Perceptual and Motor Skills, 1977,45, 715-720. @ Perceptual and Motor Skills 1977
JUDGMENTS OF TIME INTERVALS BY YOUNG CHILDREN ESTELLE R. FRIEDMAN Queens College of the City University of New York Summary.-22 preschool children were either trained (experimental group) or not trained (control group) to indicate a 15-sec. time interval by the method of production. The accuracy was significantly improved by brief training. The children werc gcnerally accurate whether attending to the s t o p watch at the right or left e a r or given sound- or light-filled intervals. Neither age nor srx differences were found. These results demonstrate the possibility of conducting research on time-estimation at an early age if the procedures are relatively short and of interest to the young child. Because most of the children were unable to count as a guide to their judgments, the inner neural clock theory is supported.
The ability of young, preschool children to make time judgments of brief intervals apparently has not previously been directly explored. There has been some question about whether or not we have an early, basic, intuitive grasp of time as proposed by Fraisse (1963) for one, or if, as has been the predominant view, it is a perception which is secondary to accomplished work and to concepts of speed (Piaget, 1969; Voyat, 1963). Children progressively learn to identify particular durations with an appropriate name such as an hour, day, week or year, but it seems they would have to build upon some kind of inner rhythm or perception. There must be a way of correlating internal impressions with the proper social designation as time language and concepts develop. Piaget ( 1969) believed that until about 7 or 8 yr. of age a child is too egocentric and inflexible to allow for any objective temporal ideas. From his viewpoint time is inherent in causality which the young child cannot comprehend, and it has to be very gradually derived from the more primitive concepts of distance and velocity. Ornstein (1969) rejected all notions of a biological clock or of a time sense and argued that time is a mental construct totally dependent upon human information-processing. However, Pavlov ( 1960) discovered that his laboratory animals could be conditioned to specific time intervals. Saliva secretion, alimentary reactions, and mild defense reflexes appeared spontaneously and accurately after regular administration of food or acid every 30, 15, or 10 min. H e proposed that organismic tissue changes influence the cerebral hemispheres and provide the physiological basis for time estimation. Dmitriev and Kochigina (1959) reviewed a series of Russian studies of various animal species including reptiles, birds and mammals, all of which were successfully conditioned to pure time and which were affected by the administration of drugs. In their studies of 8- to 14-yr.-old children, they produced conditioning to time in 5 to 13 repetitions of the stimulus. Those authors suggest that the first signal-system associations are most
716
E. R. FRIEDMAN
prominent in the formation of conditioned responses to time during the early school years, whereas the second signal system predominates in the older children. It is impressive that pupillary dilation and constriction in newborn infants are readily conditionable to a 20-sec. time interval (Fitzgerald, Lintz, Brackbill, & Adams, 1967), although results for adults are less rapid and uniform. Goldstone and Goldfarb (1966) consider all mechanical timepieces as extensions of the remarkably sensitive and delicate human clock and also suggest that at birth we have a biological metronome regulating a basic instinctual rhythm. Yet they conclude-that the capacity to render time judgments emerges at the age of 8 yr., on the basis that before then they are unsuccessful subjects in long and difficult psychophysical experiments. General time comprehension and labelling have been seen in a variety of ways as a process of growth and maturation. Ames (1946) studied the responses of children from ages 18 through 48 mo. to a series of questions and found an orderly age sequence. Springer (1952) found that only a few 4-yr.olds could tell time, at 5 yr. there was fair time accuracy with identification of the full hour, and so on with increasing complexity. Court ( 1920) provides an intensive account of one child's development of time, space and number concepts which began at 2 yr. and 9 mo. Gothberg ( 1949) found the mental age a significant factor in the mentally defective child's time concepts. By mental age of 3 interest in and comprehension of time begin. All of these studies suggest an early grasp of principles and time-language, with no dependency upon activities and speed. The purpose of the present study was to explore whether young preschool children can indeed make time judgments independently of speed, causality or sophisticated language, building on their own internal clocks. Can a brief time interval be reproduced at this early age? Can training and feedback be rationally provided, since concepts such as "bigger" and "longer" emerge only at age 3% according to the Stanford-Binet Intelligence Scale, Form L-M (Terman & . Merrill, 1960)? Counting skills are not generally sufficiently developed at this age to be u'sed in marking and matching time intervals of several seconds of duration.
