Pairings Of CS Research Articles

The effect of response-contingent feedback stimuli under two types of avoidance extinction conditions

Four groups of rats were conditioned to avoid shock in a two-way shuttlebox. During acquisition. each response both precluded a brief programmed shock and produced a I-sec feedback signal. CS termination was not permitted during either acquisition or' extinction. During extinction, response-produced or yoked feedback was combined with either 100% response-independent shock or no-shock conditions. Greatest resistance to extinction of avoidance behavior was obtained when response-produced feedback occurred in the absence of shock relative to any other combination of these events. These results, when compared to those of previous studies investigating the role of warning signal termination in combination with the presence or absence of shock in extinction (Hartley, 1968), clearly reveal a functional similarity between feedback and CS termination. The most prevalent interpretation of discriminative avoidance behavior has been the two-factor theory, originally discussed by Mowrer and Lamoreaux (1946) and more recently by Solomon and Brush (1956). According to the theory, conditioning is accomplished by both Pavlovian and operant processes. A classically conditioned fear response develops by repeated pairings of CS and US. This fear reaction motivates the subject to avoid the US. Reinforcement of avoidance occurs when fear is reduced by response-produced termination of the CS and preclusion of the US. An alternative explanation of avoidance views the CS, CS termination, and the presence or absence of the US as having discriminative rather than motivational prop­ erties (Mowrer & Jones, 1945; Sheffield, 1949). When one or all of these cues are altered during extinction, avoidance behavior declines due to generalization decrement. Thus, if a subject is avoiding either a high proportion of shocks during terminal acquisition or all of them, a no-shock extinction procedure should pro­ long extinction over a procedure in which shocks occur on all extinction trials . Similarly , any extinction pro­ cedure that alters the consequences of responding from those occurring during the acquisition phase, whether the events be CS termination, US avoidance, or any other highly discriminable events, should facilitate extinction of the behavior.

Ab initio studies of the conformers of 2-propene-1-imine

Ab initio molecular orbital calculations employing both the minimal STO-3G and the split-valence 4-31G basis sets have been applied to the four planar conformers of 2-propene-1-imine. Initial calculations revealed that geometry optimizations were needed and partial geometry optimizations using the STO-3G method have been performed. Contrary to experiment, however, the STO-3G favors the wrong conformer (TS) as the lower energy structure. 4-31G calculations, on the other hand, are in reasonable agreement with the microwave study of the compound which predicts the TA conformer as the lower energy conformer with the TS conformer being 0.9 kcal mole −1 higher in energy. The most significant geometric variation in going from the TA to the TS conformer is an opening up of the CCN angle by about 5°. A comparison of the cis—trans rotamers of 1,3-butadiene, glyoxal and acrolein with 2-propene-1-imine is also made. The 4-31G calculations indicate that the TA — CA energy difference for 2-propene-1-imine is about 2 kcal mole −1 while the corresponding value for the TS — CS pair is 2.8 kcal mole −1.

Pain-elicited aggression in the squirrel monkey: An implicit avoidance contingency

Squirrel monkeys were given either forward pairings of a bite-tube CS and shock US or backward pairings of these stimuli. Backward pairings produced stronger control of biting by the bite tube alone than did forward pairings. In a second experiment, subjects received backward pairings of US and CS with either a fixed ITI or a random ITI. Conditioned biting was obtained only when trials were presented with a fixed ITI. The magnitude of unconditioned biting was also significantly greater with the fixed ITI. It was argued that these results demonstrate that conditioning in this situation depends upon the degree to which biting predicts a relatively long shock-free period. When trials occur randomly in time, biting predicts no definite shock-free period; hence, it is not learned.

Conditioned enhancement as a function of the percentage of CS-US pairings and CS duration

Eighteen rats were trained to barpress on a variable interval 90-sec schedule of sucrose-solution reinforcement. Ss were then divided into three groups (N = 6) and exposed to a classical conditioning contingency while barpressing, in which a 2-min light CS preceded the delivery of a food pellet US on either 100%, 66%, or 33% of the CS presentations. When the response rate during the CS was compared to response rate prior to the CS, it was found that the CS response rate was directly related to the percentage of US presentation. When the CS duration was changed to 8 sec, the highest CS response rates were associated with the partial pairing of CS and US.

Acquisition, extinction, and spontaneous recovery of conditioned suppression of licking

A conditioning procedure yielding a trial-by-trial measure of the suppression of ongoing licking behavior in rats is described. In one group (N = 9), forward pairings of CS with shock produced rapid acquisition, slow extinction, and nearly complete spontaneous recovery following a 30-day “rest” period. In a second group (N = 8), initial backward pairings (shock-CS) produced supernormal suppression ratios. During CS-alone trials, supernormal performance was shown by both the backward group and a third group (N = 8), which received initial free-shock trials.

Similarity of cardiac CR forms in the rhesus monkey during several experimental procedures.

Cardiac rates of rhesus monkeys were observed in a variety of different conditioning procedures, each of which involved a visual stimulus (CS) followed by an electric shock (US). With a 30-sec CS, cardiac rate accelerated rapidly after CS onset, reached a maximum in the middle of CS, and decelerated thereafter, with a terminal CS rate often at the level of, or below, pre-CS levels. A similar biphasic cardiac rate response in CS was also observed under subsequent exposure to intermittent pairings of CS and US, avoidance of US, response-produced termination of US, and when CS-US pairings were superimposed upon an avoidance baseline, even when CS duration was varied from 12 to 60 seconds. The unusual regularity of cardiac rate responses in several different procedures may result from one or more of these factors: (a) characteristics of the rhesus monkey, (b) initial exposure to Pavlovian conditioning, or (c) the uniformity of measurement of cardiac rate employed in this study.

