Television Viewing at Home: Distances and Visual ...

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Television Viewing at Home: Distances and Visual Angles of Children and Adults John G. Nathan, Daniel R. Anderson, Diane E. Field and Patricia Collins Human Factors: The Journal of the Human Factors and Ergonomics Society 1985 27: 467 DOI: 10.1177/001872088502700410 The online version of this article can be found at: http://hfs.sagepub.com/content/27/4/467

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HUMAN

FACTORS,

1985,27(4),467-476

Television Viewing at Home: Distances and Visual Angles of Children and Adults JOHN G. NATHAN, DANIEL R. ANDERSON,l DIANE E. FIELD, and PATRICIA COLLINS, University of Massachusetts, Amherst, Massachusetts

Television viewing distances, visual angles, and viewing angles were calculated for 217 children and 149 adults from 78 families. The data were obtained from time-lapse videotapes automatically recorded in the families' homes over lO-day periods. Viewing distance increases with age, and visual angle decreases with age. Viewers aged 17 years and younger viewed at an average distance of 225.3 em, at an average visual angle of 12.3 deg, and at an average viewing angle of 23.7 deg. Adult viewers watched TV at an average distance of 336.8 em, an average visual angle of 6.6 deg, and at an average viewing angle of 23.3 deg. The best predictors of viewing location were (1) percentage of time the viewer watched TV from furniture, (2) room area, and (3) screen width.

There is little published research on the human factors of ordinary home television viewing despite television's status as the dominant news and entertainment medium. Research is desirable given recurrent public concerns about the physiological and psychological impact of television and given current intense interest in extending and redesigning transmission and receiver technology. In particular, detailed descriptions of ordinary television viewing behavior at home would be of use in evaluating the medium's impact and in providing baseline data against which the use of new technologies can be considered. The human factors aspect of present concern is the location of viewers relative to the TV screen. The design of videotext displays, the use of interactive devices, the development of new screen and audio technologies, I Requests for reprints should be sent to Daniel R. Anderson, Department of Psychology. University of Massachusetts, Amherst, MA 01003.

as well as concerns about the effects of radiation, all involve considerations of viewing distances and angles. There are, however, no published descriptive data on these aspects of television use. The present paper provides the first descriptive analyses of viewer location during normal television viewing at home. Recommendations for TV viewing location have been based primarily on perceptual and health considerations. McVey (1970), for example, recommended as optimum a viewing distance of 6.25 screen widths at a viewing angle normal to the screen thus sub tending a visual angle of 9 deg horizontally. The rationale for this recommendation is based on peripherally relevant perceptual research: Enoch (1959) had earlier reported that 9 deg was the optimal visual angle for presenting aerial photographs in search tasks. Hochberg and Brooks (1978), on the other hand, have argued that such recommendations are sim-

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1985

plistic because the complex interactions of distance, visual angle, viewing angle, picture resolution, and stimulus structure are not well understood. Other recommendations of viewing distances stem from concerns about the physical effects of television, especially with respect to radiation emitted by older color receivers. Estimates of viewers' radiation exposure have been calculated on the basis of data collected from discussions with Public Health Service employees from 741 households

in

the Washington, D.C., area (National Center for Radiological Health, 1968). These discussions indicated average viewing distances of 215.1 cm for viewers under 15 years of age and 298.4 cm for viewers over 15 years. There were no direct observations of TV viewing behavior as a validation of these distance estimates. As part of a larger study on home television viewing behavior (Anderson, Field, Collins, Lorch, and Nathan, in press), the present work examines actual TV viewing locations of adults and children. The research is not theoretically motivated but rather attempts to establish descriptive empirical information on the use of television within the home. The procedure involved analysis of timelapse videotapes of TV viewers automatically recorded in homes over lO-day periods. METHOD Subjects Seventy-eight families (three nonwhite) from metropolitan Springfield, Massachusetts, participated in the research. The families, each of which had a five-year-old child, consisted of 366 individuals (including family members and visitors). The family members ranged in age from less than 1 month to 63 years, and included 135 preschool children (69 males and 66 females), 60 elementaryschool-aged children (33 males and 27 fe-

