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The generality of overselectivity in developmentally disabled children
JOURNAL
OF EXPERIMENTAL
CHILD
PSYCHOLOGY
34,
217-230 (1982)
The Generality of Overselectivity in Developmentally Disabled Children NORMAN
B. ANDERSON AND ARNOLD RINCOVER
Universiry
of North
Carolina
at Greensboro
A growing body of research suggests that low Mental Age (MA) autistic and retarded children show a unique stimulus control deficit, one that may cause many or most of their behavioral deficiencies. This problem, stimulus overselectivity, is evidenced when a child responds only to a restricted portion of the stimulus environment when compared with normal children. The purpose of this study was to assess whether this overselectivity is general across situations or whether it is restricted to certain stimulus/task conditions. Eight autistic children, who evidenced overselectivity on a preassessment task, and 8 normal children with similar MA levels participated. All children were trained on 3 tasks to determine if overselectivity varied as a function of different stimulus conditions. Each of the 3 tasks involved training a child to respond to (i.e., touch) a card containing a circle (S +) and to avoid a blank (S -) card. In each case, the circle comprised a series of dots. The difference between the 3 circles (tasks) was the distance between the successive dots making up each circle. Also, in the minimal separation condition the dots were smaller in size and greater in number than in the larger separation conditions. Of concern was whether autistic children learned about the gestalt (i.e., the circle), which required attention to multiple cues, or whether children would overselect and respond to the dots. The results showed that (1) stimulus overselectivity was found not to be a generalized deficit in autistic subjects; instead, it varied as a function of the stimulus variables; and (2) the stimulus variables manipulated in this study similarly influenced the responding of both normal and autistic children. The implications of these data for a theory of overselectivity are discussed.
A central characteristic of autistic and profoundly retarded children is their inconsistent responding to environmental stimuli (Kanner, 1944; Rimland, 1964). This is evidenced when a child sometimes fails to respond to his name, seems unaware of people around him, or does not recognize This research was funded by Research Grant IROIHDl6373-01 from NICHD. The authors express appreciation to Dr. Eric Schopler and Judy Leonard of the TEACCH program for their cooperation and assistance, and Amy Woods, Susan Carter, and Pamela Laughon for their help throughout the project. Requests for reprints should be addressed to Dr. Arnold Rincover, Department of Psychology, University of North Carolina, Greensboro, NC 27412. 217 0022-0965/82/050217-14$02.OOM) Copyri&t 0 1982 by Academic Press, Inc. All rights of reproduction in any form reserved.
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family members. As a consequence of such behavior, observers have often described these children as “living in another world” or “withdrawn into a shell” (Kanner, 1944). It is not uncommon for them to be suspected of being blind or deaf, although vision and hearing examinations generally fail to reveal sensory abnormalities. In an attempt to understand inconsistent responding, researchers have begun to explore the nature of stimulus control in such children. A growing number of studies report a stimulus control deficit peculiar to these children as they typically respond to a more restricted portion of environmental stimuli than do normal children. In a pioneer study, Lovaas, Schreibman, Koegel, and Rehm (1971) trained groups of autistic, retarded, and normal children to respond (bar press) in the presence of a stimulus complex containing multiple relevant cues: auditory (65dBlevel white noise), visual (160-W red floodlight), and tactile (blood-pressure cuff). When the 3 cues were presented separately to assess the control over responding acquired by each, it was found that the autistic children typically responded to only one of the three cues, while normals responded to all three and retarded children typically responded to two. The term “stimulus overselectivity” (Lovaas et al., 1971) was used to denote this restricted stimulus control in autistics. After the intial study showing this stimulus control deficit, Lovaas and his colleagues began to assess whether the problem was specific to autism. Two studies have been conducted, testing normal children and developmentally disabled children with varying degrees of disability, and in both studies it was found that stimulus overselectivity was not specific to autism but instead correlated with Mental Age (MA), occurring in low MA normal and developmentally disabled children (Schover & Newsom, 1976; Wilhelm & Lovaas, 1976). Subsequent research has investigated whether stimulus overselectivity is an extensive and common problem across children and tasks. Lovaas and Schreibman (1971) presented autistic children with 2 cues rather than 3 to see if the children had been “flooded” with stimulation in the first study. Overselectivity was observed in 7 of the 9 autistic children, but was not evidenced in any of the 6 normal children, essentially replicating the findings in the first study. Studies have also assessed overselectivity when both training cues were in the same modality. Overselectivity has been found when both cues are visual (Koegel & Wilhelm, 1973) and when both cues are auditory (Reynolds, Newsom, & Lovaas, 1974). Furthermore, overselectivity has been evidenced in more complex social discriminations (Schreibman & Lovaas, 1973). For example, autistic children learned to discriminate male from female dolls on the basis of a minor unreliable cue, such as shoes, while normals learned about multiple, relevant cues (e.g., the head). Having demonstrated stimulus overselectivity, the major line of inquiry
GENERALITY
OF
OVERSELECTIVITY
219
has turned to investigating the role it may play in the behavioral deficits of autistic and retarded children. Varni, Lovaas, Koegel, and Everett (1979) reported data which suggest that stimulus overselectivity may prevent observational learning in these children. Although each child received up to 1000 trials watching a model select the correct stimulus (e.g., phone) on cue, and hand it to the teacher, autistic children often learned the motor response (i.e., to pick an object), but did not associate it with the verbal cues (e.g., “Phone”). In short, the autistics appeared to overselect on the visual cue, and learned nothing about the auditory cue. Koegel and Rincover ( 1976)) Rincover ( 1978), and Schreibman ( 1975) have shown the detrimental effects of overselectivity on prompting, where a prompt is an extra stimulus (e.g., pointing, underlining) designed to guide correct responding. In each case, it was found that the autistic child “hooked” on the prompt and learned nothing about the training stimulus. These studies suggest that overselectivity will prevent the child’s benefiting from common teaching practices. Even when learning does occur, stimulus control is often bizarre and unreliable. For example, after teaching children to discriminate 3-letter words, Rincover (1978) found that most children learned only about the first letter of the training word. After teaching simple receptive language (e.g., “Touch your nose”) and imitative tasks, Rincover and Koegel (1975) found that the newly learned tasks did not generalize to new persons and settings. An analysis of stimulus control showed that generalization was prevented by the children overselecting on an incidental unreliable cue, such as a teacher’s arm movement, which of course was not present in extraexperimental settings; the children had apparently learned nothing about the verbal instruction. Since overselectivity may interfere with observational learning, discrimination learning, social behavior, generalization, and language development, one can speculate on its possible role as a cause of many of the behavioral deficits of autistic and profoundly retarded children (cf. Lovaas et al., 1971). In this regard, an important question remains. To what extent is overselectivity a generalized phenomenon within individual children? No studies have assessed whether an overselective child would be overselective across all situations, or whether overselectivity would be evidenced only under certain task conditions. A large body of research with humans and animals shows that the presence of selective attention is often a function of task parameters. We know, for example, that the presence of a strong cue suppresses learning about a less salient, weaker cue, a phenomenon commonly labeled “overshadowing” (Sutherland & Mackintosh, 1971), and that a cue previously associated with reinforcement inhibits learning about a new relevant cue added subsequently, a phenomenon called “blocking” (Kamin, 1968). It is unclear whether the overselectivity found in autistic and retarded
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children is a function of stimulus variables, such as blocking or overshadowing, or whether overselectivity represents the generalized way in which these children attend to the world around them. It seems valuable to investigate the generality of overselectivity because identifying its determinants may have important implications for treatment. If overselectivity occurs in a generalized fashion, then treatment procedures involving attention training might be suggested, since remediating the deficits might in turn enable these children to learn from the natural environment and thereby acquire appropriate social and intellectual behavior. If, however, overselectivity is not a generalized problem but is a function of stimulus (situational) parameters, then the discovery of those stimulus variables which produce broader stimulus control might be useful in the design of new treatment techniques. Method Subjects Eight autistic children, diagnosed by agencies not associated with the experiment, participated in the present study. Each child was either mute, evidencing vowel sounds but no words, or echolalic, meaninglessly repeating words or phrases previously heard. The children displayed minimal social behavior, appearing indifferent to interpersonal contact and caresses, and a high frequency of stereotyped, repetitive motor behavior (self-stimulation), such as rocking, finger manipulations, or hand movements. The chronological ages of the children ranged from 8 to 16 years, and the mental ages from 2.5 to 5 years as measured by the Stanford-Binet Intelligence Scale or the Cattel Infant Intelligence Scale immediately prior to the study. Importantly, these children were carefully screened so that only those displaying stimulus overselectivity were selected for participation. The screening procedure is described under Preassessment. The children were solicited from local community classrooms and residential programs for autistic children and adolescents. An equal number of normal children from a day care center at the University of North Carolina at Greensboro also participated as a quasicontrol for MA (precise MA scores for these children could not be obtained). These children were of preschool age (range 3-5 years), and were selected on a random basis; the first 8 children for whom consent forms were received were selected as subjects. Setting The experiment was conducted in a small 3.7 x 5.5-m classroom that was equipped with a l-way observation mirror. Each child was seated, with his/her back to the mirror, at a table centrally located in the room. Located around the room were a number of toys and academic materials.
