Social interaction with siblings is necessary for visual imprinting of species-specific maternal preferences in ducklings (Anas platyrhynchos)

This study was conducted to examine the influence of various social rearing experiences on the development of imprinted visual maternal preferences in domestic mallard ducklings (Anas platyrhynchos) during the first 3 days of postnatal life. Twenty-four-hour-old ducklings were allowed to follow a stuffed mallard hen for 30 min. This experience resulted in a visual preference for the familiar mallard hen over an unfamiliar stuffed redhead (Aythya americana) hen in simultaneous choice tests at 48 hr and 72 hr only if the ducklings were reared in conditions allowing unrestricted social interaction with siblings, as would normally occur in nature. No visual preference for the familiar mallard model was found at 48 hr or at 72 hr if ducklings were reared in social isolation but allowed to see another duckling, reared with one duckling, or reared in a group of ducklings but denied the opportunity for direct social interaction. These results demonstrate the importance of normal social experience in the development of the visual imprinting of filial behavior in ducklings. Imprinting studies have traditionally employed isolation rearing and ignored the precocial bird's natural social context. Thus, the present findings raise doubts about the appropriateness of the usual methods of studying imprinting in the laboratory for an understanding of the process of filial imprinting in nature.     

Development of species identification in ducklings: I. Nature of perceptual deficit caused by embryonic auditory deprivation.

In simultaneous choice tests with normal and filtered maternal calls, devocal-isolated ducklings were much more likely than vocal-communal ducklings to select the mallard maternal call in which the higher frequencies were severely attenuated, thus indicating their relative insensitivity to the higher frequency components of the maternal call. On the other hand, the devocal ducklings were as adept as vocal ducklings in selecting the normal mallard maternal cal1 when it was pitted against a low-frequency attenuated mallard call. Thus, the perceptual deficiency resulting from embryonic and postnatal auditory deprivation is selective in the sense of being relegated to the higher frequency components of the maternal call. Devocalization prevents the embryo and hatchling from hearing their own vocalizations all of which happen to be in the high-frequency range (greater than or equal to 1,500 Hz).     

Prenatal experience and postnatal perceptual preferences: evidence for attentional-bias in bobwhite quail embryos (Colinus virginianus)

Previous studies have indicated that concurrent multimodal sensory stimulation can interfere with prenatal perceptual learning. This study further examined this issue by exposing 3 groups of bobwhite quail embryos (Colinus virginianus) to (a) no supplemental stimulation, (b) a bobwhite maternal call, or (c) a maternal call paired with a pulsating light in the period prior to hatching. Experiments differed in terms of the types of stimuli presented during postnatal preference tests. Embryos receiving no supplemental stimulation showed no preference between stimulus events in all testing conditions. Embryos receiving exposure to the unimodal maternal call preferred the familiar call over an unfamiliar call regardless of the presence or absence of pulsating light during testing. Embryos exposed to the call-light compound preferred the familiar call only when it was paired with the light during testing. These results suggest that concurrent multimodal stimulation does not interfere with prenatal perceptual learning by overwhelming the young organism's limited attentional capacities. Rather, multimodal stimulation biases what information is attended to during exposure and subsequent testing.     

Interactive and vicarious acquisition of auditory preferences in Northern bobwhite (Colinus virginianus) chicks

Studies examining the effects of stimulus contingency on filial imprinting have produced inconsistent findings. In the current study, day-old bobwhite chicks (Colinus virginianus) received individual 5-min sessions in which they were provided contingent, noncontingent, or vicarious exposure to a variant of a bobwhite maternal assembly call. Chicks given contingent exposure to the call showed a significant preference for the familiar call 24 hr following exposure and significantly greater preferences than chicks given noncontingent exposure. Chicks given vicarious exposure to recordings of another chick interacting with the maternal call showed significant deviations from chance responding; however, the direction of chick preference (toward the familiar or unfamiliar) depended on the particular call used. These results indicate that both direct and indirect (vicarious) exposure to stimulus contingency can enhance the acquisition of auditory preferences in precocial avian hatchlings. Precocial avian hatchlings thus likely play a more active role in directing their own perceptual and behavioral development than has typically been thought.     

