Quasi-dynamic choice models: Melioration and ratio invariance

There is continuing controversy about the behavioral process or processes that underlie the major regularities of free-operant choice such as molar matching and systematic deviations therefrom. A recent interchange between Vaughan and Silberberg and Ziriax concerned the relative merits of melioration, and a computer simulation of molecular maximizing. There are difficulties in evaluating theories expressed as computer programs because many arbitrary decisions must often be made in order to get the programs to operate. I therefore propose an alternative form of model that I term quasi-dynamic as a useful intermediate form of theory appropriate to our current state of knowledge about free-operant choice. Quasi-dynamic models resemble the game-theoretic analyses now commonplace in biology in that they can predict stable and unstable equilibria but not dynamic properties such as learning curves. It is possible to interpret melioration as a quasi-dynamic model. An alternative quasi-dynamic model for probabilistic choice, ratio invariance, has been proposed by Horner and Staddon. The present paper compares the predictions of melioration and ratio invariance for five experimental situations: concurrent variable-interval variable-interval schedules, concurrent variable-interval variable-ratio schedules, the two-armed bandit (concurrent random-ratio schedules), and two types of frequency-dependent schedule. Neither approach easily explains all the data, but ratio invariance seems to provide a better picture of pigeons' response to probabilistic choice procedures. Ratio invariance is also more adaptive (less susceptible to “traps”) and closer to the original expression of the law of effect than pure hill-climbing processes such as momentary maximizing and melioration, although such processes may come in to play on more complex procedures that provide opportunities for temporal discrimination.     

Maximizing present value: A model to explain why moderate response rates obtain on variable-interval schedules

In Phases 1 and 3, two Japanese monkeys responded on a multiple variable-ratio 80 variable-interval X schedule, where the value of X was adjusted to ensure equal between-schedule reinforcement rates. Components strictly alternated following the delivery of a food pellet, and each session ended following 50 components. Phase 2 differed from the others only in that the 50 pellets previously earned during the session were delivered together at session's end. Variable-ratio response rates did not decrease across phases, but variable-interval response rates decreased substantially during the Phase 2 procedure. This rate decrease was attributed to the food-at-session's-end manipulation removing the greater immediacy of reinforcement provided by short interresponse times relative to long interresponse times. Without this time preference for short interresponse times, the variable-interval interresponse-time reinforcement feedback function largely controlled response emission, dictating a response-rate reduction. This result was explained in terms of the economic notion of “maximizing present value.”     

Effects of methadone on alternative fixed-ratio fixed-interval performance: latent influences on schedule-controlled responding.

Effects of methadone on pigeons' key pecking were examined under four conditions selected to analyze the control of behavior under alternative fixed-ratio fixed-interval schedules. In Condition 1, pigeons pecked under one of three different alternative schedules (alternative fixed-ratio 50 fixed-interval 90 s, alternative fixed-ratio 75 fixed-interval 90 s and alternative fixed-ratio 200 fixed-interval 90 s) each week. In Condition 2, fixed-ratio 50 or fixed-ratio 75 schedules were in effect during baseline sessions, and alternative fixed-ratio 50 fixed-interval 90-s or alternative fixed-ratio 75 fixed-interval 90-s schedules were in effect during sessions in which methadone was administered. In Condition 3, effects of methadone on key pecking maintained under fixed-ratio 50 and fixed-ratio 75 schedules were examined, whereas in Condition 4 the effects of methadone on key pecking under a fixed-interval 90-s schedule as well as fixed-ratio 50 and fixed-ratio 75 schedules were investigated. Control by the fixed-interval contingency was assessed by computing the proportion of total session reinforcers delivered under the fixed-interval schedule. Methadone administration (0.5-4.0 mg/kg) shifted the predominant source of schedule control under the alternative schedule from the fixed-ratio schedule to the fixed-interval contingency. This shift was dependent on methadone dose and fixed-ratio size. Control by the fixed-interval contingency was greatest following extensive exposure to the interval component embedded within the alternative schedule (Condition 1), but was apparent to a lesser degree with even very limited exposure to the alternative fixed-ratio fixed-interval schedule (Condition 2). Interreinforcement intervals comparable to those under fixed-interval schedule were not observed under the fixed-ratio schedules presented alone (Condition 3). Repeated exposure to the fixed-interval contingency outside the context of the alternative fixed-ratio fixed-interval schedule did not engender performance changes under a fixed-ratio schedule which would mimic those of increased fixed-interval contingency control (Condition 4). These data suggest that drug administration can be used to unmask the influence of contingencies that are latent under baseline conditions and reveal influences of both past and present environmental variables.     

Heart rate reactivity in attention deficit disorder subgroups

Beat-to-beat heart rate (HR) was analyzed for 9 contiguous seconds in a warned reaction time (RT) paradigm. Imperative stimuli were tones of three intensity levels (55, 78, and 100 db); a visual warning signal occurred 5 sec before tone onset. Baseline and reward conditions were run. Normal controls were contrasted with three Attention Deficit Disorder (ADD) subgroups: ADD-only, ADD with hyperactivity (ADDH), ADD with hyperactivity and aggression (ADDHA). The ADD subgroups were predicted to show less deceleration in HR because of their problem sustaining readiness to respond. Significant sex x group differences in HR levels and change scores were found. Overall, girls had higher HR levels than boys and the ADD-only group (boys and girls) had lower HRs than the other ADD groups. But, the ADD-only boys had more marked deceleration to the warning signal and acceleration to the tones than the other ADD boys, whereas the ADD-only girls were no more reactive than the ADDH and ADDHA girls. Control girls had the highest HR levels and were the most reactive to stimuli. Control boys and ADD-only boys had similar HR levels and reaction patterns. ADD-only girls appear to be underaroused, whereas ADD-only boys do not. Results suggest that cardiac measures can provide external validation of disruptive and nondisruptive ADD subtypes.     

