was 112.56 with a SD of 6.95.

All subjects were above the norm in intelligence for adults.

10 and RT Correlations

Differential RT scores were obtained for the complex correct cue,

and the incorrect cue conditions. These scores were derived by

subtracting the mean median value of the simple RT from each of the

complex RT values. Pearson Product Moment Correlations between the

Otis IQ scores and each of the difference scores were then

calculated. Table 5 lists these. The correlation between Otis IQ and

complex differential RT was .20. This is not a significant

correlation. The correlations between intelligence and correct cue

differential RT and the incorrect cue differential RT were .38 and .39

(p < .05), respectively. Although these correlations were

significant, they are not in the expected direction. Correlation

coefficients were also calculated between intelligence and the RT mean

medians for each condition and their standard deviations. These are

also listed in Table 5. The only significant correlation found was

between intelligence and the standard deviation of simple RT, -.42

(P < -05).

Page 33: Reaction time and general intellectual ability: The ...

22

X X

XX

XX

X X X

X X

X X X X X

X X X X X X X

XX

00CM

vOeg

eg

NCSJ

VO

CO•HoTJ0)4Ju<v

rioCJo(So

00o»~4

VOo

<ro

04O

P•Hl-l4JCO

>* • U COaa> o p a; o1 *n0) ,o u p fe co

vo in • in eg ov H • rH VOII II

Oo

Page 34: Reaction time and general intellectual ability: The ...

23

Table 5*

Correlation Coefficients Between the Otis and RT Means.

Standard Deviations, and Difference Scores

RT Variable and IQ Coefficients

Mean Simple -.37

Mean Complex -.24

Mean Correct Cne .01

Mean Incorrect Cue -.02

SD of Simple -.42 *

SD of Complex -.02

SD of Correct Cue .08

SD of Incorrect Cue -.14

Difference Scores (C-S) .20

Difference Scores (CC-S) .38 *

Difference Scores (IC-S) .39 *

* E < -05

Page 35: Reaction time and general intellectual ability: The ...

24

Because of the inconsistency of this study’s results with previous

findings, a closer examination of the data was undertaken. Two

subjects were found to have RT's for the simple and complex condition

which were significantly slower than the other subjects (see Appendix

C). Another analysis was done minus these two subjects reducing the

number of subjects from 25 to 23. Mean IQ for the remaining subjects

was 113.44 with a SD of 6.54. See Figure 4 for the new frequency

distribution.

Table 6 presents the mean of mean medians and mean SD's for the RT

conditions. These are plotted in Figure 5. Only the mean median of

the simple RT appreciably changed with the deletion of the two

subjects.

Table 7 lists the correlation coefficients between IQ and the RT

condition means, standard deviations, and the difference scores. The

only significant correlation found was between the no cue and correct

cue RT difference score and IQ, -.43 (p < .05). The correlation

coefficients between IQ and the difference scores of the complex,

correct cue, and incorrect cue conditions were -.17, .06, and .11,

respectively. None of these values are significant.

Page 36: Reaction time and general intellectual ability: The ...

25

X

X

XX

X X X

XX

X XX X X

X X X X X

X X

00egpH

VOeg IDiH eg

»HoUh

eg COp H 0)Uo

oCO

egeg tpH ©»

M

C0O 1eg 3pH o

eCO

•pH00 •Pp H op H

•p0)4JM

vO 0)pH >pH do

u

<* opHp H 0o

•pH4J9eg .O

pH •pHpH U

P00•pHQ

OpH ►» •p H O CO

d HJ0) oP Q>o 1 •*->00 0) ,o

O »H Pp H &H CO

St<• <co tr>i— l • tH 'OII IIQI X CO

Page 37: Reaction time and general intellectual ability: The ...

26

Table 6

Mean of Mean Medians and Mean Standard Deviations

for Reaction Time Conditions

RT ConditionMean of

Mean of MediansMean

Standard Deviations

Simple 284.34 30.9

Complex 520.27 45.0

Correct Cue 432.22 47.95

Incorrect Cue 538.24 48.2

* All units are in milliseconds.

Page 38: Reaction time and general intellectual ability: The ...

Reaction

Tine

in Msec.

27

700

000

500

400

300

200

100

CC 1C

Figure 5 . Mean of Mean Median Reaction Times for all RT conditions.

Page 39: Reaction time and general intellectual ability: The ...