Naturalistic psychophysics: thresholds of ducklings (Anas platyrynchos) and chicks (Gallus gallus) to tones that resemble mallard calls

Neonatal ducklings and chickens were tested for responsiveness to a pulsing pure tone that was as similar as possible to the mallard maternal alarm call. It is known that ducklings momentarily cease vocalizing when they hear the alarm call and that chicks do the same when they hear pure tones. The duration of peep suppression can thus be used as a measure of whether subjects of either species heard the stimulus. Chicks might not be as sensitive as ducklings to a mallard alarm call because the signal is less significant to them. An adaptive or staircase procedure was used to estimate absolute thresholds, and group psychometric functions were reconstructed for each species from the trial-by-trial data. Ducklings had lower thresholds than chickens as well as steeper psychometric functions to this stimulus. The results suggest that more sensitive and consistent behavioral responses can be elicited by naturalistic sounds than by more arbitrary acoustic stimuli.     

Intersensory redundancy educates selective attention in bobwhite quail embryos

We assessed whether exposure to amodal properties in bimodal stimulation (e.g. rhythm, rate, duration) could educate attention to amodal properties in subsequent unimodal stimulation during prenatal development. Bobwhite quail embryos were exposed to an individual bobwhite maternal call under several experimental and control conditions during the day prior to hatching. Experimental groups received redundant auditory and visual exposure to the temporal features of an individual maternal call followed by unimodal auditory exposure to the same call immediately or after a 2-hr or 4-hr delay. Control groups received (1) the same exposure but in the reverse sequence (unimodal --> redundant bimodal), (2) asynchronous bimodal --> unimodal, (3) only unimodal exposure, or (4) only bimodal exposure. All experimental groups showed a significant preference for the familiar maternal call over a novel maternal call when tested 2 days after hatching, whereas none of the control groups showed a significant preference for the familiar call. These results indicate that intersensory redundancy can direct attention to amodal properties in bimodal stimulation and educate attention to the same amodal properties in subsequent unimodal stimulation where no intersensory redundancy is available.     

Development of species identification in ducklings: III. Maturational rectification of perceptual deficit caused by auditory deprivation.

Mute ducklings, devocalized as embryos and maintained in auditory isolation, manifest a selective high-frequency perceptual deficit vis-à-vis the maternal call of their species at 24 hr after hatching. Since it takes a rather specific auditory experiential input to rectify this high-frequency insensitivity at 24 hr, it was predicted that, in the absence of auditory experience, devocal-isolated ducklings would fail to show sufficient endogenously mediated improvement to bring them up to the level of perceptual competence of vocal-communal ducklings at any age. This hypothesis proved wrong in that the proportion of devocalized ducklings showing a preference for the normal maternal call over the greater than 825-Hz attenuated one became equivalent to the vocal ducklings at 48 hr after hatching, as did their ability to discriminate the normal maternal call from greater than 1,800-Hz attenuated maternal call. At 65 hr, however, the devocalized ducklings' performance deteriorated back to the level observed at 24 hr. Embryonic exposure to the (sibling) contact-contentment call prevents the perceptual deficit at 24 hr and the deterioration at 65 hr.     

Behavioral control by an imprinted stimulus

Newly hatched ducklings were exposed to imprinting procedures and subsequently trained to peck a key by presenting the imprinting stimulus as the reinforcing (response contingent) event. It was found that the key peck was learned only when imprinting procedures were initiated during the first 6 to 8 hr after hatch. Additional studies revealed that: (1) the duckling's distress vocalizations were reduced in the presence of the imprinting stimulus and enhanced in its absence; (2) when the ducklings had constant access to the imprinted stimulus (via a key peck), pecking responses occurred in bursts and relatively few distress vocalizations occurred; (3) the initial effect of extinction procedures was an increase in key peck rate. When, however, repeated key pecks failed to produce the imprinted stimulus, distress vocalization ensued and peck rate declined; (4) both the presentation of an unfamiliar mechanical figure and delivery of electrical shock enhanced distress vocalization and key pecks; (5) for some ducklings, certain familiar objects in the environment influenced distress calls in a manner comparable to the imprinted stimulus in that distress calls increased when these objects were removed.     

