Thursday , November 26 2020

The signaling theory of the house's sporadic status is no longer flies

For decades, evolutionary biologists have pointed to domestic vacillation as an example of the play hypothesis of the working situation.

But a multi-institutional study of ONSO is about to suggest such a theory for the birds.

The animal situation refers to the way in which physical characteristics convey information about the strength and rank of the individual in the group. Like stripes and badges in military uniform, physical signs in the animal world can tell other friends to be careful not to provoke the person who carries them.

In the world of birds, the size of the apron on the sparrow in the male house – a black stain on the feathers of the sparrow neck – was associated with the bird's level of influence in the herd. The greater the stamina, the better fighting ability, with the mites and the success of breeding some of the potential-related privileges.

Professor Shinichi Nakagawa of the School of Biological Biology and Land of Unso said that the signaling hypothesis describes a survival system designed to prevent unnecessary energy expenditure.

"Avoiding unnecessary battles is important so many species of animals have developed signals to indicate their fighting capabilities," says Professor Nakagawa.

"The size of the hairstyle of the house-known sparrows is an iconic example of such a status tag, often referred to as the" class tag. "

So it is common is this view of Dror Dror's behavior that Sir David Attenborough, in the acclaimed TV series Bird Life / (1998), devoted a few minutes of film to make an analogy between the size of sporadic fiber signs and the appropriate military rank.

But how much evidence should be linked to the size of the apron and the status of bands of sparrows at home?

Not much, the study says.

In a meta-analysis of published and unpublished studies since the idea first surfaced in the 1980s, Professor Nekegawa and his international colleagues found several trends that cast doubt on the power of the original hypothesis.


UnSW Associate Professor Shinichi Nakagawa was involved in the papers that confirmed then rejected the idea of ​​a spindle size in sparrows correlated with class.

The first was that the data published from each subsequent study examining the hypothesis showed a gradual decrease in correlation between the evidence and the original theory. In other words, as more and more data rolled over time, less and less correlation was found.

"This is a well-known phenomenon called 'bias of time-retardation'," says Professor Nakagawa.

"The initial findings usually come from a small sample size study with a large effect, but later studies with a larger sample size can reveal that the real effect is much smaller than the initial finding."

The effect size (ie, the correlation) is a measure between 1 and 1 where a score of 1 indicates a perfect positive relationship between the size of the male and the social ranks, 0 represents no one, and 1 shows a perfect negative correlation. The researchers found that in published studies, the effect size "decreased over time, and recently published effects were, on average, no longer detectable from zero."

But perhaps most was the analysis of data from unpublished studies. Not only did the size of the male's apron be less correlated with the dominant behavior observed, but the authors suspected that this was an example of "advertising bias."

A / Professor Nakagawa explains:

"The bias in advertising is a place where insignificant results, such as the inability to find a relationship or negative results, are less important," he says.

"There are many reasons for this, but two main reasons are: First, journals are less likely to get negative results as authors might have" wrong "research designs or sample size too small to detect an effect and secondly, authors do not bother publishing for the same reasons.

Interestingly, A / Professor Nakagawa was involved in earlier published studies that supported the idea of ​​gut size correlated with signal signaling.

"The original meta-analysis took place during my doctoral dissertation more than a decade ago," says Professor Nakagawa.

"Yes, I did find a strong connection between the size of the apron and the male social ranking, but I used the work that was published until then," he said.

"What it shows is the importance of updating meta-analysis."

So if there is any doubt about the relationship between the male size of the male house and the status, does the sign mean anything at all? A / Professor Nakagawa believes they do, and says this will be the subject of further research.

"One thing we know for certain is that the size of the apron is an age indicator," he says.

"Also, females seem to prefer older men as their partner, especially when it comes to mating another pair, but we do not really know if the females are using the size of the gutter to assess the age of the male or not, so it would be great to find it."

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