Psychological Reports, 1975, 37, 195-200. @ Psychological Reports 1975
EFFECTS OF FREQUENCY, DURATION OF STUDY TRIAL A N D TOTAL DURATION OF EXPOSURE O N AFFECTIVE JUDGMENTS MARY G. MARCUS AND KARL L. HAKMILLER
University of Connecticut Summary.-Studies of frequency and duration of exposure of stimuli, e.g., Chinese characters, Turkish words, faces, paintings, have traditionally been factorial, resulting in confounding among the parameters of frequency, duration of study trial, and total duration of exposure. This study attempted to separate the effects of these variables o n affective ratings. 6 0 male and female introductory psychology students served as subjects. T h e stimuli were slides of female nudes. There were three comparison conditions, each of which was itself a within-subjects design in which two levels of two variables were established and repeated measures made for a given subject. Subjects viewed the slides and then rated them o n attractiveness. Results indicate that, if total duration of exposure is held constant, no changes in judgments of attractiveness occur whereas, if total duration increases and duration of study trial o r frequency increases concurrently, increases in ratings of attractiveness, or affect, will occur.
Studies of the relationship between frequency or duration of exposure of stimuli and affective judgments of these stimuli have traditionally employed factorial designs to examine main and interactive effects. Zajonc and his colleagues have used this approach in studying the "mere exposure" effect which they define as the enhancement of affective judgments of neutral or positive stimuli by virtue of mere re-presentation of the stimuli. Thus, they have used simultaneous manipulation of frequency and duration of discrete exposures with the finding of a main effect for frequency but no consistent effect for duration of exposure. In Harrison and Zajonc's (1970) study in which Chinese ideographs were presented for exposures of 2 sec. or 10 sec. with 1, 2, 5, 10, or 25 scattered repetitions of each stimulus, liking for the stimuli increased with increased frequency of presentation but, there was no effect for duration of exposure. Harrison and Hines (1970) also manipulated frequency and duration of exposure, finding effects of both frequency and duration of exposure. However, their duration effect, alchough significant, did not conform to the predictions of the "mere exposure" hypothesis. They found that stimuli shown for 1 sec. did not produce ratings of affect different from stimuli shown for 1/25 sec. but both these stimuli were rated higher in "goodness" than those exposed for 1/10 sec. per exposure. The basic problem with all experiments which have manipulated exposure duration and frequency of exposure concurrently is that the noted effects are subject to other explanations. Frequency is generally considered to be the num-
196
M.G. MARCUS
8r
K.L. HAKMILLER
ber of exposures of a stimulus. Duration of exposure is considered to be the time from the onset to the offset of a single stimulus, but it is also (Stang, 1975) sometimes referred to as the total duration of exposure of a single stimulus. These three parameters are related in such a way that total duration of exposure is the product of frequency multiplied by duration of exposure per trial. Thus, frequency cannot be manipulated independently of total duration of exposure, and it is quite possible that those studies which have reported effects of frequency or duration of study trial are actually demonstrating effects of total duration. For example, in the Harrison and Zajonc (1970) study mentioned previously, total duration increased as frequency increased and so it is equally possible to attribute the results to a total duration phenomenon as to a frequency of exposure effect. A study by Postman and Warren ( 1972 ) lends support to the notion that total duration of exposure may indeed be the factor which is responsible for changes in affect. Tested in the present study was the total-time hypothesis of free-recall learning which states that it is the total time for presentation which determines recall, regardless of length of list to be recalled or rate of presentation. Postman and Warren found that the amount recalled did not vary across their three conditions in which they manipulated list length and rate of presentation while holding total time of presentation constant. These findings suggest that the effects of total duration should be examined in terms of "mere exposure" because total time of exposure may be critical to changes in affect as well as recall. The confounding among the parameters of frequency, duration of study trial and total duration led to the present study which sought to determine the effect of each factor upon affective judgments. T o avoid confounding, an unorthodox design with three conditions was used. In each condition, one of the parameters was held constant and the other two allowed to vary. The objective here was to allow one to conclude that, if an effect occurred in any one condition, the effect certainly could not be attributed to the factor held constant but instead could be attributed to either one of the other parameters or an interaction of both. Given the nature of the present design, it is impossible to separate out the main effects from the interactions. Thus, for example, if an effect occurred with total duration constant, the effect would be due to duration of study trial or frequency or an interaction of the two. Any over-all conclusions about the relationship between a given variable or variables and affective judgments would result from inferences based on comparison of data across the three conditions. It was hoped that the results of the present study could point to a basis for resolving divergent results of various experiments on frequency of exposure and duration of exposure.
