Response rate and reinforcement rate in Pavlovian conditioning

Four experiments used delay conditioning of magazine approach in rats to investigate the relationship between the rate of responding, R, to a conditioned stimulus (CS) and the rate, r, at which the CS is reinforced with the unconditioned stimulus (US). Rats were concurrently trained with four variable-duration CSs with different rs, either as a result of differences in the mean CS-US interval or in the proportion of CS presentations that ended with the US. In each case, R was systematically related to r, and the relationship was very accurately characterized by a hyperbolic function, R = Ar/(r +c). Accordingly, the reciprocal of these two variables-response interval, I (= 1/R), and CS-US interval, i (= 1/r) - were related by a simple affine (straight line) transformation, I = mi+b. This latter relationship shows that each increment in the time that the rats had to wait for food produced a linear increment in the time they waited between magazine entries. We discuss the close agreement between our findings and the Matching Law (Herrnstein, 1970) and consider their implications for both associative theories (e.g., Rescorla & Wagner, 1972) and nonassociative theories (Gallistel & Gibbon, 2000) of conditioning. (PsycINFO Database Record (c) 2011 APA, all rights reserved).     

Mental load,heart rate and heart rate variability

Summary Several investigators have shown that diminished sinus arrhythmia can be seen as an indication of increased mental load. The present experiment deals with the influence of different levels of mental load, operationalized as the number of binary choices per minute, on the regularity of the heart rate. Also we investigated the influence of four different rest conditions on the regularity of the heart rate.The results show that sinus arrhythmia scores differentiate significantly between several levels of mental load, but heart frequency appeared to be an even better indicator.No significant differences were found between the four rest conditions. Stability over three subsequent measurement sessions was satisfactory, and reliability within the measurement periods was very high.

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Zusammenfassung Mehrere Forscher haben gezeigt, daß abnehmende Sinusarrhythmie betrachtet werden kann als ein Indikator zunehmender mentaler Belastung.In der vorliegenden Untersuchung handelt es sich um den Einfluß verschiedener Niveaus der mentalen Belastung, operationalisiert als die Zahl der binären Wahlen pro Minute, auf die Regelmäßigkeit der Herzfrequenz.Außerdem untersuchten wir den Einfluß vier verschiedener Ruhezustände auf die Regelmäßigkeit der Herzfrequenz.Die Ergebnisse zeigen, daß auf Grund Sinusarrhythmiedaten differenziert werden kann zwischen verschiedenen Niveaus mentaler Belastung, aber die Herzfrequenz erweist sich sogar als ein besserer Indikator.Man stellte keine signifikanten Unterschiede zwischen den vier verschiedenen Ruhezuständen fest.Die Stabilität während drei verschiedener Meßperioden war befriedigend, und die Zuverlässigkeit der Messungen (reliability) innerhalb der Meßperioden war sehr groß.

     

Delay or rate of food delivery as determiners of response rate

Pigeons were confronted with two keys: a green food key and a white changeover key. Food became available for a peck to the green key after variable intervals of time (mean = 113 seconds). A single peck on the changeover key changed the color of the food key to red for a fixed period of time during which the timing of the variable-interval schedule in green was suspended and the switching option eliminated and after which the conditions associated with green were reinstated. In Experiment 1 a single food presentation was obtainable during each red-key period after a minimum delay timed from the switch. This delay and the duration of the red-key period were held constant during a condition but varied between conditions (delay = 2.5, 7.5, 15, or 30 seconds; red-period duration = 30, 60, 120, 240, or 480 seconds). In Experiment 2 additional food presentations were scheduled during a 240-second red-key period with the delay to the first food delivery held constant at 30 seconds, and the delays to later food deliveries varied over conditions. Considering the data from both experiments, the rate of switching to red was a decreasing function of the delay to the first food, the delay to the second food, and perhaps the delay to the third food after a switch. There was no clear evidence that the rate of food in the red-key period made an independent contribution. The ordering of response rates among conditions was consistent with the view that each food presentation after a response adds an incremental effect to the rate of the response and that each food presentation's contribution is a decreasing function of its delay timed from the response.     