GENERALITY
OF
OVERSELECTIVITY
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Two experimenters were also in the room, seated directly across the table from the child. One experimenter presented the child with the stimulus cards and the other was responsible for recording the child’s responses. Sessions were conducted 2 days/week for each child and lasted approximately 20 min each. General
Procedures
This study was designed to assess the generality of stimulus overselectivity. An initial preassessment (Phase 1) was therefore planned to identify those children who evidenced overselectivity. In Phase 2, each normal and overselective child participated in 3 experimental conditions. In each condition a child was taught to touch a dotted circle card (S + ) and avoid a blank card (S -). The conditions differed in terms of the size, spacing, and number of dots forming the circle (S +). After training, probe trials were introduced in which the child was presented with an unbroken circle versus the component parts of the S + (a random series of dots) and the frequency of responding to each was recorded. The purpose was twofold. The first was to discover whether children would respond to the component dots and their relative location, or whether they would overselect and respond only to the components. For a child’s responding to come under the control of the circle, he/she would have to attend not only to the dots, but also to where they are placed in relation to each other (i.e., multiple cues). A second purpose was to assess whether overselectivity varied as a function of stimulus parameters of the S+ (e.g., how close the dots were to each other). Phase I: Preassessment. A preassessment was first conducted with the autistic children to select as subjects those children who evidenced stimulus overselectivity. The first 8 children found to be overselective participated in Phase 2. Four stimuli were used in the preassessment, each containing a 2-digit number: 42, 96, 41, or 82. The stick-on numbers (E-Z Stickletters) were 7.5 cm tall and 4 cm wide, and were spaced 4.5 cm apart. These, and all of the experimental stimuli used in Phase 2, were presented on 15 X U-cm white stimulus cards. All stimulus cards were made of posterboard paper and covered with a transparent protective covering (Marvalon) so that they could be cleaned frequently. The stimuli used on training and test trials are shown in Fig. 1. Children were first trained to discriminate the number 42 (S +) from the number 96. Correct responding was reinforced with edibles (e.g., M & MS, cereal) on a continuous reinforcement (CRF) schedule until he/she responded correctly on 10 consecutive trials. The schedule of reinforcement was then thinned to a variable-ratio 2 schedule (VR-2), until a criterion of 10 consecutive correct responses was again attained, then to a VR-3 schedule, and finally to a VR-4.
ANDERSON
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AND RINCOVER
Preassessment Training
Stimuli
-
vs
-’
f-q
“S
;1]
Fi
“=
p#F
Test Stimuli
FIG. 1. Training
and test stimuli used to assess overselective responding in Phase 1.
Following training, test trials were introduced on nonreinforced trials in the VR-4 schedule to determine which of the 2 components of S + (i.e., the 4 or 2) had gained control over the child’s responding. The child was presented with the original S + card (42) versus an S - card containing the number 41 on one-half of the test trials (20 trial), and an S - card containing the number 82 on the remaining test trials (20 trials). This provided some measure of whether a child responded selectively on the basis of the number 4 during training, in which case responding to the original S + would be at chance levels when paired with the 41; or if the child was responding on the basis of the 2 in the number 42, in which case responding to the 42 would be at chance levels when it was paired with the number 82. Children who responded at chance levels (under 70%) in the presence of one or more of these S- stimuli, but above chance (80-100%) on the stimulus complex (42), were deemed overselective and selected as subjects. Phase 2: Assessment of gestalt responding. Training procedures were identical for each of the three conditions in Phase 2. First, the S + (dotted circle) and the S- (blank card) were presented simultaneously on the table, about 15 cm apart, directly in front of the child. To start a trial, the experimenter said “Touch the correct card.” If the child responded correctly, he was given an edible reinforcer and praise (e.g., “Good boy”); the experimenter said “No” if an incorrect response was made. The trial was terminated after the first response, whether correct or not, with the experimenter removing both cards from the table. The position of the S+ was randomly alternated according to a Gellerman order (Gellerman, 1933), so that the S+ was on the right as often as it was on the left. The child was given reinforcers on a continuous schedule (CRF) until 10 consecutive correct responses were observed. The sched-
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OF OVERSELECTIVITY
ule of reinforcement was then gradually thinned from CRF to a VR-4, as described for the preassessment phase, so that probe trials (described below) could be presented on the nonreinforced trials. Three tasks were used during training in Phase 2, one for each of the three experimental conditions, as shown in Fig. 2. The order of tasks was randomized. For each task, 2 cards were used, one containing a circle (9 cm in diameter) comprised of a series of dots (S +), and the other a blank card (S -). In the Small Dot condition (Task I), the dotted circle consisted of 198 dots, 1 mm in width, spaced 1 mm apart. In the Medium Dot condition (Task 2), the dotted circle consisted of 60 dots, Small
Dot
Condition
stimuli j(_>
vsri
training
Medium
Dot
stim”,i 10/ test
(Probe
Condition
“= p/
)
Large
Dot
Condition
training
S+
test stimuli
(probe
S-
I
) ioj
vs
FIG. 2. Training and test stimuli for experimental
pi
conditions in Phase 2.
