Perceptual and Motor Skills, 1991, 7 2 , 507-512.
O Perceptual and Motor Skills 1991
SEX DIFFERENCES A N D EFFECTS O F AGING ON VISUOMOTOR COORDINATION ' JEAN-LOUIS BOUCHER, SUZANNE DENIS, AND JO-ANNE LANDRIAULT
Uniuersio of Ottawa Summary.-The purpose of this study was to examine the effects of aging on men and women in processing information required to reproduce direction and distance on a visuomotor task. Subjects (45 men and 45 women) selected from three age groups (25-34 yr., 45-54 yc, 65-74 yr.) were required to estimate blindly the exact criterion location of a target-point they had identified under one of the following conditions: visual, kinesthetic, and visuokinesthetic. Errors in direction (degrees) and in distance (cm) were recorded. The analysis of the total variability in responding (E) indicated that the women of the 65- to 74-yr. age group were significantly less accurate in estimating distance than were the men of the two older age groups (45 to 54 yr., 65 to 74 yr.) and less accurate than were the women of the 25- to 34-yr. age group. No significant differences in estimating distance were found among the three age groups of men. No significant differences for direction were found between men and women.
The accuracy with which the exact position of a target-point can be estimated appears to depend primarily (1) upon the accuracy with which the position of the target and that of the reaching limb can be localized in space (Paillard, 1976) and (2) upon the efficiency with which this information can be programmed in direction and in distance (Paillard, 1976; von Hofsten, 1986). According to Paillard and Beaubaton (1978) and to von Hofsten (1986), both vision and the proprioceptors have the potential to assist in defining the spatial coordinates of direction and distance needed to program movement information and to control motoricity efficiently. I t is fairly well recognized that aging decreases the efficiency with which the senses receive and convey the information to be processed by the brain; see Welford (1980) for a review. Of all the senses, the eye seems to deteriorate noticeably after age 50 (Botwinick, 1978). Neurons and muscle cells, as nondividing cells, are also prone to the effects of aging (Geist, 1968). Aging should, therefore, be expected to affect the efficiency with which visual and kinesthetic information is received and processed by the brain. Unfortunately, very little has been reported in the literature on how aging influences one's ability to process visual and kinesthetic information with reference to the execution of a visuospatial motor task. This observation becomes particularly significant when considered within the context of sex differences.
'This study was funded by a grant from the National Science and E n ineering Council of Canada. Requests for reprints should be sent to Jean-Louis Boucher, ~ c h o o p o fHuman Kinetics, University of Ottawa, 125 University, Ottawa, Ontario, Canada K I N 6N5.
508
J-L. BOUCHER, ET AL
Some suggestions have been made in the literature to the effect that aging may not appear as early or be as noticeable in women as in men (Botwinick, 1978; Rockstein, 1958). I t seems plausible, then, to expect that the effects of aging on visuospatial motor ability may be different for the two sexes. More specifically, aging may have a different effect on the ability of men and women to process the sensorimotor information needed to program the two parameters of direction and distance that underlie the accurate positioning of a limb in space. This study attempted to verify this assumption.
Subjects The subjects were 45 women and 45 men equally (n = 15) selected from three age groups (25 to 34 yr., 45 to 54 yr., 65 to 74 y t ) . The mean ages of the groups were 29.0, 48.7, and 68.6 yr. for women, and 28.4, 49.2, and 69.9 yr. for men. They were all right-handed volunteers recruited from various social community organizations and from the professorial and support staff of the University of Ottawa. All were free from any known medical sensory, neurological, and motor deficiencies according to the information gathered by means of a questionnaire. Cognitive ability of the subjects was not considered in this study since the experimental task was analogous to everyday reaching tasks. Experimental Task Subjects were required to estimate blindly the exact spatial location of target-points which they had preselected within an experimentally defined section of a pointing surface under one of the three following conditions: visual (V), kinesthetic (K), and visuokinesthetic (VK). I n the visual condition, subjects indicated verbally to the experimenter the criterion location of the target-point. I n the kinesthetic condition, subjects blindly reached out in space to a given section of the pointing surface to identify the criterion location of the target-point. I n the visuokinesthetic condition, subjects not only saw but also felt the displaced movement of their right upper segment as it reached out across the pointing surface to identify the criterion location of the target-point . Apparatus The testing apparatus included a pointing surface, a wooden box-like structure and a metal finger splint. The pointing surface consisted of a piece of styrofoam (45 cm x 60 cm) on which four intersecting lines were drawn resulting in nine equal rectangularly shaped pointing sections sequentially numbered from 1 to 9. A white semitransparent removable score sheet was set over the styrofoam to record (1) the identified criterion locations of the target-points and (2) the accuracy with which these locations were estimated.
