Griffiths, Bigelow,

Liebson,

O’Keeffe,

O’Leary, and

Russ, 1986

(51)

Three male subjects

with histories of

heavy coffee

drinking (mean

prestudy caffeine

intake, 1530 mg/

day) and alcohol

abuse.

Subjects lived on a rasidential research ward

where access to coffee was

experimentally controlled; the caffeine

dose per cup of coffee was varied in a

mixed sequence across days (decaff, 25,

50, 100, 200, and 400 mg/cup).

Low caffeine doses (25 or 50 mg/cup)

were correlated with a slightly

higher number of cups consumed

than the decaffeinated condition in

all three subjects; for all 3 subjects,

higher doses of caffeine (50-400

mg) produced orderly dose-related

decreases in cups consumed.

Griffiths, Bigelow,

and Liebson,

1986 (49)

Six male subjects

with histories of

heavy coffee

drinking (mean

prestudy caffeine

intake, 1020 mg/

day), most of

whom had

histories of

alcohol or drug

abuse.

Subjects lived on a residential research ward

where access to coffee was

experimentally controlled; an across-day

choice procedure was used to compare

the reinforcing effects of caffeinated (100

mg/cup) versus decaffeinated coffee; on

forced-exposure days the available coffee

was identified to subjects by letter code;

on choice days, subjects made a mutually

exclusive choice between two letter-coded

coffees.

Caffeinated coffee was chosen over

decaffeinated coffee in all 6

subjects (11 out of a total of 12

tests) when testing was done under

conditions in which subjects had

been receiving caffeinated coffee

daily for a week or more before

forced-exposure and choice days.

Griffiths and

Woodson,

1988 (57)

Twelve normal

subjects with a

mean prestudy

caffeine intake of

361 mg/day.

An across-day choice procedure was used

to compare the reinforcing effects of

capsules containing caffeine (100, 200,

400, or 600 mg) versus placebo; on

forced-exposure days the available

capsules were identified to subjects by a

color code; on choice days, subjects made

a mutually exclusive choice between two

types of color-coded capsules; subjects

made 10 experimentally independent

choices at each of several dose levels;

testing occurred when subjects were

overnight abstinent from their normal

caffeine intake.

Significant caffeine choice was

demonstrated in 5 of 12 subjects at

one or more dose(s); percentage

selection of caffeine was inversely

related to dose, with 4 subjects

showing significant caffeine

avoidance at 400 and/or 600 mg.

Griffiths, Bigelow,

and Liebson,

1989 (50)

Ten male subjects

with histories of

heavy coffee

drinking (mean

prestudy caffeine

intake, 1081 mg/

day), most of

whom had

histories of

alcohol or drug

abuse.

Subjects lived on a residential research ward

where access to coffee was

experimentally controlled; in one

experiment, 6 subjects had 13

opportunities daily to ingest either a

caffeine (100 mg) or a placebo capsule; in

a second experiment, 6 subjects had 10

opportunities daily to ingest a cup of

coffee or (on different days) a capsule,

dependent upon completing a work

requirement that progressively increased

and then decreased over days; in the

second experiment, one of four conditions

was studied each day: caffeinated coffee

(100 mg/cup), decaffeinated coffee,

caffeine capsules (100 mg/capsule), or

placebo capsules.

In the first experiment, all 6 subjects

developed a clear preference for

caffeine capsules; in the second

experiment, caffeinated coffee

maintained the most self-

administration, significantly higher

than decaffeinated coffee and

placebo capsules bur not different

from caffeine capsules; both

caffeine capsules and decaffeinated

coffee were significantly higher than

placebo capsules but not different

from each other.

Hughes, Higgins,

Bickel, Hunt,

Fenwick,

Gulliver, and

Mireault, 1991

(65)

Twenty-two normal,

predominately

female subjects

with mean

prestudy coffee

intake of 5.3

cups/day (~451

mg/day caffeine).

A choice procedure was used to compare

the reinforcing effects of caffeinated (100

mg/cup) versus decaffeinated coffee; on

forced-exposure days the available coffee

was identified to subjects by letter code;

on 2-day choice tests, subjects could self-

administer both coffees; subjects were

exposed to sic experimentally independent

choice tests; subjects abstained from their

normal coffee intake on forced-exposure

and choice days; subjects were required to

consume at least 4 cups/days on forced-

exposure and choice test days.

