Longitudinal correlates of infant attention in the paired-comparison paradigm

INTELLIGENCE 13, 33-42 (1989)

Longitudinal Correlates of Infant Attention in the Paired-Comparison Paradigm JOHN COLOMBO D . W A Y N E MITCHELL JAY DODD JEFFREY T. COLDREN FRANCES DEGEN HOROWITZ

The University of Kansas

A sample of infants tested on paired-comparison visual discriminations at 4 and 7 months were tested at 16 months on tasks measuring their exploration of a novel environment, short-term spatial memory, and attention span/task persistence. Seven-month novelty preferences were related to accuracy on a spatial memory task, supporting the possibility that memory ability may carry some of the variance in correlations between infant novelty preferences and later intelligence. Also, shifting between targets during paired-comparison trials was related to infants' behavior at 16 months. Shifting at 4 months was positively related to accuracy on the memory task, and at 7 months it was positively related to several exploratory measures, supporting previous contentions that this measure may reflect different processes in early versus late infancy.

A n u m b e r o f recent studies have demonstrated that measures o f infant visual attention reflect reliable and stable individual differences (Bornstein & Benasich, 1986; C o l o m b o , Mitchell, & H o r o w i t z , 1988; C o l o m b o , Mitchell, O ' B r i e n , & H o r o w i t z , 1987a,b; Rose, F e l d m a n , & Wallace, 1988; but see M c C a l l , 1979, 1981), and account for m o d e r a t e but significant amounts o f variance in subsequent p e r f o r m a n c e on standardized intelligence tests (Fagan, 1984a,b, 1985; Fagan & M c G r a t h , 1981; Fagan & Singer, 1983; Rose, F e l d m a n , & Wallace, 1988; R o s e , Slater, & Perry, 1986; Rose & W a l l a c e , 1985; Sigman, Beckwith, C o h e n , & P a r m e l e e , 1985). H o w e v e r , the process or processes responsible for this continuity in mental functioning is still the subject of speculation. For e x a m p l e , while n o v e l t y preferences were initially interpreted as a measure of short-term recognition m e m o r y (e.g., Fagan & M c G r a t h , 1981), recent theThis work supported by grants MH41395-01, HD18290, and a grant from the KU Mental Retardation Research Center. We are grateful to the staff of the Infant Study Center (particularly Michelle Knoll) for assistance in subject recruitment, to Mary Gersh and the staff of the KU Regents Center in Shawnee Mission, KS for their cooperation, to Sue Young for deftly preparing Figure 1, and to the families who participated in this study for their generous donation of time and effort. Correspondence and requests for reprints should be sent to John Colombo or D. Wayne Mitchell, Department of Human Development, University of Kansas, Lawrence, KS 66045. 33

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COLOMBO, MITCHELL,DODD, COLDREN,AND HOROWITZ

oretical (Berg & Sternberg, 1985; Sternberg, 1985) and empirical (Fagan, 1984a,b) statements suggest that the positive response to novelty involved in the discriminative response, rather than early memory ability, carries this continuity between infant attention and later childhood intelligence. In order to explore the nature of novelty preferences (as well as some other measures of visual attention) during infancy, we retested a group of infants who had been tested on a series of paired-comparison novelty tasks at both 4 and 7 months of age. At 16 months, we assessed these infants' tendency to explore a novel environment (as a measure of their response to novelty), and their ability to find a toy hidden in one of three spatial locations (as a measure of their memory ability). In addition, we assessed the length of time they engaged in play with several toys (as a measure of their attention span). We added this last variable because of recent findings indicating a negative relationship between the typical length of infants' attentional patterns and their novelty-preference performance during middle infancy (Colombo et al., 1988). It seemed plausible that some simple attentional parameter, such as attention span or persistence, might also be responsible for some of this continuity.

METHOD Subjects Subjects in this study were a subsample of 23 16-month-olds (13 male) from a larger sample of 40 who were tested longitudinally at 4 and 7 months of age on a series of paired-comparison tasks (Colombo et al., 1988). Of the 17 infants not represented in this follow-up, 11 could not be contacted, 4 could not return because of scheduling problems (e.g., mother returning to work), and 2 refused to participate in the follow-up.