METHOD Subjects In this study the 22 children ranged in age from 2% to 5 % yr. and included 11 boys and 11 girls. Four children were from the Early Stimulation Program in New Haven and the remainder from the Gesell Institute Nursery School. Two additional children were asked to participate but had to be eliminated because one did not understand the task and the other refused to cooperate. The Experimental Group included 11 randomly assigned children, five boys and six girls, ranging in age from 29 through 68 m o , with a mean age of 49.4 mo.
CHILDREN'S TIME ESTIMATES '
717
The Control Group included six boys and five girls whose ages ranged from 42 to 68 mo., with a mean age of 53.6 mo. In the Experimental Group there were 5 children who could not count without error to 15 and in the Control Group there were 4. One child in each group could count quite fluently and beyond 15, but even these two children did not appear to use this skill in making their judgments, and it did not give them a particular advantage in the task at hand as they were not the most accurate subjects.
A Minerva stopwatch was used, a battery-driven buzzer ( a doorstop alarm which is pressed to start and has an off-switch), a flashlight, and 15 wooden blocks. Procedare The children were individually taken from their group to "play a game with the stopwatch." They were tested either in an old milk truck in the backyard of the Gesell Institute or in a separate room of the school. The Experimental Group was twice shown a 15-sec. demonstration on the stopwatch and then started and stopped the watch under guidance for a third 15-sec. interval. They were then asked to guess when it was 15 sec. while the experimenter started the watch and held it alternately to the right and left ears. The experimenter said "go" and started the watch, and the child said "stop." They were given four feedback trials during which they were shown whether they were correct or too brief or too long. Then six test trials were given on alternate ears with only the comment "fine" after each guess. Then a buzzer was sounded for 5 trials, and a flashlight shone for 5 trials, with instructions to the child to guess when they were each on for 15 sec. These aural and visual conditions were alternately presented first or second. Control subjects were given only one demonstration of a 15-sec. interval on the stopwatch. They were then given six alternating right and left ear trials, with no feedback, the experimenter only commenting, "Fine, let's try the other ear now," and they were also given the 5 trials each with the buzzer and light conditions. Time in seconds was recorded for each test trial for the child's judgment of when a 15-sec. interval had concluded. Each child was then asked to count the 15 blocks aloud to see if he or she had developed this skill. The method of production was used here, as the child controlled the time intervals on all test trials.
RESULTS The mean number of seconds was obtained for each child for the three right, the three left and the six total responses to the stopwatch at the ear conditions. These means were then averaged for the 11 Experimental and 11 Control children. For the six total trials, the Experimental Group had a mean estima-
718
E. R. FRIEDMAN
tion time of 15.54 sec., with a range from 8.84 to 25.18 sec. and an SD of 4.47. The Controls averaged 11.11 sec., tending to overestimate the passage of time, with a range of 5.51 to 16.84 sec. and an SD of 3.58. The difference ( D )between them is 4.48 sec., with a t of 2.56, which is significant at the 5% level. TABLE 1 MEANTIMES( I N SECONDS)OF EXPERIMENTAL AND CONTROLCHILDREN'S RESPONSESTo RIGHTAND LEFT EARSAND TO TOTAL(SIX) TESTTRIALS, AND TO BUZZER AND LIGHTCONDITIONS Left Total Experimental Group
Sex
Age
Right
B G G
3-11 2-5 3-11 3-8 4-7 3-8 4-10 4-5 5-8 5-1 3-7
22.67 14.00 25.00 8.33 9.33 24.33 12.67 16.33 15.33 16.67 14.00 16.24
3-10 3-7 4 4-5 4-10 3-9 5-3 5-5 5-8 4-11 3-6
18.34 7.67 12.34 8.00 6.34 4.67 13.34 10.00 13.00 9.67 16.00 10.85 15.54, S D
G G
B B G B G
B M
14.00 11.33 25.33 15.00 8.33 17.00 15.67 14.33 13.00 14.67 14.67 14.84