Sex Differences in Clinical Pain: A Multisample Study

A recent meta-analysis of the experimental pain literature revealed effect sizes of .55 for pain threshold and .57 for pain tolerance, indicating a moderate difference in pain perception between men and women, with women reporting an increased sensitivity to pain. The current study investigated the relationship between sex and clinical pain ratings, in patients seeking care at a tertiary care facility. Five samples of chronic pain patients were recruited from several diverse clinics associated with the University of Florida. Analyses of clinical pain ratings revealed similar effect sizes for all samples, ranging from –.07 to –.25, indicating small differences, with women reporting higher levels of clinical pain. This is the first paper to report effect sizes for differences in report of pain in samples of chronic pain patients presenting for treatment at a tertiary care facility.     

Sex, Aggression, and Pain: Sociobiological Implicatios for Theological Anthropology

Theological anthropology can be enriched by paying attention to insights into human behavior taken from sociobiology. The capacity for reflective self-consciousness enables the human animal to respond to basic instincts and drives in unprecedented ways. Humans follow gender-specific sexual strategies, display aggressive behavior, and respond to physical pain as do other animals. Yet human beings have the intellectual ability to express these tendencies uniquely in either destructive or constructive ways. The human being, unlike any other animal, must reckon with sexual ethics, the problem of violence, and the meaning of suffering. In developing the basic concepts of theological anthropology—good creation, natural evil, fall, sin, and image of God—sociobiological research can lead to more adequate understanding of the human.     

Norms for 439 action events: Familiarity,emotionality, motor activity,and memorability

A total of 128 male and female university students having Swedish as their mother tongue rated 439 actions on a 7-point scale in the dimensions of Familiarity, Emotionality, Motor Activity, and Memorability under instructions to imagine themselves performing each action (e.g., “to roll a ball”, “to break a match”). Overall mean ratings were higher for women than for men in all four dimensions. High reliabilities were obtained in each scale. Intercorrelations between the dimensions were low to moderate, indicating that different characteristics of the actions were assessed. It is demonstrated that the ratings of the four dimensions are in agreement with previous categorisations of actions along the same or similar dimensions and with findings related to memory performance. Furthermore, control studies performed on the Familiarity dimension show that norm values are highly correlated with ratings given by participants in standard enacting and nonenacting conditions and with ratings in a condition where objects were present. These norms offer possibilities to control for and vary item characteristics of importance in the study of actions and the memory of actions.     

Heritabilities of Common and Measure-Specific Components of the Big Five Personality Factors

Three different measures of the Big Five personality dimensions were developed from the battery of questionnaires used in the National Merit Twin Study: one from trait self-rating scales, one from personality inventory items, and one from an adjective check list. Behavior-genetic models were fit to what the three measures had in common, and to the variance distinctive to each. The results of the model fitting agreed with other recent studies in showing the Big Five dimensions to be substantially and about equally heritable, with little or no contribution of shared family environment. Heritabilities for males and females did not differ significantly. For Agreeableness and Conscientiousness, some effect of shared environment was found for measure-specific variance on the personality inventory, and for Extraversion and Neuroticism, models involving nonadditive genetic variance or twin contrast effects provided slightly better fits.     

Conjunctive schedules of response-dependent and response-independent reinforcement

Pigeons received food when they emitted the number of responses specified by a fixed-ratio schedule, and the time specified by a fixed-time schedule had elapsed. The order of meeting the response and time requirements was irrelevant. In different conditions, stimuli signalled completion of one, both, or neither requirement. Ratio size interacted with stimulus condition to determine performance. When a stimulus signalled the end of the fixed-time period, under all ratios the birds tended to respond after the stimulus appeared. When stimuli followed both components, small ratios produced responding during the fixed-time period, and other ratios resulted in responses after the time period had elapsed. With either no stimulus changes, or with a stimulus correlated with completion of the ratio alone, responding first increased and then decreased as the ratio increased. Low and high ratios produced stable response frequencies and patterns in successive intervals. Intermediate ratios resulted in two types of performance. Intervals with long initial pauses and few responses during the fixed-time period were followed by intervals with short pauses and numerous responses and vice versa. The source of these dynamic effects was hypothesized to be number of responses per reinforcer in one condition and response-reinforcer contiguity in the other.     

A COMPARISON OF THE EFFECTS OF FIXED AND VARIABLE RATIO SCHEDULES OF REINFORCEMENT ON THE BEHAVIOR OF DEAF CHILDREN

The performance of all five students in an adjustment class for deaf children was compared under fixed and variable ratio schedules of reinforcement. During the fixed ratio (FR) condition, students earned checks if they were attentive and did not engage in disruptive behavior. These checks could be exchanged for the opportunity to draw a prize from a grab bag. During the variable ratio (VR) condition, they earned a draw from the grab bag according to a variable ratio schedule with a mean ratio equal to the value of the preceding FR schedule. During the VR condition, students visually attended more and engaged in disruptive behavior less often than during the FR condition. The number of math problems completed per minute was also higher during the VR condition although no specific consequences were applied to math performance.