Procedure

Paired-Comparison Tasks. Details for the 4- and 7-month paired-comparison tasks can be found in Colombo et al. (1988). Up to 5 such tasks were conducted at each age, with each comprised of a familiarization period during which the infant accumulated some amount of fixation time (20 s at 4 months, l0 s at 7 months) to a stimulus, followed immediately by a test phase in which the familiar stimulus was paired with a novel one (again, 20 s at 4 months, l0 s at 7 months). The test phase was divided into two trials of equal length, with the lateral position of the novel and familiar targets balanced across the two trials. The stimuli used in these tasks were alphabet letters arranged in pairings which, according to adult and animal data, varied in discriminability. Three measures of interest from these 4- and 7-month tasks are reported in analyses here. The first was the mean number of fixations made during the familiarization phases. Infants were allotted a predetermined amount of accumu-

CORRELATES OF INFANTATTENTION

35

lated fixation time to targets prior to test,, but could vary in the number of distinct looks necessary to accumulate that fixation time. This variable reflects the relative duration of infants' attention to the stimuli presented, and has been implicated as a predictor of contemporaneous performance on discrimination of those stimuli (Caron, Caron, Minichiello, Weiss, & Friedman, 1977; Colombo & Atwater, 1987; Colombo et al., 1988). The second measure was infants' mean percent attention to the novel target during the test phase, which is generally taken as an index of the infant's discrimination of, and short-term memory for the familiar target (e.g., Fagan, 1984a,b, 1985). The third measure was the mean number of times the infant alternately fixated ("shifted") between the simultaneously presented targets during the test phase (Colombo & Bundy, 1983; Harris, 1973; Ruff, 1975). There are at least two interpretations of shifting. It may be interpreted as an index of the infant's confusion between the two targets presented, or as a measure of the degree to which the infant actively compares the stimuli presented, and thus might reflect the infant's motivation or engagement in the task. Data on the pattern and shortterm stability of shifting during the first year of life allow for the possibility that this measure may reflect different processes at different points during infancy. For example, the data suggest that at 4 months shifting may be determined by stimulus parameters, as increased shifting has been observed in situations where target pairs are identical (Ruff, 1975) or less discriminable from one another (Colombo et al., 1988). Perhaps due to such external influences, the measure shows relatively low test-retest reliability from one week to the next at this age. However, at 7 months shifting is not associated with stimulus discriminability or similarity, but reflects some consistent characteristic of the infant, as evidenced by high test-retest reliability (r = + .56) across a one-week interval (Colombo et al., 1988). Regardless of the specific interpretation of this measure, it is tempting to interpret shifting as a measure of higher-order information-processing components during infancy. Indeed, Brown and DeLoache (1978) have argued that patterns of visual scanning during infancy, particularly shifting, may reflect early "executive" processes.

Follow-up Procedure. The 16-month follow-up consisted of one session in which the subject's exploratory behavior, memory, and attention span/task persistence was assessed. The session was run in a 2.0 m z 4.0 m room. The session was run in three phases conducted in a constant order as described below, lasting a total of 30 to 40 min in length, and was videotaped for later scoring. a. Exploratory Behavior. The exploratory phase assessed the degree to which the child explored the room with the mother present, and under conditions where a stranger (i.e., the tester) was present or absent. The session was adapted from the design of open-field experiments run with rats during the 1950s and 1960s

36

COLOMBO, MITCHELL, DODD, COLDREN, AND HOROWITZ

(e.g., see Denenberg, 1964). In order to entice the infant to explore, four toys (a Fisher-Price wind-up clock, a Fisher-Price pull-dog, a wind-up Mickey Mouse, and a Fisher-Price pull-train) were placed in assigned positions throughout the room. Chalk lines drawn on the carpet radiating from the comer chair at .33m intervals facilitated scoring of infant behavior during this phase of the follow-up (See Figure 1). In the exploratory phase, the subject was allowed to roam freely and play with any of the toys for two 3-min blocks. For the first block, the tester sat in the room, against the wall approximately .5 m from the mother's seat, and spoke with the mother while she filled out a form. For the second block the observer left the room and the mother was instructed to fill out a questionnaire. She was asked to not restrain the infant from exploring unless the child approached the video camera. From the videotape, three variables were scored: the number of toys touched by the infant, the number of movements he or she made from one place in the room to another, and his or her average distance from the mother. Because infants made significantly more movements, touched more toys, and ventured further from their mothers when the tester was absent than when he was present (Multivariate F(3,20) = 6.90, p < . 0 1 ; see Table 1), we entered exploratory measures from the tester-absent versus tester-present blocks separately into correlational analyses.

