In this phase of the study an effort was made to determine the effect of marihuana on various psychomotor and some special mental abilities. Appraisal of these effects was made wherever possible through the use of standardized tests. A number of different tests were originally tried under varying experimental conditions on the group of 5 volunteer subjects who had never before taken marihuana. Only those tests were retained which, in the course of this preliminary investigation, demonstrated the greatest potentialities. With the tests finally selected it was hoped to measure the effect of marihuana on the following functions.

FUNCTIONS AND CAPACITIES TESTED

Static Equilibrium

This was measured by means of the Miles Ataxiameter, which is an instrument for recording body sway. The subject remains stationary in the ataxiameter with his hands at his sides and his feet together while a system of pulleys attached to a helmet on his head records the direction and degree of movement. The subject's score is the cumulative sway in all directions measured in millimeters. This test was applied to each subject for two minutes with his eyes open and two minutes with his eyes closed. Each trial was followed by a rest period of five minutes.

Hand Steadiness

Hand steadiness was measured by means of the Whipple Steadiness Tester which consists of a metal disk with a hole %6 of an inch in diameter, connected in series with dry cells, an electric counter, and a stylus. The subject was instructed to hold the stylus in the hole for two minutes without touching the metal sides. Each contact with the side of the hole was recorded and the total number of contacts gave an index of unsteadiness of hand.

Speed of Tapping

Speed of tapping was measured in somewhat the same manner as was hand steadiness. The Whipple Apparatus was used, the tapping board replacing the steadiness disk and a thicker and heavier stylus replacing the steadiness stylus. The subject tapped repeatedly on the metal plate for two minutes and the total number of taps was recorded on the counter, thereby giving a measure of motor speed.

Strength of Grip

The Collins Dynamometer was used to measure the subject's strength of grip. Three trials were made for each hand and the scores averaged.

Simple and Complex Hand and Foot Reaction Time

Special apparatus was constructed to measure simple and complex hand and foot reaction time. To measure simple hand reaction time, the subject was instructed to press down on a telegraph key and remove his hand as quickly as possible when a red light appeared on the board which stood directly before him. A Cenco counter recorded the reaction time, that is, the time which elapsed between the presentation of the stimulus and the response.

For the measurement of simple foot reaction time, the subject pressed down on a pedal with his foot, removing it as quickly as possible when the red light appeared.

For the measurement of complex (choice or discrimination) hand and foot reaction time either a red or a blue light served as a stimulus. The subject had no advance knowledge as to which color light would appear. For measuring the response with the hand, the subject pressed down on the telegraph key with the right hand and, at the sight of the red light, moved the peg from the red compartment into the center (neutral) compartment with the left hand, then removed the right hand from the key; at the appearance of the blue light, he moved the peg from the blue to the neutral compartment. For measuring complex foot reaction time, the procedure was similar to that for estimating the hand reaction time except that the right foot and the pedal were substituted for the right hand and the telegraph key.

Each subject made fifteen trials for each of the four variations.

Musical Aptitude

Musical aptitude was determined by means of the Kwalwasser-Dykema Music Tests. The eight tests administered were the tonal memory test, the quality discrimination test, the intensity discrimination test, the tonal movement test, the time discrimination test, the rhythm discrimination test, the pitch discrimination test, and the melodic taste test. The sum of the scores for these separate tests was used to give a total score for musical aptitude.

Auditory Acuity

By means of the Galton Whistle, the subjects' limits of auditory acuity were gauged for both ascending and descending frequencies. The final score was the average of the results of three trials in each direction.

Perception of Time

An attempt was made to appraise the subject's facility in estimating time by asking him to state when, after a given signal, he thought the following intervals had elapsed—fifteen seconds, one minute, and five minutes. Several trials were given for each time interval and the average of the results of the trials was taken as the final score.

Perception of Length

Subjects were asked to estimate the length of lines which were 3 inches, 5 inches, and 8 inches in length and to draw lines of 3 inches and 7 inches.

The Subjects

Fifty-four subjects were used in this part of the experiment, 36 marihuana users and 18 non-users. The two groups were equated approximately for the following factors: age, height, weight, years of formal education, and number of arrests. The age range for the user group was from 21 to 45 years with 27.9 years as an average; the age range for the non-user group was from 22 to 43 years with 29.8 years as an average. The range in height for the users was from 54 to 75 inches with a mean of 67.5 inches; for the non-users the range was from 60 to 71 inches with a mean of 66.8 inches. Range in weight for the users was from 123 to 178 pounds with 151.3 pounds as the mean, for the non-users from 115 to 180 pounds -with 149.5 pounds as the mean. The schooling of the user group ranged from no education at all to 10 years with a mean of 7.1 years; that of the non-users varied from 6 to 12 years with a mean of 8.3 years. As regards the number of arrests, the range for users was from 1 to 20 with a mean of 5.1 and for the non-users from 1 to 15 with a mean of 5.3.

