On the dynamics of generalization.
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Brain↗
Biomedical subjects
J E Staddon
Publications and source records attributed to J E Staddon.
Stochastic choice models: A comparison between Bush-Mosteller and a source-independent reward-following model.
Horner and Staddon (1987) argued that a class of reward-following processes defined by a property they termed ratio invariance is a better model for the probabilistic choice performance of pigeons than competing molecular accounts such as momentary maximizing, melioration, and the Bush-Mosteller model. The critical data were provided by choice distributions-distributions of a variable S, the proportion of Right choices, defined on a moving window typically 32 choices long-obtained under a frequency-dependent schedule. The schedule prescribed equal payoff probabilities, p(S), for both choices. p(S) was a maximum when S = 0.5 and declined linearly for S values above and below 0.5. Pigeons showed generally bimodal choice distributions with the modes at equal p(S) values. These data do not follow easily from melioration or momentary maximizing and are inconsistent with molar maximizing, but they may be consistent with Bush-Mosteller. We present here the results of computer simulations showing that the ratio-invariance model studied yields, as expected, choice modes at equal p(S) values, but that Bush-Mosteller, although capable of generating bimodal choice distributions, does not have choice modes at equal p(S) values.
Journal Article↗
The functional properties of feeding, or why we still need the black box.
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Animals↗
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.
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Typical delay determines waiting time on periodic-food schedules: Static and dynamic tests.
Pigeons and other animals soon learn to wait (pause) after food delivery on periodic-food schedules before resuming the food-rewarded response. Under most conditions the steady-state duration of the average waiting time, t, is a linear function of the typical interfood interval. We describe three experiments designed to explore the limits of this process. In all experiments, t was associated with one key color and the subsequent food delay, T, with another. In the first experiment, we compared the relation between t (waiting time) and T (food delay) under two conditions: when T was held constant, and when T was an inverse function of t. The pigeons could maximize the rate of food delivery under the first condition by setting t to a consistently short value; optimal behavior under the second condition required a linear relation with unit slope between t and T. Despite this difference in optimal policy, the pigeons in both cases showed the same linear relation, with slope less than one, between t and T. This result was confirmed in a second parametric experiment that added a third condition, in which T + t was held constant. Linear waiting appears to be an obligatory rule for pigeons. In a third experiment we arranged for a multiplicative relation between t and T (positive feedback), and produced either very short or very long waiting times as predicted by a quasi-dynamic model in which waiting time is strongly determined by the just-preceding food delay.
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Within-session meal-size effects on induced drinking.
As a control for the effects of session duration and hunger on the relation between food magnitude and induced drinking, four food-deprived rats were exposed to a variable-time 50-s schedule of food delivery in which the size of each food delivery varied randomly within sessions. Food-related behavior and schedule-induced drinking per opportunity were examined as functions of meal size and postfood time. All rats showed an inverted-U-shaped relation between drinking per opportunity and meal size. This relation was caused by variation in the percentage of intervals that contained drinking and by variation in the number of drinking bouts per interval, rather than by bout duration or by the amount of drinking within those intervals that actually contained drinking. Head-in-feeder time increased linearly with meal size. Schedule-induced drinking was entrained by food delivery in 3 of 4 subjects; the entrainment was due to regulation of the starting time of each drinking bout rather than to regulation of bout duration.
Animals↗
Minimum urine collection periods for accurate determination of creatinine clearance in critically ill patients.
The accuracy of creatinine clearance (CLcr) determinations obtained from urine collections of less than 24 hours duration and the cyclical variation in creatinine excretion were studied in 10 critically ill patients with trauma or postoperative complications. Data from patients who received drugs or had diseases known to influence creatinine production or interfere with assay methods were excluded. Twelve consecutive two-hour urine collections and midpoint blood samples were obtained for each patient. Urine and serum samples were assayed for creatinine content by kinetic and enzymatic methods, respectively. The mean 24-hour CLcr was 110.6 +/- 47.0 mL/min. Clearance values determined from 8- and 12-hour collections were within 20% of the 24-hour CLcr value, and values determined from 14- to 22-hour collections were not significantly different from the 24-hour CLcr value. Mean differences between each 2-hour interval and the 24-hour interval were not significant for the 12 collection intervals. In critically ill trauma or postsurgical patients, the 24-hour CLcr can be estimated from an 8-hour urine collection if a deviation of up to 20% from the 24-hour value is clinically acceptable. No significant cyclical variation in creatinine excretion over 24 hours was found.