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RINCOVER
each about 3 mm in width and spaced 3 mm apart. In the Large Dot condition (Task 3), the circle consisted of 20 dots, each 6 mm in width, spaced 6 mm apart. A blank card, 15 x 15 cm, served as the S- in each condition. Each child participated in all three conditions, and the order of conditions was randomized within and across children. Upon the subject’s meeting the criterion in a given training condition, probe trials were presented to determine the degree of stimulus control acquired by the gestalt (circle) versus the components (dots). For children to respond to the gestalt, they must attend to the components plus their relative location. Responding to the components alone would be deemed overselective, since it requires attention only to the dots. For this purpose, probe trials, presented on nonreinforced trials in the VR-4 schedule, consisted of a card containing an unbroken circle versus a card containing a series of random dots, and responding to each was recorded. The probe stimuli for Phase 2 of the study are illustrated in Fig. 2. The size of the dots and the thickness of the unbroken circle used during probe trials were the same as for the dots and circle used during a particular training condition. For example, in the Small Dot condition, the dots on the random dot card were the same size as the dots used in the training condition. Similarly, the lines of the unbroken circle were the same width as one of the dots in that condition. A total of 80 probe trials were presented. Sixty of these were trials with the original discrimination reinforced on the VR-4 schedule. On the remaining 20 trials the probe stimuli were presented on a nonreinforced basis. Stimulus control was indicated by 80% or more responses to either the gestalt (circle) or the components (dots) during probe trials. Recording
and Reliability
During training and testing, the experimenter and a naive observer were seated across from the child. After the experimenter presented the cards, the naive observer recorded which card the subject touched. To assess the reliability of recordings, reliability checks were made during one-fourth of the sessions in each phase of this experiment, with reliability measures equally distributed among dot conditions and children. Another recorder, naive to the experimental hypothesis, independently observed and recorded the child’s responses from behind a l-way mirror. The child was seated between the two observers (one being behind the l-way mirror) so that both were able to view the child’s responses while not being able to see the recordings of the other observer. An agreement was counted if both recorders recorded an x , or a check, on a given trial. Inter-rated reliability was calculated by dividing the total number of agreements by the total number of agreements plus disagreements and multiplying by 100. Reliability was consistently above 95% in this experiment.
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OF OVERSELECTIVITY
225
Results The results of this study are described separately for the preassessment and the assessment of gestalt responding. Phase 1: Preassessment. Phase 1 was designed to preselect children who evidenced stimulus overselectivity. A total of 10 children were given the preassessment. Figure 3 shows the results of the preassessment for 8 autistic children who evidenced overselectivity.’ Percent of correct responding is shown on the ordinate for each child; trials measuring responding to the S + (42) and its individual component parts (4 and 2) are shown on the abscissa. For 7 of the 8 children, only one of the components of the S + stimulus complex achieved control over responding. All children learned to respond to the S+ during training, as shown by 100% correct responding for each child during “42” probe trials. For 3 children (Larry, Freddie, and James), however, correct responding was maintained only by the “4” and not by the “2” while for 3 other children (Walter, Doug, and Erwin) correct responding was maintained only by the “2.” In each case correct responding was maintained above 80% for one of the components, but was reduced to chance level for the other. One subject (Greg) responded below chance levels for both Component 1 and 2. For the last subject, Mary, who was tested on different stimulus materials, correct responding was maintained only by Component 1 of the stimulus complex. Phase 2: Assessment of gestalt responding. Phase 2 was designed to determine if overselectivity is necessarily a generalized problem for these children, or if stimulus control varies across task conditions. The results for Phase 2 are shown in Fig. 4. Percent of responding to the circle, as opposed to the components (dots) of the circle, during blocks of 20 probe trials, are shown for the three stimulus conditions. The results for the autistic children are shown in the upper graph and for the normal children in the lower graph. The most important data comes from the autistic group. The results show that overselectivity was not a generalized phenomenon across task conditions. For example, the first child, Larry, exhibited 100% responding to the circle in the small and medium dot conditions, but responded overselectively to the component dots in the large dot condition. In fact, 6 of the 8 children responded to the gestalt in the small dot condition, but then responded overselectively in the large dot condition. ’ One child (Mary) did not reach criterion and therefore was trained and tested on a line adjacent to a curvilinear line: the Swere chosen because they appeared to be stimuli, and would still test overselectivity.
on the original discrimination (i.e., 42 vs 96). different task. The S+ consisted of a vertical contained a star and a circle. These stimuli less complex than the original preassessment
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I- 40m cl 20. l 0’ iz
42
0
Larry
z
Y loo: n m6
60-
2 : u
40.
i+!
0
4
2
42
4
2
Freddie
424
2
Walter
42
4
Doug
-
20. 42
4
2
42
4
Erwin
Greg
2
42
4
2
James
IS
I
'
Mary
FIG. 3. Percent of responding to S+ stimulus complex (42) and to its separate components (4 and 2), for each of 8 autistic children.
The data also show that both the autistic and normal subjects’ responding varied as a function of stimulus parameters: responding to the circle was dominant in the small dot condition, yet overselective responding (to dots) was prevalent in the large dot condition. For example, in the small dot condition, 6 of the normal children (Derrick, Troy, Kevin, Sara, Kathy, and Sharon) and 6 of the autistic children (Larry, Freddie, Walter, Doug, James, and Mary) responded to the circle, as evidenced by 80% correct responding or better. In the large dot condition only 4 normals (Derrick, Kevin, Sara, and Kathy) and 1 autistic subject (James) responded to the circle. In the medium dot condition responding
5 II: E
50
0 DERRICK
TROY
KEVIN
SARA
JUDY
KATHY
SHARON
BRUCE
4. Responding of autistic and normal children to the gestalt (circle) under three task conditions: small dot (shaded bars); medium dot (striped bars); and large dot (open bars). FIG.
GENERALITY
OF OVERSELECTIVITY
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was between these extremes, as 5 of the normal subjects (Derrick, Troy, Kevin, Sara, and Kathy) and 4 of the autistic subjects (Larry, Walter, Doug, and James) responded to the circle. An analysis of variance, for a 2-factor experiment with repeated measures on one factor, produced a significant main effect for the stimulus variables (F(1, 14) = 7.88, p < .Ol), but not for diagnosis (F(2, 28) = .14, p > .05) or the interaction (F(2, 28) = 1.12, p > .05). A post hoc Scheffe test showed a significant difference in responding between the small and large dot conditions 0, < .05), and a trend analysis further showed a significant linear trend in gestalt responding (p < .05) across the three conditions: gestalt responding decreased in a linear fashion as a function of the progression from small to medium to large dot conditions. This analysis indicated that the stimulus variables had an effect on children’s responding, but there was not a significant difference between the subject groups. Contrary to our hypothesis, the overselectivity evidenced by autistic and other children appears not to be a generalized phenomenon, but instead seems to be a function of task parameter. Additional support for the effect of stimulus variables on both groups can be seen in Fig. 5 and 6. Figure 5 shows the averaged percentage of responses to the circle (gestalt) stimulus for the autistic and normal groups, for each of the three stimulus conditions. Similarly, Fig. 6 shows the number of autistic and normal children who responded on the basis of the circle for each experimental condition. There was a decrease in both the number of gestalt responders and the percent of gestalt responding, within both groups, as the tasks progressed from small to medium to large dots. In both Fig. 5 and 6, the slopes of the lines are somewhat greater for autistics than for normals, although no significant interaction was obtained. Discussion The purpose of this experiment was to assess the generality of stimulus overselectivity in overselective children. The following results were obtained. (1) Stimulus overselectivity was found nor to be a generalized deficit in the overselective subjects identified, but instead varied as a
SMALL
MEDIUM
LAROE
5. Percent of responses to the gestalt stimulus by autistic (-) children during the small, medium, and large dot condition. FIG.
