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Computer analysis and display of movement patterns
JOURNAL
OF EXPERIMENTAL
Computer
CHILD
Analysis
PSYCHOLOGY
and
8,
Display
4@44 (1969)
of Movement
Patterns1
R. E. HERRON~AND M. J. FROBISH” University A description
of Illinois
is given of an automatic
method for producing numerical or organismfrom observational records. The method
and graphical statements about movement and inter-organism
environment interaction patterns is basedon useof Cartesianco-ordinatesto representthe position of each individual at each instant sampled. In a,ddition to statistical computations regarding distances travelled, the frequency of entry into specified territories, sociometric and other parameters, movement maps can be produced with the aid of a plotting device connected to a computer. The program can be adapted for various investigations concerning social interaction, territoriality, equipment usage, activity habits, and architectural design.
In 1960, Wright warned that progress in realizing the potential of electronic observational child study would “depend on development of analysis procedures to suit the new refinement and fidelity of its records [p. 1241.” Today, this need is vividly apparent and, as accessto simply operated electronic observational aids continues to grow, so will the backlog of unanalyzed visual records of child behavior continue to build up until suitably refined, automatic methods of analysis are widely available. A special problem exists with studies involving activity observations over periods longer than a few minutes because they tend to produce large quantities of position data which ultimately, have to be reduced to meaningful statements about the patterns of movement or interaction ‘This research was supported in part by grant MH-07346 from the National Institute of Mental Health and a grant (Project 9424) to the first author from the Illinois State Department of Mental Health. The authors thank R. J. Korb who was responsible for selecting the photographic equipment and processing the photographs ; L. Wuellner, Research Assistant, who carried out the observations; M. J. Ellis, Research Associate, and P. A. Witt, Research Assistant, for their helpful suggestions, and J. Kolmun, Statistical Consultant, who contributed advice on programming. They are also indebted to the staff, parents, and children (the subjects) of the Children’s Research Center Preschool at the University of Illinois for their kind cooperation, and Drs. W. P. Hurder and A. V. S p,apora who helped in various ways to make this research possible. ‘Now at Baylor University College of htedicine, Texas Medical Center, Houston, Texas 77025. *Now at Bradley University, Peoria, Illinois 61606. 40
ANALYSIS
OF
MOVEMENT
PATTERNS
41
involved before they can be interpreted. When the analysis has to be carried out manually, as often is the case, it is a tedious and timeconsuming task-a state of affairs which does nothing to encourage an exhaustive analysis. The method described below grew out of efforts to aut’omate a series of studies of children’s movement patterns, social interaction, territoriality, and equipment usage in an indoor play area. The purpose of this report is to outline the principle upon which the method is based and to discuss some of the potentialities and limitations. METHOD
Data Collection Spatio-temporal position da,ta were obtained by means of a time-lapse photographic system; this system was chosen in preference to film or videotape, or electronic devices such as ultrasonic or radio transmission, on account of its relatively low cost, ease of maintenance, and simplicity of operation. A remotely controlled N&on F camera was semipermanent,ly mounted in the ceiling, 9 feet above a, 291/s- X 22-foot indoor play area in the Children’s Research Center of the University of Illinois. The camera was equipped with an accessory Accura fish-eye lens fitted to a 50-mm, f 1.4, Nikkor lens and an accessory 250-exposure motor drive so that an extended sequence of time-lapse exposures could be taken automatically. The 7.5-mm focal length of the combined lenses takes in a true hemisphere and the entire play nrca was within the field of view. In a recent experiment, the photographs were taken at intervals of 10 seconds throughout a series of 15-minute play sessions,but the system includes an intcrvalometer which provides for varying the time between exposures over a wide range. The only manual step in the data acquisition process was the identification of each child’s position on each photograph in terms of Cartesian co-ordinates. A grid of three-foot squares which shows up distinctly in the photographs was used to obviate the need for manually superimposing a co-ordinate scale over each photograph. The child’s position was taken as the point on the floor which was estimated to be directly below the child’s center of gravity. This step was carried out manually for want of a suitable and inexpensive automatic procedure-the semiautomatic method previously described by Haith (1966) in this journal is not too feasible when a fish-eye lens is used for taking the photographs. Areas or “territories” enclosing certain pieces of fixed equipment were also identified by Cartesian co-ordinates. These dat)a when transferred to IBM cards served as the input to the computer-plotter.
