Bateson, P. (2000). What must be known in order to understand imprinting?, In Heyes, Cecilia (Ed); Huber, Ludwig (Ed). (2000). The evolution of cognition. Vienna series in theoretical biology. Cambridge, MA, US: The MIT Press. (pp. 85 102).

In order to understand imprinting from a behavioral standpoint, the neurophysiological subprocesses involved in such learning must be clear. The timing of the imprinting process, the features that most readily trigger learning, and the motor systems that are linked to representations stored as a result of learning are all specific to the functional context of forming a social attachment to one or both parents. The underlying neural mechanisms might be the same as those involved in other learning processes. Nevertheless, it is worth asking whether the rules involved in learning about the causal structure of the environment are different from those used in perceptual learning (of which imprinting is a special case). Time plays a different role in classical or instrumental conditioning than it does in perceptual learning. The order in which different events are experienced may matter a lot when one event causes the other. However, the order does not matter at all when the experiences are different views of the same object. Some behavioral and physiological evidence from studies of imprinting in chicks suggests that these two broad functions are served by different subprocesses but that the subprocesses are, nevertheless, in touch with each other. (PsycINFO Database Record (c) 2000 APA, all rights reserved) Record 15 of 30 in PsycINFO 1999-2000/11

Bolhuis, J. J., & Horn, G. (1997). Delayed induction of a filial predisposition in the chick after anaethesia. Physiology and Behavior, 62(6), 1235-1239.

The predisposition to filial preferences may be measured in visually naive chicks as a preference for a rotating stuffed jungle fowl hen rather than for a rotating red box. Nonspecific experience, such as handling or being placed in a running wheel in darkness for a short time, is sufficient to induce the predisposition. In Exp 1, the existence of a sensitive period for the induction of the predisposition, between approximately 14 and 42 hrs after hatching, was confirmed. The putative effect of anesthesia on the induction of the predisposition was investigated in Exp 2. Soon after hatching, dark-reared chicks received equithesin, saline, or no injections (controls). The chicks were subsequently placed in running wheels for a total of 2 hrs, at either 24 hrs or 48 hrs after hatching. The following day the chicks' preferences were tested. In the 24-hr chicks, the saline and control groups showed a significant mean preference for the stuffed fowl, whereas the equithesin group did not. In the 48-hr chicks, only the equithesin group showed a significant mean preference for the stuffed fowl. Results suggest that equithesin affects a developing filial predisposition in the domestic chick, by delaying the onset of a sensitive period for the induction of the predisposition. (PsycINFO Database Record (c) 2000 APA, all rights reserved)

Horn, G. (1998). Visual imprinting and the neural mechanisms of recognition memory. Trends in Neurosciences, 21(7), 300-305.

Reviews work designed to analyze the neural basis of recognition memory underlying visual imprinting in domestic chicks. Part of the hyperstriatum ventrale (IMHV) serves as a region for storing information in the learning process of imprinting. The author discusses synaptic changes occurring in the IMHV during imprinting, the involvement of synaptic binding and neuronal remodelling in memory, and the move from neurons towards circuits in the IMHV during imprinting. The evidence suggests that several neuronal changes, including the sprouting of axon terminals and an increase in the area of contact between pre- and postsynaptic elements, are involved in the strengthening of connections between specific groups of neurons in the CNS forming the neural basis of memory. (PsycINFO Database Record (c) 2000 APA, all rights reserved) Record 2 of 2 in PsycINFO 1996-1998

Johnson, M. H. (1999). Ontogenetic constraints on neural and behavioral plasticity: Evidence from imprinting and face processing. Canadian Journal of Experimental Psychology, 53(1), 77-90.