b. Memory Task. Following completion of the exploratory phase, infants' ability to find objects hidden under one of three inverted cups (Webb, Massar, & Nadolny, 1972) was tested. The cups were 12.5 cm tall and 7.5 cm in diameter. The objects hidden included a 3.8 cm ball, a plastic 7 cm giraffe, and a plastic 4

[]

Legend E = Experimenter M = Mother C = Video Camera T = Toy

FIG. l. Representation of room set-up for exploratory session.

CORRELATES OF INFANT ATTENTION

37

cm squirrel. The different objects were used in an effort to maintain infants' interest in the task, and were switched when the tester judged that the infant was becoming bored with the task (Webb et al., 1972). The order in which they were used was the same as listed above (i.e., ball, giraffe, squirrel). For this task, a table was placed in the middle of the room, and the mother sat with the infant on her lap with the tester on the opposite side of the table. All three cups were placed in front of the infant in a horizontal row 8 cm apart. The subject was first "warmed u p " by allowing him or her to play with the ball for a short time. It was then taken and hidden in full view under one of the cups. The infant was then distracted for 15 s with a hand puppet (a dragon or a dog, again switched if the infant became bored) and then allowed 15 s to search for the hidden toy. If no search was made after 15 s the toy was retrieved by the tester and the trial terminated. If the infant searched I correctly on his/her first attempt, the trial was also terminated. If the infant searched incorrectly, the cup was replaced, the 15 s timer reset, and the infant was allowed to search again with the toy remaining in the same hiding place. Trials with initial incorrect searches were terminated if either the infant found the toy on subsequent searches, or if the infant failed to search for 15 s. This procedure was continued for 15 trials. The order for hiding positions was constant across all subjects, but the hiding positions were counterbalanced and no position was used more than once consecutively. Preliminary analyses of infants' performance on this task indicated that about one third of the sample failed to search on the first hiding trial. It seems likely that many of the infants did not understand the task at the very beginning of this phase, or were perhaps intimated by the tester. From trials 2 through 10, however, 22 of the 23 infants searched on each trial, and the group success rate (53%) across these trials significantly exceeded chance (33%; t(21) = 4.83, p <.001). Following the trial 10, however, infants' performance was extremely variable, falling off to chance levels and again with up to 30% of the sample refusing to search. Webb et al. (1972) also report such responding in 18-montholds, attributing it to inattentiveness or boredom with numerous repetitions of the task, and we are inclined to repeat this interpretation for our present sample. For this reason, only those trials during which infants were engaged in the task and performing consistently above chance (average accuracy on trials 2-10) were used in the correlational analyses. c. Attention Span~Task Persistence. After completion of the hiding task the subject remained seated in the mother's lap and was presented sequentially with three different toys for 3 min each. This brief play assessment was modeled after "mastery motivation" tasks developed by Yarrow and his colleagues (e.g., tA "search" was operationalized as the infant touching or lifting one of the inverted cups. Lifting or touching more than one cup at a time was scored as an incorrect search.

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COLOMBO, MITCHELL, DODD, COLDREN, AND HOROWITZ

Yarrow, McQuiston, MacTurk, McCarthy, Klein, & Vietze, 1983) designed to measure task persistence/attention span during the first 2 years of life. The toys were Fisher-Price Activity Center, Child Guidance Busy Poppin' Pals, and Ambi Toys Knocky. The tester provided encouragement and/or toy demonstrations at 0, 30, and 60 s, but beyond 60 s after being given the toy, no assistance or encouragement was offered. Mothers were instructed not to interfere with the infant's playing with the toys. The toy was removed after the infant had played with it for 180 s or did not touch it for 90 consecutive s. The primary measure of interest was the mean percent of time the infant was actively involved with the three toys (Yarrow et al., 1983).

