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PubMed1983

Cognitive characteristics of the type A coronary-prone behavior pattern.

Recent findings indicate that Type As attend more to tasks defined as central, and less to tasks defined as peripheral, than do Type Bs. If this A-B difference in allocation of attention occurs naturally, as well as in response to experimental instructions, it would have implications for other phenomena, such as the process of creating a category from a series of perceptual events. It was reasoned that across a series of acquisition stimuli, Type As, compared to Type Bs, would be more responsive to the development of central tendencies in the frequency of appearance of the attributes that comprise the stimuli. That is, Type As should be more attentive to frequently occurring attributes (by virtue of their centrality in the evolving category definition) and less attentive to rarely occurring attributes. This difference in attention should lead to a difference in encoding. On a subsequent recognition-memory task, then, Type As should report with greater certainty than Type Bs that they had seen stimuli composed of frequently observed attributes and should report with greater certainty that they had not seen stimuli composed of rarely observed attributes. In a test of this reasoning, students classified as As and Bs completed a concept-formation and recognition-memory task under one of four levels of situational challenge. The predicted patterns occurred among subjects in whom moderate and high levels of challenge had been induced. The findings thus support the arguments that As and Bs process information differently and that this processing difference must be elicited by situational challenge.

Attention↗
PubMed2005

Implicit and self-attributed motives to achieve: two separate but interacting needs.

This research examined how implicit and self-attributed needs to achieve (labeled as n Ach and san Ach, respectively) combine with self-referenced and norm-referenced feedback to predict effort-related (task performance) and choice-related (task continuation) indexes of students' engagement in a mental concentration task. In Experiment 1 the authors found that in a task-focused setting, task performance was predicted by the joint effect of self-referenced feedback and n Ach, whereas task continuation was predicted by the joint effect of norm-referenced feedback and san Ach. In Experiment 2 the authors found that in an ego-focused setting, n Ach and san Ach interacted in the prediction of task performance but not of task continuation. In Experiment 3 the authors found that the effects of n Ach and san Ach on students' performance were mediated by the anticipated affective value of achievement outcomes. These findings are discussed in relation to a 2-system approach to achievement motivation.

Achievement↗
PubMed2001

Food stealing by young Norway rats (Rattus norvegicus).

Six experiments were undertaken to explore factors affecting young rats' (Rattus norvegicus) frequencies of stealing food from conspecifics when identical food is available in surplus. It was found that (a) rats would walk across a bed of pellets to steal the particular pellet a peer was eating, (b) frequency of stealing within a pair did not decrease over days, (c) rats stole unfamiliar foods more frequently than familiar foods, (d) younger rats stole from older rats more frequently than older rats stole from younger ones, (e) hungry rats stole more frequently than replete rats, and (f) rats that had stolen a pellet of unfamiliar food from an anesthetized conspecific subsequently exhibited an enhanced preference for that food. Results suggest that food stealing is a mode of active seeking of information about what foods to eat.

Animals↗
PubMed2003

Sophisticated sperm allocation in male fowl.

When a female is sexually promiscuous, the ejaculates of different males compete for the fertilization of her eggs; the more sperm a male inseminates into a female, the more likely he is to fertilize her eggs. Because sperm production is limited and costly, theory predicts that males will strategically allocate sperm (1) according to female promiscuity, (2) saving some for copulations with new females, and (3) to females producing more and/or better offspring. Whether males allocate sperm in all of these ways is not known, particularly in birds where the collection of natural ejaculates only recently became possible. Here we demonstrate male sperm allocation of unprecedented sophistication in the fowl Gallus gallus. Males show status-dependent sperm investment in females according to the level of female promiscuity; they progressively reduce sperm investment in a particular female but, on encountering a new female, instantaneously increase their sperm investment; and they preferentially allocate sperm to females with large sexual ornaments signalling superior maternal investment. Our results indicate that female promiscuity leads to the evolution of sophisticated male sexual behaviour.

Animals↗
PubMed1994

The effects of cooperative and individualistic reward on intrinsic motivation.

The effects of cooperative versus individualistic reward on students' intrinsic motivation were investigated. The controlling aspects of extrinsic reward may be heightened or produce greater ego threat in the individualistic situation when compared with a group situation. We predicted that students in the cooperative social situation would show higher levels of intrinsic motivation. Fifth-grade students from existing cooperative groups were assigned randomly to receive a tangible reward based on either cooperative or individualistic achievement for completing pattern block designs. Cooperation affected intrinsic motivation positively. Students in the cooperative dyad solved the block designs more quickly, interacted positively, and viewed the task as easier than did those in the individualistic situation, and they reported that their peers were helpful. There was little evidence that the controlling functions of reward or ego-threat were factors in producing the outcome. Some evidence supporting the importance of the social nature of cooperation was provided.

Child↗
PubMed2004

Oviposition strategies, host coercion and the stable exploitation of figs by wasps.