28

Table 7

Correlation Coefficients Between the Otis and

RT Means. Standard Deviations,

and Difference Scores

RT Variable and IQ Coefficients

Mean Simple .02

Mean Complex -.14

Mean Correct Cue .06

Mean Incorrect Cue .10

SD of Simple -.14

SD of Complex .04

SD of Correct Cue .30

SD of Incorrect Cue -.06

Difference Scores (C-S) -.17

Difference Scores (CC-S) .06

Difference Scores (IC-S) .11

Difference Scores (C-CC) -.43 *

Difference Scores (C-IC) .32

* E < .05

Page 40: Reaction time and general intellectual ability: The ...

DISCUSSION

The present study found one significant correlation between RT and

intelligence. Although Jensen (1980, p. 113) pointed out that within

all levels of intelligence, ranging from the severely retarded to

university students, there has consistently been found a negative

correlation between IQ and the intraindividual variability in RT, this

was not true for the current study. A significant negative

correlation was found between IQ and the correct cue and no cue

difference score.

It is possible to directly compare the results of the simple and

complex (no cue) conditions of this study to those of Petrie (1986).

Table 8 presents the mean RT scores and their SD's for each condition

as well as their correlations to IQ for each of the studies. As can

be seen, similar results were obtained. Although the correlation

between IQ and the simple/complex difference scores were not

significant for either study, both correlations were in the same

direction. The correlation between IQ and the SD for complex RT was

also not significant for either study. However, the present study

found a slightly positive correlation whereas Petrie's (1986) found a

slightly negative r value.

This study differs from past RT research in its use of stimulus

cueing. When subjects were presented with a cue which warned them

ahead of time which stimulus alternative they would need to respond

Page 41: Reaction time and general intellectual ability: The ...

30

Table 8.

Comparison of Sirkln and Petrie Results

Petrie Sirkin

Simple* 306.1 284.34SD of Simple 77.7 30.9

Complex 554.6 520.27SD of Complex 123.3 45.0

IQ* 113.36 113.44SD of IQ 9.60 6.54

IQ r (C-S) Difference Scores -.01 -.17IQ r SD of Complex -.16 .04

* Mean values in milliseconds.

* Otis IQ Scores

Page 42: Reaction time and general intellectual ability: The ...

31

to, every subject responded more quickly. Subjects' speed of response

became shorter than their responses to the complex RT condition

without the cue information. It is suggested that the correct cue

allowed subjects to begin preparation for the required response,

thereby reducing their RT's. The incorrect cue had the opposite

effect for the majority of the subjects. Their RT scores were

increased as a result of the incorrect cue. It appears that cues

whose functions are to confuse or trick subjects are more difficult

for subjects to weed out and ignore, possibly making any preparation

on the subjects' part more difficult. In examining the SD's for the

correct and incorrect cue conditions, it appears that the correct cue

lessens variability in subjects' performance, whereas the incorrect

cue increased intraindividual variability.

Though RT's for error responses are not reported, subjects' RT's

followed the same pattern. This is consistent with findings from

other studies (Egeth and Smith, 1967 and Hales, 1968). Egeth and

Smith (1967) concluded that incorrect responses appeared to follow the

same processes as correct responses as they were susceptible to the

same task variables. However, for incorrect responses it does not

appear that the required processes are taken to completion as with

correct responses.

The correlation between IQ and the mean median complex condition,

-.14, although not significant was in the expected direction and

consistent with previous research. When a correct cue was added to

the task, again no significant correlation with IQ was found.

Possibly, the correct cue lessens the complexity of the task rather

Page 43: Reaction time and general intellectual ability: The ...

32

than increasing it as not only did it result in a positive correlation

with IQ but was more similar to the correlation found between IQ and

the mean median RT for the simple condition.

In the first analysis a significant correlation of -.42 (p ̂ .05)

was found between IQ and SD of simple RT. When the second analysis

was completed, this correlation was reduced to -.14. The latter

correlation, although not significant, is more consistent with past

research. It should be noted that the two subjects deleted from the

second analysis also had the two lowest IQ scores.

The most unexpected finding was the correlation between IQ and the

no cue/correct cue difference score, -.43 (p ^ .05). One possibility

is that lower IQ subjects actually utilized the cueing information

more efficiently than higher IQ subjects.