Probability of shock in the presence and absence of CS in fear conditioning.

2 experiments indicate that CS-US contingency is an important determinant of fear conditioning and that presentation of US in the absence of CS interferes with fear conditioning. In Experiment 1, equal probability of a shock US in the presence and absence of a tone CS produced no CER suppression to CS; the same probability of US given only during CS produced substantial conditioning. In Experiment 2, which explored 4 different probabilities of US in the presence and absence of CS, amount of conditioning was higher the greater the probability of US during CS and was lower the greater the probability of US in the absence of CS; when the 2 probabilities were equal, no conditioning resulted. Two conceptions of Pavlovian conditioning have been distinguished by Rescorla (1967). The first, and more traditional, notion emphasizes the role of the number of pairings of CS and US in the formation of a CR. The second notion suggests that it is the contingency between CS and US which is important. The notion of contingency differs from that of pairing in that it includes not only what events are paired but also what events are not paired. As used here, contingency refers to the relative probability of occurrence of US in the presence of CS as contrasted with its probability in the absence of CS. The contingency notion suggests that, in fact, conditioning only occurs when these probabilities differ; when the probability of US is higher during CS than at other times, excitatory conditioning occurs; when the probability is lower, inhibitory conditioning results. Notice that the probability of a US can be the same in the absence and presence of CS and yet there can be a fair number of CS-US pairings. It is this that makes it possible to assess the relative importance of pairing and contingency in the development of a CR. Several experiments have pointed to the usefulness of the contingency notion. Rescorla (1966) reported a Pavlovian 1This research was supported by Grants MH13415-01 from the National Institute of Mental Health and GB-6493 from the National Science Foundation, as well as by funds from Yale University.

Classical conditioning of heart rate and Galvanic skin response in the rat.

ABSTRACTA comparison was made between classical conditioning and pseudoconditioning of heart rate (HR) and galvanic skin response (GSR) using low or high intensity shock as unconditioned stimuli (UCS). Conditioning treatment involved 5‐sec delayed conditioning, 32 trials/session for 5 sessions with shock administered randomly on half the trials. Pseudoconditioning was exactly the same except for pairing of CS and UCS.In contrast to pseudoconditioning, which produced mild acceleration of HR, minimal GSR, and frequent somatic response to the CS (as defined electromyographically), conditioning treatment produced consistent deceleration of HR, larger magnitude and frequency of GSR, and minimal overt somatic response to CS. The conditioned decelerative HR response developed rapidly and persisted throughout the experiment. Such apparent conditioning phenomena may still involve sensitization‐type effects and somatic interactions.

A study on uranyl phosphates—I: Sorption properties of uranyl hydrogen phosphate

The synthesis, analysis and properties of uranyl hydrogen phosphate are described; the sorption of some 1- to 4-valent cations and the separation of alkali cations have been studied. Qualitative conclusions have been deduced for the sorption mechanism, and selectivity coefficients for the pairs of ions Cs +NH 4 +Na +, Cs +K + and Cs +Rb + have been determined.

A FURTHER ATTEMPT AT DELAYED GSR CONDITIONING.

A delayed conditioning schedule was employed so that latency and frequency changes of all GSRs occurring in the CS‐UCS interval could be followed. Two experimental groups received initial (simultaneous) pairings of CS–UCS, and four control groups received initial CS series only, prior to the introduction of the delayed series.There was no evidence of an increase in latency of GSRs over trials, and only a slight increase in frequency over the first few trials in the control groups; this latter effect was attributed to the disinhibiting or novel effect of changing from one stimulus series to another, and not to acquisition of a conditioned response. It was concluded that no gradual increase of CR strength over trials was demonstrated.Highly significant correlations were obtained between measures of skin resistance responsiveness, such as spontaneous and orienting responses; this suggests that many so‐called measures of GSR conditioning are probably related to some factor such as response sensitivity.

Two Effects of An “Anxiety-Eliciting” CS on Human Reaction Latency

When a neutral stimulus (CS) has been paired with shock (US), the CS may be said, alternatively, to acquire aversive properties, or to elicit conditioned anxiety which is reduced by CS-termination. Whichever language is employed, CS-termination is now held to reinforce responses which precede it in time. This effect has been amply demonstrated in animals (cf. 1, 4, 5), and has been cited in the interpretation of avoidance learning (cf. 6, 7). That is, rat behavior which serves to prevent occurrence of shock has been shown to be strengthened, independently, by termination of the cue preceding shock (2, 3). While analogies between such data and neurotic or anxiety-motivated human behavior have been drawn, there seems to be no convincing demonstration of the effect in human Ss. Wickens and Platt (a), studying conditioned finger withdrawal, noted an apparent effect of CS-termination for the first third of training trials in only one of two experimental conditions. The present study, attempting to demonstrate a reinforcing effect of CStermination in man, involves, first, training trials during which CS and aversive US are paired. Then, during test trials, Ss are instructed to respond to the CS as quickly as possible by pressing a key. The study thus superimposes any effect of CS-termination on a voluntary response. The effect will be demonstrated if, granted appropriate controls, reaction latency is facilitated by response termination of the CS. The design also explores the effects of inevitable pairing of CS and US vs. omitting the US after each response.