Mother's Face Recognition in Newborn Infants: Learning and Memory

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Infant and Child Development
Inf. Child Dev. 10: 67–74 (2001)
DOI: 10.1002/icd.248

Mother’s Face Recognition in
Newborn Infants: Learning and
Memory
I.W.R. Bushnell*
Department of Psychology, University of Glasgow, Scotland, UK

Two studies are reported that address issues related to memory
for faces in young infants. The first correlates the opportunity to
view the mother’s face with expressed visual preference for that
face, and shows that very little exposure is required, with greater
levels of exposure showing stronger preferences. The second
study examines the role of delay between exposure to the moth-
er’s face and preference testing, finding that strength of prefer-
ence is not significantly impacted by a 15-min delay. Im-
plications for a model of face processing are discussed. Copy-
right © 2001 John Wiley & Sons, Ltd.
Key words: face recognition; newborn learning; newborn memory;
visual preference

There is no doubt that the human infant is capable of face discrimination and
face recognition within a surprisingly short time after birth (Field et al., 1984;
Bushnell et al., 1989; Walton et al., 1992; Pascalis et al., 1995). Just how much
experience is required of a particular face, such as the mother’s, to allow
recognition is less certain. Walton and Bower (1993) report that face ‘prototypes’
can be formed in seconds, but this is somewhat different from processing a
single face sufficiently well to retain that information over short periods, and
then preferentially attending to that face when paired with another of similar
appearance. However, it does suggest that face processing and memory estab-
lishment may be very rapid indeed.
An estimate can be made from the age of infants successfully tested in the
previously mentioned studies. The age at testing was 12–36 h in the Walton et
al. (1992) study, averaged 45 h for the Field et al. (1984) study, 78 h for Pascalis
et al. (1995), and 49 h in the Bushnell et al. (1989) study. Given that neonates
spend a considerable proportion of time asleep, the average time awake within
these periods would provide an idea of the upper time limit potentially
available to view the mother’s face.
Freudigman and Thoman (1993) report the percentage of time infants spend
in five states across the first 2 days of life (day 1 (D1) and day 2 (D2)) as: active
sleep (D1 50.7%, D2 59.5%), quiet sleep (D1 27.6%, D2 23.9%), active –quiet
transitional sleep (D1 0.4%, D2 0.3%), sleep – wake transition (D1 5.2%, D2 5.7%)

* Correspondence to: Department of Psychology, University of Glasgow, 58 Hillhead Street, Glas-
gow, G12 8QB. E-mail: ibush@psy.gla.ac.uk

68 I.W.R. Bushnell

and awake (D1 16.2%, D2 10.7%). In Sadeh et al.’s (1995) study of 2- to
3-day-olds, they observed percentage time awake as 13.7%. These figures
suggest that up to 15% of the newborn’s time is spent awake over the first few
days and, if this is combined with a rough average of 50 h-of-age at testing, we
have an estimated potential exposure of about 7.5 h in the studies mentioned. Of
course, not all the awake time, by any means, will be spent observing the
mother’s face, but just how much fixation time there will be is unclear. This is
partly the result of research on the sleep/wake cycles of newborns, having
focused on sleep patterns, rather than on what neonates are doing during
periods of alertness, probably because of a posited link between sleep variables
and central nervous system status, which makes sleep pattern a possible
predictor of future cognitive functioning.
The current study sought to identify the amount of exposure required to
establish a familiarity preference by gathering data using a time-sample
methodology to determine (a) how much contact was occurring, (b) when this
contact occurred, and (c) what the nature of the contact was, and then testing
these infants for mother– stranger discrimination performance.

STUDY 1
Method
Participants
Infants included in this study were 29 healthy fullterm newborns born at a
city hospital. Mean birthweight was 3.48 kg (S.D.= 0.48). All newborns were
neurologically normal and physiologically stable at birth, as judged by paedi-
atric examination. All had an Apgar score at 5 min of at least 8 (mean= 8.55,
S.D. =0.78). Age at the start of observation ranged from 2 to 7 h (mean= 3.76,
S.D. =0.81).
Stimuli
The preferential looking stimuli were the face of the participant’s mother and
that of a female stranger (another mother with similar hair colouring and
length).
Procedure
Twenty-nine mother – infant pairs were observed after leaving the labour suite
from their point of arrival on the maternity wards for four 2-h periods in every
24 h following the point of first access by the observer on the maternity ward.
Observation involved the use of a coding system that identified when the
infant was asleep (eyes closed); awake (unable to see mother, mother absent);
awake (potentially able to see mother within approximately 1 m, but appeared
not to be viewing face); awake (appeared to be looking at mother within
approximately 1 m). The observer made a categorization every minute over a
2-h period, and the data for the four 2-h periods were summed and extrapolated
to the full 24-h.
Two-hour periods of observation were selected for practical reasons, such as
maintaining observer attention, and because previous research has shown that
an epoch of 90 min is sufficient to ensure that a full range of states will occur
(Freudigman and Thoman, 1993). The full 24-h period was sampled because
studies reporting no diurnal sleep patterning until 6– 8-weeks-of-age have been
disputed by other research supporting systematic diurnal variation from the
neonatal period (Hellbrugge, 1960; Thoman and Whitney, 1989).

