| Home | << 1 2 3 4 5 6 7 8 9 10 >> [11–20] |
|
Nakamaru, M., & Sasaki, A. (2003). Can transitive inference evolve in animals playing the hawk-dove game? J. Theor. Biol., 222(4), 461–470.
Abstract: What should an individual do if there are no reliable cues to the strength of a competitor when fighting with it for resources? We herein examine the evolutionarily stable strategy (ESS) in the hawk-dove game, if the opponent's resource-holding potential (RHP) can only indirectly be inferred from the outcome of past interactions in the population. The strategies we examined include the classical mixed strategy in which no information on past games is utilized, the `imprinting' strategy in which a player increases/decreases its aggressiveness if it wins/loses a game, the `immediate inference' strategy in which a player can infer the strength of those opponents it fought before, and the `transitive inference' strategy in which a player can infer the strength of a new opponent through a third party with which both players have fought before. Invasibility analysis for each pair of strategies revealed that (i) the transitive-inference strategy can always invade the mixed strategy and the imprinting strategy, and itself refuses invasion by these strategies; (ii) the largest advantage for transitive inference is achieved when the number of games played per individual in one generation is small and when the cost of losing an escalated game is large; (iii) the immediate inference, rather than the transitive inference, can be an ESS if the cost of fighting is small; (iv) a strong linear ranking is established in the population of transitive-inference strategists, though it does not perfectly correlate to the ranking by actual RHPs. We found that the advantage of the transitive inference is not in its ability to correct a misassessment (it is actually the worst in doing so), but in the ability of quickly lining up either incorrect or correct assessments to form a linear dominance hierarchy.
Keywords: Hawk-dove game; Ess; Transitive inference; Resource holding potential
|
|
Miksovska, J., & Larsen, R. W. (2003). Photothermal studies of pH induced unfolding of apomyoglobin. J Protein Chem, 22(4), 387–394.
Abstract: Conformational dynamic and enthalpy changes associated with pH induced unfolding of apomyoglobin were studied using photoacoustic calorimetry and photothermal beam deflection methods. The transition between the native state and the I intermediate was induced by a nanosecond pH jump from o-nitrobenzaldehyde photolysis. Deconvolution of photoacoustic waves indicates two kinetic processes. The fast phase (T < 50 ns) is characterized by a volume expansion of 8.8 ml mol(-1). This process is followed by a volume contraction of about -22 ml mol(-1) (tau approximately 500 ns). Photothermal beam deflection measurements do not reveal any volume changes on the time scale between approximately 100 micros and 5 ms. We associate the volume contraction with structural changes occurring during the transition between the native state and the I intermediate. The lack of any processes on the ms time scale may indicate the absence of structural events involving larger conformational changes of apomyoglobin after the pH jump.
|
|
Hoang, L., Maity, H., Krishna, M. M. G., Lin, Y., & Englander, S. W. (2003). Folding units govern the cytochrome c alkaline transition. J Mol Biol, 331(1), 37–43.
Abstract: The alkaline transition of cytochrome c is a model for protein structural switching in which the normal heme ligand is replaced by another group. Stopped flow data following a jump to high pH detect two slow kinetic phases, suggesting two rate-limiting structure changes. Results described here indicate that these events are controlled by the same structural unfolding reactions that account for the first two steps in the reversible unfolding pathway of cytochrome c. These and other results show that the cooperative folding-unfolding behavior of protein foldons can account for a variety of functional activities in addition to determining folding pathways.
|
|
Buechner-Maxwell, V. A., Elvinger, F., Thatcher, C. D., Murray, M. J., White, N. A., & Rooney, D. K. (2003). Physiological Response of Normal Adult Horses to a Low-Residue Liquid Diet. Journal of Equine Veterinary Science, 23(7), 310–317.
Abstract: Abstract The anorexic or dysphagic adult horse often requires nutritional support. Providing nutrients by the enteral route is the safest and most economic choice, but the dietary options available for use in horses are somewhat limited. The objective of this study was to compare the physiologic response of normal horses with a low-residue liquid or normal diet over a 10-day feeding period. Two groups of 6 normal adult horses were maintained on 1 of 2 diets for a 10-day period. Diets were formulated to meet the caloric needs of a horse maintained in a stall. The control group was fed 70% timothy hay and 30% textured concentrate for the test period, and the experimental group received the low-residue liquid diet, similar to liquid nutritional formulas designed for human use. Clinical parameters, body weight, packed cell volume, total plasma solids, blood glucose, and serum electrolytes were recorded daily for each horse during the dietary trial period. On days 1, 5, and 10 of the study, a complete blood count, serum biochemical profile, and urinalysis were performed. Horses' serum total bilirubin concentration and pattern of weight loss differed between groups. All other physical parameters, blood chemistry, complete blood count, and urinalysis results remained within the normal reference interval for the horses regardless of diet, although some statistical differences were observed. Horses returned to pasture and free-choice grass diet without complications at the end of the dietary trial period. These results demonstrate that few differences of biologic significance were observed between horses being fed low-residue diet and horses receiving a normal diet of hay and grain over a 10-day period. (Equine Vet J 2003;23:310-317)
|
|
Weaver, A., & de Waal, F. B. M. (2003). The mother-offspring relationship as a template in social development: reconciliation in captive brown capuchins (Cebus apella). J Comp Psychol, 117(1), 101–110.