Isolation-induced aggression in newly hatched ducklings.

Newly hatched Khaki Campbell ducklings (Anas platyrhynchos domesticus) were initially housed in pairs and subsequently transferred to isolated housing conditions. Subjects living with another bird displayed filial behavior and little aggression upon encountering another duckling in a test arena. In contrast, ducklings housed in isolation exhibited aggressive pecking in addition to filial behavior when another duckling was subsequently encountered. In Experiment 2, ducklings were housed with an imprinting object (i.e., an object that elicits attachment behavior), but they were otherwise isolated from other birds. These subjects displayed little aggression when they were subsequently reunited with a conspecific, indicating that the aggression-precluding effects of social housing are not limited to the particular social stimulus with which the ducklings are housed. In Experiment 3, ducklings were again housed with an imprinting object, but this time the object was behind glass, thereby precluding tactile contact with it. Since these birds also exhibited little aggression when reunited with a conspecific, it is apparent that visual stimulation from an imprinting object is sufficient in itself to preclude subsequent aggression. These findings suggest that stimulation that elicits attachment behavior is the critical factor mediating isolation-induced aggression.     

Spontaneous generalization of abstract multimodal patterns in young domestic chicks

From the early stages of life, learning the regularities associated with specific objects is crucial for making sense of experiences. Through filial imprinting, young precocial birds quickly learn the features of their social partners by mere exposure. It is not clear though to what extent chicks can extract abstract patterns of the visual and acoustic stimuli present in the imprinting object, and how they combine them. To investigate this issue, we exposed chicks (Gallus gallus) to three days of visual and acoustic imprinting, using either patterns with two identical items or patterns with two different items, presented visually, acoustically or in both modalities. Next, chicks were given a choice between the familiar and the unfamiliar pattern, present in either the multimodal, visual or acoustic modality. The responses to the novel stimuli were affected by their imprinting experience, and the effect was stronger for chicks imprinted with multimodal patterns than for the other groups. Interestingly, males and females adopted a different strategy, with males more attracted by unfamiliar patterns and females more attracted by familiar patterns. Our data show that chicks can generalize abstract patterns by mere exposure through filial imprinting and that multimodal stimulation is more effective than unimodal stimulation for pattern learning.     

Variation in Social Facilitation of Eating Behavior in Puppies

Observations of the play behavior of same-sex, same-age dyads of preschool children were made during 10-minute play sessions. Each of the 48 children participated both with a familiar peer and with an unfamiliar peer. The hypothesis that both boys and girls would show more interaction with familiar peers than unfamiliar peers was supported for younger girls and older boys. Younger boys seemed little influenced by the familiarity of their play companion, while older girls showed more social interaction with unfamiliar peers. Results were compared with studies that used projective techniques, and it was suggested that the effects of peer familiarity may appear earlier in actual behavior than through these techniques.     

Intersensory redundancy facilitates prenatal perceptual learning in bobwhite quail (Colinus virginianus) embryos.

Information presented redundantly and in temporal synchrony across sensory modalities (intersensory redundancy) selectively recruits attention and facilitates perceptual learning in human infants. This comparative study examined whether intersensory redundancy also facilitates perceptual learning prenatally. The authors assessed quail (Colinus virginianus) embryos' ability to learn a maternal call when it was (a) unimodal, (b) concurrent but asynchronous with patterned light, or (c) redundant and synchronous with patterned light. Chicks' preference for the familiar over a novel maternal call was assessed 24 hr following hatching. Chicks receiving redundant, synchronous stimulation as embryos learned the call 4 times faster than those who received unimodal exposure. Chicks who received asynchronous bimodal stimulation showed no evidence of learning. These results provide the first evidence that embryos are sensitive to redundant, bimodal information and that it can facilitate learning during the prenatal period.     