FACTORS

males, aged 6 through 11 years), 22 adolescents (6 males and 16 females, aged 12 to 17 years), and 149 adults (71 males and 78 females, aged 18 to 63 years). As measured by the Hollingshead Four Factor Index of Social Status (1975), the families ranged from Level I (major business or professional occupations) to Level V (unskilled laborers and menial service workers). Twenty-nine (37.2%) families were at Level I, 31 (39.7%) at Level II, 14 (17.9%) at Level III, 3 (3.8%) at Level IV, and 1 (1.3%) at Level V. The modal family was at Level II, represented by medium business, minor professional, and technical occupations. Families, whose names were obtained from public birth records, were sent a letter explaining the study and later were contacted by telephone. Of those contacted, 12.2% actually completed the entire two-month procedure (which included laboratory visits and other procedures not relevant to the present paper). These families did not differ systematically on analyses of a large variety of demographic and TV viewing variables from control families who did not receive videotape equipment in their homes (Anderson et al., in press). All families were paid $25 for participation in the study. Detailed analyses of the families and selection factors appear in a paper by Anderson et al. (in press). The present descriptive analyses of viewer distance and angles are essentially incidental to the major purposes of the larger study. As such, time and expense limitations precluded testing family member's vision and audition. Table 1 provides relevant home viewing characteristics. Apparatus Each automated time-lapse video recording unitconsistedofa61.0cm x 66.0cm x 76.2 cm cart with wooden panels which contained the NEC model VC-750S black and white time-lapse videocassette deck as well as the


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TABLE 1

TV Viewing Characteristics of 78 Families Average number of televisions: Median diagonal screen size of TV most frequently used (em): Average number of rooms: Average TV viewing room size (m2) Average room area from which TV is viewable (m2)

1.7 48.3 7.0 20.5 15.8

control circuitry, time-date generator (RCA Model TC 144GB), screen splitter (TEL SS221), and battery backup devices. Connected to the cart were two video cameras. One camera (RCA Model TC1005) was equipped with a zoom lens (KOWA) and was directed at the family's TV screen. The other camera (RCA Model TC1025) was equipped with an 8.5-mm wide-angle lens with auto servo iris, which automatically compensated for changes in ambient illumination. Depending on the positioning of the cart in the TV room, the cameras were mounted either on a stand attached to the cart or on a tripod fixed to a sturdy base. Recording was initiated by the control circuitry whenever the TV set was turned on and was terminated when the set was turned off. Time-lapse recording without audio was at a ratio of 1:36 (one video frame each 1.2 s). Date and time were superimposed in one corner of the recorded image. An insert of the TV screen appeared every 18 s and remained for 6 s. An external LED signaled the family that the cassette was to be changed after 26 h of recording. Ten consecutive days of TV viewing were recorded for each family between March 1980 and December 1981.

Procedure Two or three installers went to the home of each participating family. Upon arrival, the procedure for installing the equipment was briefly explained to a parent, usually the mother, who provided information about fa-

vorite viewing locations in the room, lighting, and channel reception. At the end of the visit, the parent was instructed in the management of the videotape changes and was given telephone numbers to call at any time in case of equipment malfunction. Installation time was from 1.5 to 2 hours per unit. If more than one TV was regularly used in the home, and if the family agreed, camera uni ts were supplied for each room with a television (10 families of the present sample had multiple camera units; analyses will be presented for the most frequently used TV sets from these families). In each TV location, cameras were situated to record the TV viewing area as well as the TV screen. Of the area in the room from which a viewer could see the TV, an average of 60.9% was covered by the wide-angle lens. This area included the most likely TV viewing positions. The placement of the cart was unobtrusive but accessible for viewing the signal light and for changing the videotape. Furniture rearrangement was kept at a minimum to preserve the family's natural viewing patterns. Finally, dimensions of the TV room and its furnishings were measured, and a map was later drawn to scale. The videotapes were subsequently rated by means of time samples taken every 55 minutes of "television on" time over the lO-day recording period. The tapes were played on a Sony BVU 200 videocassette deck, which allowed playback at variable rates of speed. Two raters viewed the tapes on a high-resolution monitor, holding the tape in still frame mode to record the presence, location, and visual attention to the TV of each person in the viewing room. At each 55-minute stop of the tape, the rater coded on the scale drawing the location of a person and whether he or she was visually oriented toward the television screen. Analyses of the visual attention data will be reported in a subsequent paper (also see Anderson, in press, and Anderson


