Summary: Rivera-Gutierrez et al. (2010)

Birdsong, a multifaceted signal consisting of many traits (each under sexual selection pressure), plays an important role in both female mate choice and male-male competition. 3 hypotheses have been proposed to explain the expression of these traits: 1) one trait signals one aspect of male quality, therefore many traits represent a multidimensional message (multiple-messages hypothesis); 2) each trait signals only partial information, therefore many traits signal redundant information (redundant-signal hypothesis); 3) traits do not provide reliable information about male quality but are retained because they are not costly to produce (unreliable-information hypothesis). Rivera-Gutierrez et al. (2010) investigated whether the various components of song of 58 great tits (Parus major) was expressed differently in relation to 3 indicators of male quality (age, condition survival). They found support for all 3 hypotheses, concluding that great tit song is a multidimensional signal conveying multiple, redundant and unreliable information about male quality.

Summary: Sobel et. al (2001)

Parkinson's disease is a disorder characterised by a progressive loss of neuronal structure or function. It has a primary influence on motor control, although Parkinson's disease may also affect both cognitive and sensory processing. Patients with Parkinson's disease have recognised olfactory impairments, however, Sobel et al. (2001) suggest that this is partly a sniffing impairment. Whereas olfaction integrates both sensory and motor information, sniffing is primarily a physical or motor action. Sobel et al. (2001) tested 40 people (20 with Parkinson's and 20 age-matched healthy controls) in four olfactory tests and found that people with Parkinson's disease at lower sniff airflow rate and volume, thus were impaired at sniffing. This suggests that sniffing is a vital component of human olfaction and is thus an important component of the olfactory impairment seen in Parkinson's disease patients.

Summary: Thünken et al. 2010

Offspring survival and future reproduction can be enhanced through the provision of parental care, which also serves to increase the inclusive fitness of the parents. Parental investment theory predicts that parents should alter the level of care they provide to young based on the quality of the brood (i.e. the reproductive value) and should trade-off current investment with future care if this is likely to enhance their own lifetime reproductive success. Thünken et al. (2010) investigated this theory in the cichlid fish Pelvicachromis taeniatus, a species characterised by intense biparental brood care. They manipulated offspring quality by altering food availability (not for adults) and compared the response of parents to offspring over a period of 4 weeks. Although females generally showed higher levels of care than males, overall parental care decreased with time as offspring matured and became less vulnerable to predation. Interestingly, parents of low-quality broods (smaller average body size) showed a greater reduction in care than parents of high-quality broods, providing support for parental investment theory. Furthermore, females raising high-quality broods were more aggressive to their mating partners than females raising low-quality broods. By adjusting care relative to brood quality, parents can conserve energy for subsequent reproductive events.

Summary: Ramm & Stockley (2009)

Sperm competition theory predicts that males will respond to an increased risk of sperm competition from rivals by increasing sperm allocation and predicts that the increase in allocation will be lower when rivals are related. Furthermore, scent-based cues could provide information on the presence and identity of conspecifics and could serve as a basis for adjusting sperm allocation. Ramm & Stockley (2009) investigated whether male house mice (Mus musculus domesticus) adjust sperm allocation in response to odour-based cues of rival males present in the environment and whether they vary sperm allocation decisions according to the relatedness of rival males. In contrast to the predictions made by sperm competition theory, Ramm & Stockley (2009) found no evidence that male house mice adjust the number of sperm allocated to an ejaculate in response to odour-based cues of immediate sperm competition risk, even though male mice were sensitive to the odour cues from rival males. They suggest that the response to cues of sperm competition risk may display considerable interspecific variability.