Estrus induction in four species of voles (Microtus).

Male-induced estrus was examined in montane (Microtus montanus), meadow (M. pennsylvanicus), prairie (M. ochrogaster), and pine (M. pinetorum) voles. Duration of male contact needed for receptivity, effects of parity, and vaginal cytology were assessed. Among nulliparous females, montane voles attained receptivity with less male contact than prairie voles. Meadow and pine voles showed very low receptivity rates. Among parous females, montane and meadow voles did not differ in duration of male contact needed for receptivity and required less than prairie voles. Overall, parous females had higher receptivity rates than nulliparous females. When isolated from males, prairie and pine voles had more leukocytes and fewer cornified cells in vaginal smears than montane or meadow voles. Species differences in estrus induction are discussed in relation to species differences in social organization.     

The effects of cross-fostering on the development of social preferences in meadow voles (Microtus pennsylvanicus)

To determine the role of the parental environment in the formation of species attachments in the meadow vole (Microtus pennsylvanicus), young of this species were fostered to either meadow vole parents (in-fostered young) or to prairie vole parents (M. ochrogaster; cross-fostered young). At 50 to 60 days of age, subjects were tested for social preference in an environment that simulated the conditions of a runway system. The testing design assessed the reaction of fostered animals to a novel species (M. pinetorum) as well as to the parental and biological species. The proportion of total test time spent near stimulus animals did not vary as a function of rearing condition. However, when compared to in-fostered controls, cross-fostered meadow voles displayed increased preference for prairie voles. Novelty did not appear to be a significant factor in test animal choice. These results suggest that in meadow voles, preference for the species of social partner is dependent on postnatal experience with parents.     

Social transmission and memory of food preferences in pine voles (Microtus pinetorum)

The social transmission of food preferences is affected by factors including the length of time a preference is maintained. The authors investigated the social transmission of food preferences in pine voles (Microtus pinetorum) and whether food items had to be present for memory to persist. A demonstrator vole was fed cocoa-flavored food, a nonpreferred food. After interacting with a demonstrator vole, observer voles preferred cocoa-flavored food as compared with either naive voles that had not interacted with demonstrators or voles that had been exposed to odors. Observers retained this preference for 72 hr after interacting with an observer whether or not flavored foods were present. The ability to learn which food items are palatable and safe may benefit a generalist herbivore that has faced selection to avoid toxic baits.     

Seasonal changes in open-field behavior in wild male meadow voles (Microtus pennsylvanicus)

Open-field behavior of free-living meadow voles was measured in males held overnight in the laboratory. Movement variables were positively correlated, and had negative associations with grooming and freezing. Parameters including activity, freezing, urinating, and grooming showed annual fluctuations related to the reproductive season. Together with the results of a previous study showing castration of wild voles results in altered open-field behavior, these results emphasize the role of testicular hormones in influencing this behavior. Factor analysis identified an activity component accounting for 39% of the variation, but other parameters were little simplified by this procedure. Most factors cycled annually, and significant variation was found in all eight factors during the 4-year sample. Open-field behavior varied between different reproductive and age segments of the population, and may be related to population processes such as dispersal.     

A possible function of the preference for hind nipples in prairie voles (Microtus ochrogaster)

Prairie vole pups (Microtus ochrogaster) in laboratory cages prefer hind nipples. In this research, the author observed 8 litters of prairie voles in a seminatural environment to confirm the preference for hind nipples and to determine if young on hind nipples were groomed more frequently or dislodged less frequently than were young on other nipples. Prairie vole pups in seminatural environments preferred hind nipples; this preference was illustrated by the progressive use of more anterior nipples only as litter size increased and by the reluctance of pups to voluntarily release their hold on hind nipples. Maternal grooming of young did not vary with suckling location. Prairie vole young on hind nipples, however, were dislodged less frequently than were young on other nipples. Less frequent dislodgment from hind nipples during maternal movements may play a role in the preference for hind nipples in prairie voles.     