Adult↗
Cholecystokinin, diet palatability, and feeding regulation in rats.
Rats ate less food than normal on cyclic-ratio schedules following cholecystokinin and lithium chloride injections. Nevertheless, they defended this lower eating rate in the same way as under control conditions. The pattern of effects produced by cholecystokinin and lithium chloride resembled those following diet adulteration with citric acid and sucrose octa acetate and differed from the effects produced by increases in body weight. Cholecystokinin and lithium chloride injections also produced similar changes in the free-feeding patterns of non-deprived rats: Both meal size and intermeal intervals decreased in manner similar to the effects of citric acid and sucrose octa acetate adulteration. Interpreted in terms of a static regulatory model, these results suggest that cholecystokinin and lithium chloride suppress feeding by degrading the palatability of food, not by promoting satiety, discomfort, or illness.
Animals↗
Time and memory.
Standard animal memory tasks require judgments of event recency: Delayed matching to sample (DMTS) requires that the animal identify the stimulus seen most recently; radial-maze-type (RM) tasks require that the animal identify the place visited least recently. Delayed-reaction tasks are intermediate. I argue that time discrimination (temporal control) and event memory call on the same processes: Proactive and retroactive effects occur in both, brief events have less effect than protracted events, and increases in event duration have smaller and smaller effects. If the "ages" of past events are represented by animals in a way consistent with Weber's and Jost's laws, and if there is a limit to the number of different recencies that can be discriminated, then the major differences between these three types of memory task can be explained. DMTS performance is poor because the animal must discriminate between two sets of recencies (memory arrays) that differ only in respect of the most recent event; RM performance is good because the recencies of places visited on the current versus earlier trials are always clearly discriminable.
Animals↗
Optimization: a result or a mechanism?
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Animals↗
Operant regulation of feeding: a static analysis.
Cyclic-ratio schedules are a rapid method for studying the operant regulation of feeding rate. The cyclic method produces results comparable to traditional but time-consuming parametric methods. Performance on cyclic-ratio schedules is well described by a linear regulatory model that embodies three quantitative feedback assumptions: (a) that rate of feeding is regulated by the rate of operant behavior, (b) that taste factors have an additive effect on the rate of the operant response, and (c) that regulatory "gain" is inversely related to body weight. This model accurately describes poorer regulatory performance at high body weights and following amphetamine administration, and the effects of altered diet palatability on preferred feeding rates.
Animals↗
Hill-climbing by pigeons.
Pigeons were exposed to two types of concurrent operant-reinforcement schedules in order to determine what choice rules determine behavior on these schedules. In the first set of experiments, concurrent variable-interval, variable-interval schedules, key-peck responses to either of two alternative schedules produced food reinforcement after a random time interval. The frequency of food-reinforcement availability for the two schedules was varied over different ranges for different birds. In the second series of experiments, concurrent variable-ratio, variable-interval schedules, key-peck responses to one schedule produced food reinforcement after a random time interval, whereas food reinforcement occurred for an alternative schedule only after a random number of responses. Results from both experiments showed that pigeons consistently follow a behavioral strategy in which the alternative schedule chosen at any time is the one which offers the highest momentary reinforcement probability (momentary maximizing). The quality of momentary maximizing was somewhat higher and more consistent when both alternative reinforcement schedules were time-based than when one schedule was time-based and the alternative response-count based. Previous attempts to provide evidence for the existence of momentary maximizing were shown to be based upon faulty assumptions about the behavior implied by momentary maximizing and resultant inappropriate measures of behavior.
Journal Article↗
Behavior induced by periodic food delivery: The effects of interfood interval.
