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1.  Examination of prior contest experience and the retention of winner and loser effects 
Behavioral Ecology  2010;21(2):404-409.
In many animal taxa, prior contest experience affects future performance such that winning increases the chances of winning in the future (winner effect) and losing increases the chances of losing in the future (loser effect). It is, however, not clear whether this pattern typically arises from experience effects on actual or perceived fighting ability (or both). In this study, we looked at winner and loser effects in the jumping spider Phidippus clarus. We assigned winning or losing experience to spiders and tested them against opponents of similar fighting ability in subsequent contests at 1-, 2-, 5-, and 24-h intervals. We examined the strength of winner and loser effects, how long effects persist, as well as how experience affected perceived and actual fighting ability. Our results demonstrate that winner and loser effects are of approximately the same magnitude, although loser effects last longer than winner effects. Our results also demonstrate that previous experience alters actual fighting ability because both the assessment and escalation periods were affected by experience. We suggest that the retention time of experience effects depends on expected encounter rates as well as other behavioral and ecological factors. In systems with short breeding seasons and/or rapidly fluctuating populations, context-dependent retention of experience effects may allow males to track their status relative to the fluctuating fighting ability of local competitors without paying the costs necessary to recall or assess individual competitors.
PMCID: PMC2821427  PMID: 22476369
contest experience; fighting ability; male–male competition; perceived RHP; Phidippus clarus; winner and loser effect
2.  Experience affects the outcome of agonistic contests without affecting the selective advantage of size 
Animal behaviour  2009;77(6):1533-1538.
In the field, phenotypic determinants of competitive success are not always absolute. For example, contest experience may alter future competitive performance. As future contests are not determined solely on phenotypic attributes, prior experience could also potentially alter phenotype–fitness associations. In this study, we examined the influence of single and multiple experiences on contest outcomes in the jumping spider Phidippus clarus. We also examined whether phenotype–fitness associations altered as individuals gained more experience. Using both size-matched contests and a tournament design, we found that both winning and losing experience affected future contest success; males with prior winning experience were more likely to win subsequent contests. Although experience was a significant determinant of success in future contests, male weight was approximately 1.3 times more important than experience in predicting contest outcomes. Despite the importance of experience in determining contest outcomes, patterns of selection did not change between rounds. Overall, our results show that experience can be an important determinant in contest outcomes, even in short-lived invertebrates, and that experience alone is unlikely to alter phenotype–fitness associations.
PMCID: PMC2699276  PMID: 20161296
jumping spider; multiple competition; Phidippus clarus; previous experience; selection gradient; tournament design
3.  Assessment during aggressive contests between male jumping spiders 
Animal behaviour  2008;76(3):901-910.
Assessment strategies are an important component in game theoretical models of contests. Strategies can be either based on one’s own abilities (self assessment) or on the relative abilities of two opponents (mutual assessment). Using statistical methodology that allows discrimination between assessment types, we examined contests in the jumping spider Phiddipus clarus. In this species, aggressive interactions can be divided into ‘pre-contact’ and ‘contact’ phases. Pre-contact phases consist of bouts of visual and vibratory signaling. Contact phases follow where males physically contact each other (leg fencing). Both weight and vibratory signaling differences predicted winners with heavier and more actively signaling males winning more contests. Vibratory behaviour predicted pre-contact phase duration, with higher signaling rates and larger differences between contestants leading to longer pre-contact interaction times. Contact phase duration was predicted most strongly by the weight of losing males relative to that of winning males, suggesting that P. clarus males use self-assessment in determining contest duration. While a self-assessment strategy was supported, our data suggest a secondary role for mutual assessment (“partial mutual assessment”). After initial contest bouts, male competitors changed their behaviour. Pre-contact and contact phase durations were reduced while vibratory signaling behaviour in winners was unchanged. In addition, only vibratory signaling differences predicted winners in subsequent bouts suggesting a role of experience in determining contest outcomes. We suggest that the rules and assessment strategies males use can change depending on experience and that assessment strategies are likely a continuum between self- and mutual assessment.
PMCID: PMC2598435  PMID: 19727331
4.  Screening for cancer with computed tomography 
BMJ : British Medical Journal  2003;326(7404):1457-1458.
PMCID: PMC1126331  PMID: 12829567

Results 1-4 (4)