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Sequential analysis of visual habituation in preschool children
JOURNAL
OF EXPERIMENTAL
Sequential
CHILD
PSYCHOLOGY
24, 495-504
( 1977)
Analysis of Visual Habituation Preschool Children
in
PATRICK R. HARRISON AND E. JON SODERSTROM
The study breaks down the data from a preschool (mean age months) visual habituation experiment using a second-by-second entire process. including fixation time and onsets for habituation trials and for each intertrial interval. The results parallel those Cohen. DeLoach, and Rissman (Child flr~vlopme~zr, 1975. for infants and are described using a two-process model of visual
of students, 63 analysis of the and recovery suggested by 46, 611-617). attention.
A number of studies have established response decrement and recovery to visual stimuli in preschool children (Banta, Sciarra, & Jett, 1966; Bernal & Miller, 1970; Cantor & Cantor, 1966; Dodd & Lewis, 1969; Harrison & Ruth, 1975: Lewis & Baumel, 1970; Lewis & Goldberg, 1969; Lewis, Goldberg, & Rausch, 1967; Mackworth & Otto, 1970). These studies have included behavioral analysis (Banta, Sciarra, & Jett, 1966; Dodd & Lewis, 1969: Lewis & Baumel, 1970; Lewis, Goldberg, & Rausch, 1967: Mackworth & Otto, 1970), physiological analysis (Bernal & Miller, 1971: Lewis & Goldberg, 1969) or both (Lewis & Goldberg, 1969). In all cases, the basic unit of analysis has been the trial. The basic dependent variable has been behavioral fixation time or change in heart rate. Various techniques have also been used for smoothing the data analyzed, such as combining trials into blocks (e.g., Bernal & Miller. 1971) or combining series of habituation trials involving different stimuli (e.g., Lewis & Baumel, 1970; Lewis & Goldberg, 1969). Such analyses focus on the decrement process in a rather global fashion. Data are not provided which describe what is going on during the duration of each stimulus repetition or during each intertrial interval, or are such data sufficient for analysis of the contributions of the onset and offset properties of the stimulus. Yet the breakdown of the data from such studies to a more minute unit of analysis. with attention to the course of decrement throughout the process, would seem requisite to the aim of Requests for reprints should be addressed to Dr. Patrick R. Harrison who is now at the Department of Leadership and Law, U. S. Naval Academy, Annapolis, MD 21402. The authors would like to thank Ron Hansen and the staff of F.U.N. school for providing space and subjects for this study.
496
HARRISON
AND
SODERSTROM
researchers who hope to tie behavioral data with various theoretical models, such as that proposed by Sokolov (1963) or Groves and Thompson (1970, 1973). That such a microscopic approach can produce fruitful results has been illustrated by Cohen, DeLoach. and Rissman (1975). Cohen replaced total fixation per trial by two measures, latency of first fixation to the target stimulus (attention getting) and subsequent fixation to the target (attention holding). yielding a two-process model of infant visual attention. Attention to latency of first fixation yielded important new information. It therefore seems important to analyze the course of habituation in a more detailed and continuous fashion. This study provides a detailed analysis of the course of habituation of preschool children to visual stimuli using behavioral measures as data. My preliminary studies have produced consistent sex differences in response to visual stimulation, females showing greater fixation to stimulation than males. Such differences have not been reported in the preschool visual habituation literature. It was, therefore, our feeling that the results of Cohen’s article might be extended to the analysis of the process with preschool children. Fixation time, onsets (fixations within trials). and distribution of fixations throughout the process were considered. The guiding assumption (made in all such studies) is that when the subject is looking (fixating) at the target, he is attending to it. That this assumption is valid has been demonstrated (e.g.. Lewis & Baumel, 1970). METHOD Subjects
The subjects were 24 preschool children with mean age of 63 months and an age range from 56 to 68 months. The distributions for male and female subjects were essentially the same. The sample consisted of 12 females and 12 males randomly sampled from a local nursery school population. These subjects were randomly assigned to conditions. Apparatus A completely enclosed viewing booth was constructed in a large naturally lighted classroom. One panel of the booth could be opened and closed for admittance of the child. The stimuli were back-projected onto a 2.5cm wide and 30-cm high projection screen centerline and 107 cm from the base of the flat, black center panel of the booth. The screen was positioned such that it would be eye level to the subject seated facing it. The seat was positioned 91 cm from the screen. Data were taken by two observers external to the viewing booth through peepholes 10 cm to the left and right and 30 cm up from the viewing screen. Each observer had a small box with a depressor button which electronically triggered an
VISUAL
497
HABITUATION
Esterline Angus event recorder, recording onset, duration, and offset of each fixation. Stimuli were presented using two Kodak Carousel projectors fitted with converted T-scope shutters. Stimulus onset, duration, offset, and the intertrial interval were automatically programmed using a Lafayette repeat cycle timer which pulsed the Lafayette T-scope control unit. The programmed sequence was also automatically recorded on one pen of the Esterline Angus recorder to simplify data analysis. The other Kodak projector was continuously on, showing a filtered white light of equal subjective intensity subjectively equal throughout the process. Figure 1 shows the stimuli used in the study. Actual projection size was 20(w) x 30(h) cm. Procedure