Pigeons were exposed to fixed-time schedules of food presentation ranging from five to 300 seconds. Although consistent, stereotyped response patterns developed during interfood intervals on all schedules, there were distinct differences in the behavior observed on schedules with short, as opposed to long, intervals. During the shorter intervals, responses were performed quite vigorously, a feeder-directed terminal response was observed, and most activities were localized near the feeder. On the longer schedules, no feeder-directed terminal response developed, although the birds were usually near the feeder at the end of intervals. The predominant response involved moving about the chamber, often pacing along one of the walls. Performance during short intervals is accounted for quite well by the antagonistic-motivational state hypothesis suggested by Staddon (1977); however, performance during longer intervals is not. Behavior during interfood intervals may more accurately be classified as reflecting a single (food) motivational state and described simply in terms of Craig's (1918) appetitive behavior.
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Matching, maximizing, and hill-climbing.
In simple situations, animals consistently choose the better of two alternatives. On concurrent variable-interval variable-interval and variable-interval variable-ratio schedules, they approximately match aggregate choice and reinforcement ratios. The matching law attempts to explain the latter result but does not address the former. Hill-climbing rules such as momentary maximizing can account for both. We show that momentary maximizing constrains molar choice to approximate matching; that molar choice covaries with pigeons' momentary-maximizing estimate; and that the "generalized matching law" follows from almost any hill-climbing rule.
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Decreased feeding associated with acute hypoxia in rats.
Rats obtained less food than normal on a cyclic-ratio schedule during brief, 1-hr exposure to either moderate hypobaric hypoxia (BP = 435 Torr, PO2 approximately equal to 91 Torr) or to hypoxic hypoxia (BP = 750 Torr, PO2, approximately equal to 90 Torr), but not during hypobaric exposure with 36.5% oxygen (BP = 435 Torr, PO2 approximately equal to 159 Torr). The depressed rate of feeding associated with hypoxia was nevertheless well regulated. Interpreted in terms of a regulatory model, these results suggest that hypoxia suppresses eating because it degrades the taste of food, not because it impairs feeding regulation or general activity.
Altitude↗
Sensory superstition on multiple interval schedules.
Pigeons were exposed to multiple schedules in which an irregular repeating sequence of five stimulus components was correlated with the same reinforcement schedule throughout. Stable, idiosyncratic, response-rate differences developed across components. Components were rank-ordered by response rate; an approximately linear relation was found between rank order and the deviation of mean response rate from the overall mean rate. Nonzero slopes of this line were found for multiple fixed-interval and variable-time schedules and for multiple variable-interval schedules both when number of reinforcements was the same in all components and when it varied. The steepest function slopes were found in the variable schedules with relatively long interfood intervals and relatively short component durations. When just one stimulus was correlated with all components of a multiple variable-interval schedule, the slope of the line was close to zero. The results suggest that food-rate differences may be induced initially by different reactions to the stimuli and subsequently maintained by food.
Animals↗
Schedule-induced drinking: Elicitation, anticipation, or behavioral interaction?
We carried out five experiments with rats on fixed-time schedules in order to define the relation between drinking and individual food-pellet presentations. In Experiment 1, unsignaled extra food occurred at the end of occasional fixed intervals, and we compared subsequent drinking patterns with drinking before the extra food presentation. In Experiment 2 we presented signaled and unsignaled extra food and measured elicited and anticipatory drinking patterns. In Experiment 3, we observed the persistence of modified drinking patterns when several consecutive intervals ended with extra pellets. In Experiments 4 and 5, we varied the magnitude of food delivery across (rather than within) sessions to replicate published findings. Results show that schedule-induced drinking is neither elicited by food presentations nor induced by stimuli associated with a high food rate. All subjects seemed to follow a simple rule: during any stimulus signaling an increase in the local probability of food delivery within a session, engage in food-related behavior to the exclusion of drinking. Schedule-induced drinking appears to be the result of dynamic interactions among food-related behavior, drinking, and other motivated behavior, rather than a direct effect of the contingencies of food reinforcement.
Journal Article↗
Optimal choice.
We present a classification and theoretical analysis of discrete-trial and free-operant choice procedures in which reinforcement is assigned to one alternative only, or independently to both, is either always available or conditionally available, and is either "held" or not from trial to trial. Momentary-maximizing and (globally) optimal choice sequences are defined in terms of initializing and marker events. Free-operant choice is analyzed in terms of a clock space whose axes are the times since the last A and B choices. The analysis shows that most molar matching data are derivable from momentary maximizing, and that the momentary-maximizing hypothesis has not been adequately tested in either discrete-trial or free-operant situations.
Journal Article↗