Sex differences in spatial ability and activity in two vole species (Microtus ochrogaster and M. pennsylvanicus)

The hypothesis that sex differences in maze learning result from sex differences in activity was tested with wild-caught prairie (Microtus ochrogaster) and meadow (M. pennsylvanicus) voles. For 38 voles error production and activity were simultaneously measured in a series of 7 symmetrical mazes. Repeated-measures analyses of variance (ANOVAS) examined species, sex, maze, and interaction effects for 3 dependent variables: errors, activity, and errors/activity. The pattern of significant effects was very different for the errors and activity ANOVAS, which suggests that differential activity cannot explain differential error rates. In contrast, the pattern of effects was very similar for errors and errors/activity ANOVAS, which suggests that controls for activity do not remove differences in error production. These results fail to support the activity hypothesis.     

Social influences on parental and nonparental responses toward pups in virgin female prairie voles (Microtus ochrogaster)

Pair-bonded prairie voles (Microtus ochrogaster) are biparental after the birth of pups. However, whereas most adult virgin males are parental, most virgin females are not. In 6 experiments, influences on the parental behavior of virgin female prairie voles were examined. It was found that (a) young virgin females were more maternal than older females, (b) the postweaning sex ratio of cage-mates did not affect females' responses to pups, (c) females raised to adulthood with their parents and younger siblings present were highly parental, (d) 48-hr exposure to pups beginning at weaning increased some aspects of later maternal responding, (e) rearing to adulthood with the parents even in the absence of younger siblings also increased females' maternal responding, and (f) the increase was seen only if both parents were present. Continued parental presence promotes alloparental behavior, possibly important if daughters do not disperse from the natal nest.     

Sexual activity and satiety over an extended observation period in prairie voles (Microtus ochrogaster)

This study was designed to delineate the course of sexual satiation in prairie voles (Microtus ochrogaster). Fourteen male-female pairs were allowed to copulate freely for 24 hr under continuous observation. Copulations occurred predominantly during the first few hours and decreased in frequency thereafter. The mean number of ejaculations per pair was 5.6 (range, 2-9). Two thirds of the ejaculations occurred during the first 3 hr, and over 90% took place within the first 7 hr after the first intromission. No ejaculations were observed during the last 8 hr. These results suggest that male capacity to deliver ejaculations to a female is limited and that direct observations reveal a more limited capacity than observations made with time-lapse videotape.     

On two types of deviation from the matching law: bias and undermatching

Data on choice generally conform closely to an equation of the form: log(B₁/B₂)=a log(r₁/r₂+log k, where B₁ and B₂ are the frequencies of responding at Alternatives 1 and 2, r₁ and r₂ are the obtained reinforcement from Alternatives 1 and 2, and a and k are empirical constants. When a and k equal one, this equation is equivalent to the matching relation: B₁/B₂=r₁/r₂. Two types of deviation from matching can occur with this formulation: a and k not equal to one. In some experiments, a systematically falls short of one. This deviation is undermatching. The reasons for undermatching are obscure at present. Some evidence suggests, however, that factors favoring discrimination also favor matching. Matching (a=1) may represent the norm in choice when discrimination is maximal. When k differs from one, its magnitude indicates the degree of bias in choice. The generalized matching law predicts that bias should take this form (adding a constant proportion of responding to the favored alternative). Data from a variety of experiments indicate that it generally does.     

Differences in affiliative behavior, pair bonding, and vaginal cytology in two species of vole (Microtus ochrogaster and M. montanus)

Prairie voles (Microtus ochrogaster) and montane voles (M. montanus) display marked differences in social organization in the field. Trios of 1 male and 2 females were studied in a large enclosure for a 10-day period. Prairie voles spent 59% of the observation time in side-by-side contact, whereas montane voles spent only 7% of the time in contact. Vaginal smears indicated female-female suppression of estrus in prairie voles; female montane voles appeared to cycle in the presence of males. Male prairie voles preferentially paired and nested with 1 of the females, and vaginal estrus generally followed pair formation by 2 days. Male montane voles did not spend time preferentially with either female, even after mating. These results suggest that the contrasting mating systems of these species result from differences in the propensity for affiliative behavior and social bonding rather than from mate availability or female receptivity.     