Each child was escorted from the nursery classroom to the experimental classroom by the experimenter. The subject could see neither the apparatus nor the observers stationed behind the viewing booth. The child was seated in the viewing booth and was given a standardized instruction (Harrison & Ruth, 1975): “We are going to play a game with you. Please stay in your seat. I will come and get you when the game is over.” The experimenter then left the booth and closed the door. At no time was there contact between observers and subject. The subject was then presented with eight 30-set presentations of one pattern followed by one 30-set recovery trial using the alternate stimulus followed by another 30-set presentation of the habituation stimulus. Stimuli were counterbalanced so that an equal number of male and female subjects was given the Sl-S2-Sl sequence and the S2-Sl-S2 sequence. An intertrial interval of 10 set was used. After the tenth trial, the experimenter escorted the child back to the classroom.
I':\T'I‘KliN FIG.
I 1. Patterns
I'AI‘TF:liN used
in the
study.
II
498
HARRISON
ANDSODERSTROM
Interrater reliability was taken on all subjects. The average product moment correlation was .97, with a range from .77 to .99. RESULTS All data were taken from continuous Esterline-Angus recordings. Tire data were broken down in two ways. The first way considered both total fixation time and the number of onsets for each habituation trial, the recovery trial, and each intertrial interval. The best estimate of total fixation time per trial was taken as the mean of the fixation times reported by the two observers. Onsets refer to the number of times the subject fixated (looked toward) the target. A second, more minute breakdown consisted of a second-by-second analysis of the data record for each subject. Thus. 30 I-set contiguous data points were constructed for each trial and 10 such points for each intertrial interval. In each second, one of the following was coded: onset (looking toward the stimulus) looking, not looking, or offset (looking away from the stimulus). Thus. for each subject, a total of 390 data points was constructed. In view of the previously reported interrater reliability, only the continuous recordings for the more experienced observer were used at this level. A 2 (sex) Y 2 (counterbalanced stimuli) K 10 (habituation trials I-X and 10. and recovery trial 9) factorial ANOVA was employed for overall analysis of habituation and recovery (total fixation time per trial). The analysis yielded a main effect for sex, Ft IJO) = 6.47, p < .02. showing
VISUAL HABITUATION
499
females fixating significantly more than males, and for trials, F(9.180) = p < .OOOl. The main effect for counterbalancing and all interactions were nonsignificant. Newman-Keuls comparison (0.5 level) showed the trial 1 and trial 9 (recovery trial) means to be significantly greater than all other trial means but not significantly different from each other. All the possible pairs involving trials 2-8 plus 10 involved nonsignificant differences. Figure 2 shows overall habituation and recovery. The data were reanalyzed using the general model proposed by Lewis and Baumel (1970). The best fit curve was a negative exponential, Y = 13.06 + 18~.j”, F(1,6) = 61.13, p < .Ol, RS = .91. The observed recovery response was a distance of 9.9 standard deviation units from the predicted point on the regression line. The best fit line is superimposed on the actual data in Fig. 2. Thus, we have clear evidence for habituation and recovery. A 2 (sex) x 2 (counterbalanced stimuli) x 10 (trials) factorial ANOVA was also used to investigate the physical orientations (number of onsets) of the subjects to the display. The analysis yielded a main effect for trials, F (9,180) = 2.05, p -=c.05. No other effects or interactions were significant. Newman-Keuls comparison of the trials effect indicated that trials 1, 2, and 5 produced significantly more orientations than the recovery trial (9). The trials effect suggests a high number of fixations on early trials, with a suppression of fixations on the recovery trial. This is interesting, in view of the fact that trials 1 and 9 produced the highest total fixation time. Analysis of the intertrial interval was approached differently. Since we used the standard fixed trial length for the sake of across-subject comparisons, one could assume that three possible effects might be operating. Since fixations could be continuing at the end of each habituation trial, one might expect some carry-over into the intertrial interval. In addition, we might expect responses to both the stimulus offset and the blank slide projected during the interval. A regression analysis for overall fixation time during the intertrial interval for each trial (I -8) preceding the recovery trial suggested to a best fit linear function, Y = 4.27 + .35X, F (1,6) = 23.96. p < .Ol, R” = .80. There was also a significant negative exponential component, Y = 1.9 + 3.9r-,“z, F (I,61 = 14.05, p c: .Ol, R” = .70. The actual fixation time for the intertrial interval following recovery was 2.33 standard deviation units from the predicted point on the linear regression line. These analyses suggest that, in part, what happens during the intertrial interval reflects the habituation and recovery process. If such be the case, one would expect a predictive relationship between the two. A linear regression model was employed with habituation fixation time as the dependent variable and fixation time during the succeeding intertrial interval as the independent variable. The results were significant, F (I, 22) = 43.9, p < .Ol, R’ = .82. It would thus appear that what happens dur-
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FIG. 3. Second-by-second breakdown of the number intertrial interval, and the recovery trial.