The behavioral theory of timing: Reinforcer rate determines pacemaker rate

In the behavioral theory of timing, pulses from a hypothetical Poisson pacemaker produce transitions between states that are correlated with adjunctive behavior. The adjunctive behavior serves as a discriminative stimulus for temporal discriminations. The present experiments tested the assumption that the average interpulse time of the pacemaker is proportional to interreinforcer interval. Responses on a left key were reinforced at variable intervals for the first 25 s since the beginning of a 50-s trial, and right-key responses were reinforced at variable intervals during the second 25 s. Psychometric functions relating proportion of right-key responses to time since trial onset, in 5-s intervals across the 50-s trial, were sigmoidal in form. Average interpulse times derived by fitting quantitative predictions from the behavioral theory of timing to obtained psychometric functions decreased when the interreinforcer interval was decreased and increased when the interreinforcer interval was increased, as predicted by the theory. In a second experiment, average interpulse times estimated from trials without reinforcement followed global changes in interreinforcer interval, as predicted by the theory. Changes in temporal discrimination as a function of interreinforcer interval were therefore not influenced by the discrimination of reinforcer occurrence. The present data support the assumption of the behavioral theory of timing that interpulse time is determined by interreinforcer interval.     

Feedback functions, optimization, and the relation of response rate to reinforcer rate

The present experiment arranged a series of inverted U-shaped feedback functions relating reinforcer rate to response rate to test whether responding was consistent with an optimization account or with a one-to-one relation of response rate to reinforcer rate such as linear system theory's rate equation or Herrnstein's hyperbola. Reinforcer rate was arranged according to a quadratic equation with a maximum at a unique response rate. The experiment consisted of two phases, during which 6 Long Evans rats lever pressed for food. In the first phase of the experiment, the rats responded on six fixed-interval-plus-quadratic-feedback schedules, and in the second phase the rats responded on three variable-interval-plus-quadratic-feedback schedules. Responding in both phases was inconsistent with a one-to-one relation of response rate to reinforcer rate. Instead, different response rates were obtained at equivalent reinforcer rates. Responding did vary directly with the vertex of the feedback function in both phases, a finding consistent with optimization of reinforcer rate. The present results suggest that the feedback function relating reinforcer rate to response rate imposed by a reinforcement schedule can be an important determinant of behavior. Furthermore, the present experiment illustrates the benefit of arranging feedback functions to investigate assumptions about the variables that control schedule performance.     

Contact-free measurement of heart rate, respiration rate, and body movements during sleep

We describe a noncontact method for the ambulant measurement of basic sleep physiology parameters in humans, particularly for field studies involving sleep research and sleep disturbances. This method traces the body movements, respiration, and heart action of a person at rest or asleep on a bed, using four high-resolution force sensors installed under the bedposts. The recoil movement of the body at each heartbeat, known as the cardioballistic effect, as well as the lifting and lowering of the thorax, while breathing, causes very small shifts of the center of gravity of the bed and the subject. These shifts are reflected in the altering force distributions across the four sensors. Cardiac and respiratory parameters and the subject’s movement activity can be calculated from the sensor signals. Neither electrodes nor other kinds of transducers are in direct contact with the subject, which is the main advantage of this technique over conventional methods. Laboratory experiments were carried out to estimate validity and practicability. The method has been found to be adequate, especially for automated and unattended sleep-data collection over long periods of time.     

