Imprinting Object Research Articles

Effects of Pairing of Chicks During the Imprinting Period on Filial Responses to an Imprinting Stimulus

There are several studies which have evaluated the effects of social contact with siblings on imprinting to a maternal surrogate. However, we have no consistent effect of the social experience. Some studies have reported that social experience with siblings interferes with the establishment of imprinting, whereas other studies have reported that social experience with siblings enhances the imprinting experience.The present study examined the effects of social contact with one sibling during the imprinting sessions on imprinting to the maternal object for chicks (White Leghorn). This experimental situation is similar to the natural setting because under natural conditions imprinting occurs in a social situation which includes a parent and siblings. Next, this study investigated the interrelation between each chick's responses to its partner and those to the imprinting object.During the imprinting sessions, each chick was individually exposed to only the imprinting object under the isolated condition or exposed to both the stimulus and one sibling under the paired condition over three days after hatching. Each chick showed the better performance under the isolated condition than under the paired condition. Thus the presence of one sibling during the imprinting period weakens the strength of the imprinting.The more interesting result was that chicks who had showed a poor performance under the first paired sessions followed the stimulus well under the later isolated condition. It seems that these subjects have already fully imprinted to the stimulus in spite of poor experience of following the stimulus. This result renders dubious the significance of following as an index of the strength of imprinting.Next, it was often observed under paired conditions that as soon as a well-imprinted chick followed the stimulus, the other chick ran behind him quickly. It was also observed that this well-imprinted chick followed its partner and pecked at him frequently. We can consider there is some interrelation between social responses to a sibling and those to a surrogate mother.

Effects of response-contingency and stimulus presentation schedule on imprinting in the chick (Gallus gallus domesticus).

The effects of operant control over the presentation of a conspicuous imprinting stimulus on the formation of a filial preference were examined in day-old domestic chicks. Experimental chicks had to press one of two operant pedals to be exposed to the training object, a rotating red box. Chicks in a yoked control group received the same pattern of exposure to the object, but exposure was not contingent upon the chicks' response. In a second control group, the chicks were exposed to the object according to a fixed-interval schedule. The chicks' preferences were measured 2 hr after the end of training in a simultaneous choice test involving the red box and a novel stimulus. There was no significant difference in preference between the experimental chicks and their yoked controls. The mean preference of both groups was significantly higher than that of the fixed-interval control group, a result suggesting that a variable schedule of exposure to the training object enhances the formation of a preference. This was confirmed in a further experiment in which a variable interval/variable duration schedule of exposure to the object led to a significantly higher preference than a fixed-interval/fixed-duration exposure schedule. The results do not support the hypothesis that response contingency affects the formation of filial preferences. A variable schedule of exposure to an imprinting object accelerates the formation of a preference for that object, relative to a fixed schedule.

Research Note: Application of the Filial Imprinting Phenomenon to Broiler Chicks at a Commercial Farm

Ten thousand broiler chicks on commercial farms in Israel were imprinted to blue and red plastic boxes (20 × 20 × 40 cm) containing loud speakers (8 Ω, 12 W) equipped with a tape recorder, in which a classical music cassette had been placed. Upon reaching 3 wk of age, an attempt was made to move these chicks from the training area (A) to a new area (B) using the imprinting objects. This experiment was repeated four times: May, August and November of 1985, and in January 1986. During the warm months of May and August 30 to 60% of the experimental chicks followed the imprinting objects toward Area B. During the cold months and in all four repetitions with the controls, less than 5% of the flocks moved from Area A to Area B. Winter chicks may have been imprinted on brooder heaters. In all repetitions, most of the imprinted chicks distributed themselves equally over Area B 1 h after the doors between Areas B and A were closed. Controls, however, crowded around the door between Areas A and B resulting in the death of many chicks by asphyxiation. This study has shown that thousands of heavy strain chicks can be easily attached to an imprinting stimulus and it may be possible to apply this phenomenon for commercial purposes.

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.