8
TRIALS ITI-1)
of fixations
for each habituation
trial.
ing the intertrial interval is a reflection of what happened on the previous habituation trial. However, the fact that the best fit regression function was a decreasing linear function rather than a negative exponential, as was the habituation curve, would suggest that part of the effect cannot be accounted for as carry-over. Figure 3 includes a plot of the number of fixations during the intertrial interval for each second. It is apparent that the number of fixations during the intertrial interval is a fragile
VISUAL
I
501
HABITUATION
-
FEMALE
TRIAL FIG. 4. Ratio of total fixation females across trials.
time over
number
of onsets
(fixations
per trial)
for males and
phenomenon, with most fixations early in the interval and a fast decay to a low level of responding by the middle of the interval. The same analysis was tried using the onset data for the IT1 as the independent variable. The results were nonpredictive, with essentially zero correlation between previous habituation fixation and subsequent onsets during the ITI. Nonsignificant results were also obtained using habituation trial onsets as the dependent variable and IT1 onsets as the independent variable. The fact that females showed significantly greater fixation time than males, but at the same time similar onsets or number of fixations within trials, suggests that females look for longer periods within trials. Figure 4 shows a plot of the ratio of total fixation time per trial over the number of onsets per trial for both females and males across trials. Clearly, females are attending for longer periods of time within trials on all trials. One might assume that onsets and fixation time are correlated, yet the correlation between the two measures was nonsignificant (Y = -.14). Figure 3 shows the results of a second-by-second analysis of each habituation trial, the recovery trial, and each intertrial interval. The data point for each second represents the number of subjects fixating the stimulus during that second. Thus, the maximum amount of fixation time for any I-set section would be 24 set, or 24 subjects. Comparisons of the graphs for each trial immediately suggest some trends. There is an increase
502
HARRISON
AND
SODERSTROM
in number of fixations in all habituation trials from Second 1 to Second 2. This could be a result of an artifact, since the ongoing behavior of the organism is not accounted for. However, comparison of the last second of each IT1 with the first second of the subsequent habituation trial suggests an increase in number of fixations in all trials. This is especially apparent for the recovery trial. One could posit that during the first second a response to the stimulus onset should occur and that habituation to onset should occur, since the response would be considered part of the OR. A 2 (sex) x 2 (counterbalanced stimuli) x 10 (trials) factorial ANOVA was used to analyze the first-second fixation data for all trials. The analysis produced no significant main effects and no significant interactions. The data were reanalyzed using a regression model. No negative exponential fit was found, F (I ,6) = 3.68. Thus. there appears to be no habituation across trials during the first second of each presentation. The second trend that is apparent is that more fixations occur early than late in each trial. Trial 1 and the recovery trial (9) are exceptions to this trend. There is sustained fixation for both of these trials. A separate 2 (sex) x 10 (trials) factorial ANOVA was used to analyze number of fixations during Seconds 2, 3, and 4. The results showed no significant main effects or interactions for Seconds 2 and 3. However, for Second 4, there was a significant trials effect. F (9,198) = 3.35;~ < .Ol, and a significant sex effect, F (1,22) = 8.9, p < .Ol . There were no significant interactions. The sex effects showed females fixating more than males. The trials effect was further analyzed using a Newman-Keuls at the .05 level. Trial 1 produced significantly greater fixations than trials 5 and 7. These were the only significant comparisons to emerge. However, reanalysis using a regression procedure produced a best fit negative exponential, Y = .7 + .46e--.“,‘. F(l.6) = 9.06.1, < .05. R’ = .60. The actual recovery point was 2.9 standard deviation units from the predicted point on the regression line. This suggests that habituation is beginning early in each trial, but not until Second 4. Since trial 1 and the recovery trial represent first presentations of a particular stimulus and because the distribution of the number of fixations was comparable and distinct from other trials, an attempt was made to predict recovery using trial I total fixation time as an independent variable. The results were nonsignificant, F (I ,22) = 2.5, R” = .lO. DISCUSSION