VISUOMOTOR COORDINATION: SEX, AGE
509
A 2-cm x 2-cm block of styrofoam fastened at the center (30 cm) of the surface's edge closest and parallel to the subjects served as a starting point between trials. An open-ended wooden structure, 70 cm wide x 5 0 crn deep x 25 cm high at its lowest point and 50 crn at its highest point, rested over the pointing surface. A hinged cover allowed control for the presence of visual cues. An extremely fine and short needle was fastened vertically to the underside of a metal splint at a point corresponding approximately to the center of the third phalanx of the right index finger. Procedure Upon arrival at the testing area, each subject was requested to sit before the apparatus and to secure the metal splint on the right index finger. The pointing surface was then adjusted so that (1) the starting block coincided with the subject's sternum and (2) the index finger of the fully extended right arm could reach the center point of the more distant parallel edge of the surface. The wooden structure was adjusted so the subject's chin rested above the cover of the structure. Each subject received standardized instructions describing the task and six practice trials, two for each condition. Questions were answered. Subjects were informed that accuracy was of importance in this experiment. No reference was ever made to the speed of movement. A trial required that subjects (1) freely select and identify the criterion location of a target-point within an experimenter-defined section of the pointing surface and (2), following a 5-sec. interval, that they blindly estimate the exact location of this point. Before each trial, subjects were verbally informed of the section within w h c h the location of the target-point was to be identified. The criterion location of the target-points was selected by the subjects so as to allow them to better plan their movements and adopt more suitable reaching strategies than would have been possible if the location of the target-points had been imposed upon them. However, the sectors within which the location of each target-point had to be identified were experimentally defined to make certain that the target-points would be better distributed across the pointing surface and avoid any possible biasing effects due to the favoring by the subjects of a specific and restricted area on the pointing surface. The initial order of presentation of each of the nine sectors and for all three sensory conditions had been randomly selected prior to experimentation. This order was then systematically rotated for each subject. Under the visual condition, the subject kept the index finger on the starting block while the experimenter slowly moved in a random manner a felt-tipped pen held vertically over but not touching the area within the selected section until the subject said "stop." The experimenter recorded the criterion location of the target-point on the pointing surface. Under the kinesthetic and visuokinesthetic conditions, with the cover respectively closed
5 10
J-L. BOUCHER, ET AL.
or opened, the subject removed the index finger from the starting block and reached across the pointing surface to identify the target-point's location within the experimentally identified section. Using the needle affixed to the metal splint, the subject perforated the score sheet, waited 2 sec., and returned the finger to the starting block. The experimenter then placed a small ink dot over this perforation to identify it clearly as the criterion location of the target-point. All reproduction movements were executed in the absence of vision. At the command "reproduce," subjects removed their index finger from the starting block, reached underneath the closed cover of the wooden structure to the estimated location of the target-point, and perforated the score sheet. Having done so, the subject returned the index finger to the starting block in preparation for the next trial. One trial was given in each of the nine sectors and for each of the three sensory conditions, for a total of 27 trials per subject.
Error Recording Procedure Errors in distance were recorded as the signed longitudinal deviations (cm) of the estimated location from the criterion (0, 0) location. An overestimation of the target-point resulted in a positive error whereas an underestimation resulted in a negative error. Errors in direction were calculated as the signed angle between line Y,, i.e., the straight line extending from the center of the starting block to the criterion location of the targetpoint, and line Y,,i.e., the straight line originating from the center of the starting block to the estimated location of the target-point. The angle was recorded as negative when Y,was to the left of Y , and positive when to the right of Y,.
