Newborns discriminate schematic faces from scrambled faces

Newborns discriminate schematic faces from scrambled faces

Megan A Easterbrook

Abstract Newborn attention to, and discrimination of, facelike patterns was examined in three experiments employing 35 one- to three-day-old infants. Differential eye tracking and head turning to three moving stimuli (a schematic face, a scrambled face, and a luminance-matched blank) were measured in two of the three experiments. The newborns turned their eyes and heads farther to follow patterned stimuli, containing facelike features, than to a luminance– matched blank, but they did not turn farther to a stimulus with the features arranged in a facelike manner compared to features scrambled. A third experiment tested newborns’ ability to discriminate between the facelike and scrambled face patterns. Using an infant-controlled procedure, infants showed similar initial fixation times and similar numbers of trials to reach a 60% response decrement criterion to both patterned stimuli. Following habituation, novelty responding indicated that infants discriminated between the schematic face and the scrambled face patterns. Although infants did not show a preference for a facelike stimulus compared to a features-scrambled pattern in the present experiments, they could discriminate the two patterns based on the internal arrangement of the facial features.

Whether human newborn infants perceive face stimuli preferentially is a controversial issue. Some researchers (e.g., Johnson & Morton, 1991) argue that infants are innately drawn to the human face from birth and that this attention is the first critical step in the development of socialization. Others argue that a face pattern is perceived in a manner similar to other stimuli which share particular attributes (e.g., ovals, curves, high-contrast areas, or the optimal amount of amplitude information/pattern complexity; Kleiner, 1993). The question of whether a face is a special stimulus, perceived differently or preferentially by the newborn, is of interest to both developmental and perceptual psychologists, especially since the publication of Johnson and Morton’s (1991) two-process model of face perception.

According to Johnson and Morton (1991), newborns have a subcortical mechanism, CONSPEC, which serves to orient rudimentary attention to the human face. Its functioning declines between one and three months of age, during which period a second mechanism, CONLERN, is asserting itself. This mechanism is hypothesized to be a generic mechanism that serves to drive the infant to learn about the specifics of human faces. Because of its increasing influence on the infant’s orientation toward faces, Johnson and Morton argue that most infants approaching three months of age will show clear interest in faces. Indeed, many researchers have demonstrated a face preference in infants two months of age or older (e.g., Fantz, 1965; Haaf & Bell, 1967; Kagan, Hanker, Hen-Tove, & Lewis, 1966; Maurer & Barrera, 1981). However, support for a similar preference by newborns is equivocal. Whereas some investigators have reported demonstrating a newborn face preference (e.g., Fantz, 1963; Fitzgerald, 1968; Goren, Sarty, & Wu, 1975; Stechler, 1964), others have not (e.g., Easterbrook, Kisilevsky, Hains, & Muir, 1999; Haaf, 1974; Hershenson, 1964; Thomas, 1965).

Using adaptations of Fantz’s (1958) visual preference technique, infants’ interest in face patterns has been examined by presenting newborns with static patterns (e.g., Fantz, 1963; Hershenson, 1964), photo-images (Slater et al., 1998), or still-life faces (Bushnell, Sai, & Mullin, 1989; Pascalis, DeSchonen, Morton, Deruelle, & Fabre-Grenet, 1995). Using patterned and coloured stimuli, Fantz (1963) found that infants preferred to look at a face pattern when it was presented along with any other pattern from his stimulus set. In contrast, Hershenson (1964) reported that newborns preferred patterns of low to intermediate complexity or of intermediate illumination. Recently, Valenza, Simion, Cassia, and Umilta (1996) examined newborns’ orientations to Morton and Johnson’s (1991) config, a facelike stimulus containing two square blobs for the eyes and one square blob for the mouth. They found that the direction of newborns’ orientations did not show a face pattern preference when config was presented along with its inversion. On the other hand, when the duration of newborn fixations was examined, a preference for the upright config was found. Nevertheless, using matched photo-images of faces, Slater et al. (1998) reported that newborns orient more often to an attractive face, rather than to an unattractive face. When real faces are presented, infants have been reported to differentiate mothers’ faces from strangers’ faces only if the hairline region is visible, indicating a seeming lack of interest in the internal features of the face (Bushnell et al., 1989; Pascalis et al., 1995). In summary, studies employing static stimuli have not demonstrated conclusively that newborns are attracted to the human face, whereas studies employing real faces demonstrate infant discrimination of faces based on external features.

Kleiner (1987) argued that both the newborn’s immature visual system and the visually enhancing aspects of patterns (their amplitude, sensory information, or complexity) must be considered when examining newborn pattern preferences. Infants’ poor visual acuity is problematic for newborn studies employing static stimuli. In particular, the fovea, which is responsible for central vision, is not well developed (Teller, McDonald, Preston, & Sebris, 1986; Wilson, 1988). Newborns can detect gray stripes differing in contrast by no less than 30% (Slater, 1995), whereas adults typically detect differences of less than 1% (black and white patterns have a contrast of 100%). The newborn’s peripheral visual system is more mature. It is sensitive to areas of high contrast, movement, and other dynamic properties of stimuli, especially when the patterns are moving (Schiller, Logothetis, & Charles, 1991). For example, Johnson (1990) reported that attention to patterns seems to increase when they are placed in the periphery.

In addition to the placement of the stimulus in the peripheral visual field, certain properties of visual stimuli seem to capture the newborn’s attention. Infants look longer at visual patterns that have high-contrast regions (e.g., black and white rather than dark grey and light grey; Morison & Slater, 1985), have low-spatial frequencies (e.g., thick bars rather than thin bars, faces; Banks & Dannemiller, 1987), and are large (e.g., an 8-inch circle rather than a 4-inch circle). Thus, it would seem that the ideal stimulus to capture newborn attention should depict a high-contrast pattern of low-spatial frequency and be of sufficient size to be perceived when placed at a viewing distance of no more than 75 cm (Braddick, Atkinson, French, & Howland, 1979).

Given that newborns attend more to stimuli once they move, a preferential tracking procedure that uses large, moving, visual stimuli may be the optimal method of testing newborn visual preferences. Another advantage with this method is that it makes use of both the newborn’s looking and orientation behaviour (Berlyne, 1960).