FACTORS 1N AFFECTlVE JUDGMENT
NLETHOD Subjects
The subjects were 60 male and female introductory psychology students. There were 6 males and 14 females in each condition. The experimenter was female. Stimulus Materials and Apparatus
The stimuli were 10 colored slides of college-aged nude females. The stimuli were presented to subjects via a Kodak Carousel projector which had been programmed by a Kodak Programmer/Magnavox Tape Recorder system to expose the slides for varying time intervals. Procedure Initial presentation of stamuli.-The subject was told that all instructions would be delivered by t a F recorder. H e was then informed via tape that he would see a set of slides of nude females and that he would later be asked to make some judgments about the slides. He was also told to concentrate on the slides for the entire length of time they were exposed. There were three treatments or conditions, each of which was itself a within-subjects design in which two levels of two variables were established and repeated measures made for a given subject. When total duration was held constant, five of the nude slides were exposed 12 times each for 8 sec. o n each occasion (Set A ) while the remaining five slides were exposed 4 times each for 24 sec. (Set B ) . In the condition in which frequency was constant, half the slides were shown 4 times each for 8 sec. (Set B ) while the other half were shown 4 times each for 24 sec. each time (Set A ) . Finally, when duration of study trial was constant, all slides were shown 24 sec. with the frequency of 12 for half the slides (Set A ) and 4 for the other half (Set B ) . Two orders of presentation were used in each condition and slides were randomly assigned to levels of the variables. Attractiveness ratings.-A rating phase immediately followed the presentation of slides in each condition. The measure of affect in this experiment consisted of judgments of attractiveness of the slides. Thus, the subjects were asked to rate the 10 slides on a 0 to 100 scale, on the basis of how attractive they thought the girls in the slides were. Each of the 10 slides was presented for 4 sec. with a 4-sec. interslide interval, and subjects were asked to give ratings immediately after each slide went off. Subjects were instructed that the more they liked a slide, the higher they should rate it.
RESULTS A difference score was calculated for each subject based on the difference between slide mean ratings of attractiveness for Set A and Set B. t tests for related measures were performed comparing the differences between Set A and
M. G. MARCUS
178
&
K. L. HAKMILLER
Set B means across subjects within conditions. The results of the t tests for males and females are shown in Table 1. As indicated by the tabled data, when total duration was held constant, no differences were found between ratings of attractiveness for those slides shown more frequently and consequently for a shorter duration of study trial and ratings for those slides seen less frequently and for a longer duration of study trial. From the data one may conclude that, for both males and females, when total duration is held constant, a "mere exposure" effect does not occur. The t tests for the Frequency Constant condition indicate a significant effect .05) but none for females. The effect for males leads one to for males ( p conclude that for them, increased liking of the slides is the result of increases in duration of study trial and/or increased total duration of exposure. When duration of study trial was held constant, there is a strong effect for .01) but no effect for males. Thus, for females a relationship females ( p emerges between frequency and/or total duration of exposure and judgments of attractiveness. The data are in the direction of increased liking related to increased frequency and total duration of exposure. Inspection of the means in each condition suggests that a Sex X Treatment interaction exists in the conditions in which duration of study trial and frequency are held constant.