The gonadotropic-axis involvement in the course of the filial following response in the domestic fowl chick

The detachment process of the domestic chick from its mother, or any other imprinting object occurs between the sixth and tenth week after hatching. The present study (Experiment I), examines whether the detachment process parallels endocrine events that precede prepuberty. Immediately upon hatching, groups of heavy strain chicks were imprinted to a colored foam rubber ball for 72 hours. The bond between these chicks and the imprinting object was then tested, and plasma LH and testosterone were assayed once a week until the chicks were 10 weeks of age; the sexual development of chicks of the same strain was studied at the same time. At the outset of the detachment period (5–7 weeks) an increase in plasma testosterone and a decrease in plasma LH was found. In addition, the comb and testes showed a definite weight increase while the bursa of Fabricius showed a significant decline in weight. In Experiment II, the beginning of the detachment process was induced by injecting 3 to 4 week old chicks with testosterone-propionate, estradiol-benzoate and 5α-dihydrotestosterone. Our evidence therefore appears to demonstrate that testosterone and its metabolites induce the detachment process by the same mechanism used to stimulate sexual behavior in juvenile chicks.

Imprinting of the Peking duck (Anas platyrhynchos) and dependence on exposure to light during ontogenesis.

Embryos of Peking ducks were either incubated in complete darkness up t o hatching or were put into light one week before hatching. Control embryos were incubated under dim light conditions which corresponded broadly to the natural conditions. Under standardized imprinting conditions the controls and both groups of the light deprived ducklings showed the 'following response'. Most of the dark-incubated embryos, however, did not distinguish between imprinting and test objects of different shapes. Since most of the embryos kept in darkness only for 21 days also failed to develop the capacity for shape discrimination, there is apparently a critical period for light influences on the development of this capacity at some time during the early prenatal period.

Long-term consequences of exposure to an imprinting stimulus on ‘spontaneous’ impulse activity in the chick brain

Young chicks were exposed in a running wheel to an imprinting object, a rotating flashing red box (n = 36 chicks) or a rotating stuffed jungle fowl (n = 18). The net number of revolutions of the wheel toward the imprinting object provided a measure of approach activity during training. The chicks were subsequently anaesthetized and the ‘spontaneous’ firing rates of units were recorded simultaneously in two regions of the left forebrain hemisphere. One microelectrode penetration was made through a region, the intermediate and medial part of the hyperstriatum ventrale (IMHV) known to be critical for imprinting; simultaneously another microelectrode penetration was made through the visual Wulst. The electrodes were advanced in steps of 250 μm and the spontaneous discharge of multiple units at each site recorded. The mean firing rate from ⩾ 3 sites was calculated for IMHV and for the hyperstriatum accessorium of the Wulst. There was a negative correlation between mean firing rate of units in IMHV and approach activity for chicks trained on the box. The effect was: (i) stimulus specific since it was not found in chicks trained on the jungle fowl; and (ii) regionally specific since approach activity, depending on conditions which are described, was either not correlated or positively correlated with mean firing rate for neurones in the hyperstriatum accessorium. The positive correlation was not dependent on the training stimulus but on the presence of a visually responsive lamina deep to the hyperstriatum accessorium.

The Effects of Environmental Change on Chicks’ Responses to a Familiar Stimulus

The purpose of the present experiments was to explore chicks’ proximity seeking behaviour in relation to imprinting objects in unfamiliar settings. Experiment I showed that chicks, which were individually imprinted on a stationary imprinting object, displayed reduced proximity seeking behaviour when tested in a pen smaller than the rearing pen. This finding confirmed earlier work on the effects of changed pen size. Experiment II used continuous and intermittent noise rearing and testing conditions, in all possible combinations, and a stationary imprinting object. Increased proximity seeking was found in conditions where the auditory environment was changed from rearing to testing, a result apparently opposite to that obtained in earlier work. It is suggested that the effect of environmental change on proximity seeking may vary with the modality in which change occurs and the salience of the imprinting object.

Effects of environmental novelty on filial behavior in imprinted ducklings

Environmental novelty was manipulated in imprinted ducklings by varying the illumination level of the experimental apparatus. Bright illumination disrupted filial behavior in subjects that had received little prior exposure to the imprinting object, with approach being suppressed more when the object was stationary than when it was moving. In subjects with prolonged prior imprinting exposure, bright illumination enhanced filial behavior. These effects can be understood if one assumes that environmental novelty has an energization effect while also eliciting responses that are incompatible with filial behavior.