In 1970, Jirari was the first to use a preferential tracking procedure to test newborns’ orientation responses to moving, visual stimuli that had no external contours. She found that two-day-olds turned their eyes and heads farther to track a schematic face than to track two stimuli containing the same facial features arranged in moderately scrambled and severely scrambled arrays. Her three patterned stimuli elicited newborn eye-tracking and head-turning responses that were greater than those elicited by a blank, which was presented to estimate spontaneous eye turns and head turns. Later, she replicated this finding with nine– minute-olds (Goren et al., 1975).

Subsequently, Maurer and Young (1983) partially replicated Goren et al.’s findings (1975) with newborns ranging in age from 12 hours to 5 days. Using similar stimuli and controlling for handler bias and experimenter bias, they found that newborns turned their eyes and heads farther to pursue patterned stimuli than to pursue a blank control. Also, newborns turned their eyes farther when following the schematic face than when following Goren’s severely scrambled pattern. However, newborns tracked the face and Goren’s moderately scrambled pattern to the same extent. In contrast to Goren (Goren et al., 1975; Jirari, 1970), Maurer and Young found that newborns turned their heads equally far to the face and features-scrambled stimuli.

To date, Johnson, Dziurawiec, Ellis, and Morton (1991) have produced the most impressive replication of Goren’s (Goren et al., 1975; Jirari, 1970) work. Using only three of Goren’s stimuli (a schematic face, a scrambled face, and a blank control), they found that minute-old newborns showed greater eye turns and head turns to the intact face than to the scrambled face, both of which were tracked farther than the blank control. Like Maurer and Young (1983), Johnson et al. also controlled for potential experimenter bias by having a second experimenter judge head turns and by having the handler remain blind to the identity of the test stimulus.

Although researchers who have used a preferential tracking procedure report greater newborn pursuit of a face than a scrambled pattern, their findings vary in other ways. For example, Johnson et al. (1991) replicated Maurer and Young’s (1983) observation of greater eye turning than head turning to a facelike pattern compared to a features-scrambled pattern. This finding contrasts with Goren’s (Goren et al., 1975; Jirari, 1970) observation of greater head turning than eye turning. However, Johnson et al. replicated Goren’s finding of differences in the extent of newborns’ head turning in the pursuit of patterned stimuli, a result not found by Maurer and Young. These contradictory results obtained by three groups of investigators may have been the result of procedural differences. For example, Maurer and Young employed a baby-seat to hold infants during testing, thus providing little support for newborns to move their heads; Goren et al. employed a handler who was not blind to stimulus presentations; and, Johnson et al. used a handler blind to stimulus presentations.

Despite their procedural variations, these preferential tracking experiments demonstrated greater newborn tracking of a schematic face stimulus compared with at least one stimulus containing the same facial features scrambled. In contrast, other research has not supported this finding. For example, measuring visual pursuit with a different metric, Muir, Campbell, and Low (as cited in Muir, Humphrey, & Humphrey, 1994) failed to find differential newborn tracking among moving face and geometric patterns (checkerboard and striped patterns) of equal space– average luminance. Furthermore, Morton and Johnson (1991) reported that newborns actually tracked a checkerboard pattern farther than their schematic face patterns. Over four preferential tracking experiments, Easterbrook et al. (1999) showed several scrambled patterns to newborns along with a face pattern and a blank. In addition to the controls for experimenter bias employed by Maurer and Young (1983) and Johnson and Morton (1991), controls for stimulus distance and luminance were incorporated into the procedure. Newborns were reported to have tracked all patterns farther than the blank, but the face and scrambled stimuli were tracked equally far. So, the question remains: Is a face pattern special to newborns, eliciting more attention than other visual stimuli, or is it a salient visual stimulus because of pattern complexity?

To clarify the issue of a newborn preference for a face pattern and ability to attend to the internal features of visual stimuli, two preferential tracking experiments were conducted. Because there were differences among the procedures employed by Goren et al. (1975), Johnson et al. (1991), and Maurer and Young (1983), a previously employed design was selected for the first preferential tracking experiment: namely, that of Johnson et al. For the second preferential tracking experiment, to control for possible effects of order, a counterbalanced, CABBA CBAAB design was used. After Easterbrook et al. (1999), both of these preferential tracking experiments included two controls not previously employed. First, to control for fluctuations in stimulus distance, a free-standing protractor held the test stimulus about 18 cm from each newborn’s face. Second, the test stimulus received constant illumination regardless of its angle about the infant’s midline.

In previous experiments, it was concluded that because newborns tracked one pattern farther than another, they preferred a face like stimulus to other patterns. Such a conclusion assumes that newborns could discriminate among the patterns. However, their ability to discriminate the internal features of these face like patterns is yet to be demonstrated unequivocally. Thus, Experiment 3 used a habituation paradigm with moving stimuli to investigate the newborn’s ability to discriminate between the same, facelike stimuli employed in the first two experiments.

Experiment 1

METHOD

Participants. Ten mothers delivering at a community hospital in Southwestern Ontario provided informed written consent for their newborns to participate. Inclusion criteria were: (a) a physically uncomplicated pregnancy; (b) vaginal delivery; (c) one-three days of age; (d) birthweight of 2 2,500 grams; (e) gestational age of 37-42 weeks at birth; (f) Apgar score > 7 at 5 minutes; (g) diagnosis of a healthy term infant on first day examination. Of the 10 newborns, nine (one baby boy and eight baby girls) completed the procedure. The data of one participant were lost because of a recording error. The mean gestational age at birth was 40.6 weeks (SD = 0.7) and mean age at testing was 46 hours (SD = 9).

Stimuli and apparatus. Three different two-dimensional, white, head-shaped forms of approximately 17 cm x 19 cm were used in the present experiment. Two of the stimuli employed were computer-scanned reproductions of Morton and Johnson’s (1991) copies of Goren’s patterns. They were called the schematic face and moderately scrambled patterns (henceforth referred to as the “scrambled” pattern). In addition, we included a luminance-matched blank control, after Muir et al. (1994). Please see Figure 1 for depictions of the stimuli used.

Affixed to the centre on the back of each stimulus was a 1 cm x 2 cm metal loop with a hole that measured 4 mm wide x 13 mm high. This loop was designed to fit the bar of the protractor (described later). In this way, a stimulus could easily be slid along the bar and be positioned facing the baby.