This paper addresses the extent and limits on brain plasticity during development through the detailed study of imprinting in the domestic chick and the development of face processing in human infants. In both of these systems evidence for constraints on plasticity is reviewed. The first source of constraint comes from the basic architecture of learning mechanisms that support plasticity. With regard to the chick, a specific "Hebbian" model based on the known neural circuitry of the region of the brain involved is presented and discussed. In human infants, a more abstract model inspired by cortical circuitry is mentioned. The second source of constraint comes from biases on the nature of the stimuli selected for attention by the young organism. Both in the chick and the human there is evidence for a subcortical brain system which orients their attention toward conspecifics, and particularly to their faces. It is argued that these systems tutor, or bias the input to, the more plastic learning systems. (PsycINFO Database Record (c) 2000 APA, all rights reserved) Record 23 of 30 in PsycINFO 1999-2000/11

Kilner, R. M., & Davies, N. B. (1999). How selfish is a cuckoo chick? Animal Behaviour, 58(4), 797-808.

Studied the begging display of nestling cuckoos, Cuculus canorus, reared by reed warbler, Acrocephalus scirpaceus, hosts to test various hypotheses for the cuckoo's unusually rapid begging call. Results show that cuckoo chicks do not use their exaggerative begging to counteract host rejection: begging displays varied with hunger and functioned entirely to solicit food. Also, cuckoos do not exaggerate their begging calls simply because they need more food than a host brood. Single cuckoos grew at a similar rate to a brood of 4 reed warblers, and more slowly than a blackbird, Turdus meruls, chick. Data support 2 other hypotheses: (1) To elicit sufficent care in reed warbler nests, the cuckoo must exaggerate the vocal component of its display to compensate for its dificient visual signal compared with a host brood. Thus rapid calling reflects the way the cuckoo exploits the provisioning rules that hosts use to feed their own young; and (2) In theory, cuckoos should be more selfish than host young because their greed is unconstrained by kinship. The data are equivocal; compared with host broods, cuckoos solicited a higher provisioning rate in relation to one measure of need but not for another. (PsycINFO Database Record (c) 2000 APA, all rights reserved) Record 7 of 15 in PsycINFO 1996-1998

Kilner, R. M., Noble, D. G., & Davies, N. B. (1999). Signals of need in parent-offspring communication and their exploitation by the common cuckoo. Nature, 397(6721), 667-672.

Nestling birds present vivid gapes and produce loud calls as they solicit food, but the complexity of the display is poorly understood. Here we explain the function of reed warbler begging signals and show how they are exploited by the common cuckoo, Cuculus canorous, a brood parasite. Reed warbler parents integrate visual and vocal signals from their young to adjust their provisioning rates, and the two signals convey more accurate information about offspring need than either does alone. The cuckoo chick has a particularly striking begging display which has been suggested to be irresistible to host parents. However, we show that the cuckoo, reared alone in the nest, presents a deficient visual display, and elicits the same amount of care as a reed warbler brood only by compensating with its exaggerated vocal display. Therefore the cuckoo succeeds not through mimicry of the host brood begging signals, but by tuning into the sensory predispositions of its hosts. (PsycINFO Database Record (c) 2000 APA, all rights reserved)(journal abstract) Record 5 of 15 in PsycINFO 1999-2000/11

Nicol, A. U., Brown, M. W., & Horn, G. (1999). Is neuronal encoding of subject-object distance dependent on learning? Neuroreport: For Rapid Communication of Neuroscience Research, 10(8), 1671-1675.

Recordings were made in the intermediate and medial part of the hyperstriatum ventrale of domestic 1-day-old chicks that had been imprinted (trained) by being exposed to a training stimulus. Neurons were tested for responsiveness to the training stimulus and to an alternative stimulus at each of 3 distances (0.5 m, 1 m, and 2 m) from the chick. For responses to the training stimulus 24/78 (31%) responsive neurons were distance-sensitive (i.e., responses changed with distance). For responses to the alternative stimulus, a similar proportion of neurons was distance-sensitive (28%). Six distance-invariant neurons responded similarly at each distance: 4 to the training and 2 to the alternative stimulus. No effect of learning on distance-sensitive or distance-invariant neuronal responsiveness was found. (PsycINFO Database Record (c) 2000 APA, all rights reserved) Record 24 of 30 in PsycINFO 1999-2000/11

Parsons, C. H., & Rogers, L. J. (2000). NMDA receptor antagonists extend the sensitive period for imprinting. Physiology and Behavior, 68(5), 749-753.