Priming of Darkness-Rewarded Runway Responses in the American Cockroach (Periplaneta Americana)

Summary After cockroaches were trained to traverse an illuminated runway with darkness as the rewarding event, they were given brief “primes” of darkness in the startbox. Runway performance was enhanced, but these priming effects declined as postprime delay (i.e., the delay before a roach was permitted to leave the startbox) was increased. A second experiment found that the response enhancement was greater after primes of long duration than after primes of short duration. The present work suggests a possible distinction between the priming properties of food and water on the other hand, and darkness, brain stimulation, and an imprinting object on the other.

Acquisition of behavioral control by static visual features of an imprinting object: Species generality

Previous work had indicated that after prolonged exposure to a moving object, ducklings will direct filial responses toward that object even if it remains stationary during its presentation. The present experiment demonstrated the wide species generality of this effect by obtaining similar results in newly hatched chickens, pheasant, turkeys, and quail, as well as ducks.

Development of filial attachment to static visual features of an imprinting object

Three experiments investigated the fact that the static visual features of an imprinting object (its color, size, and shape characteristics, as represented by the object remaining stationary during its presentation) can gradually acquire control over filial behavior by virtue of their repeated spatial-temporal pairing with visual motion—an effect that has been interpreted as a process of classical conditioning. Experiment 1 found that the static features can acquire control if they are made conspicuous in some other, nonmovement way (i.e., by manipulating the relative illumination of the imprinting object). Further experiments then failed to find any qualitative difference between the behavioral control developed by conspicuous but static aspects of a duckling’s environment and the control developed by the static features of a moving object, either in terms of persistence of the acquired control (Experiment 2) or in terms of possible restrictions imposed by the sensitive period for imprinting (Experiment 3). Taken together, these results support the plausibility of a perceptual learning hypothesis, although the classical conditioning view was not itself contradicted. The present findings are also relevant to the broader issue of whether any valid distinctions exist between the behavioral control exerted by static aspects of a precocial bird’s environment and the control exerted by animate, presumably social stimuli.

Forebrain lesions and retention of imprinting in domestic chicks.

Newly-hatched domestic chicks were reared separately with one of two types of imprinting object hanging in their cages. On the 5th day discrimination tests demonstrated strong preferences for the familiar object. On the 6th day the chicks were subjected to bilateral aspiration lesions of either the anterior or the lateral forebrain and their imprinting objects removed from the cage. Discrimination tests were made on the 9th and 12th days, the imprinting objects replaced, and a final relearning test given on the 14th day. The anterior lesion group was slightly impaired in the retention and relearning tests while the lateral lesion group was drastically affected, being significantly worse than the anterior group and with choices only just significantly above random expectation in the retention tests and no different from random choice in the relearning test. It was concluded that a lateral forebrain region is necessary for retention and relearning of a previously acquired imprinted preference.

Mediating factors in chick social pecking: 1. Effects of isolation, imprinting, and peer contact

Two experiments examined the influence of periods of social isolation on rates of intersubject pecking in pairs of domestic chicks. Of central interest was the effect of an imprinting condition wherein single birds were reared with either a red or green Styrofoam object. In the first experiment, imprinted subjects were given social pecking tests in the absence of the imprinting object, while in the second study the tests for social pecking were conducted in the presence of one of the imprinting objects. In the latter test the object was familiar to one bud of a pair, but was novel to the other animal. The results of both experiments showed that the rate of intersubject pecking of the imprinted subjects was intermediate to, and statistically different from both the low pecking rate of chicks reared in pairs and the high pecking rate of chicks reared in total isolation. The presence of a familiar object during tests in the second study seemed to serve as a secure base since chicks that had been reared with that object exhibited more social pecking than did chicks that were unfamiliar with the object. However, regardless of the provision of the object the social pecking of the imprinted chicks again fell on a point intermediate to the other groups. Hypotheses concerning a) intolerance of figureground movement and b) sheer stress of isolation were advanced to account for these results.