RESULTS Means and standard deviations for all variables are presented in Table 1, and Table 2 presents the matrix of Pearson correlations computed between attentional variables from 4 and 7 months and the 16-month follow-up variables. Two variables from infancy significantly predicted memory performance at 16 months. First, 7-month novelty preferences were correlated with accuracy on the memory task at 16 months (r = + . 5 1 , p < . 0 5 ) ; that is, infants who showed

TABLE 1 Descriptive Statistics: All Variables M

SD

8.82 8.93 0.57 4.79 5.78 0.58

2.91

7.96 2.09 0.79 13.78 3.22 0.87

5.00 1.31 0.33 5.64 0.85 0.30

0.53

0.16

78.83

13.72

I. Infant Recognition Tasks

Number of Looks during familiarization, 4 months Number of Shifts, test phase, 4 months Novelty Preference, 4 months Number of Looks during familiarization, 7 months Number of Shifts, test phase, 7 months Novelty Preference, 7 months

2.72 0.09 1.87 1.73 0.07

II. Follow-up Tasks A. Exploratory tasks

Number of Movements, tester present Number of Toys Touched, tester present Mean Distance from mother, tester present (m) Number of movements, tester absent Number of Toys Touched, tester absent Mean distance from mother, tester absent (m) B. Memory Task

Accuracy of first search (Note: chance = 0.33) C. Attention Span/Persistence Task

% active involvement

39

CORRELATES OF INFANT ATTENTION TABLE 2 Intercorrelations between Infant Recognition Tasks (4 and 7 months) and Follow-up Variables (16 months) Recognition Tasks 4 months N Looks Shifts

Exploratory tasks (N = 23) Movements, T present Toys Touched, T present Distance, T present Movements, T absent Toys Touched, T absent Distance, T absent Memory Task (N = 22) Accuracy of first search

- . 10 -.17 .06 - . 20 -.24 -.08 .00

.06 .13 .27 - . 16 -.10 .24

NP

N Looks

7 months Shifts

NP

.06 -.17 -.29 .16 .23 -.01

- . 10 -.14 .16 .07 -.17 -.03

.10 .13 .15 .11 .21 .18

.36* .43** .14 .12 .09 .39**

-.53**

.02

.00

.24

.01

.31

-.15

-.29

.51"*

Attention Span/Persistence Task (N = 22)

% Active involvement

.00

-.27

Note. T = Tester, NP = Novelty Preference.

*p < .10; **p = .05; ***p < .01

h i g h n o v e l t y p r e f e r e n c e s at 7 m o n t h s w e r e m o r e successful at the m e m o r y task at 16 m o n t h s . S e c o n d , s h i f t i n g b e t w e e n targets at 4 m o n t h s also p r e d i c t e d a c c u r a c y o n the m e m o r y task at 16 m o n t h s , a l t h o u g h the r e l a t i o n s h i p was n e g a t i v e (r = - . 5 3, p < : 0 1 ) , i n d i c a t i n g t h a t i n f a n t s w h o shifted less at 4 m o n t h s o f age e x h i b ited b e t t e r p e r f o r m a n c e o n the m e m o r y task. O n e o t h e r c l u s t e r o f r e l a t i o n s h i p s e m e r g e d to s u g g e s t that h i g h e r shift rates at 7 m o n t h s w e r e a s s o c i a t e d w i t h g r e a t e r e x p l o r a t i o n at 16 m o n t h s . P o s i t i v e correlations w e r e o b s e r v e d b e t w e e n 7 - m o n t h s h i f t i n g a n d the n u m b e r o f toys t o u c h e d ( r = + .43, p < . 0 5 ) a n d w i t h the m e a n d i s t a n c e f r o m the m o t h e r w h i l e the tester was o u t o f the r o o m ( r = + . 3 9 , p = .05). T h e m e a n n u m b e r o f m o v e m e n t s m a d e b y the i n f a n t w h i l e the t e s t e r w a s in the r o o m (r = + . 3 6 ) also a p p r o a c h e d significance. N o s i g n i f i c a n t c o r r e l a t i o n s e m e r g e d i n v o l v i n g the n u m b e r o f fixations m a d e d u r i n g the f a m i l i a r i z a t i o n p h a s e at e i t h e r 4 or 7 m o n t h s . In a d d i t i o n , n o n e o f the i n f a n t a t t e n t i o n a l m e a s u r e s c o r r e l a t e d w i t h i n f a n t s ' overall p e r f o r m a n c e d u r i n g the a t t e n t i o n s p a n / t a s k p e r s i s t e n c e s e s s i o n , or w i t h a n y p o r t i o n o f the 3 - m i n u t e blocks. 2