Design Because it is regarded by some writers as the best over-all measure of performance accuracy (e.g., Henry, 1975) and, because it reflects an exact combination measure of variability and bias (Schmidt, 1982, p. 69), the total variability error (E)in distance and in direction was selected as the measure of accuracy. A multivariate anaIysis of variance with repeated measures on the sensory condition factor (B.M.D.P.4V package) was used to analyze the data. Separate analyses of variance for distance and direction were used as post hoc procedures to identify the locus of a significant effect. Simple main effects for all significant univariate interactions were tested for significance (Keppel, 1982) and followed up with the Newman-Keuls procedure using a significance level of 5%.
RESULTSAND DISCUSSION The results of the multivariate analysis of variance gave a significant interaction of sex by age (A,,,,, = 2.42, p = .05). Post hoe analyses of variance
511
VISUOMOTOR COORDINATION: SEX, AGE
indicated a significant interaction of sex by age (F,,,,= 4.59, p = .01) for distance, but none was found for direction. The analysis of the simple main effects of age for men and for women showed that aging had a significant effect on the accuracy of distance for the women (F,,8, = 4.51, p < .01) but not for that of men. The Newman-Keuls procedure indicated that women between the ages of 65 and 74 yr. were significantly less accurate in distance (2.68 cm) than women between the ages of 25 and 34 yr. (2.12 cm). Further analysis showed that women of the 65- to 74-yr. age group were significantly less accurate in distance than the men of the same age group (2.16) and the men of the 45- to 54-yr. age group (2.12 cm). The analysis showed no other significant effects for age and sex. Having calculated a constant error smaller than the total variability for all of the above significant comparisons, it appears that these differences could be attributed to the amount of variability in the scores rather than to the amount of bias (Schmidt, 1982, p. 70). TABLE 1 MEANTOTALVARIABILITY (M CM) FOR DISTANCE: SEXAND AGE 25-34
Women Men
2.12 2.38
yc.
45-54 2.35 2.12
yr.
65-74
yr
2.68 2.16
The few studies that have been reported in the literature on how aging affects one's ability to process sensory information with reference to the execution of a visuospatial motor task does not allow us to make proper comparisons between the similarities and the differences that exist between the results of this study and the work of others. Consequently, confirmation of our results has proven to be a very difficult task. We can only speculate, at this time, as to what could have produced the differences in accuracy among the groups. The age-invariant hypothesis suggests that aging has a deteriorating effect on mental operations requiring effortful activity and not on automatic unrehearsable activities such as the encoding of spatial information (Hasher & Zacks, 1979). Addressing some of the issues raised by this hypothesis, Zacks (1982) concluded that the coding of such information may be more a matter of individual peference and decision. Some evidence (Hall & Leavitt, 1977) suggests that the coding process of distance should be viewed as a flexible attentional process that can be affected by such factors as subjects' strategies and task requirements. The coding process of distance can in fact require active encoding (Marteniuk, 1973) and be mentally rehearsed (Diewert, 1976). Hall and Leavitt (1977) concluded that in some circumstances and under certain conditions the coding of distance can be processed at a perceptual or at a conceptual level. It appears that the coding of distance can sometimes require the assistance of effortful attentional oper-
5 12
J-L. BOUCHER, ET AL.