18.33 12.67 25.17 11.67 8.84 20.67 14.17 15.33 14.17 15.67 14.33 15.54
Buzzer
Light
6.60 5.80 6.40 9.60 11.40 21.80 12.60 15.40 7.20 15.00 12.40 11.75
14.40 5.00 8.40 7.00 15.80 16.40 11.80 12.60 11.60 17.40 20.40 12.80
Control Group B G G G G
B
B G B B B M
Note.-Experimental
M =
15.34 9.00 12.00 12.34 6.67 6.34 15.00 9.67 13.00 11.00 14.67 11.37 = 4.47;
16.84 8.34 12.17 10.17 6.51 5.51 14.17 9.84 13.00 10.34 15.34 11.11
Control
10.20 14.00 13.20 13.00 11.00 12.20 8.60 13.80 12.40 19.20 15.00 14.40 7.20 15.80 15.00 15.60 11.00 9.20 13.20 13.60 12.20 9.80 11.72 13.69 M = 11.11, SD = 3.58.
Small, non-significant mean differences were found between the right and left ears within each group. The value is 1.40 sec. for the experimental group and .52 sec. for the controls. There were no significant differences between the light or the buzzer conditions either within the groups or between them. Experimental buzzer mean time was 11.72 sec., light was 13.69 sec., and the difference 1.97. The mean difference between experimental and control buzzer conditions was .03 sec.; between experimental and control light conditions was .89 sec.
CHILDREN'S TIME ESTIMATES
719
The sex difference between boys and girls on the 6 total test trials was 1.86 sec.; the age difference between the children divided into two groups, age 2% through 4 (younger) and 4% through 5% (older), 2.52 sec. Neither difference is significant. The mean for the older group of children was 12.02 sec. and for the younger children 14.54 sec. The mean for the boys was 14.26 sec. and for the girls was 12.40.
DISCUSSION Over-all there is considerable accuracy in young children's production of the 15-sec. time interval. The untrained group tended to reproduce a briefer interval so that the training may teach the children to wait longer. Of the 396 recorded trials, only 31 were very brief and impulsive responses, 3 to 5 sec., and only 5 of the trials were greatly overproduced from 30 to 40 sec. in length. The only child who rejected this activity was guessing too quickly before he quit; the one child who was eliminated from the study did not understand the task and simply remained with the stopwatch at his ear for more than 60 sec. The difference between the experimental and control groups suggests that learning and improved accuracy do occur with brief training and feedback. The benefit does not transfer to the buzzer and light conditions or perhaps was not extensive enough to be retained w e r time. It was difficult to maintain the child's attention, even though there was initial high interest in the stopwatch and other apparatus. It is postulated that benefits of the training are somewhat offset by the fatigue or loss of attention taken by the extra time of the four additional training trials. Candy rewards might have improved the situation and helped sustain attention and motivation. It is assumed from the general ability of these young children to estimate time accurately that they are responding to some form of inner clock, some neurological chronometer which was not specifically dependent upon aural or visual conditions. Only two of the children could count smoothly, fluently, and rhythmically, and even they did not appear to be counting when they made their judgments. Temporal perception appears to respond to training which helps to adjust the ability more finely. In this study time estimation has been shown to be possible in preschool children in opposition to the contentions of Piaget ( 1969). Voyat ( 1963 ) , and Goldstone and Goldfarb ( 1966). The activity explored here is a combination of the internal rhythm with verbal labelling of time. After a demonstration of this brief duration and particularly after training, the children were able to reproduce it within reasonable limits without relying upon speed of any object or any work accomplished. It seems it would be worthwhile to explore this capacity to judge time intervals further at this early developmental period, possibly with briefer and longer periods of time as well, and to study the effects of certain clinical conditions such as hyperactivity upon this skill.
