Significant Increase In Preference Research Articles

Effects of colony need for water on optimal food choice in honey-bees

The effects of flower abundance on foraging selectivity were tested experimentally using honey-bees (Apis mellifera). Individual bees were offered a choice of artificial flowers, each containing either 20% or 40% sucrose solution, in either low or high flower density situations. From May to September an increase in flower density did not result in any statistically significant increase in preference for the 40% sucrose solution, whereas in October and November it did, as predicted qualitatively in models of optimal foraging theory. It was suggested that foraging selectivity is affected by the colony need for water, which is used for nest temperature regulation and for preparation of larval food. To test this hypothesis, we sprayed water into the beehive in September, there-by reducing drastically the colony need for water. After water had been sprayed, the bees foraged for the 40% sucrose solution more selectively in a high density situation than in a low density situation, whereas before spraying, this density effect had not been demonstrated. The foraging selectivity in honey-bees is discussed as a compromise between two conflicting colony needs: one for sugar, and one for water.

Attenuation of heroin reward in rats by disruption of the mesolimbic dopamine system.

The rewarding properties of systemically administered heroin were investigated with a conditioned place-preference paradigm. Reinforcing effects were observed with all doses of heroin tested (0.5, 1.0, 2.0 mg/kg) as indicated by a significant increase in preference for the place paired with drug injections. No similar change in preference was observed following saline injections. The rewarding effect of heroin (2 mg/kg) was attenuated by pretreatment with haloperidol (0.2 mg/kg), but haloperidol alone did not produce a place aversion. Lesions induced by 6-hydroxydopamine (6-OHDA) of the mesolimbic dopaminergic pathway at the level of the nucleus accumbens also attenuated the heroin-induced place preference. In contrast, depletion of central and peripheral noradrenaline induced by 6-OHDA had no significant effect on heroin-induced place preference. These data suggest an important role for the mesolimbic DA system in mediating the reinforcing effects of heroin.

Changes in Counseling Response Preference among Rehabilitation Counseling Interns

Counseling response preferences of graduate students completing internship requirements were assessed using Patterson's Rehabilitation Counseling Response Exercise during the first and final weeks of their internships at a comprehensive, multidisciplinary vocational rehabilitation center. It was hypothesized that at the end of the internship the students would show a significant increase in preference for active counseling responses and a correspondingly significant decrease in preferences for passive techniques. Five counseling responses were evaluated and change did occur as hypothesized.