Mother’s Face Recognition in Newborn Infants 69

Observation was continued for 72 h, at which point each baby was tested on
a mother – stranger discrimination task using the visual preference method.
When potential subjects were judged to be sufficiently alert for testing, they
were taken to a quiet room next to the wards and held by an experimenter in
the ‘free-head’ position. The mother and the volunteer female stranger sat
behind a white screen (2×2.5 m) with two apertures at head height (30× 25
cm), one at either side of midline, and separated by 12 cm. The faces were lit by
fluorescent tubes located above and in front. Clothing was obscured by white
sheeting sprayed with an air freshener to mask scent cues. A white-coated
observer stood centrally behind the mother and stranger viewing the infant
through an aperture and recording fixation behaviour on two buttons connected
to a portable computer.
There were two trials for each subject. Trial one started with the infant’s first
fixation on a face and terminated after 20 s fixation to either or both faces had
accrued. At this point, the infant was withdrawn while the stimuli changed side
to provide a control for side bias. The procedure was then repeated for a further
20 s fixation.
Results
The main results from state patterns averaged over the 3 days are shown in
Figure 1, where it can be seen that most of the time newborns were asleep
(61.33%), but when awake, most of their time was spent with their mother
(22.67%).
Based on observation of looking behaviour, the time infants spent with their
mother was broken down into two categories— appeared to be viewing face
(39.34% of available time) and appeared not to be viewing face (60.66% of
available time). The extent of visual preference proved to be significantly
correlated with the amount of observed fixation to the mother’s face (Spearman
Rho =0.51, p=0.01). The scattergram for these data is shown in Figure 2.
The experimental data, fixation to mother and stranger, were compared over
both trials using dependent t-tests. Trial 1 produced a significant effect, with
more time spent looking at the mother (mean= 10.88, t= 2.17, df= 28, p B 0.04,
two-tailed), as did trial 2 (mean=10.99, t =2.21, df= 28, pB 0.04, two-tailed),
and for both trials combined (mean= 21.86, t= 3.88, df= 28, pB 0.01, two-
tailed). On trial 1, 17 of the 29 infants looked more at their mother, increasing
to 20 of the 29 infants on trial 2, and 22 of the 29 infants for both trials
combined.

Figure 1. Observed activity of babies over 3 days of observation.

70 I.W.R. Bushnell

Figure 2. Preference for mother as a function of viewing time.

Discussion
The results indicate that an increased opportunity to view the mother’s face is
associated with stronger visual preference levels. The fact that a positive
correlation was found is, perhaps, consistent with infants gradually learning
their mother’s face over a period of hours and showing clearer preferences as
learning becomes better established, rather than the process being very rapid in
the style of imprinting (Johnson and Horn, 1988). However, a series of stepwise
functions across individuals can underlie an apparent smooth function, and it
may be that there is a primary threshold effect whereby infants have to
accumulate a certain amount of face exposure before reliably showing preferen-
tial looking.
Just how much exposure to the mother’s face may be required is not
answered by these data with certainty. The infant with the least exposure (1 h)
looked more at his/her mother’s face, but seven infants with between 2 and 5 h
of fixation did not show a preference. However, all seven infants with more
than 5.5 h of fixation did show a preference for their mother. The data thus
indicate that very little viewing of the mother’s face is required for some infants
to show a preference, and this amount could be aggregated even with the very
young sample (age range of 12– 36 h) assessed by Walton et al. (1992).
To what extent these results can be generalized to other infants in other
situations remains to be seen. There are considerable differences in the struc-
tures and procedures associated with different maternity hospitals, and the early
experience of mothers and infants will, therefore, differ considerably. One
difference from previous studies is the amount of time spent in sleep, which is
lower than that reported elsewhere, for example, Brown (1964). However, there
are very large individual differences in all studies (one of Brown’s babies,
for example, was awake 63% of the time), and thus, there is considerable