720
E. R.,FRIEDMAN
REFERENCES AMES,L. B. Development of sense of time in children. Journal of Genetic Psychology, 1946.. 68.. 97-125. COURT,S. R. A. Number, time and space in the first five years. Pedagogical Seminary, 1920, 27, 71-89. DMITRIEV, A. S., & KOCHIGINA,A. W. Importance of time as a stimulus of conditioned reflex activity. Psychological Bulletin, 1959, 56, 106-132. FI'IZGERALD, R. E., LINK?, L. M., BRACKBILL,Y., & ADAMS,G. Time perception and conditioning an autonomic response in human infants. Perceptual and Motor Skills, 1967, 24, 479-486. FRAISSE,P. T h e psychology of time. New York: Harper & Row, 1963. GOLDSTONE,S., & GOLDFARB,J. L. Perception of time b children. In A. H. Kidd & J. L. Rivoire (Eds.), Perceptual dez,elopment in cKildren. New York: International Universities Press, 1966. Pp. 445-486. GOTHBERG.L. Mentally defective children's understanding of time. American Journal of Mental Deficiency, 1949, 5 3 , 441-453. ORNSTEIN,R. E. On the experience of time. New York: Penguin, 1969. PAVLOV,I. P. Conditioned reflexes. New York: Dover, 1960. PIAGET, J. T h e child's conception of time. London: Routledge, 1969. SPRINGER,D. Development in y n g children of understanding time and the clock. Journal of Genetic Psycho ogy, 1952, 80, 83-96. TERMAN,L. M., & MERRILL,M. A. Stanford.Binet Intelligence Scale. Form L-M. Boston: Houghton Mifflin, 1960. VOYAT,G. Le perception du temps. Archirles des Psychologie, 1963, 39, 1 - 1 0 ,
Accepted Augurt 9, 1977.
JUDGMENTS OF TIME INTERVALS BY YOUNG CHILDREN ESTELLE R. FRIEDMAN Queens College of the City University of New York Summary.-22 preschool children were either trained (experimental group) or not trained (control group) to indicate a 15-sec. time interval by the method of production. The accuracy was significantly improved by brief training. The children werc gcnerally accurate whether attending to the s t o p watch at the right or left e a r or given sound- or light-filled intervals. Neither age nor srx differences were found. These results demonstrate the possibility of conducting research on time-estimation at an early age if the procedures are relatively short and of interest to the young child. Because most of the children were unable to count as a guide to their judgments, the inner neural clock theory is supported.
The ability of young, preschool children to make time judgments of brief intervals apparently has not previously been directly explored. There has been some question about whether or not we have an early, basic, intuitive grasp of time as proposed by Fraisse (1963) for one, or if, as has been the predominant view, it is a perception which is secondary to accomplished work and to concepts of speed (Piaget, 1969; Voyat, 1963). Children progressively learn to identify particular durations with an appropriate name such as an hour, day, week or year, but it seems they would have to build upon some kind of inner rhythm or perception. There must be a way of correlating internal impressions with the proper social designation as time language and concepts develop. Piaget ( 1969) believed that until about 7 or 8 yr. of age a child is too egocentric and inflexible to allow for any objective temporal ideas. From his viewpoint time is inherent in causality which the young child cannot comprehend, and it has to be very gradually derived from the more primitive concepts of distance and velocity. Ornstein (1969) rejected all notions of a biological clock or of a time sense and argued that time is a mental construct totally dependent upon human information-processing. However, Pavlov ( 1960) discovered that his laboratory animals could be conditioned to specific time intervals. Saliva secretion, alimentary reactions, and mild defense reflexes appeared spontaneously and accurately after regular administration of food or acid every 30, 15, or 10 min. H e proposed that organismic tissue changes influence the cerebral hemispheres and provide the physiological basis for time estimation. Dmitriev and Kochigina (1959) reviewed a series of Russian studies of various animal species including reptiles, birds and mammals, all of which were successfully conditioned to pure time and which were affected by the administration of drugs. In their studies of 8- to 14-yr.-old children, they produced conditioning to time in 5 to 13 repetitions of the stimulus. Those authors suggest that the first signal-system associations are most
716
E. R. FRIEDMAN