A free-standing tripod, which held the test stimulus, consisted of a stand, a protractor, and a metal bar. The stand was 80 cm high. The protractor was marked in 5 deg increments, starting from Oo at the centre and extending to 90 deg on both the left and right sides. It was 36 cm wide at the base and 21 cm high at the apex and was affixed to the top of the stand. A movable, vertical, 3 mm x 12 mm, metal bar bent at a 90 deg angle and weighted at the bottom, was anchored to the stand below the face of the protractor. In the resting position, a weight served to keep the bar positioned at the centre line (the baby’s midline or 0 deg mark) of the protractor. As the bar, with the stimulus attached, moved from midline it passed over the demarcations on the protractor. Two 100-watt spotlights illuminated the test stimulus at every position from 0 deg to 90 deg on both the right and left sides. These lights were located behind the protractor and positioned to focus on white sheets to achieve uniform lighting of the test stimulus. The test room was dimly lit, receiving only natural light through windows.

A Cohu 3310 solid-state CCD camera with a Cosmican TV zoom lens recorded each infant’s eye tracking and head turning during testing. The camera was placed high above the handler’s head at a distance of approximately 1.5 m. Connected to the camera was a Hitachi VT-F540A VHS video recorder, which recorded newborn responding during the test sessions. To determine the extent of visual tracking during testing, the handler viewed a 30 cm x 41 cm monitor located in the testing room.

A black, 6 cm letraset line was placed in the centre of a 1 cm x 6 cm piece of micropore surgical tape. The surgical tape, with the black line, was placed in the middle of each infant’s forehead before testing. During testing, the letraset line was used as a reference point against the demarcations on the protractor to help determine the angle of the newborn’s visual fixation when looking at the test stimulus.

Procedure. Newborns were brought to the laboratory in a quiet, alert state. Parents were invited to view the procedure through a glass partition from an adjacent room or to return to view the videotape later. Each newborn was then held supine on the handler’s lap, which was covered by a folded blanket approximately 8 cm thick. The handler sat facing the protractor with the infant positioned underneath the arm of the metal bar, facing a stimulus. The handler centred the newborn’s head (referencing with the letraset line) at the Oa line of the protractor. The handler supported the newborn’s neck region with her left hand to facilitate head movements (for details, see Muir & Field, 1979). She also supported the infant’s back with her arm and the blanket. Holding the infant in this way freed the handler’s right arm to move the metal bar that held the test stimulus.

Once the infant was in midline position and fixating the stimulus, the protractor was used to move the stimulus slowly to one side, at such a rate that it just preceded the infant’s eye movements. The experimenter stood behind the handler during testing and removed and replaced the stimuli on the bar of the protractor. When fixation of the stimulus stopped for about 5 s, the handler made judgments of the degree of eye turning by comparing the position of the pupils with the degrees on the protractor as seen on the TV monitor. Such judgments were made via the television image because this ensured that the handler could not see a reflection of the test stimulus on the infant’s cornea. Simultaneously, the experimenter made judgments of the degree of head turning by comparing the letraset line on the infant’s forehead with the degrees on the protractor. These were audio-recorded on the videotape and manually recorded.

The three stimuli were intermixed and randomly presented, once on the left side and once on the right side, to each newborn; the order and side of stimulus presentations were counterbalanced across subjects. Each stimulus was shown twice to each side for a total of six scores. Following Johnson et al. (1991), a criterion of one eye turn or head turn > 60o per side was used. Because the largest possible turn is 90, a ceiling effect may occur if infants are required to make such large turns. However, this is not expected because others have not reported this problem (e.g., Johnson et al.). A maximum of seven attempts were made to elicit tracking that would meet this criterion (Goren et al., 1975; Johnson et al., 1991). If criterion was not reached, a trial was concluded and the next begun.

Eye turns and head turns were scored twice by the experimenter. First, they were scored online during testing. Later, they were scored from videotape (live-tape judgments). Intraclass reliabilities were calculated using a method described by Shrout and Fleiss (1979). A person naive to the experiment also scored head turns for 20% of the videotaped sessions. The intraclass rs ranged from .96 to .99. Given the high reliability among judges’ scores across both experiments, only the experimenter’s scores were used in the data analyses.

RESULTS

The data were analyzed to determine whether newborns tracked the upright face farther than the scrambled stimulus and both of these farther than the blank. The data obtained for eye turns and head turns were analyzed separately. The data were initially analyzed for a main effect of direction. The degree of rotation for both directions was then averaged to produce a single mean score for each stimulus before testing for a main effect of stimulus. The same computations were done for the eye-tracking and head-turning data. For repeated measures analysis of variance (ANOVA) tests, Greenhouse-Geisser conservative probabilities are reported. For all statistical tests, the level of significance was set at an alpha of .05.

Eye turning. The mean eye turn results are shown in Table 1. A two-way ANOVA with two within factors (3 stimuli x 2 directions) and orthogonal contrasts were used to compare the amount of eye turning. A significant main effect of stimulus was found, F(2, 8) = 9.66, MSE = 861.76. Neither a significant effect of direction, nor an interaction of stimulus with direction, was found. These data indicate that eye tracking of the blank control differed significantly from tracking of the schematic face, F(1,8) = 9.71, MSE = 1,441.84, and the scrambled stimulus, F(1,8) = 10.05, MSE = 1,241.32. The degree of eye turning did not differ between the patterned stimuli.

Because averaged data could be influenced by a few infants making large turns, individual eye and head turns toward the two patterned stimuli were examined. The results of the individual responding were similar to averaged data. Four infants turned farthest to the schematic face, two toward the scrambled face, one turned farthest and indiscriminately to both patterned stimuli, and two turned equally to track all stimuli.

Head turning The mean head turn results are also shown in Table 1. An ANOVA (3 stimuli x 2 directions) was applied to the head-turning data. A significant main effect was found for stimulus, F(2,16) = 6.57, MSE = 428.97. No significant direction or interaction effects were found. Turning toward the blank control differed significantly from turning toward the schematic face, F(1,8) = 6.67, MSE = 979.34, and the scrambled stimulus, F(1,8) = 10.93, MSE = 811.11.

