Perceptual nnd Motor Skills, 1977,44, 783-786. @ Perceptual and Motor Skills 1977

EFFECT OF WEIGHT AND SEX ON PERCEPTION OF LINE LENGTH LILLIAN L. GIBBS AND ROSEMARE ANDERSON' W a k e Forest Uniuer~ity Sttrnmasy.-56 obese and 103 normal-weight college students were asked to make line-length estimations of lines on either a light or dark background. Analysis of the results showed significant interactions between weight and contrast and sex and contrast, with the line estimations by women and normalweight individuals being more dependent on rhe contrast.

Schnchter's (1971) stimulus-binding hypothesis suggests that obese individuals are more responsive to excernal than internal stimuli for they eat more when external food stimuli are salient rather than absent. However, normalweight individuals more often eat in response to visceral stimuli (e.g., Schachter, 1971). Recently, Rodin ( 1973), Rodin and Slochower ( 1974), Stutz, Warm, and Woods ( 1974), and Rodin ( 1975) have demonstrated differences between obese and normal-weight individuals on a few non-consummatory behaviors. Specifically obese subjects evidenced greater incidental learning when excernal cues were relevant to the task, lower proofreading accuracy with increased audio distraction, and lower accuracy in temporal perception which is dependent on internal physiological cues. These differences may reflect the hypothesized differences in obese and normal-weight subject's responsiveness to external stimuli. Where the responsiveness to external stimulation is facilitating to performance, the obese subject's performance improves; where responsiveness is debilitating the obese subject's performance declines. This research investigated the effect of obese and normal-weight dassification on a different non-consummatory task, the perception of line-length. To heighten the salience of the line the line was contrasted against a light and dark background. It was predicted that increases in contrast will result in significant differences in the line-length estimations of obese and normal-weight subjects. However, the direction of this difference was not predicted since contrast may provide facilitating or debilitating information. Sex of subjects was included as an independent variable since sex differences are often found on spatial-perceptual tasks.

METHOD One hundred and fifty-nine undergraduate students participated as part of their research requirements for introductory psychology. Subjects were not forewarned that 'This article is based on a senior thesis supervised by the second author and submitted by the first author in partial fulfillment of the honors program in psychology at Wake Forest University. Requests for reprints should be sent to Lillian Gibbs, Department of Psychology, University of Florida, Gainesville, Florida 32611.

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L. L.

GIBBS

&

R. ANDERSON

the experiment dealt with weight and were free to sign up for 4/2-hr. sessions during a period of approximately 1 mo. Unfortunately, the number of subject-hours available was underestimated, resulting in unequal cell sizes in the design. Subjects were classified as either normal-weight or overweight. They were classified as overweight if they met two out of the folIowing three weight indicators: ( 1 ) above average desirable weight calculated from the Metropolitan Life Insurance Company (1959) norms for ideal weight, ( 2 ) above 27 mm for women and 15 mm for men on the skinfold measure taken with the Lange Skinfold Caliper (Montoye, 1970), and ( 3 ) che experimenter's subjective evaluation of each subject's weight. The third indicator involved a simple normal-weight/overweight evaluation of each subject by one of the two experimenters. This weight indicator was included because visual inspection of subjects in a pilot study indicated that some of them who were clearly overweight did not meet the other two criteria. The inter-judge reliability of a subset of 50 students between the two experimenters was .78. Subjects not meeting two of the three overweight indicators were classified as normal-weight. Table 1 illustrates the physical characteristics of the male and female subjects who were classified as either overweight or normal-weight. Male and female subjects who were classified as overweight were quite different on the two weight measures and quite similar in age and height from subjects classified as normal in weight. TABLE 1 Subjects

n

Males 65 Normal-weight Overweight 28 Females Normal-weight 38 Overweight 28 * M % weight deviation from

M ~ g e

M ~ o ~ g b t

Mwalehr

Deviation*

19.1 5 ft., 11 in. (1.80 m ) 18.6 5 ft., 10 in. (1.78 m )

159.7 1b. (72.44 kg) 193.0 1b. (87.54 kg)

.OO .21

18.9 5 ft., 5 in. (1.65 m ) 18.9 5 ft., 5 in. (1.65 m )

120.0 1b. (54.43 kg) 140.7 Lb. (63.82 kg)

.02 .20

height norm.