prominent in the formation of conditioned responses to time during the early school years, whereas the second signal system predominates in the older children. It is impressive that pupillary dilation and constriction in newborn infants are readily conditionable to a 20-sec. time interval (Fitzgerald, Lintz, Brackbill, & Adams, 1967), although results for adults are less rapid and uniform. Goldstone and Goldfarb (1966) consider all mechanical timepieces as extensions of the remarkably sensitive and delicate human clock and also suggest that at birth we have a biological metronome regulating a basic instinctual rhythm. Yet they conclude-that the capacity to render time judgments emerges at the age of 8 yr., on the basis that before then they are unsuccessful subjects in long and difficult psychophysical experiments. General time comprehension and labelling have been seen in a variety of ways as a process of growth and maturation. Ames (1946) studied the responses of children from ages 18 through 48 mo. to a series of questions and found an orderly age sequence. Springer (1952) found that only a few 4-yr.olds could tell time, at 5 yr. there was fair time accuracy with identification of the full hour, and so on with increasing complexity. Court ( 1920) provides an intensive account of one child's development of time, space and number concepts which began at 2 yr. and 9 mo. Gothberg ( 1949) found the mental age a significant factor in the mentally defective child's time concepts. By mental age of 3 interest in and comprehension of time begin. All of these studies suggest an early grasp of principles and time-language, with no dependency upon activities and speed. The purpose of the present study was to explore whether young preschool children can indeed make time judgments independently of speed, causality or sophisticated language, building on their own internal clocks. Can a brief time interval be reproduced at this early age? Can training and feedback be rationally provided, since concepts such as "bigger" and "longer" emerge only at age 3% according to the Stanford-Binet Intelligence Scale, Form L-M (Terman & . Merrill, 1960)? Counting skills are not generally sufficiently developed at this age to be u'sed in marking and matching time intervals of several seconds of duration.
METHOD Subjects In this study the 22 children ranged in age from 2% to 5 % yr. and included 11 boys and 11 girls. Four children were from the Early Stimulation Program in New Haven and the remainder from the Gesell Institute Nursery School. Two additional children were asked to participate but had to be eliminated because one did not understand the task and the other refused to cooperate. The Experimental Group included 11 randomly assigned children, five boys and six girls, ranging in age from 29 through 68 m o , with a mean age of 49.4 mo.
CHILDREN'S TIME ESTIMATES '
717
The Control Group included six boys and five girls whose ages ranged from 42 to 68 mo., with a mean age of 53.6 mo. In the Experimental Group there were 5 children who could not count without error to 15 and in the Control Group there were 4. One child in each group could count quite fluently and beyond 15, but even these two children did not appear to use this skill in making their judgments, and it did not give them a particular advantage in the task at hand as they were not the most accurate subjects.
A Minerva stopwatch was used, a battery-driven buzzer ( a doorstop alarm which is pressed to start and has an off-switch), a flashlight, and 15 wooden blocks. Procedare The children were individually taken from their group to "play a game with the stopwatch." They were tested either in an old milk truck in the backyard of the Gesell Institute or in a separate room of the school. The Experimental Group was twice shown a 15-sec. demonstration on the stopwatch and then started and stopped the watch under guidance for a third 15-sec. interval. They were then asked to guess when it was 15 sec. while the experimenter started the watch and held it alternately to the right and left ears. The experimenter said "go" and started the watch, and the child said "stop." They were given four feedback trials during which they were shown whether they were correct or too brief or too long. Then six test trials were given on alternate ears with only the comment "fine" after each guess. Then a buzzer was sounded for 5 trials, and a flashlight shone for 5 trials, with instructions to the child to guess when they were each on for 15 sec. These aural and visual conditions were alternately presented first or second. Control subjects were given only one demonstration of a 15-sec. interval on the stopwatch. They were then given six alternating right and left ear trials, with no feedback, the experimenter only commenting, "Fine, let's try the other ear now," and they were also given the 5 trials each with the buzzer and light conditions. Time in seconds was recorded for each test trial for the child's judgment of when a 15-sec. interval had concluded. Each child was then asked to count the 15 blocks aloud to see if he or she had developed this skill. The method of production was used here, as the child controlled the time intervals on all test trials.