The microscopic analysis of the habituation process suggests some interesting extensions of our current knowledge concerning visual habituation of preschool children. We have demonstrated a clear overall habituation and recovery effect fitting a negative exponential. Further analysis of trial 1 and the recovery trial using a regression procedure adds support to
VISUAL
HABITUATION
503
the contention that recovery is an independent process. The overall results then are consonant with those of Lewis and Baumel(1970) and fit conceptually with the basic idea of OR habituation (Sokolov, 1963) and sensitization (Groves & Thompson. 1970. 1973; Thompson, Groves, Teyler, & Roemer, 1973). Further. it appears that the habituation is occurring early in the intervals but not in the first 3 sec. The data for Seconds 1 through 3 show no evidence of habituation. One could conclude, then, that the attention-getting component of the process is not habituating (Cohen et ul., 1975), but habituation starts early in each interval (by Second 4). We also see a significant sex difference, with females fixating longer than males but at the same time showing similar onsets or fixations within intervals. Analysis of the total fixation time per trial over number of onsets per trial suggests females attended for longer periods of time within trials on all trials. This suggests that females are capable of more sustained attention than males. The work of Pederson and Bell (1970). for example, provides convergence with this finding. The results are suggestive of the two-process model of visual attention suggested by Cohen et al. ( 1975). His model was derived from data on 4month-old infants. Similar results emerge from our study of preschoolers. One could posit two processes: an attention-getting process and an attention-holding process. The low correlation between fixations and onsets suggest that they are independent. It would also appear that it is the attention-holding process that is habituating. REFERENCES Banta.
T. J., Sciarra. J., & Jett, J. Nursery school children’s observation responses to novel, complex and asymmetrical complex stimuli. Percepption nerd P.sychophysics, 1966, 1, 165-167. Bernal, M. E., & Miller, W. H. Electrodermal and cardiac responses of schizophrenic children to sensory stimuli. Psychophysi&gg. 1970. 7, 155- 168. Cantor, J. H., & Cantor, G. N. Functions relating children’s observing behavior to amount and recency of stimulus familiarization. Jolrrnal oj’Experimenra/ Psychology. 1966, 72, 8.59-863. Cohen. L. B.. DeLoach, J. S., & Rissman. M. W. The effect of stimulus complexity on infant visual attention and habituation. Child Development, 1975, 46, 61 l-617. Dodd. C., & Lewis. M. The magnitude of the orienting response in children as a function of changes in color and contour. Jolcrrml of’E.rperimenru/ Child Psychology, 1969. 8, 296-305. Groves, P. M., &Thompson. R. F. A dual process theory of habituation: Neural mechanisms. In H. V. L. Peake & M. J. Herz (Eds.). Habituation. New York: Academic Press, 1973. Vol. 2, pp. 175-205. Groves, P. M., & Thompson, R. F. Habituation: A dual-process theory. Psyc~hdogiccd Rrviaw, 1970, 77. 419-450. Harrison, P. R.. & Ruth, M. D. The effects of antecedent instruction on visual habituation of preschool children. Bit&tin nj’Ps~chonotnic Socirf~. 1975. 5, 105- 108.
504
HARRISON
AND SODERSTROM
Lewis, M., & Baumel, M. H. A study in the ordering of attention. Percepptltal and Motor Skills, 1970, 31, 979-990. Lewis, M., & Goldberg, S. The acquisition and violation of expectancy: An experimental paradigm. Journal oj’Experimentu1 Child Psychology, 1969. 7, 70-80. Lewis, M., Goldberg, S.. & Rausch, M. Attention distribution as a function of novelty and familiarity. Psyhonomic Science, 1967, 7, 227-228. Mackworth, N. H.. 8.1Otto, D. A. Habituation of the visual orienting response in young children. Perception und Psychophysics, 1970, 7. 173- 178. Pedersen, F. A., & Bell, R. Q. Sex differences in preschool children without histories of complicationsofpregnancyanddelivery. Derelopmentu/Ps?‘choio~~~ 1970,3,10-15. Sokolov, Y. N. Perceptiorl and the conditioned reflex. New York: MacMillan Co.. 1963. Thompson. R. F.. Groves, P. M.. Teyler. T. J., & Roemer. R. A. A dual-process theory of habituation: Theory and behavior. In H. V. S. Peake & M. J. Herz (Eds.). Habitution New York: Academic Press, 1973. Vol. I, pp. 239-271. RECEIVED: July 7, 1976; REVISED: December 14. 1976.
