Cross-country relationships between life expectancy,intertemporal choice and age at first birth

Humans, like other animals, typically discount the value of delayed rewards relative to those available in the present. From an evolutionary perspective, prioritising immediate rewards is a predictable response to high local mortality rates, as is an acceleration of reproductive scheduling. In a sample of 46 countries, we explored the cross-country relationships between average life expectancy, intertemporal choice, and women's age at first birth. We find that, across countries, lower life expectancy is associated with both a smaller percentage of people willing to wait for a larger but delayed reward, as well as a younger age at first birth. These results, which hold when controlling for region and economic pressure (GDP-per capita), dovetail with findings at the individual level to suggest that life expectancy is an important ecological predictor of both intertemporal and reproductive decision-making.     

The stay/switch model describes choice among magnitudes of reinforcers

The stay/switch model is an alternative to the generalized matching law for describing choice in concurrent procedures. The purpose of the present experiment was to extend this model to choice among magnitudes of reinforcers. Rats were exposed to conditions in which the magnitude of reinforcers (number of food pellets) varied for staying at alternative 1, switching from alternative 1, staying at alternative 2 and switching from alternative 2. A changeover delay was not used. The results showed that the stay/switch model provided a good account of the data overall, and deviations from fits of the generalized matching law to response allocation data were in the direction predicted by the stay/switch model. In addition, comparisons among specific conditions suggested that varying the ratio of obtained reinforcers, as in the generalized matching law, was not necessary to change the response and time allocations. Other comparisons suggested that varying the ratio of obtained reinforcers was not sufficient to change response allocation. Taken together these results provide additional support for the stay/switch model of concurrent choice.     

Some effects of procedural variables on operant choice behavior

Procedural variables are concerned with the way subjects contact stimulus, response, and reinforcer variables and relations in an experiment. Procedural variables may therefore be understood as tools that allow researchers and theorists to explore the generality of their conceptions of independent variables, behavioral processes, and quantitative laws of behavior. The present article reviews data from several studies showing how procedural variables can influence the outcome of operant choice experiments, even when nominal independent variables remain constant. An important theoretical issue raised by these data is whether researchers have most usefully identified the independent variables that they incorporate into their quantitative models. Particular attention is paid to how procedural variables can influence the measure of reinforcement frequency over time that best correlates with the distribution of choice responding over time.     

Contingency discriminability and the generalized matching law describe choice on concurrent ratio schedules of wheel-running reinforcement

Belke (2010) showed that on concurrent ratio schedules, the difference in ratio requirements required to produce near exclusive preference for the lower ratio alternative was substantively greater when the reinforcer was wheel running than when it was sucrose. The current study replicated this finding and showed that this choice behavior can be described by the matching law and the contingency discriminability model. Eight female Long Evans rats were exposed to concurrent VR schedules of wheel-running reinforcement (30s) and the schedule value of the initially preferred alternative was systematically increased. Two rats rapidly developed exclusive preference for the lower ratio alternative, but the majority did not - even when ratios differed by 20:1. Analysis showed that estimates of slopes from the matching law and the proportion of reinforcers misattributed from the contingency discriminability model were related to the ratios at which near exclusive preference developed. The fit of these models would be consistent with misattribution of reinforcers or poor discrimination between alternatives due to the long duration of wheel running.     

Discounting the freedom to choose: implications for the paradox of choice

Organisms prefer to make their own choices. However, emerging research from behavioral decision making sciences has demonstrated that there are boundaries to the preference for choice. Specifically, many decision makers find an extensive array of choice options to be aversive, often leading to negative emotional states and poor behavioral outcomes. This study examined the degree to which human participants discounted hypothetical rewards that were (a) delayed, (b) probabilistic, and (c) chosen from a large array of options. The present results suggest that the "paradox of choice" effect may be explained within a discounting model for individual patterns of decision making.     