RESULTS The mean number of seconds was obtained for each child for the three right, the three left and the six total responses to the stopwatch at the ear conditions. These means were then averaged for the 11 Experimental and 11 Control children. For the six total trials, the Experimental Group had a mean estima-
718
E. R. FRIEDMAN
tion time of 15.54 sec., with a range from 8.84 to 25.18 sec. and an SD of 4.47. The Controls averaged 11.11 sec., tending to overestimate the passage of time, with a range of 5.51 to 16.84 sec. and an SD of 3.58. The difference ( D )between them is 4.48 sec., with a t of 2.56, which is significant at the 5% level. TABLE 1 MEANTIMES( I N SECONDS)OF EXPERIMENTAL AND CONTROLCHILDREN'S RESPONSESTo RIGHTAND LEFT EARSAND TO TOTAL(SIX) TESTTRIALS, AND TO BUZZER AND LIGHTCONDITIONS Left Total Experimental Group
Sex
Age
Right
B G G
3-11 2-5 3-11 3-8 4-7 3-8 4-10 4-5 5-8 5-1 3-7
22.67 14.00 25.00 8.33 9.33 24.33 12.67 16.33 15.33 16.67 14.00 16.24
3-10 3-7 4 4-5 4-10 3-9 5-3 5-5 5-8 4-11 3-6
18.34 7.67 12.34 8.00 6.34 4.67 13.34 10.00 13.00 9.67 16.00 10.85 15.54, S D
G G
B B G B G
B M
14.00 11.33 25.33 15.00 8.33 17.00 15.67 14.33 13.00 14.67 14.67 14.84
18.33 12.67 25.17 11.67 8.84 20.67 14.17 15.33 14.17 15.67 14.33 15.54
Buzzer
Light
6.60 5.80 6.40 9.60 11.40 21.80 12.60 15.40 7.20 15.00 12.40 11.75
14.40 5.00 8.40 7.00 15.80 16.40 11.80 12.60 11.60 17.40 20.40 12.80
Control Group B G G G G
B
B G B B B M
Note.-Experimental
M =
15.34 9.00 12.00 12.34 6.67 6.34 15.00 9.67 13.00 11.00 14.67 11.37 = 4.47;
16.84 8.34 12.17 10.17 6.51 5.51 14.17 9.84 13.00 10.34 15.34 11.11
Control
10.20 14.00 13.20 13.00 11.00 12.20 8.60 13.80 12.40 19.20 15.00 14.40 7.20 15.80 15.00 15.60 11.00 9.20 13.20 13.60 12.20 9.80 11.72 13.69 M = 11.11, SD = 3.58.
Small, non-significant mean differences were found between the right and left ears within each group. The value is 1.40 sec. for the experimental group and .52 sec. for the controls. There were no significant differences between the light or the buzzer conditions either within the groups or between them. Experimental buzzer mean time was 11.72 sec., light was 13.69 sec., and the difference 1.97. The mean difference between experimental and control buzzer conditions was .03 sec.; between experimental and control light conditions was .89 sec.
CHILDREN'S TIME ESTIMATES
719
The sex difference between boys and girls on the 6 total test trials was 1.86 sec.; the age difference between the children divided into two groups, age 2% through 4 (younger) and 4% through 5% (older), 2.52 sec. Neither difference is significant. The mean for the older group of children was 12.02 sec. and for the younger children 14.54 sec. The mean for the boys was 14.26 sec. and for the girls was 12.40.