OF EXPERIMENTAL
Sequential
CHILD
PSYCHOLOGY
24, 495-504
( 1977)
Analysis of Visual Habituation Preschool Children
in
PATRICK R. HARRISON AND E. JON SODERSTROM
The study breaks down the data from a preschool (mean age months) visual habituation experiment using a second-by-second entire process. including fixation time and onsets for habituation trials and for each intertrial interval. The results parallel those Cohen. DeLoach, and Rissman (Child flr~vlopme~zr, 1975. for infants and are described using a two-process model of visual
of students, 63 analysis of the and recovery suggested by 46, 611-617). attention.
A number of studies have established response decrement and recovery to visual stimuli in preschool children (Banta, Sciarra, & Jett, 1966; Bernal & Miller, 1970; Cantor & Cantor, 1966; Dodd & Lewis, 1969; Harrison & Ruth, 1975: Lewis & Baumel, 1970; Lewis & Goldberg, 1969; Lewis, Goldberg, & Rausch, 1967; Mackworth & Otto, 1970). These studies have included behavioral analysis (Banta, Sciarra, & Jett, 1966; Dodd & Lewis, 1969: Lewis & Baumel, 1970; Lewis, Goldberg, & Rausch, 1967: Mackworth & Otto, 1970), physiological analysis (Bernal & Miller, 1971: Lewis & Goldberg, 1969) or both (Lewis & Goldberg, 1969). In all cases, the basic unit of analysis has been the trial. The basic dependent variable has been behavioral fixation time or change in heart rate. Various techniques have also been used for smoothing the data analyzed, such as combining trials into blocks (e.g., Bernal & Miller. 1971) or combining series of habituation trials involving different stimuli (e.g., Lewis & Baumel, 1970; Lewis & Goldberg, 1969). Such analyses focus on the decrement process in a rather global fashion. Data are not provided which describe what is going on during the duration of each stimulus repetition or during each intertrial interval, or are such data sufficient for analysis of the contributions of the onset and offset properties of the stimulus. Yet the breakdown of the data from such studies to a more minute unit of analysis. with attention to the course of decrement throughout the process, would seem requisite to the aim of Requests for reprints should be addressed to Dr. Patrick R. Harrison who is now at the Department of Leadership and Law, U. S. Naval Academy, Annapolis, MD 21402. The authors would like to thank Ron Hansen and the staff of F.U.N. school for providing space and subjects for this study.
496
HARRISON
AND
SODERSTROM
researchers who hope to tie behavioral data with various theoretical models, such as that proposed by Sokolov (1963) or Groves and Thompson (1970, 1973). That such a microscopic approach can produce fruitful results has been illustrated by Cohen, DeLoach. and Rissman (1975). Cohen replaced total fixation per trial by two measures, latency of first fixation to the target stimulus (attention getting) and subsequent fixation to the target (attention holding). yielding a two-process model of infant visual attention. Attention to latency of first fixation yielded important new information. It therefore seems important to analyze the course of habituation in a more detailed and continuous fashion. This study provides a detailed analysis of the course of habituation of preschool children to visual stimuli using behavioral measures as data. My preliminary studies have produced consistent sex differences in response to visual stimulation, females showing greater fixation to stimulation than males. Such differences have not been reported in the preschool visual habituation literature. It was, therefore, our feeling that the results of Cohen’s article might be extended to the analysis of the process with preschool children. Fixation time, onsets (fixations within trials). and distribution of fixations throughout the process were considered. The guiding assumption (made in all such studies) is that when the subject is looking (fixating) at the target, he is attending to it. That this assumption is valid has been demonstrated (e.g.. Lewis & Baumel, 1970). METHOD Subjects
The subjects were 24 preschool children with mean age of 63 months and an age range from 56 to 68 months. The distributions for male and female subjects were essentially the same. The sample consisted of 12 females and 12 males randomly sampled from a local nursery school population. These subjects were randomly assigned to conditions. Apparatus A completely enclosed viewing booth was constructed in a large naturally lighted classroom. One panel of the booth could be opened and closed for admittance of the child. The stimuli were back-projected onto a 2.5cm wide and 30-cm high projection screen centerline and 107 cm from the base of the flat, black center panel of the booth. The screen was positioned such that it would be eye level to the subject seated facing it. The seat was positioned 91 cm from the screen. Data were taken by two observers external to the viewing booth through peepholes 10 cm to the left and right and 30 cm up from the viewing screen. Each observer had a small box with a depressor button which electronically triggered an
VISUAL
497
HABITUATION
Esterline Angus event recorder, recording onset, duration, and offset of each fixation. Stimuli were presented using two Kodak Carousel projectors fitted with converted T-scope shutters. Stimulus onset, duration, offset, and the intertrial interval were automatically programmed using a Lafayette repeat cycle timer which pulsed the Lafayette T-scope control unit. The programmed sequence was also automatically recorded on one pen of the Esterline Angus recorder to simplify data analysis. The other Kodak projector was continuously on, showing a filtered white light of equal subjective intensity subjectively equal throughout the process. Figure 1 shows the stimuli used in the study. Actual projection size was 20(w) x 30(h) cm. Procedure