Mother’s Face Recognition in Newborn Infants 71

opportunity for sample variation. A similarly broad range of individual differ-
ences was found in Freudigman and Thoman’s (1993) sample, where the mean
time awake on day 1 was 16.2%, with an S.D. of 7.33. In Sadeh et al.’s (1995)
study of 2 –3-day-olds, they observed percentage time awake as 13.7%, with an
S.D. of 11.0.
An important influence in this study may have been an observer effect.
Mothers were obviously aware of the observation process, no matter how
discreet, and were also briefed about the experimenter’s interest in infant face
recognition. This may have led to greater levels of attention being paid to the
infants in this sample, and perhaps more state manipulation to increase time in
an alert state. Previous research on state has tended to utilize sensor pads and
automatic recording of motility, which would have reduced any observer effect.
Individual differences are also relevant. For example, it is evident that the
amount of time spent in quiet sleep in human newborns appears to be a
function of exposure to stressors encountered in the birth process (Brown, 1964;
Emde et al., 1971), thus stressed babies will sleep more than average on the first
day or two of life. This sample was selected on the basis of high Apgar scores,
and low birth trauma would have been expected.

STUDY 2

Delay and Recognition
Another memory related factor when testing maternal face recognition is the
delay between the last exposure to the mother and testing of preference. This
can be very short when the experimental set-up is well organized and infants
are alert and attentive. Under other circumstances, the delay may be far longer
where, for example, the state of the infant is unsuitable, or where real faces are
used and ‘stimuli’ have to be settled in the experimental set-up. Few researchers
in the field seem to have paid attention to this issue, and delays are rarely
specified in experimental reports, an exception being Pascalis et al.’s (1995)
study, where the typical delay time is stated to be 3 min, and yet, infants
reliably recognized their mother’s face. Also Pascalis and de Schonen (1994)
previously reported that infants who had been briefly familiarized to a pho-
tograph of a face recognized that face after a 2-min delay.
Cognitive psychologists working with adult memory are, of course, very
aware of temporal factors in any experimental situation where memory is being
assessed. Delay may, at the very least, introduce noise into the testing process,
though it may be a very interesting factor in its own right, for example, in
‘priming’ and ‘mere-exposure’ studies (Tulving and Shacter, 1990; Seamon et al.,
1995).
This study was, therefore, conducted to test the robustness of infant memory
for their mother’s face by directly comparing two conditions of delay, the two
intervals selected being B5 min and \ 15 min from the last sight of their
mother’s face to first seeing their mother in the experimental situation as a
stimulus. These durations were selected on practical grounds, the shorter
representing the normal range in two previous studies (Bushnell et al., 1989;
Pascalis et al., 1995), and a longer period that, on past experience, allowed for
infant state to be maintained. The same visual preference method was used, as
in the first study, with two counterbalanced trials, where 20 s fixation was
accumulated per trial.

72                                                                     I.W.R. Bushnell

Method
Participants
   Infants included in this study were 30 healthy fullterm newborns born at a
city hospital. Nine other infants were excluded from the study sample due to
fretting (short delay n =3; long delay n= 4) and falling asleep (short delay
n =1; long delay n = 1). All newborns were neurologically normal and physio-
logically stable at birth, as judged by paediatric examination. All had an Apgar
score at 5 min of at least 8 (mean= 8.57, S.D.= 0.63). Age at time of testing
ranged from 45 to 93 h (mean=64.83, S.D.= 14.96). Mean birthweight was 3.22
kg (S.D. = 0.31). Fifteen infants were included in the short delay condition
(mean age in hours=65.47, S.D.= 15.66; mean birthweight= 3.31 kg, S.D.=
0.35), and 15 infants were included in the long delay condition (mean age in
hours = 64.12, S.D.=14.74; mean birthweight= 3.12kg, S.D.= 0.24).
Stimuli
  The stimulus faces were the face of the participant’s mother and that of a
female stranger (another mother with similar hair colouring and length).
Procedure
   An observer used a stopwatch to measure the time between the infant last
having the opportunity to see the mother’s face and the time at which testing
commenced. Infants were randomly assigned to one of the two delay groups
according to a predetermined sequence. Each baby was tested on a mother–
stranger discrimination task, using the same visual preference method that was
adopted in study 1.
Results
   The percentage looking time to the mother was analysed in an analysis of
variance (ANOVA; 2 delays× 2 trials), with trials as repeated measures. No
simple main effects were significant (delay: F(1,12)= 0.24, p= 0.63; trial:
F(1,12)= 0.16, p=0.70), nor was the interaction significant (F(1,12)= 0.35, p=
0.56). Short and long delay conditions were compared over both trials combined
using dependent t-tests. The 5-min delay (range 3–5 min) for both trials
combined produced a significant effect, with more time spent looking at the
mother (mean= 22.8, t = 2.93, df= 14, p B 0.02, two-tailed). The 15-min delay
(range 15–18 min) over both trials combined also showed a significant prefer-
ence for the mother (mean=22.15, t = 2.36, df= 14, pB 0.04, two-tailed). With
the short delay, 11 of the 15 infants looked more at their mother, while with the
long delay, nine of the 15 infants looked more at their mother.