and normal (---)
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ANDERSON
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AND RINCOVER
- - -_O-__ ‘0
SMALL
MEDIUM
LARGE
FIG. 6. Number of autistic (-4 and normal(---) children responding to gestalt under each experimental condition (small, medium, and large dots).
function of the stimulus variables associated with the task; and (2) the stimulus variables manipulated in this study similarly influenced the responding of both normal and autistic children. The data showing that the autistic and normal children were at times overselective suggests that overselectivity may not be central to the problems of autistic and retarded children. If overselectivity is to be implicated as a primary cause of disabilities, one might then expect that overselective normal children would also exhibit severe behavioral deficits. Even though the autistic and normal subjects performed similarly on the assessment of gestalt responding, there was little similarity in behavioral deficiencies between the two groups. Similarly, finding that stimulus overselectivity was in part a function of task variables, rather than a generalized problem in the developmentally disabled children, also contradicts the theory that overselectivity may be a cause of their behavior deficits, since this notion assumes that the children are overselective across all or most learning situations. Instead, the data suggest that stimulus variables may play an important role in determining whether overselectivity will occur. Although the results suggest that stimulus factors play a role in overselectivity, the precise stimulus dimensions that brought about the changes in stimulus control are not clear. In the present study, it was found that three stimulus variables-size, spacing, and number of dotscould rogerher be manipulated to bring about variations in the stimulus control over autistic children’s responding. It remains possible, however, that gestalt responding was facilitated specifically by an increase in the size or number of dots making up the circle, a decrease in the spacing between dots, or some combination of these three factors. Further analysis of the specific dimensions that did influence responding would seem to be invaluable since the results may aid in the design of new treatment strategies. If it is found that one of these variables, such as the distance or spacing between stimulus components, is the functional factor in determining overselectivity, then it would be helpful to develop treatment procedures aimed at systematically teaching children to respond to cues that are spaced progressively farther apart. Alternatively, one could design teaching methods that do not strain their
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restricted range of attention. For example, prompting procedures that utilized prompts located closer to the target stimulus may help ensure that both stimuli fall within their range of attention and come to control responding. Similar innovations could also be designed if changes in size or number of component features are found to occasion stimulus overselectivity. The present data may also advance our understanding of stimulus overselectivity in developmentally disabled children. It has been found that, when presented with multiple relevant cues, low MA autistic and retarded children typically respond only to one cue. We wondered if this stimulus overselectivity, since it has been replicated in a number of studies (e.g., Rincover & Koegel, 1975; Koegel & Wilhelm, 1973; Reynolds et al., 1974; Koegel & Rincover, 1976), might be the generalized way in which many of these children view their world. The data showing that most of the overselective autistic children responded to the gestalt in one (small dot) condition seems, however, to refute the notion that they do not (at least at times) respond to multiple cues, since gestalt responding necessarily required responding to more than one cue (i.e., stimulus components and their relative location). The present data may suggest that the notion of tunnel vision plays a contributing role in stimulus overselectivity. Perhaps the only stimuli that would become functional for an overselective child would be those in his or her restricted field or “tunnel” of vision. One way of conceptualizing tunnel vision is in terms of the relative location or distance between cues. If a child’s responding is under the control of one stimulus (S,), then the probability of that child responding to another stimulus (S,) simultaneously would be, in part, a function of its distance from S,. Using this hypothesis, the functional element in overselectivity may not be the number of cues involved, but rather the relative locution of those cues. Support for a tunnel vision hypothesis was found in the present study when autistic children were observed to respond more often to the gestalt when the dots making up the stimulus were closer together. If a child responds on the basis of only a restricted portion or area of a stimulus, one would expect the child’s responding to be controlled more by the gestalt when there was more information (i.e., more dots) in that area that indicated or gave the appearance of a line or curve. Conversely, the fewer the number of dots in his/her field of attention, the more difficult it would be to identify the pattern. REFERENCES Gellerman, L. W. Chance order of alternating stimuli in visual discrimination Journal
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Kamin, L. J. “Attention-like” Miami
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processes in classical conditioning.
on the prediction
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Fla.: Univ. of Miami Press, 1968, 9-31.
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Kanner, L. Early infantile autism. Journal of Pediatrics, 1944, 25, 21 l-217. Koegel, R. L., & Rincover, A. Some detrimental effects of using extra stimuli to guide learning in normal and autistic children. Journal of Abnormal Child Psychology, 1976, 4, 59-71. Koegel, R. L., & Wilhelm, H. Selective responding to multiple visual cues by autistic children. Journal of Experimental Child Psychology, 1973, 15, 442-453. Lovaas, 0. I., & Schreibman, L. Stimulus overselectivity of autistic children in a twostimulus situation. Behaviour Research and Therapy, 1971, 9, 305-310. Lovaas, 0. I., Schreibman, L., Koegel, R., & Rehm, R. Selective responding by autistic children to multiple sensory input. Journal ofAbnormal Psychology, 1971,77,21 l-222. Reynolds, G. S. Attention in the pigeon. Journal of the Experimental Analysis of Behavior, 1961. 4, 203-208. Reynolds, B. S., Newsom, C. D., & Lowaas, 0. I. Auditory overselectivity in autistic children. Journal of Abnormal Child Psychology, 1974, 2, 253-263. Rimland, B. Infantile autism. New York: Appleton-Century-Crofts, 1964. Rincover, A. Variables affecting stimulus fading and discriminative responding in psychotic children. Journal of Abnormal Psychology, 1978, 87, 541-553. Rincover, A., & Koegel, R. L. Setting generality and stimulus control in autistic children. Journal of Applied Behavior Analysis, 1975, 8, 235-246. Schover, L. R., & Newson, C. D. Overselectivity, developmental level, and overtraining in autistic and normal children. Journal of Abnormal Child Psychology, 1976, 4, 289-298. Schreibman, L. Effects of within-stimulus and extra-stimulus prompting on discrimination learning in autistic children. Journal of Applied Behavior Analysis, 1975, 8, 91-l 12. Schreibman, L., & Lovaas, 0. I. Overselective responding to social stimuli by autistic children. Journal of Abnormal Child Psychology, 1973, 1, 152-168. Sutherland, N. S., & Mackintosh, N. J. Mechanisms of animal discrimination learning. New York: Academic Press, 1971. Varni, J., Lovaas, 0. I., Koegel, R. L., & Everett, N. L. An analysis of observational learning in autistic and normal children. Journal of Abnormal Child Psychology, 1979, 7, 31-43. Wilhelm, H., & Lovaas, 0. I. Stimulus overselectivity: A common feature in autism and mental retardation. American Journal of Mental Deficiency, 1976, 81, 227-241. RECEIVED:
September 23, 1980;
REVISED
November 23, 1981.