Much more research is needed in the area of RT and the use of

cues. The present study restricted subjects to university students

which seriously limits its generalizability to other populations.

Particularly with the finding that lower IQ subjects may have utilized

the cues more than higher IQ subjects, clearly the next step would be

to compare two distinct populations such as the mentally retarded with

university students.

Page 44: Reaction time and general intellectual ability: The ...

Appendix A

Instructions

Please have a seat at the computer terminal. You've been asked to

participate in a study dealing with the speed of reaction time. Right

now I'm going to spend some time explaining what the task will be and

in a short while I'll show you a model of the task you'll be doing.

On the screen you will see eight rectangles which will correspond

to the placement of your fingers on this keyboard. You'll be placing

your fingers on the bottom row of keys closest to the shift keys, like

this.

(Demonstration)

Under the rectangles you'll see either a single dot or eight dots; one

for each rectangle. When one of the dots goes dark, your task is to

press the corresponding key as quickly as possible. Accuracy is not

important; only speed. There will be four conditions you will be

responding to. They are a single cue, no cue, an incorrect cue, and a

correct cue. When the model comes up on the screen, you will hear a

tone. The tone will sound prior to the start of each trial. The tone

is only to let you know the trial has begun. Do not use it as a cue

to press the key as the time between the tone and the start of the

trial is varied from trial to trial.

What you will see first is an example of the single cue

condition. A single dot will appear under one of the rectangles which

will then go dark. Remember, when the dot goes dark, you are to

respond by pressing the corresponding key as quickly as possible.

Okay, let's take a look at the model before trying some practice

trials.

Page 45: Reaction time and general intellectual ability: The ...

34

(Model appears on CRT screen)

Did you see how it was a blank dot and then went dark? It's at

this point that you want to press the corresponding key as quickly as

you can. In this case that would be the V key.

Now, all eight circles and rectangles are going to show and one

will go dark. Next I'm going to show you what the cue will look

like. During the practice and actual trials the cue will be a quick

flash. This will also be an example of the incorrect cue condition.

Please focus on the rectangle farthest to the left.

Okay, continue focusing on the left rectangle and tell me if you

see the flash. This is how the flash will be from this point on.

Any question about your task so far?

Okay, let's do some practice runs. Place your fingers on the

bottom row keys like this.

(Demonstrate)

If you focus your eyes here, in the center of the rectangles, you will

find the task easier than if you scan the rectangles and dots. So,

try and keep your eyes focused at this central area. I'll be

controlling the pace of the trials with this control. Let's begin.

(Practice Trials)

Think you have the hang of it or would you like some more practice?

You'll be doing a total of 160 trials. The counter is in the top

right corner of the screen. If at any time you feel you'd like a rest

between the trials, please ask and we'll take a break. Any questions?

Okay, remember to keep your eyes focused in the center and to

respond as quickly as possible. I'm not interested in accuracy and

Page 46: Reaction time and general intellectual ability: The ...

35

it's expected that you'll make mistakes. Don't worry about the

errors. Your speed of response is what is important. Let's get

started.

Page 47: Reaction time and general intellectual ability: The ...

36

Appendix B

Table 9

Mean of Median and Standard Deviation for

RT Conditions bv Individual Fingers

RT Condition

Fingers S C CC IC

Lt Little 1 300.2 482.2 407.6 512.357.2 60.7 66.5 50.5

Lt Ring 2 297.1 532.2 453.7 533.660.9 80.0 78.9 78.3

Lt Middle 3 297.0 577.6 496.9 620.969.6 82.4 91.0 84.3

Lt Index 4 292.9 504.2 400.9 524.360.74 62.0 62.7 63.7

Rt Index 5 290.3 499.7 397.0 507.754.3 52.2 49.4 53.2

Rt Middle 6 302.9 564.4 453.6 574.4112.9 91.9 68.4 75.4

Rt Ring 7 309.1 529.6 477.6 543.0103.6 82.5 79.0 96.3

Rt Little 8 304.3 500.2 410.2 515.752.3 51.5 56.0 58.5

a Mean of Mean is the top figure and SD the bottom figure.

Page 48: Reaction time and general intellectual ability: The ...