42
HERRON
Computer
Analysis
AND
FROBISH
a,nd Plotter
Display
Once the position data are in the form of Cartesian co-ordinates the computer-plotter can be programed to yield various permutations of the following numerical and graphical data : 1. Each child’s changes in position during each play session displayed graphically, in chronological order, on a plan view of the play area (Fig. 1). 2. The distance represented by the total changes in position of each child per play session and the mean distance for each child over all sessions. 3. The aggregate distance between each child and each of the other children for each exposure and for each play session. 4. The mean distance between each child and each of the other children during each play session computed and displayed as a function of time (i.e., with succeeding play sessions). 5. The frequency of entry of each child into each of the specified territories for each play session computed and displayed as a function of time. 6. The frequency each child is alone in each territory per play session and the incidence of solitary a,ctivity computed and displayed as a function of time. 7. The frequency each child is accompanied by selected permutations of other children in each territory per play session computed and displayed as a function of time. 8. The aggregate frequency of entries by all children into each of the specified territories for each play session computed and displayed as a function of time. All of the above output components have yet to be incorporated into a single program and this may seldom be necessary because of the considerable breadth of inquiry which such a program would represent. St&ice it to say that these computations and displays are within the capa,city of current computer-plotter combinations and that additional parameters or more elaborate statistical treatments can be added with little difficulty. The graphical displays shown in Figure 1 were produced with the aid of a program written in Fortran II for an IBM 7094 computer and a CalComp 670-564 (California Computer Products) plotter. The figure is composed of two “movement maps,” drawn automatically by the plotter, which indicate the positions and changes of position of two children during the same play session, with Child A’s map on the left and Child
ANALYSIS
OF
MOVEMENT
PATTERNS
FIG. 1. Corresponding movement patterns of two children by a computer-plotter. (For explanation, see text.)
43
drawn
automatically
B’s map on the right. Each map covers the same indoor play area. The area was liberally distributed with various pieces of play equipment, such as large hollow blocks, ladders, and a see-saw. The apparatus was omitted here in order to simplify reading of the map, but the relative positions of immovable objects can be added if desired, by means of a template. Differences between the two children in their foca,l points of interest and their movement patterns during the period in question show up quite distinctly. DISCUSSION
The above method has certain fairly obvious limitations-an important one is illustrated in the above examples. Movements between the points (showing the child’s position every 10 seconds) which the plotter joins up with straight lines to form the map are completely missed. This illustrates the need to carefully consider such matters as the sampling interval and the use of random versus regular intervals. Such decisions will be influenced greatly by the exigencies of each experimental situation as will the reliability and validity of the method. But, preliminary findings indicate that, with reasonable care, high levels of reliability and validity
are attainable.
44
HERRON
A&-D
FROBISH
Until an automatic method of recor,ding co-ordinate dnt,a and punching this information on cards or another suitable medium is developed, analysis of the pictures will rema,in a formidable undertaking except where the observations are limited to very short periods or a long interval between exposures is used. There is also the limitation, where photographic or other direct visual recording media are used, that the subject may disappear wholly or partially from view (by getting equipment between themselves and the lens). However, these limitations reside in the data acquisition system and not in the analysis procedure. Once position data are in the form of Cartesian co-ordinates, many different mathematical and statistical manipulations are possible. The above list of output components is not an exhaustive one; new elements can be programed as the need arises, for example, with some adjustments the analysis can be adapted to cope with three-dimensional position data, or to analyze and display movement patterns throughout a complex of rooms or an entire building. The method is now being applied in two somewhat different spheres of behavioral research-children’s play and hospital design-where the users’ claim that it is proving to be a useful research tool. REFERENCES HAITH, M. Journal WRIGHT, H. research
M. A semi-automaticprocedure for measuringchangesin position. of Experimental
Child
Psychology,
1966, 3, 23MQ5.