Using their imprinting paradigm, the authors show that normal, dark-reared chicks lose the ability to imprint after the second day post-hatching. Further, they report that chicks treated 10 hr after hatching with a mixture of the noncompetitive NMDA receptor antagonist ketamine (55 mg/kg) and the alpha-sub-2-adrenergic receptor agonist xylazine (6 mg/kg) were able to imprint on day 8 after hatching, whereas controls treated with saline did not imprint. They now show that the effect of the ketamine-xylazinc mixture can be mimicked by treating chicks with ketamine alone or with another noncompetitive NMDA receptor antagonist, MK-801 (5 mg/kg). Treating chicks with a single dose of ketamine (55 mg/kg) or with a single dose of xylazine (6 mg/kg) failed to produce the effect on the sensitive period. However, prolonging the action of ketamine by treating chicks with two doses of ketamine (at 10 and 12 hr after hatching) did allow imprinting on day 8. In contrast, prolonging the action of xylazine had no effect on the sensitive period for imprinting. Chicks treated with MK-801 were also able to imprint on day 8. Thus, there is evidence that the NMDA receptor system is involved in the mechanisms that control the sensitive period for imprinting. (PsycINFO Database Record (c) 2000 APA, all rights reserved) Record 18 of 30 in PsycINFO 1999- 2000/11

Taylor, S. E., Klein, L. C., Lewis, B. P., Gruenewald, T. L., Gurung, R. A. R., & Updegraff, J. A. (2000). Biobehavioral responses to stress in females: Tend-and-befriend, not fight-or-flight. Psychological Review, 107(3), 411-429.

The human stress response has been characterized, both physiologically and behaviorally, as "fight-or-flight." Although fight-or-flight may characterize the primary physiological responses to stress for both males and females, we propose that, behaviorally, females' responses are more marked by a pattern of "tend-and-befriend." Tending involves nurturant activities designed to protect the self and offspring that promote safety and reduce distress; befriending is the creation and maintenance of social networks that may aid in this process. The biobehavioral mechanism that underlies the tend-and-befriend pattern appears to draw on the attachment-caregiving system, and neuroendocrine evidence from animal and human studies suggests that oxytocin, in conjunction with female reproductive hormones and endogenous opioid peptide mechanisms, may be at its core. This previously unexplored stress regulatory system has manifold implications for the study of stress. (PsycINFO Database Record (c) 2000 APA, all rights reserved)(journal abstract) Record 11 of 30 in PsycINFO 1999-2000/11


Ziegler, T. E. (2000). Hormones associated with non-maternal infant care: A review of mammalian and avian studies. Folia Primatologica, 71(1-2), 6-21.

Hormonal changes during non-maternal infant care have been demonstrated in many cooperatively breeding bird species, some monogamous rodents and two species of New World primates. Coevolution of hormones and social traits may have provided for the different breeding systems that occur today. Several hormones have been shown to covary with the breeding systems of vertebrates.

Elevated levels of the hormone prolactin with male parenting behaviors are common to many birds, rodents and the callitrichid monkeys Callithrix jacchus and Saguinus oedipus.

In birds, prolactin may be elevated in both male and female breeders during various stages of nest building, egg laying, incubating and feeding of young. Testosterone levels appear to have an inverse relationship to prolactin levels during infant care in birds and rodents, but this relationship has not been examined for primates. In cooperatively breeding birds, helpers who remain at the nest also have elevated levels of prolactin when displaying parental care behaviors. Prolactin levels are elevated in helper callitrichid monkeys during the postpartum period. Hormonal regulation of non- maternal care may occur due to a complex interaction of many hormones and neurotransmitters. (PsycINFO Database Record (c) 2000 APA, all rights reserved) Record 4 of 12 in PsycINFO 1999- 2000/11

(Callithrix jacchus = common marmoset and Saguinus oedipus = cottontop tamarin: small new world monkeys)