A test of the reproductive cost hypothesis for sexual size dimorphism in Yarrow's spiny lizard Sceloporus jarrovii.

1. Trade-offs between reproduction and growth are central assumptions of life-history theory, but their implications for sexual size dimorphism (SSD) are poorly understood. 2. Adult male Yarrow's spiny lizards Sceloporus jarrovii average 10% larger than adult females. In a low-altitude (1700 m) population, this SSD develops because males grow more quickly than females during the first year of life, particularly during the first female reproductive season. This study tests the hypothesis that SSD develops because female growth is constrained by energetic costs of reproduction. 3. To test for a growth cost of reproduction, I compared growth rates of free-living females that differed, either naturally or experimentally, in reproductive status. Females that naturally delayed reproduction until their second year grew more quickly than females that reproduced as yearlings, and ovariectomized yearlings grew more quickly and to larger sizes than reproductive controls. 4. To determine whether SSD develops in the absence of this inferred reproductive cost, I also studied a high-altitude (2500 m) population in which all females delay reproduction until their second year. Sex differences in growth trajectories were similar to those observed at low altitude, such that males averaged 10% larger than females even prior to female reproduction. 5. Although female growth may be constrained by reproduction, multiple lines of evidence indicate that this cost is insufficient to explain the full magnitude of SSD in S. jarrovii. First, differences in growth of reproductive and nonreproductive females are not observed until the final month of gestation, by which time SSD is already well developed. Second, the growth benefit accruing from experimental inhibition of reproduction accounts for only 32% of the natural sex difference in body size. Finally, SSD develops well in advance of female reproduction in a high-altitude population with delayed maturation.

Personality and the subjective assessment of hearing aids.

Relatively little is known about the influence of patients' personality features on the responses they make to self-assessment items used to measure the outcome of a hearing aid fitting. If the personality of the hearing aid wearer has a significant influence on self-report outcome data, it would be important to explore the relevant personality variables and to be cognizant of their effects when using subjective outcome data to justify decisions about clinical services or other matters. This investigation explored the relationship between several personality attributes and responses to the Abbreviated Profile of Hearing Aid Benefit (APHAB). It found that more extroverted patients tend to report more hearing aid benefit in all speech communication situations. In addition, patients with a more external locus of control tend to have more negative reactions to loud environmental sounds, both with and without amplification. Anxiety also played a small additional role in determining APHAB responses. Although personality variables were found to explain a relatively small amount of the variance in APHAB responses (usually around 10%), these outcomes should alert practitioners and researchers to the potential effects of personality variables in all self-report data.