37Appendix C

Table 10

Mean Reaction Times. Standard Deviations, and

Mean Reaction Time Differences for

Each Subject for Each Condition

Means SD Diffs\J tip_IQ_ S C CC IC S C CC IC CS CCS ICS

1) 112 308 558 481 592 64 76 51 51 250 173 2832) 111 269 511 411 571 17 60 48 64 242 142 3023) 106 306 573 488 581 55 50 63 61 267 181 2754)* 102 508 552 458 590 121 79 109 85 44 -50 815) 110 275 531 429 544 20 105 80 65 256 154 2696) 119 246 392 298 421 20 25 51 70 246 52 1757) 127 279 529 440 538 20 69 57 59 250 161 2588) 111 342 536 469 562 39 42 63 83 194 127 2219) 108 288 515 427 509 14 29 24 31 227 140 221

10) 116 284 506 400 477 19 24 46 37 223 116 19411) 113 254 560 444 513 29 44 30 55 306 189 25812) 110 248 556 450 525 14 46 80 75 308 202 27713) 107 306 529 423 559 24 45 33 75 223 117 25214) 108 221 413 325 435 14 32 25 46 192 104 21515) 116 267 494 417 548 26 91 52 72 227 150 28116) 107 256 569 448 519 26 124 94 55 313 192 26317) 123 277 517 463 577 21 62 95 88 240 186 30018)* 103 433 577 438 569 89 59 57 59 144 4 13519) 127 269 542 469 585 22 70 81 61 273 200 31720) 106 265 486 369 481 19 42 43 57 221 104 21721) 115 319 504 433 573 45 72 76 81 185 115 25422) 108 288 527 471 558 20 47 45 73 240 183 27123) 118 333 525 483 579 42 70 41 45 192 150 24624) 109 327 579 465 600 67 62 33 70 252 138 27325) 122 315 517 442 533 26 38 52 19 202 127 219

* Subjects deleted from second analysis.

Page 49: Reaction time and general intellectual ability: The ...

38

Appendix D

Table 11

Fastest Reaction Time For Each RT Condition For Each Subject

S C F I

1) 242 458 408 5422) 242 442 325 4923) 242 475 425 5084) 408 408 342 4755) 242 408 325 4426) 208 358 225 2587) 258 442 325 442

/■NCO 275 475 408 4759) 275 458 392 475

10) 242 458 325 42511) 208 508 408 42512) 225 475 358 39213) 275 475 392 47514) 208 375 275 35815) 242 325 342 40816) 208 458 342 44217) 242 392 342 45818) 358 508 358 50819) 242 442 358 45820) 242 425 308 39221) 275 408 308 50823) 258 442 392 45823) 258 408 425 52524) 258 508 408 52525) 275 458 358 508

Page 50: Reaction time and general intellectual ability: The ...

REFERENCES

Bockrath, D.A. (1980). The relationship between reaction time and both

intelligence and achievement in normal, gifted, EMR, and LD

populations. Dissertation Abstracts InternationalP 41. 3484A.

(University Microfilms No. 8100719).

Brainard, R.W., Irby, T.S., Fitts, P.M., and Alluisi, E.A. (1962).

Some variables influencing the rate of gain of information.

Journal of Experimental Psychology. 63(2), 105-110.

Carlsen, J.S., and Jensen, C.M. (1982). Reaction time, movement time,

and intelligence: A replication and extension. Intelligence. £,

265-274.

Carroll, J.B. (1987). Jensen's mental chronometry: Some comments and

questions. In Modgil, S. and Modgil C. (Ed.), Arthur Jensen.

Consensus and Controversy (pp. 297-307). New York, Philadelphia,

and London: The Falmer Press.

Edwards, A.L. (1976). An introduction to linear regression and

correlation. San Francisco: W. H. Freeman and Company.

Egeth, H. and Smith, E.E. (1967). On the nature of errors in a choice

reaction task. Psvchonomic Science. 8(8), 345-346.

Eysenck, H. (1987). Intelligence and reaction time: The contribution

of Arthur Jensen. In Modgil, S. and Modgil, C. (Ed.), Arthur

Jensen. Consensus and Controversy (pp. 285-295). New York,

Philadelphia, and London: The Falmer Press.

Page 51: Reaction time and general intellectual ability: The ...

40

Gay, G. J. (1981). Complex reaction time and general Intelligence:

Is there a correlation? Unpublished master's thesis, University of Nevada, Las Vegas.

Hale, D. (1968). The relation of correct and error responses in a

serial choice reaction task. Psvchonomic Science. 13(6), 299-300.