EFFECTS OF FREQUENCY, DURATION OF STUDY TRIAL A N D TOTAL DURATION OF EXPOSURE O N AFFECTIVE JUDGMENTS MARY G. MARCUS AND KARL L. HAKMILLER
University of Connecticut Summary.-Studies of frequency and duration of exposure of stimuli, e.g., Chinese characters, Turkish words, faces, paintings, have traditionally been factorial, resulting in confounding among the parameters of frequency, duration of study trial, and total duration of exposure. This study attempted to separate the effects of these variables o n affective ratings. 6 0 male and female introductory psychology students served as subjects. T h e stimuli were slides of female nudes. There were three comparison conditions, each of which was itself a within-subjects design in which two levels of two variables were established and repeated measures made for a given subject. Subjects viewed the slides and then rated them o n attractiveness. Results indicate that, if total duration of exposure is held constant, no changes in judgments of attractiveness occur whereas, if total duration increases and duration of study trial o r frequency increases concurrently, increases in ratings of attractiveness, or affect, will occur.
Studies of the relationship between frequency or duration of exposure of stimuli and affective judgments of these stimuli have traditionally employed factorial designs to examine main and interactive effects. Zajonc and his colleagues have used this approach in studying the "mere exposure" effect which they define as the enhancement of affective judgments of neutral or positive stimuli by virtue of mere re-presentation of the stimuli. Thus, they have used simultaneous manipulation of frequency and duration of discrete exposures with the finding of a main effect for frequency but no consistent effect for duration of exposure. In Harrison and Zajonc's (1970) study in which Chinese ideographs were presented for exposures of 2 sec. or 10 sec. with 1, 2, 5, 10, or 25 scattered repetitions of each stimulus, liking for the stimuli increased with increased frequency of presentation but, there was no effect for duration of exposure. Harrison and Hines (1970) also manipulated frequency and duration of exposure, finding effects of both frequency and duration of exposure. However, their duration effect, alchough significant, did not conform to the predictions of the "mere exposure" hypothesis. They found that stimuli shown for 1 sec. did not produce ratings of affect different from stimuli shown for 1/25 sec. but both these stimuli were rated higher in "goodness" than those exposed for 1/10 sec. per exposure. The basic problem with all experiments which have manipulated exposure duration and frequency of exposure concurrently is that the noted effects are subject to other explanations. Frequency is generally considered to be the num-
196
M.G. MARCUS
8r
K.L. HAKMILLER
ber of exposures of a stimulus. Duration of exposure is considered to be the time from the onset to the offset of a single stimulus, but it is also (Stang, 1975) sometimes referred to as the total duration of exposure of a single stimulus. These three parameters are related in such a way that total duration of exposure is the product of frequency multiplied by duration of exposure per trial. Thus, frequency cannot be manipulated independently of total duration of exposure, and it is quite possible that those studies which have reported effects of frequency or duration of study trial are actually demonstrating effects of total duration. For example, in the Harrison and Zajonc (1970) study mentioned previously, total duration increased as frequency increased and so it is equally possible to attribute the results to a total duration phenomenon as to a frequency of exposure effect. A study by Postman and Warren ( 1972 ) lends support to the notion that total duration of exposure may indeed be the factor which is responsible for changes in affect. Tested in the present study was the total-time hypothesis of free-recall learning which states that it is the total time for presentation which determines recall, regardless of length of list to be recalled or rate of presentation. Postman and Warren found that the amount recalled did not vary across their three conditions in which they manipulated list length and rate of presentation while holding total time of presentation constant. These findings suggest that the effects of total duration should be examined in terms of "mere exposure" because total time of exposure may be critical to changes in affect as well as recall. The confounding among the parameters of frequency, duration of study trial and total duration led to the present study which sought to determine the effect of each factor upon affective judgments. T o avoid confounding, an unorthodox design with three conditions was used. In each condition, one of the parameters was held constant and the other two allowed to vary. The objective here was to allow one to conclude that, if an effect occurred in any one condition, the effect certainly could not be attributed to the factor held constant but instead could be attributed to either one of the other parameters or an interaction of both. Given the nature of the present design, it is impossible to separate out the main effects from the interactions. Thus, for example, if an effect occurred with total duration constant, the effect would be due to duration of study trial or frequency or an interaction of the two. Any over-all conclusions about the relationship between a given variable or variables and affective judgments would result from inferences based on comparison of data across the three conditions. It was hoped that the results of the present study could point to a basis for resolving divergent results of various experiments on frequency of exposure and duration of exposure.