OF EXPERIMENTAL
CHILD
PSYCHOLOGY
34,
217-230 (1982)
The Generality of Overselectivity in Developmentally Disabled Children NORMAN
B. ANDERSON AND ARNOLD RINCOVER
Universiry
of North
Carolina
at Greensboro
A growing body of research suggests that low Mental Age (MA) autistic and retarded children show a unique stimulus control deficit, one that may cause many or most of their behavioral deficiencies. This problem, stimulus overselectivity, is evidenced when a child responds only to a restricted portion of the stimulus environment when compared with normal children. The purpose of this study was to assess whether this overselectivity is general across situations or whether it is restricted to certain stimulus/task conditions. Eight autistic children, who evidenced overselectivity on a preassessment task, and 8 normal children with similar MA levels participated. All children were trained on 3 tasks to determine if overselectivity varied as a function of different stimulus conditions. Each of the 3 tasks involved training a child to respond to (i.e., touch) a card containing a circle (S +) and to avoid a blank (S -) card. In each case, the circle comprised a series of dots. The difference between the 3 circles (tasks) was the distance between the successive dots making up each circle. Also, in the minimal separation condition the dots were smaller in size and greater in number than in the larger separation conditions. Of concern was whether autistic children learned about the gestalt (i.e., the circle), which required attention to multiple cues, or whether children would overselect and respond to the dots. The results showed that (1) stimulus overselectivity was found not to be a generalized deficit in autistic subjects; instead, it varied as a function of the stimulus variables; and (2) the stimulus variables manipulated in this study similarly influenced the responding of both normal and autistic children. The implications of these data for a theory of overselectivity are discussed.
A central characteristic of autistic and profoundly retarded children is their inconsistent responding to environmental stimuli (Kanner, 1944; Rimland, 1964). This is evidenced when a child sometimes fails to respond to his name, seems unaware of people around him, or does not recognize This research was funded by Research Grant IROIHDl6373-01 from NICHD. The authors express appreciation to Dr. Eric Schopler and Judy Leonard of the TEACCH program for their cooperation and assistance, and Amy Woods, Susan Carter, and Pamela Laughon for their help throughout the project. Requests for reprints should be addressed to Dr. Arnold Rincover, Department of Psychology, University of North Carolina, Greensboro, NC 27412. 217 0022-0965/82/050217-14$02.OOM) Copyri&t 0 1982 by Academic Press, Inc. All rights of reproduction in any form reserved.
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family members. As a consequence of such behavior, observers have often described these children as “living in another world” or “withdrawn into a shell” (Kanner, 1944). It is not uncommon for them to be suspected of being blind or deaf, although vision and hearing examinations generally fail to reveal sensory abnormalities. In an attempt to understand inconsistent responding, researchers have begun to explore the nature of stimulus control in such children. A growing number of studies report a stimulus control deficit peculiar to these children as they typically respond to a more restricted portion of environmental stimuli than do normal children. In a pioneer study, Lovaas, Schreibman, Koegel, and Rehm (1971) trained groups of autistic, retarded, and normal children to respond (bar press) in the presence of a stimulus complex containing multiple relevant cues: auditory (65dBlevel white noise), visual (160-W red floodlight), and tactile (blood-pressure cuff). When the 3 cues were presented separately to assess the control over responding acquired by each, it was found that the autistic children typically responded to only one of the three cues, while normals responded to all three and retarded children typically responded to two. The term “stimulus overselectivity” (Lovaas et al., 1971) was used to denote this restricted stimulus control in autistics. After the intial study showing this stimulus control deficit, Lovaas and his colleagues began to assess whether the problem was specific to autism. Two studies have been conducted, testing normal children and developmentally disabled children with varying degrees of disability, and in both studies it was found that stimulus overselectivity was not specific to autism but instead correlated with Mental Age (MA), occurring in low MA normal and developmentally disabled children (Schover & Newsom, 1976; Wilhelm & Lovaas, 1976). Subsequent research has investigated whether stimulus overselectivity is an extensive and common problem across children and tasks. Lovaas and Schreibman (1971) presented autistic children with 2 cues rather than 3 to see if the children had been “flooded” with stimulation in the first study. Overselectivity was observed in 7 of the 9 autistic children, but was not evidenced in any of the 6 normal children, essentially replicating the findings in the first study. Studies have also assessed overselectivity when both training cues were in the same modality. Overselectivity has been found when both cues are visual (Koegel & Wilhelm, 1973) and when both cues are auditory (Reynolds, Newsom, & Lovaas, 1974). Furthermore, overselectivity has been evidenced in more complex social discriminations (Schreibman & Lovaas, 1973). For example, autistic children learned to discriminate male from female dolls on the basis of a minor unreliable cue, such as shoes, while normals learned about multiple, relevant cues (e.g., the head). Having demonstrated stimulus overselectivity, the major line of inquiry
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has turned to investigating the role it may play in the behavioral deficits of autistic and retarded children. Varni, Lovaas, Koegel, and Everett (1979) reported data which suggest that stimulus overselectivity may prevent observational learning in these children. Although each child received up to 1000 trials watching a model select the correct stimulus (e.g., phone) on cue, and hand it to the teacher, autistic children often learned the motor response (i.e., to pick an object), but did not associate it with the verbal cues (e.g., “Phone”). In short, the autistics appeared to overselect on the visual cue, and learned nothing about the auditory cue. Koegel and Rincover ( 1976)) Rincover ( 1978), and Schreibman ( 1975) have shown the detrimental effects of overselectivity on prompting, where a prompt is an extra stimulus (e.g., pointing, underlining) designed to guide correct responding. In each case, it was found that the autistic child “hooked” on the prompt and learned nothing about the training stimulus. These studies suggest that overselectivity will prevent the child’s benefiting from common teaching practices. Even when learning does occur, stimulus control is often bizarre and unreliable. For example, after teaching children to discriminate 3-letter words, Rincover (1978) found that most children learned only about the first letter of the training word. After teaching simple receptive language (e.g., “Touch your nose”) and imitative tasks, Rincover and Koegel (1975) found that the newly learned tasks did not generalize to new persons and settings. An analysis of stimulus control showed that generalization was prevented by the children overselecting on an incidental unreliable cue, such as a teacher’s arm movement, which of course was not present in extraexperimental settings; the children had apparently learned nothing about the verbal instruction. Since overselectivity may interfere with observational learning, discrimination learning, social behavior, generalization, and language development, one can speculate on its possible role as a cause of many of the behavioral deficits of autistic and profoundly retarded children (cf. Lovaas et al., 1971). In this regard, an important question remains. To what extent is overselectivity a generalized phenomenon within individual children? No studies have assessed whether an overselective child would be overselective across all situations, or whether overselectivity would be evidenced only under certain task conditions. A large body of research with humans and animals shows that the presence of selective attention is often a function of task parameters. We know, for example, that the presence of a strong cue suppresses learning about a less salient, weaker cue, a phenomenon commonly labeled “overshadowing” (Sutherland & Mackintosh, 1971), and that a cue previously associated with reinforcement inhibits learning about a new relevant cue added subsequently, a phenomenon called “blocking” (Kamin, 1968). It is unclear whether the overselectivity found in autistic and retarded