2We tested the possibility that relations for exploratory and attention-span measures might emerge in infants' behavior was analyzed within smaller intervals than the 3-min blocks used here by coding data in intervals as small as 10s and building up to longer (20, 30, 60 s) analysis intervals. However, these finer-grained analyses did not yield any consistent relationships between these measures and infants' visual behavior in the paired-comparison task.

40

C O L O M B OMITCHELL, , DODD, COLDREN, AND HOROWITZ DISCUSSION

The data from this short-term longitudinal study demonstrate continuity from attentional measures in infancy to early toddlerhood. While such continuity has been demonstrated from infancy to school age in previous research (e.g., Fagan, 1984a, 1985), these results are significant because they implicate memory and discrimination abilities as potential contributors to that continuity. Novelty preferences at 7 months predicted success on a short-term memory task at 16 months in which performance was not directly dependent upon a novelty-based response. These results suggest that while the positive response to novelty may indeed carry some of the variance shared between infant attentional tasks and later IQ (Berg & Steinberg, 1985), individual memory ability may also contribute to the developmental continuity o f early stimulus processing tasks from infancy. A set of secondary findings involves the measure of shifts between targets during paired-comparison phases. Infants who shifted less between targets at 4 months during paired-comparison test phases performed better on the 16-month memory task than infants who shifted more. If shifting between paired targets during the first half of the first year of life reflects the degree of difficulty encountered in discrimination or recognition of visual patterns (Colombo et al., 1988; Ruff, 1975), one interpretation of this relationship might be that infants having trouble with visual discrimination or memory at 4 months also show lower performance on a memory task 1 years later. 3 The negative relationship between 4-month shifting and 16-month memory performance contrasts with the positive relationship observed between 7-month shifting and increased exploration at 16 months. It may still be possible to conceptualize this measure in terms of some executive process (Brown & DeLoache, 1978); At 4 months shifting may indicate stimulus or task confusion, but at 7 months it may more closely represent some ability to direct or allocate attention (e.g, actively compare stimuli). At 7 months, shifting might be also taken to reflect some indication of the infant's tempo or pace; This would account for the positive relationships between shifting at this age with several variables that reflect a subsequent tendency for exploration or movement about in a novel environment. At the very least, these findings support the contention (Colombo et al., 1988) that this measure reflects different processes at different ages during the first year. The correlates of infant attention and the relationships shown between mea-

3One puzzling aspect of this finding is that shift rate was not particularly reliable from one week to the next (i.e., the test-retest correlation of this variable at 4 months was about + .20; Colombo et al., 1988). The psychometrics of infant attention are complex and curious (Colombo, 1987). For example, stability correlations may exceed within-sessioncorrelations (Rose et al., 1988), or infancy measures may correlate more highly with measures in later childhood than they do with themselves over brief test-retest periods (McCall, 1985). This finding further punctuates the need for a more precise understanding of the internal and external determinants of individual differences in early attention and cognition.

CORRELATES OF INFANT ATTENTION

41

sures from the early months of life to measures during the second year lend further support to the mounting notion that infancy may hold important precursors of later information processing that relate to intelligence (e.g., Bornstein & Sigman, 1986). While our results provide encouragement for future research in the area, substantial interpretive cautions are clearly warranted with regard to the present study. First, the study was decidedly exploratory, in which several significant correlations emerged from a number of variables. Second, the sample size was relatively small. Third, although we did not observe significant relationships between infant novelty preferences and toddler exploration or attention span, we cannot clearly preclude the contribution of a response-to-novelty component to relationships between early novelty preferences and later intelligence from these data. Finally, the correlations reported here account for only moderate amounts of variance; the larger portion of the variance in later behavior from infancy clearly remains unaccounted for. We would stress that a full accounting for developmental continuity from infancy should include tactics that seek to precisely identify (a) behaviors that foreshadow underlying processes that may constitute intelligence, and (b) those environmental conditions that shape these processes most successfully.

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