Each child was escorted from the nursery classroom to the experimental classroom by the experimenter. The subject could see neither the apparatus nor the observers stationed behind the viewing booth. The child was seated in the viewing booth and was given a standardized instruction (Harrison & Ruth, 1975): “We are going to play a game with you. Please stay in your seat. I will come and get you when the game is over.” The experimenter then left the booth and closed the door. At no time was there contact between observers and subject. The subject was then presented with eight 30-set presentations of one pattern followed by one 30-set recovery trial using the alternate stimulus followed by another 30-set presentation of the habituation stimulus. Stimuli were counterbalanced so that an equal number of male and female subjects was given the Sl-S2-Sl sequence and the S2-Sl-S2 sequence. An intertrial interval of 10 set was used. After the tenth trial, the experimenter escorted the child back to the classroom.
I':\T'I‘KliN FIG.
I 1. Patterns
I'AI‘TF:liN used
in the
study.
II
498
HARRISON
ANDSODERSTROM
Interrater reliability was taken on all subjects. The average product moment correlation was .97, with a range from .77 to .99. RESULTS All data were taken from continuous Esterline-Angus recordings. Tire data were broken down in two ways. The first way considered both total fixation time and the number of onsets for each habituation trial, the recovery trial, and each intertrial interval. The best estimate of total fixation time per trial was taken as the mean of the fixation times reported by the two observers. Onsets refer to the number of times the subject fixated (looked toward) the target. A second, more minute breakdown consisted of a second-by-second analysis of the data record for each subject. Thus. 30 I-set contiguous data points were constructed for each trial and 10 such points for each intertrial interval. In each second, one of the following was coded: onset (looking toward the stimulus) looking, not looking, or offset (looking away from the stimulus). Thus. for each subject, a total of 390 data points was constructed. In view of the previously reported interrater reliability, only the continuous recordings for the more experienced observer were used at this level. A 2 (sex) Y 2 (counterbalanced stimuli) K 10 (habituation trials I-X and 10. and recovery trial 9) factorial ANOVA was employed for overall analysis of habituation and recovery (total fixation time per trial). The analysis yielded a main effect for sex, Ft IJO) = 6.47, p < .02. showing
VISUAL HABITUATION
499
females fixating significantly more than males, and for trials, F(9.180) = p < .OOOl. The main effect for counterbalancing and all interactions were nonsignificant. Newman-Keuls comparison (0.5 level) showed the trial 1 and trial 9 (recovery trial) means to be significantly greater than all other trial means but not significantly different from each other. All the possible pairs involving trials 2-8 plus 10 involved nonsignificant differences. Figure 2 shows overall habituation and recovery. The data were reanalyzed using the general model proposed by Lewis and Baumel (1970). The best fit curve was a negative exponential, Y = 13.06 + 18~.j”, F(1,6) = 61.13, p < .Ol, RS = .91. The observed recovery response was a distance of 9.9 standard deviation units from the predicted point on the regression line. The best fit line is superimposed on the actual data in Fig. 2. Thus, we have clear evidence for habituation and recovery. A 2 (sex) x 2 (counterbalanced stimuli) x 10 (trials) factorial ANOVA was also used to investigate the physical orientations (number of onsets) of the subjects to the display. The analysis yielded a main effect for trials, F (9,180) = 2.05, p -=c.05. No other effects or interactions were significant. Newman-Keuls comparison of the trials effect indicated that trials 1, 2, and 5 produced significantly more orientations than the recovery trial (9). The trials effect suggests a high number of fixations on early trials, with a suppression of fixations on the recovery trial. This is interesting, in view of the fact that trials 1 and 9 produced the highest total fixation time. Analysis of the intertrial interval was approached differently. Since we used the standard fixed trial length for the sake of across-subject comparisons, one could assume that three possible effects might be operating. Since fixations could be continuing at the end of each habituation trial, one might expect some carry-over into the intertrial interval. In addition, we might expect responses to both the stimulus offset and the blank slide projected during the interval. A regression analysis for overall fixation time during the intertrial interval for each trial (I -8) preceding the recovery trial suggested to a best fit linear function, Y = 4.27 + .35X, F (1,6) = 23.96. p < .Ol, R” = .80. There was also a significant negative exponential component, Y = 1.9 + 3.9r-,“z, F (I,61 = 14.05, p c: .Ol, R” = .70. The actual fixation time for the intertrial interval following recovery was 2.33 standard deviation units from the predicted point on the linear regression line. These analyses suggest that, in part, what happens during the intertrial interval reflects the habituation and recovery process. If such be the case, one would expect a predictive relationship between the two. A linear regression model was employed with habituation fixation time as the dependent variable and fixation time during the succeeding intertrial interval as the independent variable. The results were significant, F (I, 22) = 43.9, p < .Ol, R’ = .82. It would thus appear that what happens dur-
500
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25
4
SECONDS WITHIN (HABITUATION-:
FIG. 3. Second-by-second breakdown of the number intertrial interval, and the recovery trial.
