Life-cycle preferences over consumption and health: when is cost-effectiveness analysis equivalent to cost-benefit analysis?

This paper studies life-cycle preferences over consumption and health status. We show that cost-effectiveness analysis is consistent with cost-benefit analysis if the Lifetime utility function is additive over time, multiplicative in the utility of consumption and the utility of health status, and if the utility of consumption is constant over time. We derive the conditions under which the lifetime utility function takes this form, both under expected utility theory and under rank-dependent utility theory, which is currently the most important nonexpected utility theory. If cost-effectiveness analysis is consistent with cost-benefit analysis, it is possible to derive tractable expressions for the willingness to pay for quality-adjusted life-years (QALYs). The willingness to pay for QALYs depends on wealth, remaining life expectancy, health status, and the possibilities for intertemporal substitution of consumption. (C) 1999 Elsevier Science B.V. All rights reserved.

Prey capture and accommodation in the sandlance, Limnichthyes fasciatus (Creediidae; Teleostei)

The eyes of the sandlance, Limnichthyes fasciatus (Creediidae. Teleostei) move independently and possess a refractive cornea, a convexiclivate fovea and a non-spherical lens giving rise to a wide separation of the nodal point from the axis of rotation of the eye much like that of a chameleon. To investigate this apparent convergence of the visual optics in these phylogenetically disparate species, we examine feeding behaviour and accommodation in the sandlance with special reference to the possibility that sandlances use accommodation as a depth cue to judge strike length. Frame-by-frame analysis of over 2000 strikes show a 100% success rate. Explosive strikes are completed in 50 ms over prey distances of four body lengths. Close-up video confirms that successful strikes can be initiated monocularly (both normally and after monocular occlusion) showing that binocular cues are not necessary to judge the length of a strike. Additional means of judging prey distance may also be derived from parallax information generated by rotation of the eye as suggested for chameleons. Using photorefraction on anaesthetised sandlances, accommodative changes were induced with acetylcholine and found to range between 120 D and 180 D at a speed of 600-720 D s(-1). The large range of accommodation (25% of the total power) is also thought to be mediated by corneal accommodation where the contraction of a unique cornealis muscle acts to change the corneal curvatures.

Size-based predation by kookaburras (Dacelo novaeguineae) on lizards (Eulamprus tympanum : Scincidae): what determines prey vulnerability?

Lizards and birds are both popular model organisms in behavioural ecology, but the interactions between them have attracted little study. Given the putative importance of birds as predators of diurnal Lizards, it is of considerable interest to know which traits (of lizards as well as birds) influence the outcome of a predatory attempt. We studied predation by giant terrestrial kingfishers (kookaburras, Dacelo novaeguineae: Alcedinidae) on heliothermic diurnal lizards (highland water skinks, Eulamprus tympanum: Scincidae), with particular reference to the role of prey (lizard) size. Our approach was twofold: to gather direct evidence (sizes of lizards consumed in the field, compared to those available) and indirect evidence rite-related shifts in lizard behaviour). We quantified the size structure of a natural population of skinks (determined by an extensive mark-recapture program), and compared it to the sizes of wild lizards taken by kookaburras (determined by analysis of prey remains left at the birds' nests,. Kookaburras showed size-based predation: they preyed mainly on small and medium-sized rather than large lizards in the field. However, the mechanism producing this bias remains elusive. It is not due to any distinctive behavioural attributes (locomotor ability, activity level, habitat usage) of the lizards of the size class disproportionately taken by the kookaburras. The greater vulnerability of subadult lizards may reflect subtle ontogenetic shifts in ecological and behavioural traits, but our data suggest that great caution is needed in inferring patterns of vulnerability to predation from indirect measures based on either the prey or the predator alone. Instead, we need direct observations on the interaction between the two.