ations. If this constitutes a valid explanation, then the coding of distance could be subject to the effects of the aging process. However, men did not differ in estimating distance regardless of their age group. I t is perhaps an indication that the coding of distance remains an automatic process in men regardless of age whereas, for women, it requires the assistance of some effortful attentional operations. The fact that, for women, the middle-age group did not differ significantly from the two other groups may be indicative of some transitional period. Further study is needed to substantiate this suggestion and to confirm the findings of this study. REFERENCES BOTWINICK, J. (1978) Aging and behavior. New York: Springer. DIEWERT, G. L. (1976) The role of vision and kinesthesis in coding of rwo-dimensional movement information. Journal of Human Movement Studies, 2, 191.198 implications. St. GUST, H. (1968) The psychological arpects of the aging process with ~ocrolo~~cal Louis, MO: Warren H . Green. HALL,C., & LEAVITT,J. L. (1977) Encoding and retention characterist~csof direction and distance. Journal of Human Movement Studies, 3, 88-98. HASHER,L., & ZACKS,R. (1979) Automatic and effortful processes in memory. Journal of Experimental Psychology: General, 108, 356-388. HENRY, F. M. (1975) Absolute error versus "E" in target accuracy. Journal of Motor Behavior, 7, 227-228. KEPPEL,G. (1982) Design and analysis: a researcher? handbook. Englewood Cliffs, NJ: PrenticeHall. MARTEN^, R. G. (1973) Retention characteristics of motor short-term memory cues. Journal of Motor Behavior, 5, 249-259. PAILLARD, J. (1976) Le codage nerveux des commandes mocrices. Revue d'EEG et de Nertrophysiologic, 6, 453-472. PAILLARD, J., & BEAUBATON, D. (1978) De la coordination visuo-motrice I'organisation de la saisie manuelle. In H. Hecean & M. Jeannerod (Eds.), Du contrhle de [a mohicitk ir l'ornunisation du -neste. Paris. France: Masson. Po. 225-260. ROCKSTEIN, M. (1958) Heredity and longevity in the animal kingdom. Journal of Gerontology, 13(Suppl. 2), 7-12. SCHMIDT,R. (1982) Motor control and learning. Champaign, IL: Human Kinetics. VON HOFSTEN,C. (1986) Early spatial perception taken in reference to manual action. Acta Psychologica, 63, 323-335. WELFORD,A. T. (1980) Sensory, perce tual, and motor processes in older adults. In J. E. Birren & R. Bruce (Eds.), Handfook of mental health ofaging. Englewood Cliffs, NJ: Prentice-Hall. Pp. 192-213. ZACKS,R. (1982) Encoding strategies used by young and elderly adults in a keeping track task. Journal of Gerontology, 37, 203-211. - -
Accepted March 11, 1991.
O Perceptual and Motor Skills 1991
SEX DIFFERENCES A N D EFFECTS O F AGING ON VISUOMOTOR COORDINATION ' JEAN-LOUIS BOUCHER, SUZANNE DENIS, AND JO-ANNE LANDRIAULT
Uniuersio of Ottawa Summary.-The purpose of this study was to examine the effects of aging on men and women in processing information required to reproduce direction and distance on a visuomotor task. Subjects (45 men and 45 women) selected from three age groups (25-34 yr., 45-54 yc, 65-74 yr.) were required to estimate blindly the exact criterion location of a target-point they had identified under one of the following conditions: visual, kinesthetic, and visuokinesthetic. Errors in direction (degrees) and in distance (cm) were recorded. The analysis of the total variability in responding (E) indicated that the women of the 65- to 74-yr. age group were significantly less accurate in estimating distance than were the men of the two older age groups (45 to 54 yr., 65 to 74 yr.) and less accurate than were the women of the 25- to 34-yr. age group. No significant differences in estimating distance were found among the three age groups of men. No significant differences for direction were found between men and women.
The accuracy with which the exact position of a target-point can be estimated appears to depend primarily (1) upon the accuracy with which the position of the target and that of the reaching limb can be localized in space (Paillard, 1976) and (2) upon the efficiency with which this information can be programmed in direction and in distance (Paillard, 1976; von Hofsten, 1986). According to Paillard and Beaubaton (1978) and to von Hofsten (1986), both vision and the proprioceptors have the potential to assist in defining the spatial coordinates of direction and distance needed to program movement information and to control motoricity efficiently. I t is fairly well recognized that aging decreases the efficiency with which the senses receive and convey the information to be processed by the brain; see Welford (1980) for a review. Of all the senses, the eye seems to deteriorate noticeably after age 50 (Botwinick, 1978). Neurons and muscle cells, as nondividing cells, are also prone to the effects of aging (Geist, 1968). Aging should, therefore, be expected to affect the efficiency with which visual and kinesthetic information is received and processed by the brain. Unfortunately, very little has been reported in the literature on how aging influences one's ability to process visual and kinesthetic information with reference to the execution of a visuospatial motor task. This observation becomes particularly significant when considered within the context of sex differences.