Significant choice of caffeinated

coffee over decaffeinated coffee

was demonstrated in 10 of 22

subjects; occurrence of headache

on forced-exposure day tended to

predict subsequent caffeine

preference.

Hughes, Hunt,

Higgins, Bickel,

Fenwick, and

Pepper, 1992

(66)

Eight normal,

predominately

female subjects

who had already

participated in

Hughes et al.,

1991 (65).

A choice procedure identical to that of

Hughes et al., 1991 (65) was used, except

that subjects were exposed to up to 6

experimentally independent choice tests at

each of several caffeine doses (25, 50, 150, and

200 mg/cup).

Significant choice of caffeinated

coffee over decaffeinated coffee

was demonstrated at 25, 50, 150,

and 200 mg/cup in 2 of 6, r of 8, 3

of 6, and 0 of 3 subjects,

respectively; occurrence of

headache on forced-exposure day

predicted subsequent caffeine

preference.

Oliveto, Hughes,

pepper, Bickel,

and Higgins,

1991 (89)

Eleven normal

subjects who

consumed 1.5 to

7 cups coffee/day

(~128-595 mg/

day caffeine).

A choice procedure similar to that of Hughes

et al., 1991 (65) was used, except that

subjects were not required to drink a

minimum number of cups of coffee;

subjects were exposed to 6 experimentally

independent choice tests at each of

several caffeine doses (12.5, 25, 50, and

100 mg/cup).

Significant choice of caffeinated

coffee over decaffeinated coffee

was demonstrated at 12.5, 25, 50,

and 100 mg/cup in 0 of 2,2 of 11

5 of 11, and 5 of 10 subjects,

respectively.

Oliveto, Hughes,

Higgins, Bickel,

Pepper, Shea,

and Fenwick,

1992 (88)

Ten normal subjects

with mean

prestudy coffee

intake of 3.9

cups/day (~332

mg/day caffeine).

A choice procedure similar to that of Hughes

et al., 1991 (65) was used to compare the

reinforcing effects of caffeinated (100 mg/

cup) versus decaffeinated coffee, except    

that in one condition the subjects were not

required to drink a minimum number of

cups of coffee.

Significant choice of caffeinated

coffee over decaffeinated coffee

was demonstrated in only 1 of 10

subjects, and this occurred only in

the condition in which subjects

were not required to drink a

minimum number of cups of coffee.

Hughes, Oliveto,

Bickel, Higgins,

and Valliere,

1992 (68)

Nine normal

subjects with

mean prestudy

caffeinated soda

intake of  5.4

sodas/day (~194

mg/day caffeine).

A choice procedure similar to that of Hughes

et al., 1991 (65!popup(ch161ref65)) was used to compare the   

reinforcing effects of caffeinated soda (25,

50, or 100 mg/soda) versus decaffeinated

soda.

Significant choice of caffeinated soda

over decaffeinated soda was

demonstrated in 4 of 9 subjects at

one or more dose(s).

Silverman,

Mumford, and

Griffiths, 1994

(100)

Eight normal

subjects with

mean prestudy

intake of 214 mg/

day.

Subjects were initially trained in a 100-mg

caffeine versus placebo drug

discrimination using letter-coded capsules;

using the same letter codes, across-day

drug versus drug and drug versus money

choice procedures were used to assess

caffeine reinforcing effects when subjects

were required to engage in a computer

vigilance activity or a relaxation activity

following capsule ingestion; subjects made

10 choices in each condition; choices were

not experimentally independent.

In a condition in which subjects could

choose to take either caffeine or

placebo with either vigilance or

relaxation activities, significant

caffeine choice was demonstrated

in 6 of 6 subjects with vigilance but

with only 1 of 6 with relaxation; in a

condition in which subjects could

choose between capsules and

money, in 6 of 7 subjects, the

maximum monetary value at which

capsules were chosen over money

was significantly higher for caffeine

in vigilance than for placebo in

either activity; in contrast, for 2 of 7

subjects, this value was higher for

caffeine in relaxation than for

placebo in either activity.