Dynamics of choice and frequency of environment change

Recent research has examined the effects on behavioral adjustment of a range of within-session changes in the reinforcer ratio available from two alternatives. Regularities between extended patterns of behavior (choice) and a distribution of food deliveries (expressed as a food-rate ratio) have emerged from such studies. To assess the generality of these findings, the present study manipulated rats' experience in the choice situation. Sixteen rats were divided into two groups of eight rats each. Seven non-signaled food-rate ratios were arranged to occur for responses on two concurrently available levers. Group 1 experienced a different food-rate ratio every day; each ratio provided 70 food deliveries, and none of the seven ratios operated for 2 consecutive days. Group 2 experienced the same sequence of food-rate ratios, except that each food-rate ratio remained in effect for 17 consecutive days (providing 70 food deliveries per session), after which a different food-rate ratio was selected for the next 17 sessions. In all cases, preference was adjusted to changes in food-rate ratios. Estimates of sensitivity to changes in food-rate ratios increased with an increasing number of sessions (i.e., experience in the choice situation).     

Four-alternative choice violates the constant-ratio rule

Six pigeons responded on a four-key concurrent variable-interval schedule in which a 27:9:3:1 distribution of reinforcers between the keys changed every 10 reinforcers. Their behaviour quickly came under the control of this changing four-way reinforcer ratio. However, preference between a pair of keys depended not only on the relative reinforcer rates on those keys, but also on the absolute levels of those rates. This contradicts the constant-ratio rule that underpins the matching approach to choice, but is predicted by a contingency-discriminability model that assumes that organisms may occasionally misattribute reinforcers to a response that did not produce them. Reinforcers produced strong preference pulses, or transient increases in responding on the just-reinforced key. Despite accurate tracking of the reinforcer ratio, reinforcers obtained late in components and from leaner keys still produced strong pulses, suggesting both extended and local control of behaviour. Patterns of switching between keys were graded and similarly controlled by the reinforcer rates on each key. Whether considered in terms of switching, local preference pulses, or extended preference, behaviour was controlled by a rapidly changing four-way reinforcer ratio in a graduated, continuous manner that is unlikely to be explained by a simple heuristic such as fix-and-sample.     

Effects of unpredictable changes in initial-link duration on choice and timing

Four pigeons responded in a concurrent-chains procedure in which terminal-link schedules were fixed-interval (FI) 10 s and FI 20 s. Across sessions, the location of the shorter terminal-link changed according to a pseudorandom binary sequence. Each session, the variable-interval initial-link schedule value was sampled from a uniform distribution that ranged from 0.01 to 30 s. On some terminal links, food was withheld to obtain measures of temporal control. Terminal-link delays determined choice (log initial-link response ratios) and timing (start and stop times on no-food trials) measures, which stabilized within the 1st half of each session. Preference for the shorter terminal-link delay was a monotonically decreasing function of initial-link duration. There was no evidence of control by initial-link durations from previous sessions.     

Nicotine consumption of several mouse strains using a two bottle choice paradigm

The two bottle choice paradigm provides a convenient method for the rapid screening of preferences of nicotine and a variety of other substances in rodents. A non-expensive, home-made bottle system with low fluid loss due to leakage or evaporation is introduced. Using this system, we tested nicotine preference of the mouse strains NMRI, C3H/J, DBA/2, ST/bJ, C57BL/6 and a cross between male A/J and female NMRI. Our results show different nicotine preference of tested mice with high nicotine preference of C57BL/6, a lower preference of C3H/J, A/J×NMRI, DBA/2 and NMRI and the lowest of ST/bJ.     

Effects of a parasitic nematode on male mate choice in a livebearing fish with a coercive mating system (western mosquitofish, Gambusia affinis)

Studies of choice in steady state have shown that sensitivity to reinforcement increases with increasing fixed-ratio changeover (FR CO) requirements. We assessed the generality of this finding with choice in transition. Food deliveries were programmed according to concurrent variable-interval (VI) schedules. Seven different VI pairs arranged ratios of food deliveries (left/right) of 27:1, 9:1, 3:1, 1:1, 1:3, 1:9, and 1:27 at a constant overall rate across components. Within sessions, all seven ratios were presented in random order. Each component lasted for 10 food deliveries; components were separated by 60-s blackouts. A changeover lever required 1, 2, 4, 8, 16, 32, and 64 responses to alternate between two main levers. Redeterminations to all FR COs, but 64 responses, were obtained in descending order. Choice adjusted rapidly to rapid changes in the reinforcer ratio, tracking the lever associated with the highest probability of reinforcer. Sensitivity to reinforcement increased with increasing FR CO, replicating the negatively accelerated function found in our earlier study. With successive reinforcers in components, however, sensitivity reached asymptote values sooner with the largest (8, 16, and 32 responses), than with the smallest (1, 2, and 4 responses), FR CO requirements.     