Foundations of infants' social group evaluations

Previous research has suggested that infants exhibit a preference for familiar over unfamiliar social groups (e.g., preferring individuals from their own language group over individuals from a foreign language group). However, because past studies often employ forced‐choice procedures, it is not clear whether infants' intergroup preferences are driven by positivity toward members of familiar groups, negativity toward members of unfamiliar groups, or both. Across six experiments, we implemented a habituation procedure to independently measure infants' positive and negative evaluations of speakers of familiar and unfamiliar languages. We report that by 1 year of age, infants positively evaluate individuals who speak a familiar language, but do not negatively evaluate individuals who speak an unfamiliar language (Experiments 1 and 2). Several experiments rule out lower‐level explanations (Experiments 3–6). Together these data suggest that children's early social group preferences may be shaped by positive evaluations of familiar group(s), rather than negative evaluations of unfamiliar groups.     

Early social experience and responses to visual social stimuli in young monkeys

Juvenile stumptailed macaques (Macaca arctoides) were given preference tests in which they could approach an empty chamber, a mirror, a familiar conspecific, or an unfamiliar conspecific. Control subjects tended to withdraw from the mirror, and threatened the stranger more than did monkeys whose early social experience had occurred exclusively in darkness. Both groups explored the familiar stimulus animal most of all, but the group socialized in the dark showed most positive behavior when in the empty chamber. In a second study peer-reared infants responded more appropriately to slides of conspecifics than did infants reared with a mirror as the main source of social input. Infants reared only with a peer were also strongly attracted to a mirror, whereas infants reared only with mirrors preferred a film of an unfamiliar agemate. The results suggest that early visual social stimulation is important in the development of aggression and other social behaviors, and that novelty and complexity are important aspects of social stimuli that interact with effects of early experience. Study 2 was conducted while the first author was in receipt of a Postgraduate Research Studentship from the U.K. Science Research Council. The DTU tapes were analyzed using a computer program developed with the help of SRC grant B/RG 98910 to A. Chamove. This latter grant also supported the study from which the preference test data were taken.     

Cattle discriminate between familiar and unfamiliar conspecifics by using only head visual cues

Faces have features characteristic of the identity, age and sex of an individual. In the context of social communication and social recognition in various animal species, facial information is relevant for discriminating between familiar and unfamiliar individuals. Here, we present two experiments aimed at testing the ability of cattle (Bos taurus) to visually discriminate between heads (including face views) of familiar and unfamiliar conspecifics represented as 2D images. In the first experiment, we observed the spontaneous behaviour of heifers when images of familiar and unfamiliar conspecifics were simultaneously presented. Our results show that heifers were more attracted towards the image of a familiar conspecific (i.e., it was chosen first, explored more, and given more attention) than towards the image of an unfamiliar one. In the second experiment, the ability to discriminate between images of familiar and unfamiliar conspecifics was tested using a food-rewarded instrumental conditioning procedure. Eight out of the nine heifers succeeded in discriminating between images of familiar and unfamiliar conspecifics and in generalizing on the first trial to a new pair of images of familiar and unfamiliar conspecifics, suggesting a categorization process of familiar versus unfamiliar conspecifics in cattle. Results of the first experiment and the observation of ear postures during the learning process, which was used as an index of the emotional state, provided information on picture processing in cattle and lead us to conclude that images of conspecifics were treated as representations of real individuals.     

Development of species identification in ducklings: II. Experimental prevention of perceptual deficit caused by embryonic auditory deprivation.