8
TRIALS ITI-1)
of fixations
for each habituation
trial.
ing the intertrial interval is a reflection of what happened on the previous habituation trial. However, the fact that the best fit regression function was a decreasing linear function rather than a negative exponential, as was the habituation curve, would suggest that part of the effect cannot be accounted for as carry-over. Figure 3 includes a plot of the number of fixations during the intertrial interval for each second. It is apparent that the number of fixations during the intertrial interval is a fragile
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FEMALE
TRIAL FIG. 4. Ratio of total fixation females across trials.
time over
number
of onsets
(fixations
per trial)
for males and
phenomenon, with most fixations early in the interval and a fast decay to a low level of responding by the middle of the interval. The same analysis was tried using the onset data for the IT1 as the independent variable. The results were nonpredictive, with essentially zero correlation between previous habituation fixation and subsequent onsets during the ITI. Nonsignificant results were also obtained using habituation trial onsets as the dependent variable and IT1 onsets as the independent variable. The fact that females showed significantly greater fixation time than males, but at the same time similar onsets or number of fixations within trials, suggests that females look for longer periods within trials. Figure 4 shows a plot of the ratio of total fixation time per trial over the number of onsets per trial for both females and males across trials. Clearly, females are attending for longer periods of time within trials on all trials. One might assume that onsets and fixation time are correlated, yet the correlation between the two measures was nonsignificant (Y = -.14). Figure 3 shows the results of a second-by-second analysis of each habituation trial, the recovery trial, and each intertrial interval. The data point for each second represents the number of subjects fixating the stimulus during that second. Thus, the maximum amount of fixation time for any I-set section would be 24 set, or 24 subjects. Comparisons of the graphs for each trial immediately suggest some trends. There is an increase
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in number of fixations in all habituation trials from Second 1 to Second 2. This could be a result of an artifact, since the ongoing behavior of the organism is not accounted for. However, comparison of the last second of each IT1 with the first second of the subsequent habituation trial suggests an increase in number of fixations in all trials. This is especially apparent for the recovery trial. One could posit that during the first second a response to the stimulus onset should occur and that habituation to onset should occur, since the response would be considered part of the OR. A 2 (sex) x 2 (counterbalanced stimuli) x 10 (trials) factorial ANOVA was used to analyze the first-second fixation data for all trials. The analysis produced no significant main effects and no significant interactions. The data were reanalyzed using a regression model. No negative exponential fit was found, F (I ,6) = 3.68. Thus. there appears to be no habituation across trials during the first second of each presentation. The second trend that is apparent is that more fixations occur early than late in each trial. Trial 1 and the recovery trial (9) are exceptions to this trend. There is sustained fixation for both of these trials. A separate 2 (sex) x 10 (trials) factorial ANOVA was used to analyze number of fixations during Seconds 2, 3, and 4. The results showed no significant main effects or interactions for Seconds 2 and 3. However, for Second 4, there was a significant trials effect. F (9,198) = 3.35;~ < .Ol, and a significant sex effect, F (1,22) = 8.9, p < .Ol . There were no significant interactions. The sex effects showed females fixating more than males. The trials effect was further analyzed using a Newman-Keuls at the .05 level. Trial 1 produced significantly greater fixations than trials 5 and 7. These were the only significant comparisons to emerge. However, reanalysis using a regression procedure produced a best fit negative exponential, Y = .7 + .46e--.“,‘. F(l.6) = 9.06.1, < .05. R’ = .60. The actual recovery point was 2.9 standard deviation units from the predicted point on the regression line. This suggests that habituation is beginning early in each trial, but not until Second 4. Since trial 1 and the recovery trial represent first presentations of a particular stimulus and because the distribution of the number of fixations was comparable and distinct from other trials, an attempt was made to predict recovery using trial I total fixation time as an independent variable. The results were nonsignificant, F (I ,22) = 2.5, R” = .lO. DISCUSSION