The degree of head turning did not differ between the patterned stimuli. The individual head turns were similar to averaged data. Four infants turned farthest to the schematic face, three toward the scrambled face, one turned equally to track the face and the blank, and one turned farthest to the blank.

DISCUSSION

The results of the present experiment demonstrated that newborns will pursue patterned stimuli farther than a blank, but they track the face and the scrambled patterns to the same extent. These results are surprising in light of reports by others (e.g., Goren et al., 1975; Johnson et al., 1991; Maurer & Young, 1983) that infants prefer to track the facelike pattern. Like the infants in Maurer and Young’s (1983) experiment, the infants in the present experiment showed greater eye turning than head turning. However, whereas Maurer and Young had observed very little eye tracking or head turning (an average of about 35 deg and 20 deg, respectively), our infants had large eye turns and head turns (on average about 60 deg and 40 deg, respectively). The greater degree of turning probably occurred because our infants were held rather than placed in an infant seat. A handler supporting the infant’s head and neck can facilitate, without influencing, turning.

The failure to replicate the results of earlier experiments regarding preference for a facelike stimulus may have resulted because the procedure permitted a variation in the number of stimulus presentations per trial (between one and seven attempts per stimulus per side) in attempting to obtain a response of at least 60. This procedure could have resulted in a ceiling effect because the maximum response was 90 deg . Experiment 2 was designed to address this issue. Experiment 2

Experiment 2 was designed so that each stimulus was shown a fixed number of times per trial regardless of the extent of eye turns or head turns. If the results of Experiment 1 occurred because of a methodological problem, then this experiment should demonstrate preferential looking to the facelike pattern.

METHOD

The selection of participants, stimuli and apparatus, and procedure were the same as those used in Experiment 1 with the exceptions noted below.

Participants. Thirteen newborns were recruited from a community teaching hospital in Southeastern Ontario and 10 completed the procedure (five baby boys, five baby girls). Three newborns became fussy during testing, hence their data were excluded from the analyses. For the remaining infants, their mean gestational age at birth was 39.7 weeks (SD = 0.9) and the mean age at testing was 30 hours (SD = 8).

Design. The design consisted of two 15-trial blocks as follows: CCC AAA BBB BBB AAA and CCC BBB AAA AAA BBB, with order counterbalanced over subjects. Following three presentations of the blank stimulus (c), each of the two patterned stimuli (A and B) was presented in sets of three trials with side of stimulus presentation counterbalanced over the three-trial sets and the two blocks. Fewer presentations of a blank stimulus (c) were planned because of previous observations. Newborns become fussy with repeated exposure to the blank and it is then difficult to recapture their attention to subsequent patterned stimuli (Easterbrook, 1994).

Rather than presenting stimuli from one to seven times like in Experiment 1, stimuli were presented a fixed number of times, provided that the infant fixated them each time (two 15-trial blocks or 30 presentations). No criterion for eye or head turning was set.

RESULTS

Eye turning. The mean eye turn results are shown in Table 2. A two-way ANOVA with two within factors (3 stimuli x 2 directions) and orthogonal contrasts was used to compare the eye-turning data. A significant main effect of stimulus was found, F(2, 16) – 77.40, MSE = 203.48, with no significant effects of direction nor an interaction. Turning toward the blank control differed significantly from turning to the schematic face, F(1,9) = 98.20, MSE = 232.18, and the scrambled stimulus, F(1,9) = 173.03, MSE = 141.13. Again, eye turning toward the two patterned stimuli was equivalent.

Individual eye turns were similar to the averaged data. The degree of eye turning did not differ between the patterned stimuli. Although seven infants turned slightly farther to track the scrambled pattern than to track the face, none tracked the blank farthest.

Head turning. The mean head turn results are also shown in Table 2. When the ANOVA (3 stimuli x 2 directions) and orthogonal contrasts were repeated for the head-turning data, the results showed that there was a significant effect of stimulus, F(2, 16) = 32.47, MSE = 175.26, and of direction, F(1,9) – 6.67, USE = 206.57, and an interaction between type of stimulus and direction, F(2,18) = 3.63, MSE = 138.86. When a featured stimulus was presented, turning to the right was approximately 15 farther than turning to the left, but when the blank was presented turning to the left and right did not differ.

Head turning toward the blank control differed significantly from turning toward the schematic face, F(1,9) = 45.09, MSE = 198.49, and the scrambled stimulus, F(1,9) = 66.56, MSE = 121.68. No significant differences were found between the degree of turning toward the face stimulus and the scrambled stimulus. The head turns toward the stimuli were approximately 25 deg less than the eye turns. Individual head turns were similar to the averaged data. The degree of head turning did not differ between the patterned stimuli. Five infants turned farthest to the face and another five turned farthest to the scrambled pattern. None turned farthest to the blank.

DISCUSSION

The results of this study replicated those of Experiment 1. Both eye turning and head turning were greater toward the featured stimuli than toward the blank. However, there were no significant differences in turning toward the schematic face and scrambled stimulus. Therefore, variations in the number of stimulus presentations per trial are not likely responsible for the lack of differential tracking of the patterned stimuli. Also, as in Experiment 1, eye turns were greater than head turns. However, unlike Experiment 1, which did not reveal an effect of direction, newborns in the present experiment turned their heads farther to the right than they did to the left for the patterned stimuli, but not for the blank.

Given estimated accounts of the newborn’s visual acuity, the results of Experiments 1 and 2 may have occurred if newborns are unable to discriminate the internal features of a pattern. That is, the issue of a discrimination ability precludes that of a newborn face preference. Experiment 3 was designed to address this issue.

Experiment 3

Experiment 3 uses a different metric (looking time) and a different paradigm (habituation) to examine the newborn’s ability to discriminate between the same two patterned stimuli used in Experiments 1 and 2. Habituation paradigms capitalize on the phenomenon of response decline to a repeatedly presented stimulus. Alert newborns fixate a salient visual stimulus, initially. With repeated presentations of the same stimulus, they look at it less. Whether the decrease in fixation time is determined statistically over a fixed number of trials or is a criterion set by the experimenter, the response decline is assumed to indicate a loss of interest (Caron & Caron, 1968; Fantz, 1964; Slater, Morison, Town, & Rose, 1985). Response recovery to either the re-presented original stimulus following a dishabituating stimulus (classical habituation) or to a novel stimulus (discrimination) is assumed to indicate information processing (Bornstein, 1989; Fantz, 1964).