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and Field, 1983). Individuals were included as subjects only if they were observed a minimum of three times in the television viewing room and could be identified by age in a viewing diary maintained by the family. The average number of observations per individual for the 10 days was 16.6 and ranged from 3 to 62. Working from the coded viewing locations on the scale drawings, three measures were computed for each observation of each viewer. Viewing distance was measured from the viewer to the center of the television screen. Visual angle was computed as the angle sub tended horizontally by the TV screen with respect to the viewer. Measurements of vertical angles were not obtained, as they were very difficult to estimate and only rarely deviated substantially from that horizontal plane normal to the approximate plane formed by the screen surface. In addition, the viewing angle was defined as the acute angle formed by the line of gaze to the center of the screen and the line normal to the center of the screen. RESULTS Five dependent variables were derived from the observations of the viewing locations: absolute distance, relative distance in screen widths, percentage of observations in which the viewer was closer than 91.4 cm to the screen, visual angle (deg), viewing angle (deg), and percentage of observations in which the viewer was sitting or lying on furniture. Analyses considered averages of all viewing locations of each subject as well as modal (most typical) viewing location of each subject. Average and modal values were in general agreement; modal values are reported here unless otherwise indicated. Table 2 indicates for each dependent variable the average modal value and standard deviation as a function of age grouping: preschool (zero through 5 years), school-aged (6

FACTORS

through 11 years), adolescents (12 through 17 years), and adults (18 through 63 years). Age Grouping x Sex analyses of variance revealed significant age differences for absolute distance, F(3,358) = 35.7, p < 0.001; relative distance, F(3,358) = 24.7, p < 0.001; and visual angle, F(3,358) = 9.5, p < 0.001. Although there was no significant age trend of viewing angle, the proportion of observations that a viewer was extremely close (91.4 cm or less) to the TV steadily decreased with age, F(3,358) = 13.5, p < 0.001. The tendency to view TV while sitting or lying on a chair or couch increased with age so that adults almost always viewed TV from furniture, F(3,358) = 55.6, p < 0.001. The only significant effect related to sex was that males viewed slightly closer (257.8 em) than females (283.2 em), F(1,358) = 4.9, P < 0.05. Children are more variable in their viewing locations than are adults. Table 2 indicates the average of each subject's standard deviation of viewing distance as a function of age group: variability in viewing location decreases with age, F(3,358) = 16.1, p < 0.001. These analyses support our qualitative observation of the videotapes to the effect that, relative to children, adults view television from a favorite location, almost always on a given couch or chair. Children tend to be more active in front of the TV, often playing on the floor, and often moving from place to place in the room. They are also more likely than adults to be extremely close to the TV. This extremely close viewing tended to come from a few children who typically sat close to the TV set; 10.1% of children had their modal position within 91.4 cm, whereas only one adult typically viewed that close to the TV (he usually viewed while lying on the floor with his head right in front of the screen). Individual differences in viewing locations are illustrated separately for children and adults by the cumulative percentage frequency distributions in Figures 1, 2, 3, and 4.


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DISTANCES

TABLE 2

Average Values and (Standard Deviations) for TV Viewing Position as a Function of Age Group Age Group Preschool

135

n

Typical distance (cm)

School Age 60

Adolescent

Adult

22

149

228.6 (111.5)

220.2 (91.4)

218.4 (95.8)

336.8 (97.5)

5.9 (3.3)

5.7 (2.7)

5.6 (2.3)

Percentage of observations closer than 91.4 cm

11.2 (17.4)

8.9 (15.6)

5.7 (15.3)

8.6 (3.0) 1.3 (6.6)

Typical visual angle (deg)

12.3 (12.5)

13.0 (16.2)

10.6 (5.0)

6.6 (2.6)

Typical viewing angle (deg)

24.1 (19.0)

22.1 (17.8)

25.2 (15.4)

23.3 (15.3)

Percentage of observations on furniture

45.6

56.8

65.0

83.6

Average individual distance standard deviation (cm)

86.4

78.7

59.4

58.9

Relative typical distance

(W)

A single representation of the modal viewing locations that combines the data in Figures 2, 3, and 4 is shown in the scatter plot of

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< C~I) Figure 1. Cumulative percentage distribution of typical viewing distances in children (squares) and adults (plus signs). DISTANCE

Figure 5. The origin of the plot represents the center of the TV screen, and distances from the center of the screen are represented as screen widths. Data for children are plotted in the upper half of the figure and adult data are plotted in the lower half of the figure (actual position to the right or left of the screen was not coded). The dotted lines radiating from the origin represent viewing angle in 10deg increments, and the circles tangential to the center of the screen indicate regions of constant visual angle (4, 6, 8, 10,20, and 30 deg). The plot clearly reveals the betweensubjects variability and the relative differences between child and adult modal viewing locations. In a preliminary effort to account for choice of viewing location, we performed stepwise multiple linear regression analyses for the children as a combined group and separately for adults. Dependent variables were absolute distance, visual angle, and viewing angle. One set of analyses utilized viewable room area and characteristics of the TV set


472-August,

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1985

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