Behavioral control by stimulus components of an imprinting object

In the first of three experiments, ducklings that had received prolonged exposure to the visibly moving imprinting object subsequently suppressed ongoing distress vocalization both during brief presentations of the moving object and during brief presentations of its initially neutral stimulus components (i.e., its auditory and static visual features). Only presentations of the moving object were followed by priming aftereffects (namely, enhancement of distress vocalization over a baseline rate). In Experiment 2, weak, but reliable, priming effects were detected after very long presentations of the auditory and static visual features. Experiment 3 found that these features strongly suppressed low, but not high, rates of distress vocalization, while the visibly moving object strongly suppressed both high and low rates. These studies suggest that initially neutral features of an imprinting object acquire the same sort of behavioral control as is exerted by the object when it is in motion, but that this control is somewhat weaker.

Imprinting: Effects of discrepancy from rearing conditions on approach to a familiar imprinting object in a novel situation.

Imprinting: Effects of discrepancy from rearing conditions on approach to a familiar imprinting object in a novel situation.

Discrimination learning in chicks previously exposed to the discriminanda

Three experiments are described. The ability of chicks to discriminate shape or colored stimuli after being exposed to both discriminanda in an imprinting situation is compared with the discriminative ability of chicks not previously exposed. In two of the three experiments, we found no differences between the groups, although in the third, the group previously exposed to the discriminanda showed an impairment in discriminative ability. Our negative results are not in accordance with those of Bateson and Chantrey (1972), who attribute the learning impairment to a prior “classifying together” of the stimuli, a mechanism enabling the chick to respond to differing views of the imprinting object as representative of the same object.

Surrogate mothering in White Leghorn chicks

The present study investigated the effectiveness of two types of surrogates in reducing isolation-related death rates occurring between the 4th and 7th days after hatching in chicks. A red tennis ball suspended from the cage ceiling was as effective as group rearing in maintaining a low death rate (25% and 12%, respectively). A flashing light was ineffective in reducing death rate compared to rearing in isolation (72% and 75%, respectively). This supports Harlow’s work with infant monkeys on the importance of tactile stimulation and extends it to a lower species than had been previously considered. The flashing light was probably ineffective because the chicks were unable to achieve physical contact with the light. It was not determined that all chicks received enough food to survive. It is likely that the chick‘s need for stimulation in the form of a touchable imprinting object is prepotent over its hunger drive. Although all chicks were observed eating, some may have spent energy and time seeking contact with an imprinting object that was impossible to attain, thus failing to engage in sufficient eating behavior.

The relative effectiveness of an inanimate stimulus and a live surrogate during imprinting in Japanese quail, Coturnix coturnix japonica.

It has been demonstrated repeatedly that stimuli vary in their effectiveness in eliciting and maintaining imprinting. Agreement has not been reached, however, with regard to the ideal imprinting model for laboratory studies. This situation is in part a result of the inability to replicate precisely natural parameters in the laboratory. Thus laboratory results are often inconsistent with field research. In order to develop a more biologically appropriate imprinting stimulus, a live Japanese quail hen was conditioned to serve as an imprinting object. An imprinting study was then performed to assess the dimensions of effectiveness of the live model. Comparisons between the live model and a decoy yielded different patterns of imprinting in young Japanese quail.

Modification of ducklings' filial behavior by aversive stimulation.

Three experiments examined the effects of aversive stimulation in the context of imprinting. In Experiment 1, newly hatched ducklings were electrically shocked in either the presence or absence of an imprinting stimulus, and both their tendency to follow the stimulus when it was presented alone and their preference for it over novel stimuli were subsequently assessed. The results indicated that the shock enhanced the subjects' tendency to follow the imprinting stimulus in the nonchoice situation regardless of whether the ducklings were shocked in its presence or absence. If, however, the electrical shocks were associated with the presence of the imprinting stimulus, they also reversed the ducklings' usual preference for the imprinting object over the novel stimuli. Comparable effects were obtained in the second experiment in which 5-day-old ducklings were electrically shocked in either the presence or absence of a novel, fear-eliciting imprinting stimulus. In Experiment 3, electrical shock was administered to newly hatched ducklings independently of their exposure to an imprinting stimulus, and it was found that, relative to older ducklings that received the same treatment, the newly hatched subjects subsequently displayed less emotionally in fear-eliciting situations. The results were interpreted as suggesting that there are at least three distinct effects of aversive stimulation in the context of imprinting-motivational, associative, and developmental.