Recently, Laplante, Orr, Neville, Vorkapich, and Sasso (1996) demonstrated newborn response decline and novelty responding using visual stimuli that moved back and forth on a horizontal plane. In the habituation phase, the stimulus was repeated until the mean of fixations over the three most recent, and consecutive trials declined to at least 60% of the mean fixation over the first three stimulus trials (i.e., modified infant-controlled procedure). Three trials of a novel stimulus followed this response decline. For the present experiment, Laplante et al.’s habituation procedure was employed because it required the use of moving stimuli, as did the first two experiments reported here. The purpose of the present experiment was to determine if newborns could discriminate between the schematic face and the scrambled pattern used in Experiments 1 and 2. If infants discriminate the two patterned stimuli, then following habituation to one stimulus, renewed responding should be observed when the second stimulus is presented during the dishabituation or novelty trials.

METHOD

The selection of new participants, the stimuli and apparatus, and the procedure were similar to those used in Experiment 1 with the exceptions noted below.

Participants. Eighteen healthy, term newborns (10 baby boys, 8 baby girls) were recruited from the hospital in Southwestern Ontario. Of these, the data of two baby girls were lost because of recording errors. The mean age at testing was 48 hours (SD = 25).

Stimuli and apparatus. Slightly smaller versions (13 cm x 10 cm) of the schematic face and the scrambled face were employed. A metal plate on the back of each stimulus permitted its attachment to a magnet located within Laplante et al.’s (Laplante, Orr, Crilley, & Pardy, 1993; Laplante et al., 1996) viewing chamber (71 cm high x 50 cm deep). A stimulus moved at a rate of 1.2 deg s along a horizontal track in the viewing chamber over a range of 14 deg of visual angle to either side of an infant’s midline. The stimulus started from the centre of the visual chamber, travelled 12.7 cm to the right (i.e., newborn’s right), reversed its direction and travelled 25.4 cm to the left, reversed direction and travelled 12.7 cm to the centre. The distance between the stimulus and the newborn was approximately 50 cm.

The newborn’s eye region was videorecorded using a black and white 25 mm video monitor connected to a PV23D-K/P-43-K Compact VHS Panasonic Palmcorder. A three– button mouse connected to an IBM personal computer allowed an experimenter to record fixation times online during testing.

Procedure. Infants were randomly assigned to either a classical habituation procedure or a novelty response procedure. In the classical habituation procedure (n = 8), infants received a habituation phase during which stimulus trials continued until the mean duration of the infants’ attention over three consecutive trials had decreased by at least 60% of that over the first three baseline trials. Once the response decrement criterion was reached, a novelty phase began. This phase included three trials of a novel stimulus; it was followed by a recovery phase that included three trials of the original stimulus re-presented. The two stimuli (a schematic face; b – scrambled face) were presented in counterbalanced order across participants as follows: a/b/a or bZa/b.

The novelty response procedure included a lag control. For this procedure, infants (n = 8) received the habituation phase as described above. However, a lag control phase followed the response decline to criterion, during which presentation of the original stimulus was continued for three additional trials. Subsequently, a novel stimulus was presented for three trials. The two stimuli (a = schematic face; b – scrambled face) were presented in counterbalanced order across participants as follows: a/a/b or b/b/a. For both procedures, the original repeating stimulus (a or b) was presented over the first three stimulus trials and average looking time was calculated. Once fixations declined to criterion, the infants in the classical habituation procedure received three trials of a novel stimulus (b if the original was a, or a if it was b) followed by three trials of the original stimulus. Infants in the novelty/lag control procedure continued to receive the original stimulus for an additional three trials and then received a novel stimulus (a to b or b to a) for three trials. The lag design controlled for any spontaneous cyclic activity.

Two experimenters carried out the procedure. A handler selected the stimulus for presentation, placed the stimulus inside the viewing box, and held the infant in an upright position facing the display window. A trial began once the infant was in position with his/her eyes clearly seen on a video monitor by a second experimenter. The second experimenter depressed a foot pedal that opened the display window, lit the interior of the viewing box, and set the stimulus in motion. After 30 s, the stimulus stopped moving and the handler moved the infant so that s/he faced away from the display window. To keep the second experimenter blind to the classical habituation and lag designs, the handler removed each stimulus, placed it on an adjacent table, selected the same or a different stimulus, and placed the stimulus back inside the box. Once the next stimulus was in position, the display window was closed, the infant was moved to the testing position, and the next trial began. The intertrial interval was approximately 30 s.

During stimulus presentations, the second experimenter scored visual fixation time from the video monitor, depressing a computer mouse button whenever newborns fixated the test stimulus. Infant fixation of the test stimulus was judged to have occurred when at least 50% of the newborn’s pupils were covered by the reflection of the stimulus. The reflections were blurred preventing identification of the stimulus.1 The computer calculated the average fixation times over the first three trials. Computations were continued over successive three-trial blocks with the average fixation of the last three trials displayed on a monitor visible only to the handler who selected the stimuli. When a response decrement of 60% of the initial looking time occurred, the habituation phase ended and the novel (or lag control) phase was initiated.

Average fixation times were grouped into four, 3-trial blocks for analyses. For classical habituation, Block 1 included the first three trials of the habituation phase and Block 2 included the last three trials; Block 3 included the three novelty trials and Block 4 included the three recovery trials. For the lag design, Block 1 and Block 2 were the same as for the classical habituation design; Block 3 included the three post-criterion lag trials and Block 4 included the three novelty trials. Given the high reliability between online scores and videotape scores (Intraclass r = .84), live scores were used in the data analyses.

RESULTS AND DISCUSSION

Group equivalence. The mean fixation times are shown in Figure 2. To determine differential initial responding and/or response decline to the two patterned stimuli (a = facelike, b = scrambled), fixation times from the baseline and habituation trials (b /a/b, b /b/a) were examined. We used a two-way ANOVA with one between factor (Group Habituation, order a and b and Lag, order a and b) and one within factor (Block – 1 and 2). Only a significant effect of block, F(1,14) = 253.51, MSE = 3.83, was found. For all data combined, fixation time averaged 20.80 s (SD = 4.44) over the initial three trials (Block 1) and 9.79 s (SD = 0.69) over the final three habituation trials (Block 2). There was no effect of group and no interaction indicating that, over the habituation phase, both stimuli (a and b) were equivalent in terms of the visual attention they elicited from newborns. Because there were no significant differences in responding between the two stimuli within each design group, the data from a and b were combined.