The lines used were 3/4 in. (1.91 cm) wide, flat black and 4 in. (10.16 c m ) , 9 in. (22.86 cm), and 12 in. (30.48 cm) lengths. They were centered at eye level on Homosite boards, 18 x 23 in. (45.72 un X 58.42 cm), which were painted light or dark grey. The paint tones were obtained by mixing black pigment with a quart of white flat Sherwin Williams paint, 1/32 oz. (.92 ml) for the light grey contrast, 3/16 oz. (2.77 ml) for the dark grey contrast. The grey boards were enclosed on both sides by boards of equal size, forming a tri-board panel which rested on the desk and produced a visually restricted environment. Above the tri-board panel was an ordinary study lamp with a 40-w bulb, the only source of light in the room. The Lange Skinfold Caliper measured the thickness of the pinched, folded skin plus subcutaneous fat tissue, an assessment of total body fat. Measurement was taken on the upper right triceps, the site which gives the most consistent and accurate measure (Montoye, 1970). Each subject. was randomly assigned to conditions of either light or dark contrast and of either a 4-, 9-, or 12-in. line. Each subject was asked to estimate the length of a line id inches using only visual inspection. H e made his estimation while seated in a darkened

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PERCEPTION OF LINE LENGTH

room in front of the tri-board panel, and after the experimenter uncovered the line. The experimenter then recorded the subject's sex, age, weight, height, and skinfold thickness. RESULTS AND DISCUSSION The results illustrated in Table 2 were analyzed using a 2 X 2 X 2 X 3 (sex X weight classification X contrast X line-length) least square analysis of variance. This analysis resulted in significant main effects for sex (Fl,l.?S= 5.27, 9 < .05), conuast (F2,136= 5.37, p < .05 ), and line-length (Fn,lns = 566.88, .p < .001), and significant interactions between sex and contrast (F1,1:3:, = 10.86, p < ,001), and weight by contrast ( F 1 . 1 3 ~= 6.26, p .01).


. While the interaction between sex, weight classification, and contrast was not significant, it is impossible to interpret the results without looking at the effect of contrast on the four groups of subjects. That is, the tendency for normal-weight subjects to give longer estimations to dark than light contrast was negligible among the males and marked among the females, and the tendency for females to give longer estimations to dark than light contrast was negligible among overweight women and marked among normal-weight. women. Thus the estimations made by normal-weight women were quite different than those made by subjects in the other three groups, making it impossible to evaluate the effect of contrast on estimations made by over- and normal-weight individuals, without considering the subject's sex. Moreover, the males' estimations show that overweight males did show a tendency toward greater reactivity to contrast than did normal-weight males as originally hypothesized for male and female subjects. REFERENCES LIFE INSURANCE COMPANY.New weight standards for men and womMETROPOLITAN , 40, 1-4. en. Statistical B ~ l l e f i n1959,

MONTOYE, H. J. (Ed.) An introduction to measurement in physical education. Vol. 2. Indianapolis, Ind.: Phi Epsilon Kappa Fraternity, 1970. RODIN, J. Effect of distraction on the performance of obese and normal subjects. Iorirnal of Comparative and Physiological Psychology, 1973, 8 3 , 68-78. RODIN,J. Causes and consequences of time perception differences in overweight and normal-weight people. Journal of Personality and SocMl Psychology, 1975, 32, 761-766. RODIN,J., & SLOCHOWER, J. Fat chance for a favor: obese-normal differences in compliance and incidental learning. Journal of Personality and Social Psychology, 1974, 29, 557-565. SCHACHTER, S. Some extraordinary facts about obese humans and rars. American Psychologist, 197 1, 26, 129-144. STUTZ, R. M., W W , J. S., & WOODS, W. A. Temporal perception in obese and normalweight subjects: a test of the stimulus-binding hypothesis. Bulletin of the Psychonomic Society, 1974, 3, 23-24.

Accepted February 18, 1977.

Effect of weight and sex on perception of line length.

Perceptual nnd Motor Skills, 1977,44, 783-786. @ Perceptual and Motor Skills 1977 EFFECT OF WEIGHT AND SEX ON PERCEPTION OF LINE LENGTH LILLIAN L. GI...
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