Discussion
In both short and long delay conditions there was greater fixation to the
mother’s face on both trials combined, and it must, therefore, be concluded that
a longer delay than 15 min is required to remove the recognition effect
altogether. It further suggests that memory for the mother’s face is very stable,
and established in a long-term store within a few days of birth.
   Some points relating to the research design need to be considered. One would
expect poorer performance in the higher delay group as a result of the greater
probability of state changes in infants this young. A longer delay (in excess of
15 min) is more likely to lead to the infant changing state, usually to one that is
less optimal for testing. However, there were approximately equal numbers of
testing problems in both conditions. Another relevant factor may be the amount

Copyright © 2001 John Wiley & Sons, Ltd.                Inf. Child Dev. 10: 67 – 74 (2001)

Mother’s Face Recognition in Newborn Infants 73

of active looking at the mother’s face in the period before the delay was
measured. An infant that had been looking at his/her mother for some time
before the delay may perform differently from an infant with minimal con-
tact. However, this information was not recorded. If further studies are de-
signed to extend the delay beyond 15 min, these methodological points
should be taken into account.

CONCLUSIONS

Overall, these studies support the ability of newborns to rapidly process
sufficient information about their mother’s face, and to store that information
in a stable memory system to allow effective recognition memory, as demon-
strated by preferential looking. Very little active viewing of the mother’s face
is required to establish this memory, although the significant correlation be-
tween exposure and amount of preference indicates that the preference
strengthens with experience. This could be the result of the face being more
effectively processed and discriminated with increased viewing experience. It
may, however, be that the preference for the mother’s face is itself being
strengthened, or indeed, both processes (discrimination and attraction) may
be strengthening.
The attraction factor is important, as mother– stranger discrimination
throughout the first months of life demonstrates a preference for the mother,
the ‘familiar’ stimulus. This result is quite different from other infant percep-
tion research, where there is a consistent preference for novelty (Slater, 1993),
and thus, greater attention to the mother is not an effect of habituation or of
being familiarized to the mother for some time prior to being tested. Infants
can, however, be habituated to their mother’s face. Field et al. (1984) reported
that infants who showed an initial preference for their mother’s face could be
systematically habituated to that face, and subsequently looked significantly
longer at a stranger’s face.
Special modules, such as Conspec and Conlern, can help to explain atten-
tion to faces and discrimination amongst faces, but not a familiarity prefer-
ence (Johnson and Morton, 1991; Morton and Johnson, 1991). Indeed, Dailey
and Cottrell (1999) provide support from their neural network modelling that
a specialized face processing ‘module’ need not be innately specified, but
may be a straightforward consequence of early experience.
An alternative model, the sensory– ecology model (Bushnell, 1998) allows
for infant attention being captured by a multisensory system that is intensely
motivated to engage the infant, systematically placing itself at a position
where it is most likely to be perceived, and then acting in an intelligent way
to maintain and develop focused attention. Experience in gathering data in
the first study confirms that, for most infants, that system is the mother, who
represents the most frequently available external stimulus during the waking
periods of the first few days of life. The mother is also the primary source of
need gratification before and after birth, and her voice is readily recognized
and preferred to another female’s voice soon after birth (Querleu et al., 1984),
possibly based on prenatal learning (Hepper, 1991). Positive attraction may
transfer to the mother’s face through association, or as a result of the early
integration of the sensory systems (Slater and Kirby, 1998).

74                                                                            I.W.R. Bushnell

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Copyright © 2001 John Wiley & Sons, Ltd.                       Inf. Child Dev. 10: 67 – 74 (2001)

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