The matching game: Testing for the generality of the matching law

The matching law suggests that animals will allocate responses as a function of reinforcer availability; that is, if one choice produces more reinforcement, a greater proportion of total responding will be allocated to that choice. Indeed, there tends to be a match between response allocation and proportions of reinforcers delivered, given each of those choices. A computer game that delivers simulated coins of experimenter-selected denominations for responding on either of two keys was developed to test the generality of the matching law. The data suggest that even within a single 10-min session, matching functions may be obtained (although undermatching was the rule in the present results). This program may also be used to test various accounts of the matching law.     

Role of female aggression in prevention of infanticidal behavior in male common voles,Microtus arvalis (Pallas, 1779)

Infanticidal behavior of male common voles (Microtus arvalis) was investigated in relation to the age of unfamiliar pups. Sires from 18 pairs were removed after parturition of their offspring and replaced by unfamiliar males at different ages of the neonates. In group 1, containing six females with their offspring, the new male was introduced into the females' cages on day 1 after the parturition. In group 2 the new male was introduced on day 5 after parturition and in group 3 on day 9 after parturition. The male was removed after 3 days and the neonates recounted. Male common voles killed up to 100% of the neonates in litters containing neonates younger than 9 days by rapid bites to the head of the neonates (groups 1 and 2, mortality rates of 0.86 and 0.38). However, with older pups, a mortality rate of 0.06 was observed while 33% of the intruder males showed signs of injuries (group 3). These findings show that infanticidal behavior of male common voles represents one factor of pup mortality. The results are discussed in relation to changes in the degree of maternal aggression and in the context of the social system of the common vole for solving the conflict between postpartum estrous mating and infanticidal behavior of male common voles. Aggr. Behav. 23:293–298, 1997. © 1997 Wiley-Liss, Inc.     

Levels of aggregation and the generalized matching law.

Concurrent operant behavior is often described using molar response tendencies measured over many sessions. In contrast, other models relate the allocation of behavior to momentary or molecular processes that operate over shorter periods. In this article, a formal model of the statistical properties of molecular behavioral matching is developed. Molar matching is the result when many individual bouts of responding are aggregated. However, behavioral allocation at the molecular level will differ from the molar result. The model indicates that aggregation effects should be controlled in analyses of matching and that the comparison of molecular theories of concurrent operant behavior with molecular models of matching performance affords ideographic analyses of choice behavior.     

Social and environmental factors influence the suppression of pup-directed aggression and development of paternal behavior in captive meadow voles (Microtus pennsylvanicus)

During summer, female meadow voles (Microtus pennsylvanicus) maintain territories and males do not engage in paternal care. As day length shortens, territories dissolve and males nest with females and young. Because paternal behavior has never been studied in free-living meadow voles during colder months or in the laboratory under short photoperiods, the authors examined whether males housed in short day (SD) lengths exhibited more frequent or better quality paternal behavior than males housed in long day (LD) lengths. Sexually and parentally inexperienced (naive) SD males exhibited proportionally more and qualitatively better paternal care than naive LD males. SD males were more responsive than LD males to classic social cues associated with prepartum aggression inhibition and paternal onset. SD sires also displayed qualitatively better paternal behavior than LD sires. These data suggest that meadow vole paternal state is regulated by specific social and environmental cues that may contain reliable information about ecological conditions that favor paternal care.     