Abstract: Mother-offspring (MO) relationship quality was investigated to determine its influence on the development of reconciliation--affiliation between opponents shortly after a fight--because it influenceswhat distressed youngsters learn about calming down. Data were longitudinal and cross-sectional observational samples of 38 MO pairs of monkeys across 24 months. An MO relationship quality index (RQI) classified each pair as secure or insecure. Reconciliation emerged in infancy.Secure youngsters had an appeasing conciliatory style, and insecure youngsters had an agitated conciliatory style. Conclusions are that reconciliation develops from the attachment behavior system and MO RQI is related to the particular conciliatory style youngsters develop by affecting how aroused they are by conflict and the subsequent socializing they seek to calm down.
|
|
Klein, E. D., & Zentall, T. R. (2003). Imitation and affordance learning by pigeons (Columba livia). J Comp Psychol, 117(4), 414–419.
Abstract: The bidirectional control procedure was used to determine whether pigeons (Columba livia) would imitate a demonstrator that pushed a sliding screen for food. One group of observers saw a trained demonstrator push a sliding screen door with its beak (imitation group), whereas 2 other groups watched the screen move independently (possibly learning how the environment works) with a conspecific either present (affordance learning with social facilitation) or absent (affordance learning alone). A 4th group could not see the screen being pushed (sound and odor control). Imitation was evidenced by the finding that pigeons that saw a demonstrator push the screen made a higher proportion of matching screen pushes than observers in 2 appropriate control conditions. Further, observers that watched a screen move without a demonstrator present made a significantly higher proportion of matching screen pushes than would be expected by chance. Thus, these pigeons were capable of affordance learning.
Keywords: Animals; *Behavior, Animal; Columbidae; Cues; *Imitative Behavior; *Learning; Odors; Sound
|
|
Call, J., Brauer, J., Kaminski, J., & Tomasello, M. (2003). Domestic dogs (Canis familiaris) are sensitive to the attentional state of humans. J Comp Psychol, 117(3), 257–263.
Abstract: Twelve domestic dogs (Canis familiaris) were given a series of trials in which they were forbidden to take a piece of visible food. In some trials, the human continued to look at the dog throughout the trial (control condition), whereas in others, the human (a) left the room, (b) turned her back, (c) engaged in a distracting activity, or (d) closed her eyes. Dogs behaved in clearly different ways in most of the conditions in which the human did not watch them compared with the control condition, in which she did. In particular, when the human looked at them, dogs retrieved less food, approached it in a more indirect way, and sat (as opposed to laid down) more often than in the other conditions. Results are discussed in terms of domestic dogs' social-cognitive skills and their unique evolutionary and ontogenetic histories.
|
|
Stoinski, T. S., & Whiten, A. (2003). Social learning by orangutans (Pongo abelii and Pongo pygmaeus) in a simulated food-processing task. J Comp Psychol, 117(3), 272–282.
Abstract: Increasing evidence for behavioral differences between populations of primates has created a resurgence of interest in examining mechanisms of information transfer between individuals. The authors examined the social transmission of information in 15 captive orangutans (Pongo abelii and Pongo pygmaeus) using a simulated food-processing task. Experimental subjects were shown 1 of 2 methods for removing a suite of defenses on an “artificial fruit.” Control subjects were given no prior exposure before interacting with the fruit. Observing a model provided a functional advantage in the task, as significantly more experimental than control subjects opened the fruit. Within the experimental groups, the authors found a trend toward differences in the actual behaviors used to remove 1 of the defenses. Results support observations from the wild implying horizontal transfer of information in orangutans and show that a number of social learning processes are likely to be involved in the transfer of knowledge in this species.
|
|
Horowitz, A. C. (2003). Do humans ape? Or do apes human? Imitation and intention in humans (Homo sapiens) and other animals. J Comp Psychol, 117(3), 325–336.
Abstract: A. Whiten, D. M. Custance, J.-C. Gomez, P. Teixidor, and K. A. Bard (1996) tested chimpanzees' (Pan troglodytes) and human children's (Homo sapiens) skills at imitation with a 2-action test on an “artificial fruit.” Chimpanzees imitated to a restricted degree; children were more thoroughly imitative. Such results prompted some to assert that the difference in imitation indicates a difference in the subjects' understanding of the intentions of the demonstrator (M. Tomasello, 1996). In this experiment, 37 adult human subjects were tested with the artificial fruit. Far from being perfect imitators, the adults were less imitative than the children. These results cast doubt on the inference from imitative performance to an ability to understand others' intentions. The results also demonstrate how any test of imitation requires a control group and attention to the level of behavioral analysis.
|
|
Shapiro, A. D., Janik, V. M., & Slater, P. J. B. (2003). A gray seal's (Halichoerus grypus) responses to experimenter-given pointing and directional cues. J Comp Psychol, 117(4), 355–362.
Abstract: A gray seal (Halichoerus grypus) was trained to touch a target on its left or right by responding to pointing signals. The authors then tested whether the seal would be able to generalize spontaneously to altered signals. It responded correctly to center pointing and head turning, center upper body turning, and off-center pointing but not to head turning and eye movements alone. The seal also responded correctly to brief ipsilateral and contralateral points from center and lateral positions. Pointing gestures did not cause the seal to select an object placed centrally behind it. Like many animals in similar studies, this gray seal probably did not understand the referential character of these gestures but rather used signal generalization and experience from initial operant conditioning to solve these tasks.
|