A t-test was used to determine if there were group differences in the average number of trials to reach criterion. No significant differences were found between the classical habituation (M = 5.5 trials, SD = 2.7) and lag designs (M = 6.6 trials, SD = 4.1).

Stimulus discrimination. To determine whether newborns discriminated the schematic face from the scrambled face, two 2-way ANOVAs with one between factor (Stimulus – a, b) and one within factor (Blocks – 1, 2, 3, 4) were conducted separately on the data sets from the two designs. Only a significant effect of blocks was found for both the classical habituation design, F(2,12) = 11.93, MSE = 22.96, and the lag design, F(2,10) = 21.70, MSE = 32.94. Trend analyses showed a significant cubic effect, F(1,6) = 21.02, MSE = 12.49, for the classical habituation group and a significant quadratic effect, F(1,6) = 162.12, MSE = 5.27, for the lag group. For the former, following response decline to the schematic face (or the scrambled face), newborns recovered responding to the scrambled face (or schematic face; Block 3) and then responding declined when the schematic face (or scrambled face) was re-presented (Block 4). For the lag design, following response decline to criterion (Block 2), response decline continued when the same stimulus (either the schematic or the scrambled face) continued to be presented (Block 3). When the novel stimulus was presented (Block 4), newborn attention to the visual target increased. Therefore, both groups recovered responding during the novelty trials, indicating that the newborns had discriminated between the two stimuli.

Data from both design groups were analyzed to examine novelty responding and response recovery. A two-way ANOVA with one between factor (Group – Classical, Lag) and one within factor (Blocks – 1, 2, 3, 4) revealed a significant main effect of blocks, F(2,27) = 27.88, MSE = 23.62, qualified by a Group x Block interaction, F(2, 27) = 9.43,

MSE = 23.62 (see Figure 2). Trend analyses demonstrated trends of both quadratic by group, F(1,14) = 34.23, MSE = 6.14, (the top panel of Figure 2 illustrates that this trend characterizes the responses of the lag design group) and Cubic x Group, F(1,14) = 21.96, MSE = 9.90 (the lower panel of Figure 2 illustrates that this trend characterizes the responses of the classical habituation group).

Because response recovery following habituation is sometimes short-lived (e.g., Kisilevsky & Muir, 1991; Laplante et al., 1993), a post-hoc analysis examined newborn responding on the first recovery trial of the classical habituation group using a two-way ANOVA with one between factor (Stimulus – face, scrambled face) and one within factor (Trials – trial 3 of block 2, habituation, trial 1 of block 3, novelty, and trial 1 of block 4, recovery). Although there was no main effect, the duration of attention paid to the test stimulus at habituation trial 3 (M = 5.44, SD = 4.1) was found to be less than that at recovery trial 1 (M = 14.31, SD = 7.0), F(1,6) = 11.90, MSE = 52.96. This difference demonstrates that newborns’ responding had recovered on the first recovery trial. There was no significant difference in responding between novelty trial 1 (M = 9.75, SD = 7.1) and recovery trial 1.

Post-hoc analysis of the first recovery trial suggested dishabituation. Recovery occurred on the first trial but was not observed when responding was averaged over the three recovery trials. This behaviour replicates work by Kisilevsky and Muir (1991). Also, it is in keeping with the work of Groves and Thompson (1970), who demonstrated that habituation occurs more rapidly during a second presentation of the repeating stimulus. In the present experiment, only three trials separated the first and second series of the habituating stimulus.

General Discussion

The habituation/dishabituation paradigm used in Experiment 3 proved to be more sensitive than the preferential tracking procedure used in Experiments 1 and 2. It demonstrated that newborns can discriminate between two stimuli that differ only in the arrangement of an identical set of internal features. For every participant tested, looking time increased during novelty trials. These results support Valenza et al.’s (1996) report that newborns’ fixation behaviour is a better indicator of their ability to discriminate than is their orientation behaviour.

The results of Experiments 1 and 2 demonstrated that newborns turn their eyes and heads to follow patterned stimuli containing facelike features, regardless of their arrangement. The newborn eye-turning scores to the two patterned stimuli were similar, between 84 deg and 86 deg in Experiment 1, and 69 deg and 71 deg in Experiment 2. In both experiments, newborns oriented farther to facelike stimuli than to the blank. These results indicate that newborns do not perceive a schematic face as special, although they do prefer to track patterns more than a blank.

Experiment 3 supported the results of the preferential tracking experiments, showing that newborns do not prefer a face pattern to a scrambled face pattern. Newborns reached habituation after the same number of trials regardless of whether the habituation stimulus was the face or the scrambled stimulus. Furthermore, newborns spent a similar amount of time fixating both patterned stimuli over the baseline, habituation, and novelty trials.

It is unknown why newborns’ tracking responses in the present preferential tracking experiments failed to replicate other reports (e.g., Goren et al. 1975; Johnson et al., 1991; Maurer & Young, 1983) that newborns turn farther to pursue a moving schematic face as opposed to scrambled patterns. Clearly, the failure to replicate others’ findings was not due to the newborns’ poor visual acuity because infants in the habituation experiment did discriminate the two patterns, which had elicited similar amounts of their attention. Because other preferential tracking experiments have reported that newborns turn 5o, 10o (Goren et al.), and 8o Johnson et al., 1991) farther to track an intact face pattern as opposed to scrambled faces, it may be that responding in the present tracking experiments was at a ceiling and small differences could not be detected.

Alternately, it may be that newborns’ responses to patterned stimuli are based on a combination of the physical properties of the stimuli and the acuity of the newborn’s visual system (see Kleiner, 1993, for discussion). Newborns may be responding to the placement of internal features shared by these stimuli, in particular, the eyes. The scrambled face contained two eyes lying on a horizontal plane at the bottom of the face; the facelike stimulus contained the same two eyes lying on a horizontal plane at the top of the face. This explanation is supported by recent evidence suggesting that humans may have special processors for detecting pairs of eyes (Baron-Cohen, 1995), which may be necessary for social responding (Phillips, Baron-Cohen, & Rutter, 1992). To address this alternate explanation in future experiments, pattern complexity and luminance need to be varied systematically.