The microscopic analysis of the habituation process suggests some interesting extensions of our current knowledge concerning visual habituation of preschool children. We have demonstrated a clear overall habituation and recovery effect fitting a negative exponential. Further analysis of trial 1 and the recovery trial using a regression procedure adds support to
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the contention that recovery is an independent process. The overall results then are consonant with those of Lewis and Baumel(1970) and fit conceptually with the basic idea of OR habituation (Sokolov, 1963) and sensitization (Groves & Thompson. 1970. 1973; Thompson, Groves, Teyler, & Roemer, 1973). Further. it appears that the habituation is occurring early in the intervals but not in the first 3 sec. The data for Seconds 1 through 3 show no evidence of habituation. One could conclude, then, that the attention-getting component of the process is not habituating (Cohen et ul., 1975), but habituation starts early in each interval (by Second 4). We also see a significant sex difference, with females fixating longer than males but at the same time showing similar onsets or fixations within intervals. Analysis of the total fixation time per trial over number of onsets per trial suggests females attended for longer periods of time within trials on all trials. This suggests that females are capable of more sustained attention than males. The work of Pederson and Bell (1970). for example, provides convergence with this finding. The results are suggestive of the two-process model of visual attention suggested by Cohen et al. ( 1975). His model was derived from data on 4month-old infants. Similar results emerge from our study of preschoolers. One could posit two processes: an attention-getting process and an attention-holding process. The low correlation between fixations and onsets suggest that they are independent. It would also appear that it is the attention-holding process that is habituating. REFERENCES Banta.
T. J., Sciarra. J., & Jett, J. Nursery school children’s observation responses to novel, complex and asymmetrical complex stimuli. Percepption nerd P.sychophysics, 1966, 1, 165-167. Bernal, M. E., & Miller, W. H. Electrodermal and cardiac responses of schizophrenic children to sensory stimuli. Psychophysi&gg. 1970. 7, 155- 168. Cantor, J. H., & Cantor, G. N. Functions relating children’s observing behavior to amount and recency of stimulus familiarization. Jolrrnal oj’Experimenra/ Psychology. 1966, 72, 8.59-863. Cohen. L. B.. DeLoach, J. S., & Rissman. M. W. The effect of stimulus complexity on infant visual attention and habituation. Child Development, 1975, 46, 61 l-617. Dodd. C., & Lewis. M. The magnitude of the orienting response in children as a function of changes in color and contour. Jolcrrml of’E.rperimenru/ Child Psychology, 1969. 8, 296-305. Groves, P. M., &Thompson. R. F. A dual process theory of habituation: Neural mechanisms. In H. V. L. Peake & M. J. Herz (Eds.). Habituation. New York: Academic Press, 1973. Vol. 2, pp. 175-205. Groves, P. M., & Thompson, R. F. Habituation: A dual-process theory. Psyc~hdogiccd Rrviaw, 1970, 77. 419-450. Harrison, P. R.. & Ruth, M. D. The effects of antecedent instruction on visual habituation of preschool children. Bit&tin nj’Ps~chonotnic Socirf~. 1975. 5, 105- 108.
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Lewis, M., & Baumel, M. H. A study in the ordering of attention. Percepptltal and Motor Skills, 1970, 31, 979-990. Lewis, M., & Goldberg, S. The acquisition and violation of expectancy: An experimental paradigm. Journal oj’Experimentu1 Child Psychology, 1969. 7, 70-80. Lewis, M., Goldberg, S.. & Rausch, M. Attention distribution as a function of novelty and familiarity. Psyhonomic Science, 1967, 7, 227-228. Mackworth, N. H.. 8.1Otto, D. A. Habituation of the visual orienting response in young children. Perception und Psychophysics, 1970, 7. 173- 178. Pedersen, F. A., & Bell, R. Q. Sex differences in preschool children without histories of complicationsofpregnancyanddelivery. Derelopmentu/Ps?‘choio~~~ 1970,3,10-15. Sokolov, Y. N. Perceptiorl and the conditioned reflex. New York: MacMillan Co.. 1963. Thompson. R. F.. Groves, P. M.. Teyler. T. J., & Roemer. R. A. A dual-process theory of habituation: Theory and behavior. In H. V. S. Peake & M. J. Herz (Eds.). Habitution New York: Academic Press, 1973. Vol. I, pp. 239-271. RECEIVED: July 7, 1976; REVISED: December 14. 1976.