The empirical question of thresholds and mechanisms of mate choice

Summary Theoretical discussions concerning how animals might best sample and select mates have suggested that individuals could base decisions either on a sample of mates (sampled-based decisions) or on a threshold of comparison (threshold-based decisions). Recent theoretical work demonstrates that threshold-based mating decisions generate higher expected fitness than sample-based mating decisions when search costs exist. Empirical results from most unmanipulated systems, however, either conclude that females make sample-based decisions or are inconclusive. A few experimental studies designed to detect mating thresholds purport to demonstrate threshold-based choice but an examination of these studies indicates such conclusions were premature. We believe that few examples of threshold-based choice exist because protocols designed to identify mating thresholds were often inconsistent with models of threshold choice. We suggest that future empirical work strive not to document mating thresholdsper se. Rather, future work might best reveal decision rules by manipulating the distribution of quality among potential mates; such manipulations predict uniquely how females using sample-based and threshold-based decision rules should behave.     

DN2菌降解烟碱的动力学及其应用研究

研究了菌株DN2降解烟碱的特性和对烟草废弃物中烟碱的降解情况。结果表明,该菌降解烟碱的最适条件为接种量为5 %,温度30 ℃,初始pH值为6.5。在该条件下,对初始烟碱浓度为500 mg/L的降解过程进行考察。结果表明,未经烟碱诱导的降解曲线呈倒S曲线,半衰期为17.43 h;经烟碱诱导的降解曲线符合Eckenfelder动力学模型,半衰期为4.10 h。添加0.1 %(质量分数)葡萄糖,可提高菌株DN2的烟碱耐受浓度,达5000 mg/L。菌株DN2能够降解烟草废弃物水提液中的烟碱（烟碱含量约为2220 mg/L）,60 h时烟碱的降解率为95.22 %,表明该菌在治理烟碱污染环境方面具有应用价值。     

Choice between contingencies of variation: Effects of the requirement of variation upon preference

The present study investigated whether choices between contingencies of variation are affected by the degree of variability required. For such, five pigeons were exposed to a concurrent chain schedule. In the initial links, responses in one key initiated the terminal link with the most stringent variation requirement while responses in the other key initiated the terminal link with the least stringent variation requirement. In both terminal links, four-responses sequences were reinforced according to a variation criterion, which favored less frequent and less recent sequences. The probability of reinforcement in the terminal link with the least stringent criterion was manipulated in order to generate similar percentage and rate of reinforcers in both terminal links. Choices for the terminal link with the least stringent criterion were more frequent than choices for the terminal link with the most stringent criterion. It is possible that situations that demand lower levels of behavior variability are chosen due to the lower response cost correlated to those situations.     

Active Transport of Nicotine by the Isolated Choroid Plexus In Vitro

Abstract: In vitro , the transport of [¹⁴C]nicotine into the isolated choroid plexus, the anatomical locus of the blood–CSF barrier, was studied. The isolated rabbit choroid plexus accumulated [¹⁴C]nicotine by two processes: an active saturable transport process and a nonsaturable process. The [¹⁴C]nicotine accumulation process by choroid plexus was not due to binding or intracellular metabolism of the [¹⁴C]nicotine. The [¹⁴C]nicotine accumulation process in isolated choroid plexus was inhibited by weak bases, including tolazoline and lidocaine, but not by the weak acid probenecid. The accumulation process was decreased 60% by iodoacetate and dinitrophenol and by low temperatures. These results are consistent with previous autoradiographic evidence showing the choroid plexus concentrated [¹⁴C]nicotine in vivo , and suggest that the choroid plexus may transfer nicotine between blood and CSF in vivo .     