This research was supported by Natural Science and Engineering Research Council (NSERC) of Canada operating grants awarded to B. S. Kisilevsky (NSERC 0GP0041862), D. W. Muir (NSERC # 44279-95), and an NSERC Postgraduate Scholarship (PGS 3 137205) awarded to D. P. Laplante. Some of these data were presented at the International Conference on Infant Studies held in Providence, Rhode Island, April, 1996. We would like to thank Helen Killan, Kelli Neville, and Lisa Vorkapich for their assistance in running these experiments, and Sylvia Hains who provided statistical advice. Also, we thank the parents of the newborns who participated in this research. Correspondence concerning this article should be addressed to Dr. M. A. Easterbrook, Assistant Professor, Department of Psychology, Nipissing University, 100 College Drive, P.O. Box 5002, North Bay, Ontario P1B 8L7 (E-mail: megane@ dns3.unipissing.ca).

From videotape records, two naive observers’ correct detections of the stimulus presented to each newborn did not differ from chance.

References

Banks, M. S., & Dannemiller, J. L. (1987). Infant visual psychophysics. In J. Osofsky (Ed.), Handbook of infant development (2nd ed.). New York: Wiley & Sons, Inc. Baron-Cohen, S. (1995). Mindblindness: An essay on autism and theory of mind. ” Cambridge, MA: MIT Press. Berlyne, D. E. (1960). Conflict, arousal and curiosity. Toronto, ON: McGraw Hill.

Bornstein, M. H. (1989). Information processing (habituation) in infancy and stability in cognitive development. Human Development, 32, 129-136.

Braddick, O., Atkinson, J., French, J., & Howland, H. C. (1979). A photorefractrive experiment of infant accommodation. Vision Research, 19, 1319-1330.

Bushnell, I. W. R., Sai, F., & Mullin, J. T. (1989). Neonatal recognition of the mother’s face. British Journal of Developmental Psychology, 7, 3-15.

Caron, R. S., & Caron, A. J. (1968). The effect of repeated exposure and stimulus complexity on visual fixation in infants. Psychonomic Science, 10, 207-208. Easterbrook, M. A. (1994). Newborn head turning to facelike stimuli. Infant Behaviour and Development, 17, 619.

Easterbrook, M. A., Kisilevsky, B. S., Hains, S.MJ., & Muir, D. VP. (1999). Faceness or complexity: Evidence from newborn visual tracking of facelike stimuli. Infant Behaviour and Development, 1, 17-35.

Fantz, R. L. (1958). Pattern vision in young infants. Psychological

Record, 8, 43-49.

Fantz, R. L. (1963). Pattern vision in newborn infants. Science, 140, 296-297.

Fantz, R. L. (1964). Visual experience in infants: decreased attention to familiar patterns relative to novel ones. Science, 140, 296-297.

Fantz, R. L. (1965). Ontogeny of perception. In A. M. Schrier, H. F. Harlow, & F. Stollnitz (Eds.), Behaviour of nonhuman primates: Modern research trends. New York: Academic Press. Goren, C., Sarty, M., & Wu, P. (1975). Visual following and pattern discrimination of face-like stimuli by newborn infants. Pediatrics, 56, 544-549. Groves, P. H., & Thompson, R. F. (1970). Habituation: A dual-process theory. Psychological Review, 77, 419-450. Haaf, R. A. (1974). Complexity and facial resemblances as determinants of response to schematic face stimuli by 5- and 10-week-old infants. Journal of Experimental Child Psychology, I8. 480487.

Haaf, R. A., & Bell, R. Q. (1967). A facial dimension in visual discrimination by human infants. Child Development, 38, 893-899.

Hershenson, M. (1964). Visual discrimination in the human newborn. Journal of Comparative and Physiological Psychology, 58, 270-276.

Jirari, C. G., (1970). Form perception, innate form preferences and visually mediated head turning in human neonates. Dissertation, Committee on Human Development, University of Chicago.

Johnson, M. H. (1990). Cortical maturation and the development of visual attention in early infancy. Journal of Cognitive Neuroscience, 2, 81-95.

Johnson, M. H., Dziurawiec, S., Ellis, H., & Morton, J. (1991). Newborn preferential tracking of face-like stimuli and its subsequent decline. Cognition, 40, 1-19. Johnson, M. H., & Morton, J. (1991). Biology and cognitive development. The case of face recognition. Cambridge, MA: Blackwell.

Kagan, J., Hanker, B. A., Hen-Tov, A., & Lewis, M. (1966). Infants’ differential reactions to familiar and distorted faces. Child Development, 37, 519-532.

Kisilevsky, B. S., & Muir, D. W. (1991). Human fetal and subsequent newborn responses to sound and vibration. Infant Behaviour and Development, 14, 1-26.

Kleiner, K. A. (1987). Amplitude and phase spectra as indices of infants’ pattern preferences. Infant Behaviour and Development, 10, 49-59.

Kleiner, K.A. (1993). Specific vs. non-specific face recognition device. In B. de Boysson-Bardies, S. de Schonen, P. Jusczyk, P. McNeilage, & J. Morton (Eds.), Developmental neurocognition. Speech and face processing in the first year of life (NATO ASI series, Vol. 69, pp. 103-108). Netherlands: Kluwer Academic Publishers.

Laplante, D. P., Orr, R. R., Crilley, D., & Pardy, S. (1993). Discrimination of stimulus movements by newborn infants: Methodological considerations. Canadian Psychology, 34, 338. Laplante, D. P., Orr, R. R., Neville, K., Vorkapich, L., & Sasso, D. (1996). Discrimination of stimulus rotation by newborns. Infant Behaviour and Development, 19, 271-279.

Maurer, D., & Barrera, M. (1981). Infants’ perception of natural and distorted arrangements of a schematic face. Cbi/d Development, 52, 196-202.

Maurer, D., & Maurer, C. (1988). The world of the newborn. New York: Basic Books.