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children is a function of stimulus variables, such as blocking or overshadowing, or whether overselectivity represents the generalized way in which these children attend to the world around them. It seems valuable to investigate the generality of overselectivity because identifying its determinants may have important implications for treatment. If overselectivity occurs in a generalized fashion, then treatment procedures involving attention training might be suggested, since remediating the deficits might in turn enable these children to learn from the natural environment and thereby acquire appropriate social and intellectual behavior. If, however, overselectivity is not a generalized problem but is a function of stimulus (situational) parameters, then the discovery of those stimulus variables which produce broader stimulus control might be useful in the design of new treatment techniques. Method Subjects Eight autistic children, diagnosed by agencies not associated with the experiment, participated in the present study. Each child was either mute, evidencing vowel sounds but no words, or echolalic, meaninglessly repeating words or phrases previously heard. The children displayed minimal social behavior, appearing indifferent to interpersonal contact and caresses, and a high frequency of stereotyped, repetitive motor behavior (self-stimulation), such as rocking, finger manipulations, or hand movements. The chronological ages of the children ranged from 8 to 16 years, and the mental ages from 2.5 to 5 years as measured by the Stanford-Binet Intelligence Scale or the Cattel Infant Intelligence Scale immediately prior to the study. Importantly, these children were carefully screened so that only those displaying stimulus overselectivity were selected for participation. The screening procedure is described under Preassessment. The children were solicited from local community classrooms and residential programs for autistic children and adolescents. An equal number of normal children from a day care center at the University of North Carolina at Greensboro also participated as a quasicontrol for MA (precise MA scores for these children could not be obtained). These children were of preschool age (range 3-5 years), and were selected on a random basis; the first 8 children for whom consent forms were received were selected as subjects. Setting The experiment was conducted in a small 3.7 x 5.5-m classroom that was equipped with a l-way observation mirror. Each child was seated, with his/her back to the mirror, at a table centrally located in the room. Located around the room were a number of toys and academic materials.
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Two experimenters were also in the room, seated directly across the table from the child. One experimenter presented the child with the stimulus cards and the other was responsible for recording the child’s responses. Sessions were conducted 2 days/week for each child and lasted approximately 20 min each. General
Procedures
This study was designed to assess the generality of stimulus overselectivity. An initial preassessment (Phase 1) was therefore planned to identify those children who evidenced overselectivity. In Phase 2, each normal and overselective child participated in 3 experimental conditions. In each condition a child was taught to touch a dotted circle card (S + ) and avoid a blank card (S -). The conditions differed in terms of the size, spacing, and number of dots forming the circle (S +). After training, probe trials were introduced in which the child was presented with an unbroken circle versus the component parts of the S + (a random series of dots) and the frequency of responding to each was recorded. The purpose was twofold. The first was to discover whether children would respond to the component dots and their relative location, or whether they would overselect and respond only to the components. For a child’s responding to come under the control of the circle, he/she would have to attend not only to the dots, but also to where they are placed in relation to each other (i.e., multiple cues). A second purpose was to assess whether overselectivity varied as a function of stimulus parameters of the S+ (e.g., how close the dots were to each other). Phase I: Preassessment. A preassessment was first conducted with the autistic children to select as subjects those children who evidenced stimulus overselectivity. The first 8 children found to be overselective participated in Phase 2. Four stimuli were used in the preassessment, each containing a 2-digit number: 42, 96, 41, or 82. The stick-on numbers (E-Z Stickletters) were 7.5 cm tall and 4 cm wide, and were spaced 4.5 cm apart. These, and all of the experimental stimuli used in Phase 2, were presented on 15 X U-cm white stimulus cards. All stimulus cards were made of posterboard paper and covered with a transparent protective covering (Marvalon) so that they could be cleaned frequently. The stimuli used on training and test trials are shown in Fig. 1. Children were first trained to discriminate the number 42 (S +) from the number 96. Correct responding was reinforced with edibles (e.g., M & MS, cereal) on a continuous reinforcement (CRF) schedule until he/she responded correctly on 10 consecutive trials. The schedule of reinforcement was then thinned to a variable-ratio 2 schedule (VR-2), until a criterion of 10 consecutive correct responses was again attained, then to a VR-3 schedule, and finally to a VR-4.
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Preassessment Training
Stimuli
-
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Fi
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Test Stimuli
FIG. 1. Training
and test stimuli used to assess overselective responding in Phase 1.
Following training, test trials were introduced on nonreinforced trials in the VR-4 schedule to determine which of the 2 components of S + (i.e., the 4 or 2) had gained control over the child’s responding. The child was presented with the original S + card (42) versus an S - card containing the number 41 on one-half of the test trials (20 trial), and an S - card containing the number 82 on the remaining test trials (20 trials). This provided some measure of whether a child responded selectively on the basis of the number 4 during training, in which case responding to the original S + would be at chance levels when paired with the 41; or if the child was responding on the basis of the 2 in the number 42, in which case responding to the 42 would be at chance levels when it was paired with the number 82. Children who responded at chance levels (under 70%) in the presence of one or more of these S- stimuli, but above chance (80-100%) on the stimulus complex (42), were deemed overselective and selected as subjects. Phase 2: Assessment of gestalt responding. Training procedures were identical for each of the three conditions in Phase 2. First, the S + (dotted circle) and the S- (blank card) were presented simultaneously on the table, about 15 cm apart, directly in front of the child. To start a trial, the experimenter said “Touch the correct card.” If the child responded correctly, he was given an edible reinforcer and praise (e.g., “Good boy”); the experimenter said “No” if an incorrect response was made. The trial was terminated after the first response, whether correct or not, with the experimenter removing both cards from the table. The position of the S+ was randomly alternated according to a Gellerman order (Gellerman, 1933), so that the S+ was on the right as often as it was on the left. The child was given reinforcers on a continuous schedule (CRF) until 10 consecutive correct responses were observed. The sched-
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ule of reinforcement was then gradually thinned from CRF to a VR-4, as described for the preassessment phase, so that probe trials (described below) could be presented on the nonreinforced trials. Three tasks were used during training in Phase 2, one for each of the three experimental conditions, as shown in Fig. 2. The order of tasks was randomized. For each task, 2 cards were used, one containing a circle (9 cm in diameter) comprised of a series of dots (S +), and the other a blank card (S -). In the Small Dot condition (Task I), the dotted circle consisted of 198 dots, 1 mm in width, spaced 1 mm apart. In the Medium Dot condition (Task 2), the dotted circle consisted of 60 dots, Small
Dot
Condition
stimuli j(_>
vsri
training
Medium
Dot
stim”,i 10/ test
(Probe
Condition
“= p/
)
Large
Dot
Condition
training
S+
test stimuli
(probe
S-
I
) ioj
vs
FIG. 2. Training and test stimuli for experimental
pi
conditions in Phase 2.