Nicotine Leads to Improvements in Behavioral Impairment and an Increase in the Nicotine Acetylcholine Receptor in Transgenic Mice

Nicotine is the principal psychoactive ingredient in cigarette smoke, and has been associated with health problems in humans. However, the pure form of nicotine may prove to be a valuable pharmaceutical agent for the treatment of AD. However, the beneficial effects of nicotine remain a matter of much controversy. In order to clarify this issue, 12-month-old transgenic mice, expressing neuron-specific enolase (NSE)-controlled APPsw, were treated with low, middle, and high doses of nicotine for 6 months. Herein, we have concluded that the nicotine-treated groups evidenced improvements in behavior and increases in the nicotine acetylcholine receptor, nAchRα7. These findings provide experimental evidence that nicotine effects an improvement in impaired memory, and that this improvement is associated with an increase in nAchRα7. Thus, nicotine may prove a good preventative or therapeutic modality for AD patients.     

一株高浓度烟碱降解菌的筛选、分离和初步鉴定

采用以烟碱为唯一碳源氮源的选择培养基,从烟草和植烟土壤中分离筛选出15株高浓度烟碱降解的菌株,其中菌株D9烟碱降解能力最强,其烟碱降解率为82%,耐受烟碱的最高浓度为8 g/L。经常规形态特征、16S rDNA同源序列以及系统进化树分析,初步鉴定该菌株为类似氧化微杆菌,命名为Microbacterium sp. GYC29。本研究为微生物降解烟碱的研究及应用提供了菌种资源。     

Body weight manipulation,reinforcement value and choice between sucrose and wheel running: A behavioral economic analysis

Twelve female Long-Evans rats were exposed to concurrent variable (VR) ratio schedules of sucrose and wheel-running reinforcement (Sucrose VR 10 Wheel VR 10; Sucrose VR 5 Wheel VR 20; Sucrose VR 20 Wheel VR 5) with predetermined budgets (number of responses). The allocation of lever pressing to the sucrose and wheel-running alternatives was assessed at high and low body weights. Results showed that wheel-running rate and lever-pressing rates for sucrose and wheel running increased, but the choice of wheel running decreased at the low body weight. A regression analysis of relative consumption as a function of relative price showed that consumption shifted toward sucrose and interacted with price differences in a manner consistent with increased substitutability. Demand curves showed that demand for sucrose became less elastic while demand for wheel running became more elastic at the low body weight. These findings reflect an increase in the difference in relative value of sucrose and wheel running as body weight decreased. Discussion focuses on the limitations of response rates as measures of reinforcement value. In addition, we address the commonalities between matching and demand curve equations for the analysis of changes in relative reinforcement value.     

尼古丁对牙周炎大鼠牙周膜成纤维细胞的毒性作用

目的:观察尼古丁对牙周炎大鼠牙周膜成纤维细胞(PDLFs)增殖的抑制作用及对细胞周期分布的影响,探讨尼古丁的细胞毒性作用,为口腔疾病的预防及治疗提供基础。方法:选取30只SD大鼠,采用丝线结扎联合口内接种细菌的方法建立牙周炎大鼠模型。将不同浓度的尼古丁分别作用于大鼠的牙周膜成纤维细胞(PDLFs)中,观察大鼠牙周组织的变化情况,MTT法测定细胞增殖活性,分析不同浓度尼古丁对PDLFs增殖的抑制作用。结果:实验组大鼠牙周组织胶原纤维束排列紊乱,有炎症细胞浸润;对照组大鼠牙龈未见红肿或出血。尼古丁可抑制PDLFs增殖,并且呈浓度依赖性,随着浓度的增加,对PDLFs增殖的抑制作用增强,差异具统计学意义(P0.05)。与对照组相比,不同浓度尼古丁作用下牙周炎大鼠牙周膜成纤维细胞周期的分布率明显不同(P0.05)。结论:尼古丁对牙周膜成纤维细胞增殖具有明显的抑制作用,尼古丁的浓度影响牙周组织的修复重构能力。