Maurer, D., & Young, R. E. (1983). Newborn’s following of natural and distorted arrangements of facial features. Infant Behaviour and Development, 127-131.

Morison, V., & Slater, A. (1985). Contrast and spatial frequency components in visual perferences of newborns. Perception, 14, 345-348.

Morton, J., & Johnson, M. (1991). CONSPEC and CONLERN: A Two-Process Theory of Infant Face Recognition. Psychological Review, 98, 164-181.

Muir, D. W., & Field, J. (1979). Newborn infants orient to sounds. Child Development, SO, 431-436. Muir, D. W., Humphrey, D. E., & Humphrey, G. K. (1994). Pattern and space perception in young infants. Spatial Vision, 8,141-165.

Pascalis, O., DeSchonen, S., Morton, J., Deruelle, C., &

Fabre-Grenet, M. (1995). Mother’s face recognition by neonates: A replication and an extension. Infant Behaviour and Development, 18, 79-85.

Phillips, W., Baron-Cohen, S., & Rutter, M. (1992). The role of eye contact in the detection of goals. Evidence from normal toddlers and children with autism or mental handicap. Development and Psychopathology, 4, 375-383. Schiller, P. H., Logothetis, N. K., & Charles, E. R. (1991). Parallel pathways in the visual system: Their role in perception at isolulminance. Neurosychologia, 29, 433-441.

Shrout, P. E., & Fleiss, J. L. (1979). Intraclass correlations: Uses in assessing rater reliability. Psychological Bulletin, 86, 420428. Slater, A., Morison, V., Town, C., & Rose, D. (1985). Movement perception and identity constancy in the new-born baby. British Journal of Developmental Psychology, 3, 211-220. Slater, A., Von der Schulenburg, C., Brown, E., Badenoch, M., Butterworth, G., Parsons, S., & Samuels, C. (1998). Newborn infants prefer attractive faces. Infant Behaviour fi Development, 21, 345-354.

Stechler, G. (1964). Newborn attention as affected by medication during labour. Science, 144, 315-317. Teller, D. Y., McDonald, M., Preston, K., & Sebris, S. (1986). Assessment of visual acuity in infants and children: The acuity care procedure. Developmental Medicine and Child Neurology, 28, 779-789.

Thomas, H. (1965). Visual-fixation responses of infants to stimuli of varying complexity. Child Development, 36, 629-638. Valenza, E., Simion, F., Cassia, V. M., and Umilta, C. (1996). Face preference at birth. Journal of Experimental Psychology, 22, 892-903.

Wilcox, B., & Clayton, F. (1968). Infant visual fixation on motion pictures of the human face. Journal of Experimental Psychology, 6, 22-37.

Wilson, H. (1988). Development of spatiotemporal mechanisms in infant vision. Vision Research, 28, 611-628. Date of acceptance: April 8, 1999

Sommaire

Savoir si un visage revet un interet particulier pour les nouveaux-nes est important pour qui veut dresser le profil du developpement de la socialisation normale des etres humains. Une technique de suivi des schemes preferentiels a permis de verifier si les nouveaux-nes avaient ou non une preference innee pour un visage. Cette technique suppose qu’on mesure le deplacement des yeux et de la tete du nouveau-ne lorsqu’il suit des images en deux dimensions, noir et blanc et tres visibles qui lui sont presentees une seule fois. L’image que le nouveau-ne suit le plus loin du regard est presumee etre celle qu’il prefere. Au moyen de cette methode, quelques chercheurs soutiennent que les nouveauxnes ont bel et bien une preference pour un visage, d’autres pas.

On a donc procede a deux experiences pour sonder davantage cette question de preference chez le nouveau-ne. Le deplacement des yeux et de la the de 19 nouveaux-nes de deux jours a ete observe pour determiner s’ils reagiraient differemment a trois images distinctes : un visage, une image brouillee et une silhouette lumineuse. Les resultats ont demontre que les nouveaux-nes suivaient davantage du regard les images que la silhouette lumineuse, mais qu’ils etaient tout aussi attentif au visage qu’a l’image brouillee. Cette reaction demontre que les nouveaux-nes n’ont pas de preference pour une image qui represente un visage.

Comme l’acuite visuelle est peu developpee chez le nouveau-ne, la capacite chez lui de faire une distinction entre des images peut supplanter la question de preference pour un

visage. L’enregistrement des modulations de l’attention chez le nouveau-ne par suite de la presentation de stimuli tant6t nouveaux, tantot repetitifs s’avere un moyen efficace pour determiner quelles caracteristiques des stimuli les nouveauxnes peuvent capter. Ainsi, pour verifier s’ils sont en mesure ou non de distinguer un visage d’une image brouillee, 1’experience 3 a eu recours a une procedure d’habituation a des stimuli mobiles. On a presente a 16 nouveaux-nes de deux jours des stimuli repetitifs, soit le visage ou l’image floue, jusqu’a ce que l’attention qu’ils leur portent apres trois essais consecutifs d’habituation ait diminue de 60 % par rapport a la duree d’attention moyenne enregistrke lors des trois premiers essais de base. Des qu’il y avait accoutumance au visage, on presentait l’image floue(ou vice et versa pour 8 des 16 nouveaux-nes qui s’etaient habitues, eux, a la presentation de l’image floue), et du coup le nouveau-ne etait plus attentif. Cette reaction a un stimulus nouveau signifie que les nouveaux-nes peuvent distinguer un visage d’un stimulus flou.

Regle generale, les resultats indiquent que les nouveauxnes peuvent faire une difference entre un visage et une image floue, mais qu’ils ne preferent ni l’un ni l’autre. Pour sonder davantage le concept voulant que l’attention du nouveau-ne change lorsqu’on lui presente des images visuelles moderement stimulantes (p. ex. un visage ou une image floue), les prochaines experiences devraient varier systematiquement la complexite et la luminance des images utilisees.

MEGAN A. EASTERBROOK, Nipissing University

B. S. KISILEVSKY and D. W. MUIR, Queen’s University

D. P. LAPLANTE, Universite de Montreal and Hopital Louis-H. Lafontaine

Copyright Canadian Psychological Association Sep 1999

Provided by ProQuest Information and Learning Company. All rights Reserved