'This study was funded by a grant from the National Science and E n ineering Council of Canada. Requests for reprints should be sent to Jean-Louis Boucher, ~ c h o o p o fHuman Kinetics, University of Ottawa, 125 University, Ottawa, Ontario, Canada K I N 6N5.
508
J-L. BOUCHER, ET AL
Some suggestions have been made in the literature to the effect that aging may not appear as early or be as noticeable in women as in men (Botwinick, 1978; Rockstein, 1958). I t seems plausible, then, to expect that the effects of aging on visuospatial motor ability may be different for the two sexes. More specifically, aging may have a different effect on the ability of men and women to process the sensorimotor information needed to program the two parameters of direction and distance that underlie the accurate positioning of a limb in space. This study attempted to verify this assumption.
Subjects The subjects were 45 women and 45 men equally (n = 15) selected from three age groups (25 to 34 yr., 45 to 54 yr., 65 to 74 y t ) . The mean ages of the groups were 29.0, 48.7, and 68.6 yr. for women, and 28.4, 49.2, and 69.9 yr. for men. They were all right-handed volunteers recruited from various social community organizations and from the professorial and support staff of the University of Ottawa. All were free from any known medical sensory, neurological, and motor deficiencies according to the information gathered by means of a questionnaire. Cognitive ability of the subjects was not considered in this study since the experimental task was analogous to everyday reaching tasks. Experimental Task Subjects were required to estimate blindly the exact spatial location of target-points which they had preselected within an experimentally defined section of a pointing surface under one of the three following conditions: visual (V), kinesthetic (K), and visuokinesthetic (VK). I n the visual condition, subjects indicated verbally to the experimenter the criterion location of the target-point. I n the kinesthetic condition, subjects blindly reached out in space to a given section of the pointing surface to identify the criterion location of the target-point. I n the visuokinesthetic condition, subjects not only saw but also felt the displaced movement of their right upper segment as it reached out across the pointing surface to identify the criterion location of the target-point . Apparatus The testing apparatus included a pointing surface, a wooden box-like structure and a metal finger splint. The pointing surface consisted of a piece of styrofoam (45 cm x 60 cm) on which four intersecting lines were drawn resulting in nine equal rectangularly shaped pointing sections sequentially numbered from 1 to 9. A white semitransparent removable score sheet was set over the styrofoam to record (1) the identified criterion locations of the target-points and (2) the accuracy with which these locations were estimated.
VISUOMOTOR COORDINATION: SEX, AGE
509
A 2-cm x 2-cm block of styrofoam fastened at the center (30 cm) of the surface's edge closest and parallel to the subjects served as a starting point between trials. An open-ended wooden structure, 70 cm wide x 5 0 crn deep x 25 cm high at its lowest point and 50 crn at its highest point, rested over the pointing surface. A hinged cover allowed control for the presence of visual cues. An extremely fine and short needle was fastened vertically to the underside of a metal splint at a point corresponding approximately to the center of the third phalanx of the right index finger. Procedure Upon arrival at the testing area, each subject was requested to sit before the apparatus and to secure the metal splint on the right index finger. The pointing surface was then adjusted so that (1) the starting block coincided with the subject's sternum and (2) the index finger of the fully extended right arm could reach the center point of the more distant parallel edge of the surface. The wooden structure was adjusted so the subject's chin rested above the cover of the structure. Each subject received standardized instructions describing the task and six practice trials, two for each condition. Questions were answered. Subjects were informed that accuracy was of importance in this experiment. No reference was ever made to the speed of movement. A trial required that subjects (1) freely select and identify the criterion location of a target-point within an experimenter-defined section of the pointing surface and (2), following a 5-sec. interval, that they blindly estimate the exact location of this point. Before each trial, subjects were verbally informed of the section within w h c h the location of the target-point was to be identified. The criterion location of the target-points was selected by the subjects so as to allow them to better plan their movements and adopt more suitable reaching strategies than would have been possible if the location of the target-points had been imposed upon them. However, the sectors within which the location of each target-point had to be identified were experimentally defined to make certain that the target-points would be better distributed across the pointing surface and avoid any possible biasing effects due to the favoring by the subjects of a specific and restricted area on the pointing surface. The initial order of presentation of each of the nine sectors and for all three sensory conditions had been randomly selected prior to experimentation. This order was then systematically rotated for each subject. Under the visual condition, the subject kept the index finger on the starting block while the experimenter slowly moved in a random manner a felt-tipped pen held vertically over but not touching the area within the selected section until the subject said "stop." The experimenter recorded the criterion location of the target-point on the pointing surface. Under the kinesthetic and visuokinesthetic conditions, with the cover respectively closed
5 10
J-L. BOUCHER, ET AL.