Choice and rate of reinforcement

Pigeons' responses in the presence of two concurrently available (initial-link) stimuli produced one of two different (terminal-link) stimuli. The rate of reinforcement in the presence of one terminal-link stimulus was three times that of the other. Three different pairs of identical but independent variable-interval schedules controlled entry into the terminal links. When the intermediate pair was in effect, the pigeons distributed their (choice) responses in the presence of the concurrently available stimuli of the initial links in the same proportion as reinforcements were distributed in the mutually exclusive terminal links. This finding was consistent with those of earlier studies. When either the pair of larger or smaller variable-interval schedules was in effect, however, proportions of choice responses did not match proportions of reinforcements. In addition, matching was not obtained when entry into the terminal links was controlled by unequal variable-interval schedules. A formulation consistent with extant data states that choice behavior is dependent upon the amount of reduction in the expected time to primary reinforcement, as signified by entry into one terminal link, relative to the amount of reduction in expected time to reinforcement signified by entry into the other terminal link.     

Suicide rate and skin color

In two previously described samples of 53 and 43 nations, higher suicide rates of men, women, and the elderly population consistently corresponded to lighter skin color. This ecological (aggregate-level) association was independent of national differences in affluence, as measured by per capita Gross Domestic Product.     

Temporal inhibition: effects of changes in rate of reinforcement and rate of responding

Pigeons were trained to key peck on several multiple schedules in which the first of two components was always a simple fixed-interval schedule. The rate of responding at the beginning of the constant fixed-interval schedule was found to decrease with increases in the rate of reinforcement associated with the other component of the multiple schedule, but remained unchanged with decreases in the rate of responding associated with the other component. These results were interpreted as being consistent with the view that the presence and magnitude of the temporal inhibitory effects observed in a given fixed-interval schedule are a function of the properties of reinforcing stimuli, rather than of changes in the rate of responding associated with the time interval immediately preceding the fixed interval in question.     

Random fluctuations of response rate

A simple model for fluctuating interresponse times is developed and studied. It involves a mechanism that generates regularly spaced excitations, each of which can trigger off a response after a random delay. The excitations are not observable, but their periodicity is reflected in a regular patterning of responses. The probability distribution of the time between responses is derived and its properties are analyzed. Several limiting cases are also examined.This paper was completed while the writer was a visiting summer scientist at the Lincoln Laboratory, Lexington, Mass.     

Matching and conditioned reinforcement rate

Attempts to examine the effects of variations in relative conditioned reinforcement rate on choice have been confounded by changes in rates of primary reinforcement or changes in the value of the conditioned reinforcer. To avoid these problems, this experiment used concurrent observing responses to examine sensitivity of choice to relative conditioned reinforcement rate. In the absence of observing responses, unsignaled periods of food delivery on a variable-interval 90-s schedule alternated with extinction on a center key (i.e., a mixed schedule was in effect). Two concurrently available observing responses produced 15-s access to a stimulus differentially associated with the schedule of food delivery (S+). The relative rate of S+ deliveries arranged by independent variable-interval schedules for the two observing responses varied across conditions. The relation between the ratio of observing responses and the ratio of S+ deliveries was well described by the generalized matching law, despite the absence of changes in the rate of food delivery. In addition, the value of the S+ deliveries likely remained constant across conditions because the ratio of S+ to mixed schedule food deliveries remained constant. Assuming that S+ deliveries serve as conditioned reinforcers, these findings are consistent with the functional similarity between primary and conditioned reinforcers suggested by general choice theories based on the concatenated matching law (e.g., contextual choice and hyperbolic value-added models). These findings are inconsistent with delay reduction theory, which has no terms for the effects of rate of conditioned reinforcement in the absence of changes in rate of primary reinforcement.     

Morbidity rate in delirium tremens

On evaluating an analysis of 105 cases of delirium tremens over a period of five years in a psychiatric base-unit, the following findings were obtained: Delirium tremens, particularly in conjunction with secondary diseases, constitutes a life-endangering medical emergency and requires intensive medical treatment. Letality was 8,57%. The morbidity-rate and the relapse-rate showed a clearly marked increase; the age of contracting the disease had its frequency peak between 30 and forty, i. e. earlier than in many other statistical surveys. Epileptic attacks as symptoms starting off or accompanying delirium occurred in almost one third of our delirium patients. The impact which these attacks have on the development in the course of process-like alcoholism was discussed.