Harvey, N. (1980). Non-informative effects of stimuli functioning as

cues. Quarterly Journal of Experimental Psychology. 32. 413-425.

Hick, W.E. (1952). On the rate of gain of information. Quarterly

Journal of Experimental Psychology. 4, 11-26.

Hyman, R. (1953). Stimulus information as a determinant of reaction

time. Journal of Experimental Psychology. 45f 188-196.

Jensen, A.R. and Munro, E. (1979). Reaction time, movement time, and

intelligence. Intelligence. 121-126.

Jensen, A.R. (1980). Chronometric analysis of intelligence. Journal

of Social and Biological Structures. 103-120.

Jensen, A.R. (1980). Bias in mental testing. New York: The Free

Press.

Jensen, A.R. (1982). The chronometry of intelligence. In R.J.

Sternberg (Ed.), Advances in the Psychology of Human Intelligence

(pp. 255-310). Hillsdale, NJ: Erlbaum Associates.

Jensen, A.R., Cohn, S.J., and Cohn, C.M.G. (1989). Speed of

information processing in academically gifted youths and their

siblings. Personality and Individual Differences, lfi(l), 29-33.

Jensen, A.R., Schafer, E.W.P., and Crinella, F.M. (1981). Reaction

time, evoked brain potentials, and psychometric g in the severely

retarded. Intelligence. 5, 179-197.

Page 52: Reaction time and general intellectual ability: The ...

41

Lally, M. and Nettelbeck, T. (1977). Intelligence, reaction time, and

inspection time. American Journal of Mental Deficiencyf 82(3),

273-281.

Lehrl, S. and Fischer, B. (1988). The basic parameters of human

information processing: Their role in the determination of

intelligence. Personality and Individual Differences. 9(5),

883-896.

Longstreth, L.E. (1984). Jensen's reaction-time investigations of

intelligence: A critique. Intelligence. £, 139-160.

Nettlebeck, T. and Kirby, N.H. (1983). Measures of timed performance

and intelligence. Intelligence. 2, 39-52.

Otis, A.S. (1954). Otis quick-scoring mental ability tests: Manual of

directions for gamma test (rev, ed.1. New York: Harcourt, Brace

and World, Inc..

Petrie, C. (1986). Differential reaction time and general intellectual

ability. Unpublished master's thesis, University of Nevada, Las

Vegas.

Posner, M.I., Snyder, C.R.R., and Davidson, B.J. (1980). Attention

and the detection of signals. Journal of Experimental Psychology:

General. 109(2), 160-174.

Roth, E. (1964). Die geschwindigkeit der verabeitung von information

und ihr zusammenhang mit intelligenz. Zeitschrift fur

Experimentelle und Angewante Psychologies. 11. 616-622.

Sen, A., Jensen, A.R., Sen, A.K., and Arora, I. (1983). Correlation

between reaction time and intelligence in psychometrically similar

groups in America and India. Applied Research in Mental

Retardation. 4, 139-152.

Page 53: Reaction time and general intellectual ability: The ...

42

Small, M.A. (1985). Speed of information processing and Intelligence.

Unpublished master's thesis, University of Nevada, Las Vegas.

Small, M.A., Raney, J.F., Knapp, T.J. (1985). Complex reaction time

and general intelligence: A refinement. Journal of Genetic

Psychology. 148(4)f 405-414.

Small, M.A., Raney, J.F., and Knapp, T.J. (1987). Comparison of two

reaction-time tasks and their relation to intelligence. Perceptual

and Motor Skills, 65, 867-870.

Smith, 6. and Stanley, 6. (1980). Relationships between measures of

intelligence and choice reaction time. Bulletin of the Psvchonomic

Society. 16(1), 8-10.

Sternberg, R. (1987). 'Gee, There's more than g!': A critique of

Arthur Jensen's Views on Intelligence. In Modgil, S. and Modgil, C.

(Ed.), Arthur Jensen. Consensus and Controversy (pp. 237-249). New

York, Philadelphia and London: The Falmer Press.

Vernon, P.A. (1983). Speed of information processing and general

intelligence. Intelligence. 7, 53-70.

Vernon, P.A. (1981). Speed of information processing and intelligence.

Unpublished doctoral dissertation, University of California,

Berkeley.

Welford, A.T. (1980). Reaction times. London: Academic Press.