F. Observationalchild study. In P. H. Mussen (Ed.), Handbook methods in child development. New York: Wiley, 1960. Pp. 71-139.
for
OF EXPERIMENTAL
Computer
CHILD
Analysis
PSYCHOLOGY
and
8,
Display
4@44 (1969)
of Movement
Patterns1
R. E. HERRON~AND M. J. FROBISH” University A description
of Illinois
is given of an automatic
method for producing numerical or organismfrom observational records. The method
and graphical statements about movement and inter-organism
environment interaction patterns is basedon useof Cartesianco-ordinatesto representthe position of each individual at each instant sampled. In a,ddition to statistical computations regarding distances travelled, the frequency of entry into specified territories, sociometric and other parameters, movement maps can be produced with the aid of a plotting device connected to a computer. The program can be adapted for various investigations concerning social interaction, territoriality, equipment usage, activity habits, and architectural design.
In 1960, Wright warned that progress in realizing the potential of electronic observational child study would “depend on development of analysis procedures to suit the new refinement and fidelity of its records [p. 1241.” Today, this need is vividly apparent and, as accessto simply operated electronic observational aids continues to grow, so will the backlog of unanalyzed visual records of child behavior continue to build up until suitably refined, automatic methods of analysis are widely available. A special problem exists with studies involving activity observations over periods longer than a few minutes because they tend to produce large quantities of position data which ultimately, have to be reduced to meaningful statements about the patterns of movement or interaction ‘This research was supported in part by grant MH-07346 from the National Institute of Mental Health and a grant (Project 9424) to the first author from the Illinois State Department of Mental Health. The authors thank R. J. Korb who was responsible for selecting the photographic equipment and processing the photographs ; L. Wuellner, Research Assistant, who carried out the observations; M. J. Ellis, Research Associate, and P. A. Witt, Research Assistant, for their helpful suggestions, and J. Kolmun, Statistical Consultant, who contributed advice on programming. They are also indebted to the staff, parents, and children (the subjects) of the Children’s Research Center Preschool at the University of Illinois for their kind cooperation, and Drs. W. P. Hurder and A. V. S p,apora who helped in various ways to make this research possible. ‘Now at Baylor University College of htedicine, Texas Medical Center, Houston, Texas 77025. *Now at Bradley University, Peoria, Illinois 61606. 40
ANALYSIS
OF
MOVEMENT
PATTERNS
41
involved before they can be interpreted. When the analysis has to be carried out manually, as often is the case, it is a tedious and timeconsuming task-a state of affairs which does nothing to encourage an exhaustive analysis. The method described below grew out of efforts to aut’omate a series of studies of children’s movement patterns, social interaction, territoriality, and equipment usage in an indoor play area. The purpose of this report is to outline the principle upon which the method is based and to discuss some of the potentialities and limitations. METHOD
Data Collection Spatio-temporal position da,ta were obtained by means of a time-lapse photographic system; this system was chosen in preference to film or videotape, or electronic devices such as ultrasonic or radio transmission, on account of its relatively low cost, ease of maintenance, and simplicity of operation. A remotely controlled N&on F camera was semipermanent,ly mounted in the ceiling, 9 feet above a, 291/s- X 22-foot indoor play area in the Children’s Research Center of the University of Illinois. The camera was equipped with an accessory Accura fish-eye lens fitted to a 50-mm, f 1.4, Nikkor lens and an accessory 250-exposure motor drive so that an extended sequence of time-lapse exposures could be taken automatically. The 7.5-mm focal length of the combined lenses takes in a true hemisphere and the entire play nrca was within the field of view. In a recent experiment, the photographs were taken at intervals of 10 seconds throughout a series of 15-minute play sessions,but the system includes an intcrvalometer which provides for varying the time between exposures over a wide range. The only manual step in the data acquisition process was the identification of each child’s position on each photograph in terms of Cartesian co-ordinates. A grid of three-foot squares which shows up distinctly in the photographs was used to obviate the need for manually superimposing a co-ordinate scale over each photograph. The child’s position was taken as the point on the floor which was estimated to be directly below the child’s center of gravity. This step was carried out manually for want of a suitable and inexpensive automatic procedure-the semiautomatic method previously described by Haith (1966) in this journal is not too feasible when a fish-eye lens is used for taking the photographs. Areas or “territories” enclosing certain pieces of fixed equipment were also identified by Cartesian co-ordinates. These dat)a when transferred to IBM cards served as the input to the computer-plotter.