or opened, the subject removed the index finger from the starting block and reached across the pointing surface to identify the target-point's location within the experimentally identified section. Using the needle affixed to the metal splint, the subject perforated the score sheet, waited 2 sec., and returned the finger to the starting block. The experimenter then placed a small ink dot over this perforation to identify it clearly as the criterion location of the target-point. All reproduction movements were executed in the absence of vision. At the command "reproduce," subjects removed their index finger from the starting block, reached underneath the closed cover of the wooden structure to the estimated location of the target-point, and perforated the score sheet. Having done so, the subject returned the index finger to the starting block in preparation for the next trial. One trial was given in each of the nine sectors and for each of the three sensory conditions, for a total of 27 trials per subject.
Error Recording Procedure Errors in distance were recorded as the signed longitudinal deviations (cm) of the estimated location from the criterion (0, 0) location. An overestimation of the target-point resulted in a positive error whereas an underestimation resulted in a negative error. Errors in direction were calculated as the signed angle between line Y,, i.e., the straight line extending from the center of the starting block to the criterion location of the targetpoint, and line Y,,i.e., the straight line originating from the center of the starting block to the estimated location of the target-point. The angle was recorded as negative when Y,was to the left of Y , and positive when to the right of Y,.
Design Because it is regarded by some writers as the best over-all measure of performance accuracy (e.g., Henry, 1975) and, because it reflects an exact combination measure of variability and bias (Schmidt, 1982, p. 69), the total variability error (E)in distance and in direction was selected as the measure of accuracy. A multivariate anaIysis of variance with repeated measures on the sensory condition factor (B.M.D.P.4V package) was used to analyze the data. Separate analyses of variance for distance and direction were used as post hoc procedures to identify the locus of a significant effect. Simple main effects for all significant univariate interactions were tested for significance (Keppel, 1982) and followed up with the Newman-Keuls procedure using a significance level of 5%.
RESULTSAND DISCUSSION The results of the multivariate analysis of variance gave a significant interaction of sex by age (A,,,,, = 2.42, p = .05). Post hoe analyses of variance
511
VISUOMOTOR COORDINATION: SEX, AGE
indicated a significant interaction of sex by age (F,,,,= 4.59, p = .01) for distance, but none was found for direction. The analysis of the simple main effects of age for men and for women showed that aging had a significant effect on the accuracy of distance for the women (F,,8, = 4.51, p < .01) but not for that of men. The Newman-Keuls procedure indicated that women between the ages of 65 and 74 yr. were significantly less accurate in distance (2.68 cm) than women between the ages of 25 and 34 yr. (2.12 cm). Further analysis showed that women of the 65- to 74-yr. age group were significantly less accurate in distance than the men of the same age group (2.16) and the men of the 45- to 54-yr. age group (2.12 cm). The analysis showed no other significant effects for age and sex. Having calculated a constant error smaller than the total variability for all of the above significant comparisons, it appears that these differences could be attributed to the amount of variability in the scores rather than to the amount of bias (Schmidt, 1982, p. 70). TABLE 1 MEANTOTALVARIABILITY (M CM) FOR DISTANCE: SEXAND AGE 25-34
Women Men
2.12 2.38
yc.