The effects of predator odors in mammalian prey species: A review of field and laboratory studies

wPrey species show specific adaptations that allow recognition, avoidance and defense against predators. For many mammalian species this includes sensitivity towards predator-derived odors. The typical sources of such odors include predator skin and fur, urine, feces and anal gland secretions. Avoidance of predator odors has been observed in many mammalian prey species including rats, mice, voles, deer, rabbits, gophers, hedgehogs, possums and sheep. Field and laboratory studies show that predator odors have distinctive behavioral effects which include (1) inhibition of activity, (2) suppression of non-defensive behaviors such as foraging, feeding and grooming, and (3) shifts to habitats or secure locations where such odors are not present. The repellent effect of predator odors in the field may sometimes be of practical use in the protection of crops and natural resources, although not all attempts at this have been successful. The failure of some studies to obtain repellent effects with predator odors may relate to (1) mismatches between the predator odors and prey species employed, (2) strain and individual differences in sensitivity to predator odors, and (3) the use of predator odors that have low efficacy. In this regard, a small number of recent studies have suggested that skin and fur-derived predator odors may have a more profound lasting effect on prey species than those derived from urine or feces. Predator odors can have powerful effects on the endocrine system including a suppression of testosterone and increased levels of stress hormones such as corticosterone and ACTH. Inhibitory effects of predator odors on reproductive behavior have been demonstrated, and these are particularly prevalent in female rodent species. Pregnant female rodents exposed to predator odors may give birth to smaller litters while exposure to predator odors during early life can hinder normal development. Recent research is starting to uncover the neural circuitry activated by predator odors, leading to hypotheses about how such activation leads to observable effects on reproduction, foraging and feeding. (c) 2005 Elsevier Ltd. All rights reserved.

Children and economic development: Family size, gender preferences and human capital formation - theory and Indian cases

In the light of Gary Becker's economic theory of the family, considers how economic cost and benefit factors can influence the size of families that parents decide to have. Some support for the importance of such factors is found from results of structured interviews with wives in Kondh-dominated villages in western Orissa. These results are at variance with the hypothesis of Malthus about population growth. Factors that may alter the optimal family size as development proceeds are discussed. It is found in our sampling that, on the whole, there is a preference for daughters rather than sons although this is not as strong in the Kondh-dominated villages as in poor villages in the Santal tribal belt of West Bengal. While in the Kondh-dominated villages some discrimination in access to education in favour of boys compared to girls is present, little such or no such discrimination occurs in relation to access to food and medical attention. In the villages surveyed in the West Bengal Santal tribal belt, discrimination in favour of boys is more pronounced than in the Kondh-dominated area in Orissa. While economic considerations help to explain gender discrimination between boys and girls, we find that social and cultural factors also play a major role. Parents in a similar economic situation seem to display substantially different patterns of gender discrimination between children depending on their social and cultural content. It seems that the extent to which economic theories of the family explain family preferences and behaviour depend significantly on the social and cultural context in which they are to be applied.

Psychometric evaluation of the Early/Late Preferences Scale

This paper examines the psychometric quality of the Early/Late Preferences Scale (PS) relative to that of the Composite Morningness Scale (CS). Questionnaires were completed by 670 undergraduate students aged 16-37 years (mean 22.5), of whom 64% were female. Both scales displayed satisfactory inter-item correlations and similar total mean scores to those reported previously, although the CS had higher variability. Principal axis factor analysis produced single-factor solutions for both scales, although loadings for Items 7 and 9 on the PS were low. Internal consistencies for both scales were good (PS=0.86, CS=0.90) with only a small improvement achieved by deleting Items 7 and 9 from the PS. Test-retest reliability over 11 weeks was good for both scales (PS=0.92, CS=0.89). Differences between morning, evening and intermediate groups in self-rated alertness at different times of day, and significant correlations with other indices of morning-evening orientation, provided evidence of validity for both scales. These results indicate that PS is psychometrically comparable with CS. In view of its simpler format and lower cultural specificity, PS may be considered a preferable measure for most applications.

Development of preferences for the human body shape in infancy

Two studies investigated the development of infants' visual preferences for the human body shape. In Study 1, infants of 12,15 and 18 months were tested in a standard preferential looking experiment, in which they were shown paired line drawings of typical and scrambled bodies. Results indicated that the 18-month-olds had a reliable preference for the scrambled body shapes over typical body shapes, while the younger infants did not show differential responding. In Study 2, 12- and 18-month-olds were tested with the same procedure, except that the typical and scrambled body stimuli were photographic images. The results of Study 2 again indicated that only the 18-month-olds had a reliable preference for the scrambled body shapes. This finding contrasts sharply with infants' precocious preferences for human faces, suggesting that infants' learning about human faces and human bodies follow different developmental trajectories. (C) 2002 Elsevier Science B.V. All rights reserved.