42
HERRON
Computer
Analysis
AND
FROBISH
a,nd Plotter
Display
Once the position data are in the form of Cartesian co-ordinates the computer-plotter can be programed to yield various permutations of the following numerical and graphical data : 1. Each child’s changes in position during each play session displayed graphically, in chronological order, on a plan view of the play area (Fig. 1). 2. The distance represented by the total changes in position of each child per play session and the mean distance for each child over all sessions. 3. The aggregate distance between each child and each of the other children for each exposure and for each play session. 4. The mean distance between each child and each of the other children during each play session computed and displayed as a function of time (i.e., with succeeding play sessions). 5. The frequency of entry of each child into each of the specified territories for each play session computed and displayed as a function of time. 6. The frequency each child is alone in each territory per play session and the incidence of solitary a,ctivity computed and displayed as a function of time. 7. The frequency each child is accompanied by selected permutations of other children in each territory per play session computed and displayed as a function of time. 8. The aggregate frequency of entries by all children into each of the specified territories for each play session computed and displayed as a function of time. All of the above output components have yet to be incorporated into a single program and this may seldom be necessary because of the considerable breadth of inquiry which such a program would represent. St&ice it to say that these computations and displays are within the capa,city of current computer-plotter combinations and that additional parameters or more elaborate statistical treatments can be added with little difficulty. The graphical displays shown in Figure 1 were produced with the aid of a program written in Fortran II for an IBM 7094 computer and a CalComp 670-564 (California Computer Products) plotter. The figure is composed of two “movement maps,” drawn automatically by the plotter, which indicate the positions and changes of position of two children during the same play session, with Child A’s map on the left and Child
ANALYSIS
OF
MOVEMENT
PATTERNS
FIG. 1. Corresponding movement patterns of two children by a computer-plotter. (For explanation, see text.)
43
drawn
automatically
B’s map on the right. Each map covers the same indoor play area. The area was liberally distributed with various pieces of play equipment, such as large hollow blocks, ladders, and a see-saw. The apparatus was omitted here in order to simplify reading of the map, but the relative positions of immovable objects can be added if desired, by means of a template. Differences between the two children in their foca,l points of interest and their movement patterns during the period in question show up quite distinctly. DISCUSSION
The above method has certain fairly obvious limitations-an important one is illustrated in the above examples. Movements between the points (showing the child’s position every 10 seconds) which the plotter joins up with straight lines to form the map are completely missed. This illustrates the need to carefully consider such matters as the sampling interval and the use of random versus regular intervals. Such decisions will be influenced greatly by the exigencies of each experimental situation as will the reliability and validity of the method. But, preliminary findings indicate that, with reasonable care, high levels of reliability and validity
are attainable.
44
HERRON
A&-D
FROBISH
Until an automatic method of recor,ding co-ordinate dnt,a and punching this information on cards or another suitable medium is developed, analysis of the pictures will rema,in a formidable undertaking except where the observations are limited to very short periods or a long interval between exposures is used. There is also the limitation, where photographic or other direct visual recording media are used, that the subject may disappear wholly or partially from view (by getting equipment between themselves and the lens). However, these limitations reside in the data acquisition system and not in the analysis procedure. Once position data are in the form of Cartesian co-ordinates, many different mathematical and statistical manipulations are possible. The above list of output components is not an exhaustive one; new elements can be programed as the need arises, for example, with some adjustments the analysis can be adapted to cope with three-dimensional position data, or to analyze and display movement patterns throughout a complex of rooms or an entire building. The method is now being applied in two somewhat different spheres of behavioral research-children’s play and hospital design-where the users’ claim that it is proving to be a useful research tool. REFERENCES HAITH, M. Journal WRIGHT, H. research
M. A semi-automaticprocedure for measuringchangesin position. of Experimental
Child
Psychology,
1966, 3, 23MQ5.
F. Observationalchild study. In P. H. Mussen (Ed.), Handbook methods in child development. New York: Wiley, 1960. Pp. 71-139.
for