FACTORS 1N AFFECTlVE JUDGMENT
NLETHOD Subjects
The subjects were 60 male and female introductory psychology students. There were 6 males and 14 females in each condition. The experimenter was female. Stimulus Materials and Apparatus
The stimuli were 10 colored slides of college-aged nude females. The stimuli were presented to subjects via a Kodak Carousel projector which had been programmed by a Kodak Programmer/Magnavox Tape Recorder system to expose the slides for varying time intervals. Procedure Initial presentation of stamuli.-The subject was told that all instructions would be delivered by t a F recorder. H e was then informed via tape that he would see a set of slides of nude females and that he would later be asked to make some judgments about the slides. He was also told to concentrate on the slides for the entire length of time they were exposed. There were three treatments or conditions, each of which was itself a within-subjects design in which two levels of two variables were established and repeated measures made for a given subject. When total duration was held constant, five of the nude slides were exposed 12 times each for 8 sec. o n each occasion (Set A ) while the remaining five slides were exposed 4 times each for 24 sec. (Set B ) . In the condition in which frequency was constant, half the slides were shown 4 times each for 8 sec. (Set B ) while the other half were shown 4 times each for 24 sec. each time (Set A ) . Finally, when duration of study trial was constant, all slides were shown 24 sec. with the frequency of 12 for half the slides (Set A ) and 4 for the other half (Set B ) . Two orders of presentation were used in each condition and slides were randomly assigned to levels of the variables. Attractiveness ratings.-A rating phase immediately followed the presentation of slides in each condition. The measure of affect in this experiment consisted of judgments of attractiveness of the slides. Thus, the subjects were asked to rate the 10 slides on a 0 to 100 scale, on the basis of how attractive they thought the girls in the slides were. Each of the 10 slides was presented for 4 sec. with a 4-sec. interslide interval, and subjects were asked to give ratings immediately after each slide went off. Subjects were instructed that the more they liked a slide, the higher they should rate it.
RESULTS A difference score was calculated for each subject based on the difference between slide mean ratings of attractiveness for Set A and Set B. t tests for related measures were performed comparing the differences between Set A and
M. G. MARCUS
178
&
K. L. HAKMILLER
Set B means across subjects within conditions. The results of the t tests for males and females are shown in Table 1. As indicated by the tabled data, when total duration was held constant, no differences were found between ratings of attractiveness for those slides shown more frequently and consequently for a shorter duration of study trial and ratings for those slides seen less frequently and for a longer duration of study trial. From the data one may conclude that, for both males and females, when total duration is held constant, a "mere exposure" effect does not occur. The t tests for the Frequency Constant condition indicate a significant effect .05) but none for females. The effect for males leads one to for males ( p conclude that for them, increased liking of the slides is the result of increases in duration of study trial and/or increased total duration of exposure. When duration of study trial was held constant, there is a strong effect for .01) but no effect for males. Thus, for females a relationship females ( p emerges between frequency and/or total duration of exposure and judgments of attractiveness. The data are in the direction of increased liking related to increased frequency and total duration of exposure. Inspection of the means in each condition suggests that a Sex X Treatment interaction exists in the conditions in which duration of study trial and frequency are held constant.