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each about 3 mm in width and spaced 3 mm apart. In the Large Dot condition (Task 3), the circle consisted of 20 dots, each 6 mm in width, spaced 6 mm apart. A blank card, 15 x 15 cm, served as the S- in each condition. Each child participated in all three conditions, and the order of conditions was randomized within and across children. Upon the subject’s meeting the criterion in a given training condition, probe trials were presented to determine the degree of stimulus control acquired by the gestalt (circle) versus the components (dots). For children to respond to the gestalt, they must attend to the components plus their relative location. Responding to the components alone would be deemed overselective, since it requires attention only to the dots. For this purpose, probe trials, presented on nonreinforced trials in the VR-4 schedule, consisted of a card containing an unbroken circle versus a card containing a series of random dots, and responding to each was recorded. The probe stimuli for Phase 2 of the study are illustrated in Fig. 2. The size of the dots and the thickness of the unbroken circle used during probe trials were the same as for the dots and circle used during a particular training condition. For example, in the Small Dot condition, the dots on the random dot card were the same size as the dots used in the training condition. Similarly, the lines of the unbroken circle were the same width as one of the dots in that condition. A total of 80 probe trials were presented. Sixty of these were trials with the original discrimination reinforced on the VR-4 schedule. On the remaining 20 trials the probe stimuli were presented on a nonreinforced basis. Stimulus control was indicated by 80% or more responses to either the gestalt (circle) or the components (dots) during probe trials. Recording
and Reliability
During training and testing, the experimenter and a naive observer were seated across from the child. After the experimenter presented the cards, the naive observer recorded which card the subject touched. To assess the reliability of recordings, reliability checks were made during one-fourth of the sessions in each phase of this experiment, with reliability measures equally distributed among dot conditions and children. Another recorder, naive to the experimental hypothesis, independently observed and recorded the child’s responses from behind a l-way mirror. The child was seated between the two observers (one being behind the l-way mirror) so that both were able to view the child’s responses while not being able to see the recordings of the other observer. An agreement was counted if both recorders recorded an x , or a check, on a given trial. Inter-rated reliability was calculated by dividing the total number of agreements by the total number of agreements plus disagreements and multiplying by 100. Reliability was consistently above 95% in this experiment.
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Results The results of this study are described separately for the preassessment and the assessment of gestalt responding. Phase 1: Preassessment. Phase 1 was designed to preselect children who evidenced stimulus overselectivity. A total of 10 children were given the preassessment. Figure 3 shows the results of the preassessment for 8 autistic children who evidenced overselectivity.’ Percent of correct responding is shown on the ordinate for each child; trials measuring responding to the S + (42) and its individual component parts (4 and 2) are shown on the abscissa. For 7 of the 8 children, only one of the components of the S + stimulus complex achieved control over responding. All children learned to respond to the S+ during training, as shown by 100% correct responding for each child during “42” probe trials. For 3 children (Larry, Freddie, and James), however, correct responding was maintained only by the “4” and not by the “2” while for 3 other children (Walter, Doug, and Erwin) correct responding was maintained only by the “2.” In each case correct responding was maintained above 80% for one of the components, but was reduced to chance level for the other. One subject (Greg) responded below chance levels for both Component 1 and 2. For the last subject, Mary, who was tested on different stimulus materials, correct responding was maintained only by Component 1 of the stimulus complex. Phase 2: Assessment of gestalt responding. Phase 2 was designed to determine if overselectivity is necessarily a generalized problem for these children, or if stimulus control varies across task conditions. The results for Phase 2 are shown in Fig. 4. Percent of responding to the circle, as opposed to the components (dots) of the circle, during blocks of 20 probe trials, are shown for the three stimulus conditions. The results for the autistic children are shown in the upper graph and for the normal children in the lower graph. The most important data comes from the autistic group. The results show that overselectivity was not a generalized phenomenon across task conditions. For example, the first child, Larry, exhibited 100% responding to the circle in the small and medium dot conditions, but responded overselectively to the component dots in the large dot condition. In fact, 6 of the 8 children responded to the gestalt in the small dot condition, but then responded overselectively in the large dot condition. ’ One child (Mary) did not reach criterion and therefore was trained and tested on a line adjacent to a curvilinear line: the Swere chosen because they appeared to be stimuli, and would still test overselectivity.
on the original discrimination (i.e., 42 vs 96). different task. The S+ consisted of a vertical contained a star and a circle. These stimuli less complex than the original preassessment
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I- 40m cl 20. l 0’ iz
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0
Larry
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Y loo: n m6
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Freddie
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4
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Erwin
Greg
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James
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Mary
FIG. 3. Percent of responding to S+ stimulus complex (42) and to its separate components (4 and 2), for each of 8 autistic children.
The data also show that both the autistic and normal subjects’ responding varied as a function of stimulus parameters: responding to the circle was dominant in the small dot condition, yet overselective responding (to dots) was prevalent in the large dot condition. For example, in the small dot condition, 6 of the normal children (Derrick, Troy, Kevin, Sara, Kathy, and Sharon) and 6 of the autistic children (Larry, Freddie, Walter, Doug, James, and Mary) responded to the circle, as evidenced by 80% correct responding or better. In the large dot condition only 4 normals (Derrick, Kevin, Sara, and Kathy) and 1 autistic subject (James) responded to the circle. In the medium dot condition responding
5 II: E
50
0 DERRICK
TROY
KEVIN
SARA
JUDY
KATHY
SHARON
BRUCE
4. Responding of autistic and normal children to the gestalt (circle) under three task conditions: small dot (shaded bars); medium dot (striped bars); and large dot (open bars). FIG.
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was between these extremes, as 5 of the normal subjects (Derrick, Troy, Kevin, Sara, and Kathy) and 4 of the autistic subjects (Larry, Walter, Doug, and James) responded to the circle. An analysis of variance, for a 2-factor experiment with repeated measures on one factor, produced a significant main effect for the stimulus variables (F(1, 14) = 7.88, p < .Ol), but not for diagnosis (F(2, 28) = .14, p > .05) or the interaction (F(2, 28) = 1.12, p > .05). A post hoc Scheffe test showed a significant difference in responding between the small and large dot conditions 0, < .05), and a trend analysis further showed a significant linear trend in gestalt responding (p < .05) across the three conditions: gestalt responding decreased in a linear fashion as a function of the progression from small to medium to large dot conditions. This analysis indicated that the stimulus variables had an effect on children’s responding, but there was not a significant difference between the subject groups. Contrary to our hypothesis, the overselectivity evidenced by autistic and other children appears not to be a generalized phenomenon, but instead seems to be a function of task parameter. Additional support for the effect of stimulus variables on both groups can be seen in Fig. 5 and 6. Figure 5 shows the averaged percentage of responses to the circle (gestalt) stimulus for the autistic and normal groups, for each of the three stimulus conditions. Similarly, Fig. 6 shows the number of autistic and normal children who responded on the basis of the circle for each experimental condition. There was a decrease in both the number of gestalt responders and the percent of gestalt responding, within both groups, as the tasks progressed from small to medium to large dots. In both Fig. 5 and 6, the slopes of the lines are somewhat greater for autistics than for normals, although no significant interaction was obtained. Discussion The purpose of this experiment was to assess the generality of stimulus overselectivity in overselective children. The following results were obtained. (1) Stimulus overselectivity was found nor to be a generalized deficit in the overselective subjects identified, but instead varied as a
SMALL
MEDIUM
LAROE
5. Percent of responses to the gestalt stimulus by autistic (-) children during the small, medium, and large dot condition. FIG.