Reinforcer magnitude (sucrose concentration) and the matching law theory of response strength

This experiment investigated the relationship between reinforcer magnitude (sucrose concentration) and response rate. The purpose was to evaluate the behavior of two parameters of an equation that predicts absolute response rate as a function of reinforcement rate and two free parameters. According to Herrnstein's (1970) theory of reinforced behavior, one parameter of this "response-strength equation" measures the efficacy of the reinforcer maintaining responding and the other parameter measures motoric components of response rate, such as response duration. Seven rats served as subjects. Experimental sessions consisted of a series of five different variable-interval schedules of reinforcement, each in effect for 5 minutes. Within each session, obtained reinforcement rates varied over more than a 30-fold range, from about 20 per hour to 700 per hour. The reinforcer was sucrose solution, and, between sessions, its concentration was varied from 0.0 to 0.64 molar (0 to 21.9%). For sucrose concentrations of 0.16 to 0.64 m, response rate was a negatively accelerated function of reinforcement rate. Increases in sucrose concentration increased response rates maintained by low but not high reinforcement rates. This pattern of changes corresponds to a change in the reinforcement-efficacy parameter of the response-strength equation. In contrast, the motor-performance parameter did not change as a function of sucrose concentration. These findings are inconsistent with the results of a similar study (Bradshaw, Szabadi, & Bevan, 1978) but support Herrnstein's theory of reinforced behavior.     

The applied importance of research on the matching law

In this essay, we evaluate the applied implications of two articles related to the matching law and published in the Journal of the Experimental Analysis of Behavior, May 1994. Building on Mace's (1994) criteria for increasing the applied relevance of basic research, we evaluate the applied implications of basic research studies. Research by Elsmore and McBride (1994) and Savastano and Fantino (1994) involve an extension of the behavioral model of choice. Elsmore and McBride used rats as subjects, but arranged a multioperant environment that resembles some of the complex contingencies of human behavior. Savastino and Fantino used human subjects and extended the matching law to ratio and interval contingencies. These experiments contribute to a growing body of knowledge on the matching law and its relevance for human behavior.     

The general matching law describes choice on concurrent variable-interval schedules of wheel-running reinforcement.

Six male Wistar rats were exposed to concurrent variable-interval schedules of wheel-running reinforcement. The reinforcer associated with each alternative was the opportunity to run for 15 s, and the duration of the changeover delay was 1 s. Results suggested that time allocation was more sensitive to relative reinforcement rate than was response allocation. For time allocation, the mean slopes and intercepts were 0.82 and 0.008, respectively. In contrast, for response allocation, mean slopes and intercepts were 0.60 and 0.03, respectively. Correction for low response rates and high rates of changing over, however, increased slopes for response allocation to about equal those for time allocation. The results of the present study suggest that the two-operant form of the matching law can be extended to wheel-running reinforcement. 'I'he effects of a low overall response rate, a short Changeover delay, and long postreinforcement pausing on the assessment of matching in the present study are discussed.     

Application of the matching law to pitch selection in professional baseball

This study applied the generalized matching equation (GME) to pitch selection in professional baseball. The GME was fitted to the relation between pitch selection and hitter outcomes for five professional baseball pitchers during the 2014 Major League Baseball season. The GME described pitch selection well. Pitch allocation varied across different game contexts such as inning, count, and number of outs in a manner consistent with the GME. Finally, within games, bias decreased for four of the five pitchers and the sensitivity parameter increased for three of the five pitchers. The results extend the generality of the GME to multialternative natural sporting contexts, and demonstrate the influence of context on behavior in natural environments.     

Application of the generalized matching law to chess openings: A gambit analysis

During the opening moves of a chess game, a player (typically White) may offer a number of gambits, which involve sacrificing a chess piece for an opponent for capture to achieve long-term positional advantages. One of the most popular gambits is called the Queen's Gambit and involves White offering a pawn to Black, which will open a lane for White's Queen if accepted by Black. In the present study, the generalized matching law (GML) was applied to chess openings involving the Queen's Gambit using over 71,000 archived chess games. Overall, chess players' opening moves involving the Queen's Gambit exhibited orderly matching as predicted by the GML, and the GML accounted for more variance in players' chess decision making as their relative playing experience increased. This study provides support for the generality of the GML and its application to complex operant behavior outside of laboratory contexts.