Devocalized-isolated ducklings are relatively insensitive to the higher frequencies in their species' maternal call 24 hr after hatching. To assess the efficacy of various sounds in preventing this high-frequency perceptual deficit, devocalized-isolated embryos were exposed to one of three calls and tested with normal versus high-frequency attenuated maternal calls 24 hr after hatching. The embryonic vocalization (contact-contentment call) that most closely matched the region of the devocalized ducklings' greatest insensitivity (1,500-2,500 Hz) proved most efficacious in remedying (preventing) the high-frequency perceptual deficit. Exposure to the embryonic alarm-distress call was somewhat effective, whereas exposure to low-frequency white noise was not effective at all. This finding suggests that the normal development of innate behavior is partially dependent upon prior experience as well as upon intrinsic processes of neural maturation. Although normally occurring embryonic auditory experience does not induce the preference for the maternal call in this species, such experience does contribute to the sharpness of the discriminative basis of the preference 24 hr after hatching.     

Aggressive reactions of ducklings to a nonliving target object

This study asked whether ducklings' forceful pecks at a nonliving target object could be validly identified as aggressive. Previously isolated ducklings were exposed to a small cylindrical object that could serve as a target for aggressive pecks and as an object for attachment. After initially attempting to flee from the target, they vigorously pecked at it and also showed signs of the formation of a social (imprinting) attachment. In all important respects this pattern of behavior was identical to the pattern of escape, aggressive pecks, and attachment seen when a previously isolated duckling first encounters a conspecific. Social housing, a manipulation which attenuates aggression against live targets in ducklings and other species, reduced pecking at the nonliving target object. Early aversive stimulation, which enhances aggression against live targets, increased pecking at the object. These findings support the use of nonliving targets in the study of aggression in ducklings.     

The development of infants' preference for motherese

Generally, infants prefer infant-directed (ID) to adult-directed (AD) speech. Mostly, researchers have used unfamiliar female voices in these studies. We investigated preferences for maternal ID speech in 1- and 4-month-olds. Using a procedure in which infants controlled access to voices by fixating a visual display, infants listened to recordings of natural female ID and AD speech. In Experiment 1, 1-month-olds heard recordings of maternal ID and AD speech, but these infants showed no preference for maternal ID speech. In Experiment 2, 1-month-olds heard the same ID and AD speech tapes but were not familiar with the speakers. Contrary to Experiment 1, these infants preferred ID speech. In Experiment 3, 4-month-olds heard recordings of maternal ID and AD speech and showed a significant preference for ID speech. Collectively, these results suggest that infant attention to ID speech depends on both speaker-general and speaker-specific characteristics, with interesting developmental changes occuring during early infancy.     

Intrinsic interest and the novelty-familiarity interaction

According to the interaction hypothesis of interest, the inherent interestingness of a communication or a situation will be maximal when novel and familiar elements are simultaneously present. This is illustrated in three experimental demonstrations, where students were to indicate their interest (a) in book titles (more and less well-known authors best and least known works); (b) in reports by foreign journalists about everyday life in Norway (familiar topic) and in Honduras (less familiar); and (c) in meeting tourists of different nationalities at more and less familiar geographical locations. The results show that the preference function for novelty will be ascending or descending dependent upon the familiarity or unfamiliarity of other aspects of the situation. Thus, Norwegian subjects were not very curious about unfamiliar British authors least known works, whereas they would very much like to read what journalists from unfamiliar countries write about Norway. Also, they preferred meeting tourists from unfamiliar countries, as long as the meeting took place in a familiar city. In a foreign city, the order of preference was reversed.     

Nature reversed: Diminishing intensity of the maternal call affects approach behaviour of chicks

Skinner (1974) suggested that ducklings could be taught to move away from an imprinting object provided the natural consequences of approach behaviour was reversed. We constructed an apparatus in which approach behaviour toward an audio-visual stimulus caused reduced amplitude of a maternal call, whereas movement away caused an increase in amplitude. Chicks (Experiment 1) trained in this apparatus approached the training stimulus, but to a lesser degree than chicks exposed to calls of constant amplitude. Highly active experimental chicks kept a larger distance to the stimulus than passive chicks. Thus the reversal of the natural consequences of approaching influenced filial behaviour. However, a training period of three hours did not influence approach behaviour in the direction predicted by Skinner (1974). A second group of chicks (Experiment 2) which could increase the call amplitude by moving in one direction without being able to localize the sound source was more influenced by the amplitude gradient than Experiment I-chicks.