DISCUSSION Over-all there is considerable accuracy in young children's production of the 15-sec. time interval. The untrained group tended to reproduce a briefer interval so that the training may teach the children to wait longer. Of the 396 recorded trials, only 31 were very brief and impulsive responses, 3 to 5 sec., and only 5 of the trials were greatly overproduced from 30 to 40 sec. in length. The only child who rejected this activity was guessing too quickly before he quit; the one child who was eliminated from the study did not understand the task and simply remained with the stopwatch at his ear for more than 60 sec. The difference between the experimental and control groups suggests that learning and improved accuracy do occur with brief training and feedback. The benefit does not transfer to the buzzer and light conditions or perhaps was not extensive enough to be retained w e r time. It was difficult to maintain the child's attention, even though there was initial high interest in the stopwatch and other apparatus. It is postulated that benefits of the training are somewhat offset by the fatigue or loss of attention taken by the extra time of the four additional training trials. Candy rewards might have improved the situation and helped sustain attention and motivation. It is assumed from the general ability of these young children to estimate time accurately that they are responding to some form of inner clock, some neurological chronometer which was not specifically dependent upon aural or visual conditions. Only two of the children could count smoothly, fluently, and rhythmically, and even they did not appear to be counting when they made their judgments. Temporal perception appears to respond to training which helps to adjust the ability more finely. In this study time estimation has been shown to be possible in preschool children in opposition to the contentions of Piaget ( 1969). Voyat ( 1963 ) , and Goldstone and Goldfarb ( 1966). The activity explored here is a combination of the internal rhythm with verbal labelling of time. After a demonstration of this brief duration and particularly after training, the children were able to reproduce it within reasonable limits without relying upon speed of any object or any work accomplished. It seems it would be worthwhile to explore this capacity to judge time intervals further at this early developmental period, possibly with briefer and longer periods of time as well, and to study the effects of certain clinical conditions such as hyperactivity upon this skill.
720
E. R.,FRIEDMAN
REFERENCES AMES,L. B. Development of sense of time in children. Journal of Genetic Psychology, 1946.. 68.. 97-125. COURT,S. R. A. Number, time and space in the first five years. Pedagogical Seminary, 1920, 27, 71-89. DMITRIEV, A. S., & KOCHIGINA,A. W. Importance of time as a stimulus of conditioned reflex activity. Psychological Bulletin, 1959, 56, 106-132. FI'IZGERALD, R. E., LINK?, L. M., BRACKBILL,Y., & ADAMS,G. Time perception and conditioning an autonomic response in human infants. Perceptual and Motor Skills, 1967, 24, 479-486. FRAISSE,P. T h e psychology of time. New York: Harper & Row, 1963. GOLDSTONE,S., & GOLDFARB,J. L. Perception of time b children. In A. H. Kidd & J. L. Rivoire (Eds.), Perceptual dez,elopment in cKildren. New York: International Universities Press, 1966. Pp. 445-486. GOTHBERG.L. Mentally defective children's understanding of time. American Journal of Mental Deficiency, 1949, 5 3 , 441-453. ORNSTEIN,R. E. On the experience of time. New York: Penguin, 1969. PAVLOV,I. P. Conditioned reflexes. New York: Dover, 1960. PIAGET, J. T h e child's conception of time. London: Routledge, 1969. SPRINGER,D. Development in y n g children of understanding time and the clock. Journal of Genetic Psycho ogy, 1952, 80, 83-96. TERMAN,L. M., & MERRILL,M. A. Stanford.Binet Intelligence Scale. Form L-M. Boston: Houghton Mifflin, 1960. VOYAT,G. Le perception du temps. Archirles des Psychologie, 1963, 39, 1 - 1 0 ,
Accepted Augurt 9, 1977.