A classic example of a mutualism is the one between fig plants (Ficus) and their specialized and obligate pollinating wasps. The wasps deposit eggs in fig ovules, which the larvae then consume. Because the wasps derive their fitness only from consumed seeds, this mutualism can persist only if the wasps are prevented from laying eggs in all ovules. The search for mechanisms that can limit oviposition and stabilize the wasp-seed conflict has spanned more than three decades. We use a simple foraging model, parameterized with data from two Ficus species, to show how fig morphology reduces oviposition rates and helps to resolve the wasp-seed conflict. We also propose additional mechanisms, based on known aspects of fig biology, which can prevent even large numbers of wasps from ovipositing in all ovules. It has been suggested that in mutualistic symbioses, the partner that controls the physical resources, in this case Ficus, ultimately controls the rate at which hosts are converted to visitors, regardless of relative evolutionary rates. Our approach provides a mechanistic implementation of this idea, with potential applications to other mutualisms and to theories of virulence.

Animals↗
PubMed2006

What's in it for me? Self-regard precludes altruism and spite in chimpanzees.

Sensitivity to fairness may influence whether individuals choose to engage in acts that are mutually beneficial, selfish, altruistic, or spiteful. In a series of three experiments, chimpanzees (Pan troglodytes) could pull a rope to access out-of-reach food while concomitantly pulling another piece of food further away. In the first study, they could make a choice that solely benefited themselves (selfishness), or both themselves and another chimpanzee (mutualism). In the next two experiments, they could choose between providing food solely for another chimpanzee (altruism), or for neither while preventing the other chimpanzee from receiving a benefit (spite). The main result across all studies was that chimpanzees made their choices based solely on personal gain, with no regard for the outcomes of a conspecific. These results raise questions about the origins of human cooperative behaviour.

Altruism↗
PubMed2004

Finger competition dynamics in rotating Hele-Shaw cells.

We report analytical results for the development of interfacial instabilities in rotating Hele-Shaw cells. We execute a mode-coupling approach to the problem and examine the morphological features of the fluid-fluid interface at the onset of nonlinear effects. The impact of normal stresses is accounted for through a modified pressure jump boundary condition. A differential equation describing the early nonlinear evolution of the interface is derived, being conveniently written in terms of three relevant dimensionless parameters: viscosity contrast A , surface tension B , and gap spacing b . We focus our study on the influence of these parameters on finger competition dynamics. It is deduced that the link between finger competition and A , B , and b can be revealed by a mechanism based on the enhanced growth of subharmonic perturbations. Our results show good agreement with existing experimental and numerical investigations of the problem both in low and high A<0 limits. In particular, it is found that the condition of vanishing A suppresses the dynamic competition between fingers, regardless of the value of B and b . Moreover, our study enables one to extract analytical information about the problem by exploring the whole range of allowed values for A , B , and b . Specifically, it is verified that pattern morphology is significantly modified when the viscosity contrast -1< or =A< or =1 varies: increasingly larger values of A>0 (A<0) lead to enhanced competition of outward (inward) fingers. Within this context the role of B and b in determining different finger competition behaviors is also discussed.

Journal Article↗
PubMed2004

Spatial distribution of competing ions around DNA in solution.

The competition of monovalent and divalent cations for proximity to negatively charged DNA is of biological importance and can provide strong constraints for theoretical treatments of polyelectrolytes. Resonant x-ray scattering experiments have allowed us to monitor the number and distribution of each cation in a mixed ion cloud around DNA. These measurements provide experimental evidence to support a general theoretical prediction: the normalized distribution of each ion around polyelectrolytes remains constant when ions are mixed at different ratios. In addition, the amplitudes of the scattering signals throughout the competition provide a measurement of the surface concentration parameter that predicts the competition behavior of these cations. The data suggest that ion size needs to be taken into account in applying Poisson-Boltzmann treatments to polyelectrolytes such as DNA.

Cations↗
PubMed2006

Health promotion and some implications of consumer choice.

AIM: To stimulate debate around how health promotion practices add to the choices confronting consumers in a health market place and some implications as a consequence. BACKGROUND: We live in a world characterized by consumerism, in which health professionals must compete with a wide array of other producers for the consumer's attention. EVALUATION: A critical review of consumer choice related to health applying theoretical insights from the works by Zygmunt Bauman. KEY ISSUES: Nurses working at influencing the health status of consumers at an individual level (whatever the setting) need to understand how to address the acknowledgement that people are confronted with a multiplicity of choices (good and bad) in their daily lives and from which they need to make a choice. How health promotion practices are 'sold' to consumers is an important consideration for nurses. CONCLUSIONS: The possibility for nurses to talk past consumers and vice versa exists. Choices made by consumers are premised on what is 'sold', how, by whom and why and has a lot to do with how to get the attention of the consumer.

Attitude to Health↗