45-54 2.35 2.12
yr.
65-74
yr
2.68 2.16
The few studies that have been reported in the literature on how aging affects one's ability to process sensory information with reference to the execution of a visuospatial motor task does not allow us to make proper comparisons between the similarities and the differences that exist between the results of this study and the work of others. Consequently, confirmation of our results has proven to be a very difficult task. We can only speculate, at this time, as to what could have produced the differences in accuracy among the groups. The age-invariant hypothesis suggests that aging has a deteriorating effect on mental operations requiring effortful activity and not on automatic unrehearsable activities such as the encoding of spatial information (Hasher & Zacks, 1979). Addressing some of the issues raised by this hypothesis, Zacks (1982) concluded that the coding of such information may be more a matter of individual peference and decision. Some evidence (Hall & Leavitt, 1977) suggests that the coding process of distance should be viewed as a flexible attentional process that can be affected by such factors as subjects' strategies and task requirements. The coding process of distance can in fact require active encoding (Marteniuk, 1973) and be mentally rehearsed (Diewert, 1976). Hall and Leavitt (1977) concluded that in some circumstances and under certain conditions the coding of distance can be processed at a perceptual or at a conceptual level. It appears that the coding of distance can sometimes require the assistance of effortful attentional oper-
5 12
J-L. BOUCHER, ET AL.
ations. If this constitutes a valid explanation, then the coding of distance could be subject to the effects of the aging process. However, men did not differ in estimating distance regardless of their age group. I t is perhaps an indication that the coding of distance remains an automatic process in men regardless of age whereas, for women, it requires the assistance of some effortful attentional operations. The fact that, for women, the middle-age group did not differ significantly from the two other groups may be indicative of some transitional period. Further study is needed to substantiate this suggestion and to confirm the findings of this study. REFERENCES BOTWINICK, J. (1978) Aging and behavior. New York: Springer. DIEWERT, G. L. (1976) The role of vision and kinesthesis in coding of rwo-dimensional movement information. Journal of Human Movement Studies, 2, 191.198 implications. St. GUST, H. (1968) The psychological arpects of the aging process with ~ocrolo~~cal Louis, MO: Warren H . Green. HALL,C., & LEAVITT,J. L. (1977) Encoding and retention characterist~csof direction and distance. Journal of Human Movement Studies, 3, 88-98. HASHER,L., & ZACKS,R. (1979) Automatic and effortful processes in memory. Journal of Experimental Psychology: General, 108, 356-388. HENRY, F. M. (1975) Absolute error versus "E" in target accuracy. Journal of Motor Behavior, 7, 227-228. KEPPEL,G. (1982) Design and analysis: a researcher? handbook. Englewood Cliffs, NJ: PrenticeHall. MARTEN^, R. G. (1973) Retention characteristics of motor short-term memory cues. Journal of Motor Behavior, 5, 249-259. PAILLARD, J. (1976) Le codage nerveux des commandes mocrices. Revue d'EEG et de Nertrophysiologic, 6, 453-472. PAILLARD, J., & BEAUBATON, D. (1978) De la coordination visuo-motrice I'organisation de la saisie manuelle. In H. Hecean & M. Jeannerod (Eds.), Du contrhle de [a mohicitk ir l'ornunisation du -neste. Paris. France: Masson. Po. 225-260. ROCKSTEIN, M. (1958) Heredity and longevity in the animal kingdom. Journal of Gerontology, 13(Suppl. 2), 7-12. SCHMIDT,R. (1982) Motor control and learning. Champaign, IL: Human Kinetics. VON HOFSTEN,C. (1986) Early spatial perception taken in reference to manual action. Acta Psychologica, 63, 323-335. WELFORD,A. T. (1980) Sensory, perce tual, and motor processes in older adults. In J. E. Birren & R. Bruce (Eds.), Handfook of mental health ofaging. Englewood Cliffs, NJ: Prentice-Hall. Pp. 192-213. ZACKS,R. (1982) Encoding strategies used by young and elderly adults in a keeping track task. Journal of Gerontology, 37, 203-211. - -
Accepted March 11, 1991.