The two groups differed radically with respect to race. Of the 36 marihuana users, 11 (31 per cent) were white, 18 (50 per cent) were Negroes, and 7 (19 percent) were Puerto Ricans. Of the 18 non-users, 12 (67 per cent) were white, 6 (33 per cent) were Negroes, and none were Puerto Rican.

In addition, the user group was analyzed with respect to the age when the marihuana habit was begun, the duration of the habit, the number of marihuana cigarettes generally smoked per day, and the period of deprivation. The variation of the habit as already described for the entire group of users applies to the 36 subjects studied here.

Procedure

The tests were first administered to the subjects before they had taken marihuana, then about a week later when they were under the influence of 2 cc. of marihuana, and finally another week later after 5 cc.1 of marihuana had been administered. On each occasion the psychomotor tests for static equilibrium, hand steadiness, tapping, strength of grip, and reaction time were repeated at hourly intervals for eight successive hours in order that the time-effects of marihuana might be determined.2 The other tests, that is, those measuring musical ability, auditory acuity, visual memory, and perception of time and length were given to the subjects while in the un-drugged condition and from three to four hours after the drug had been administered. The music tests were given under normal conditions and after 5 cc. of marihuana had been administered, but not under 2 cc. dosage.

In almost all instances the marihuana was given in the morning shortly after breakfast and generally after a day when no drug had been taken in order that "hangover" effects might be avoided. For the most part the subjects rested and did little or nothing except the prescribed tests on days when marihuana was taken.

The equilibrium, steadiness, tapping and strength of grip tests were given together on one day and the different forms of the reaction-time test on another day. Ordinarily four or five days elapsed between retests.

In addition to being tested after standard doses of the marihuana concentrate had been ingested, 11 users and 9 non-users were tested after smoking marihuana cigarettes.3 The cigarettes weighed from 4 to 8 grains each. Most of the subjects smoked five cigarettes, two non-users smoked only three, and one nonuser smoked four. The tests with cigarettes were given at quarter-hour, half-hour and hour intervals.

Summary and Conclusions

1. The effect of marihuana on the psychomotor functions depends primarily on the complexity of the function tested. Simpler functions like speed of tapping and simple reaction time are affected only slightly by large doses (5 cc.) and negligibly, if at all, by smaller doses (2 cc.). On the other hand, the more complex functions like static equilibrium, hand steadiness, and complex reaction time may be affected adversely to a considerable degree by the administration of both large and small doses of marihuana.

2. The function most severely affected is body steadiness and hand steadiness. The ataxia is general in all directions rather than predominant in any particular axis.

3. The effects produced by larger doses (5 cc.) are systematically, though not necessarily proportionately, greater than those brought about by small doses.

4. The time required by the drug to exert its maximum effect varies somewhat with the function and size of dose, but, on the whole, time curves for both functions and dosages have similarity of form. The effect of the drug begins from one to two hours after ingestion and reaches its peak at the fourth hour, after which it declines so that by the eighth hour most of it is dissipated.

5. When marihuana is taken in cigarette form the psychomotor effects are similar in character and trend to those observed after the ingestion of the drug but they occur much sooner and taper off more quickly.

6. The effects seem to be essentially the same for women as for men, except that women are sometimes affected maximally at the second or third hour after the drug is administered. In women the return to the normal condition is in some instances quicker and more abrupt than it is in the men.

7. Non-users generally seem to be more affected by the drug when it is ingested than are users.

8. Auditory acuity is not affected by marihuana.

9. There is no evidence that musical ability, of non-musicians at least, is improved by marihuana.

10. The ability to estimate short periods of time and short linear distances is not measurably affected by the ingestion of marihuana.

1 A dose of 5 cc. of marihuana proved "too much" for many non-user subjects in the sense that ingestion of this amount was often followed by nausea and general symptoms of malaise which interfered with further testing. For this reason the higher dose for non-users was sometimes reduced to 3 cc. or 4 cc. In all, only 6 of the non-user subjects took the 5 cc. dose. Accordingly, although the higher dosage is referred to as 5 cc. it should be noted that the actual amount used varied from 3 cc. to 5 cc.

2 The scores for the first 25 users and 6 non-users were obtained every half hour, but since there was little difference between the half-hourly and hourly results it was decided to record hourly scores only, except for the first half hour.

3 A short experiment in which placebos were employed was also tried on these subjects. An attempt was made to have the placebos simulate the marihuana as much as possible but unfortunately the placebo pills had a distinctive taste which rendered them easily identifiable. The subjects referred to them as the "licorice" pills or the "blanks." While the experiment was completed and resulted in some interesting findings, the factors which might have invalidated the results were so serious that these experiments are not reported at this time.