and normal (---)
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- - -_O-__ ‘0
SMALL
MEDIUM
LARGE
FIG. 6. Number of autistic (-4 and normal(---) children responding to gestalt under each experimental condition (small, medium, and large dots).
function of the stimulus variables associated with the task; and (2) the stimulus variables manipulated in this study similarly influenced the responding of both normal and autistic children. The data showing that the autistic and normal children were at times overselective suggests that overselectivity may not be central to the problems of autistic and retarded children. If overselectivity is to be implicated as a primary cause of disabilities, one might then expect that overselective normal children would also exhibit severe behavioral deficits. Even though the autistic and normal subjects performed similarly on the assessment of gestalt responding, there was little similarity in behavioral deficiencies between the two groups. Similarly, finding that stimulus overselectivity was in part a function of task variables, rather than a generalized problem in the developmentally disabled children, also contradicts the theory that overselectivity may be a cause of their behavior deficits, since this notion assumes that the children are overselective across all or most learning situations. Instead, the data suggest that stimulus variables may play an important role in determining whether overselectivity will occur. Although the results suggest that stimulus factors play a role in overselectivity, the precise stimulus dimensions that brought about the changes in stimulus control are not clear. In the present study, it was found that three stimulus variables-size, spacing, and number of dotscould rogerher be manipulated to bring about variations in the stimulus control over autistic children’s responding. It remains possible, however, that gestalt responding was facilitated specifically by an increase in the size or number of dots making up the circle, a decrease in the spacing between dots, or some combination of these three factors. Further analysis of the specific dimensions that did influence responding would seem to be invaluable since the results may aid in the design of new treatment strategies. If it is found that one of these variables, such as the distance or spacing between stimulus components, is the functional factor in determining overselectivity, then it would be helpful to develop treatment procedures aimed at systematically teaching children to respond to cues that are spaced progressively farther apart. Alternatively, one could design teaching methods that do not strain their
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restricted range of attention. For example, prompting procedures that utilized prompts located closer to the target stimulus may help ensure that both stimuli fall within their range of attention and come to control responding. Similar innovations could also be designed if changes in size or number of component features are found to occasion stimulus overselectivity. The present data may also advance our understanding of stimulus overselectivity in developmentally disabled children. It has been found that, when presented with multiple relevant cues, low MA autistic and retarded children typically respond only to one cue. We wondered if this stimulus overselectivity, since it has been replicated in a number of studies (e.g., Rincover & Koegel, 1975; Koegel & Wilhelm, 1973; Reynolds et al., 1974; Koegel & Rincover, 1976), might be the generalized way in which many of these children view their world. The data showing that most of the overselective autistic children responded to the gestalt in one (small dot) condition seems, however, to refute the notion that they do not (at least at times) respond to multiple cues, since gestalt responding necessarily required responding to more than one cue (i.e., stimulus components and their relative location). The present data may suggest that the notion of tunnel vision plays a contributing role in stimulus overselectivity. Perhaps the only stimuli that would become functional for an overselective child would be those in his or her restricted field or “tunnel” of vision. One way of conceptualizing tunnel vision is in terms of the relative location or distance between cues. If a child’s responding is under the control of one stimulus (S,), then the probability of that child responding to another stimulus (S,) simultaneously would be, in part, a function of its distance from S,. Using this hypothesis, the functional element in overselectivity may not be the number of cues involved, but rather the relative locution of those cues. Support for a tunnel vision hypothesis was found in the present study when autistic children were observed to respond more often to the gestalt when the dots making up the stimulus were closer together. If a child responds on the basis of only a restricted portion or area of a stimulus, one would expect the child’s responding to be controlled more by the gestalt when there was more information (i.e., more dots) in that area that indicated or gave the appearance of a line or curve. Conversely, the fewer the number of dots in his/her field of attention, the more difficult it would be to identify the pattern. REFERENCES Gellerman, L. W. Chance order of alternating stimuli in visual discrimination Journal
of Genetic
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Kamin, L. J. “Attention-like” Miami
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Kanner, L. Early infantile autism. Journal of Pediatrics, 1944, 25, 21 l-217. Koegel, R. L., & Rincover, A. Some detrimental effects of using extra stimuli to guide learning in normal and autistic children. Journal of Abnormal Child Psychology, 1976, 4, 59-71. Koegel, R. L., & Wilhelm, H. Selective responding to multiple visual cues by autistic children. Journal of Experimental Child Psychology, 1973, 15, 442-453. Lovaas, 0. I., & Schreibman, L. Stimulus overselectivity of autistic children in a twostimulus situation. Behaviour Research and Therapy, 1971, 9, 305-310. Lovaas, 0. I., Schreibman, L., Koegel, R., & Rehm, R. Selective responding by autistic children to multiple sensory input. Journal ofAbnormal Psychology, 1971,77,21 l-222. Reynolds, G. S. Attention in the pigeon. Journal of the Experimental Analysis of Behavior, 1961. 4, 203-208. Reynolds, B. S., Newsom, C. D., & Lowaas, 0. I. Auditory overselectivity in autistic children. Journal of Abnormal Child Psychology, 1974, 2, 253-263. Rimland, B. Infantile autism. New York: Appleton-Century-Crofts, 1964. Rincover, A. Variables affecting stimulus fading and discriminative responding in psychotic children. Journal of Abnormal Psychology, 1978, 87, 541-553. Rincover, A., & Koegel, R. L. Setting generality and stimulus control in autistic children. Journal of Applied Behavior Analysis, 1975, 8, 235-246. Schover, L. R., & Newson, C. D. Overselectivity, developmental level, and overtraining in autistic and normal children. Journal of Abnormal Child Psychology, 1976, 4, 289-298. Schreibman, L. Effects of within-stimulus and extra-stimulus prompting on discrimination learning in autistic children. Journal of Applied Behavior Analysis, 1975, 8, 91-l 12. Schreibman, L., & Lovaas, 0. I. Overselective responding to social stimuli by autistic children. Journal of Abnormal Child Psychology, 1973, 1, 152-168. Sutherland, N. S., & Mackintosh, N. J. Mechanisms of animal discrimination learning. New York: Academic Press, 1971. Varni, J., Lovaas, 0. I., Koegel, R. L., & Everett, N. L. An analysis of observational learning in autistic and normal children. Journal of Abnormal Child Psychology, 1979, 7, 31-43. Wilhelm, H., & Lovaas, 0. I. Stimulus overselectivity: A common feature in autism and mental retardation. American Journal of Mental Deficiency, 1976, 81, 227-241. RECEIVED:
September 23, 1980;
REVISED
November 23, 1981.