THE β-STRATEGY: AN ALTERNATIVE AND POWERFUL COGNITIVE STRATEGY WHEN PERFORMING SENSORY DISCRIMINATION TESTS

For discrimination tests not requiring the nature of the difference to be specified in the instructions, such as the triangle, duo-trio and same-different protocols, it is usually assumed that the decision rule used by the subject in order to generate an answer involves the comparison of the relative sensory distances between the samples. However, there is evidence that an alternative cognitive strategy, the β-strategy, involving the absolute categorization of the sensations could be used by the subject when performing these protocols. This paper introduces the characteristics of this alternative strategy by discussing its statistical power (higher than the traditional strategies) and by describing means of investigating which strategy is used by the subject during an experiment as well as illustrating the experimental conditions that might facilitate the use of this particular decision rule.     

Off‐host aggregation in the non‐fed,female brown dog tick,Rhipicephalus sanguineus (Latreille), is induced by tick excreta and enhanced by low relative humidity

We report that Rhipicephalus sanguineus (Ixodida: Ixodidae) faeces and its main component, guanine, act as assembly pheromones in short‐range Petri plate bioassays. Arrestment activity in response to guanine was lower than that in response to natural excreta, indicating the presence of other active ingredients in natural excreta. The selective removal of appendages was used to establish the important roles played by the palps and the front pair of legs in the detection of the pheromone. Reaction to chemically pure guanine at varying concentrations occurred without a dose response; thus only the presence of guanine, not a critical amount, is required to induce assembly. Higher speed and intensity of clustering occurred at 33% relative humidity (RH). We conclude that female adults of R. sanguineus are more prone to assemble under dry conditions that match the arid microhabitats preferred by this species and that this tendency allows this tick to reside in human dwellings and dog kennels that maintain standards of comfort at 30–50% RH. Cleaning or removing tick excreta‐covered surfaces on which ticks aggregate from within and around human dwellings may prove useful as a means of interfering with the establishment of off‐host clusters of R. sanguineus.