The Topography of Sexually Conditioned Behaviour: Effects of a Trace Interval

In a trace conditioning procedure, subjects were presented with a 30-sec conditioned stimulus (CS) followed by a 30-sec trace interval. Delayed conditioning consisted of a 60-sec CS presentation followed by an unconditioned stimulus (US). Although conditioning developed with both procedures, the topography of the conditioned response differed. Sexual conditioned approach was evident in all of the subjects during the presentation of the CS. Traceconditioned subjects moved away from the area where the CS had been presented during the trace interval but remained closer to the CS location than did an unpaired control. This reduction in the spatial specificity of the conditioned response was interpreted from a behaviour systems perspective. The trace interval presumably increased the perceived separation between the CS and the US and therefore elicited conditioned behaviour less specifically directed towards the CS.     

Acquisition of the classically conditioned eyeblink response in humans over the life span

Human subjects ranging in age from 18 to 85 years underwent classical conditioning of the eyeblink response to a tone conditioned stimulus (CS) and an air-puff unconditioned stimulus (UCS). There was a decline in percentage of conditioned responses with age. This decline was most noticeable in subjects over age 50. These conditioning deficits were not due to age-related changes in sensitivity to the tone CS or the air-puff UCS, nor could the conditioning deficits be attributed to an age-related decline in general cognitive abilities or to changes in spontaneous blink rates. The results are discussed in terms of using the classically conditioned eyeblink in humans in conjunction with the classically conditioned nictitating membrane response in rabbits as a model system for studying the neurobiology of age-related conditioning deficits.     

Latent inhibition and stimulus generalization of the classically conditioned nictitating membrane response in rabbits (Oryctolagus cuniculus) following dorsal hippocampal ablation.

Rabbits received 0 to 450 exposures of a tone conditioned stimulus (CS) prior to classical defensive conditioning of the nicitating membrane response based on an infraorbital eye shock unconditioned stimulus. Tone preexposure resulted in retarded conditioning in normal rabbits. This latent inhibition effect was not present in animals with bilateral dorsal hippocampectomy produced by aspiration. Control animals with bilateral neocortical and callosal aspiration lesions demonstrated a latent inhibition effect similar to that shown by normal nonoperated animals. The failure of CS preexposure to retard conditioning in hippocampal rabbits was not due to differences in threshold of the conditioned response to the CS or to differences in response mechanisms as determined by tests of habituation and dishabituation of the unconditioned response. A subsequent experiment employed combined-cue summation tests to confirm the fact that preexposure did not endow the tone with conditioned as well as latent inhibitiory properties. Finally, tests of stimulus generalization along the auditory frequency dimension indicated flatter relative gradients for hippocampals than for nonoperated controls, with cortical controls in between. These findings were discussed in terms of Douglas' model of hippocampal function.     

Potentiation of the acoustic startle response by a conditioned stimulus paired with acoustic startle stimulus in rats

The hypothesis that the standard acoustic startle habituation paradigm contains the elements of Pavlovian fear conditioning was tested. In a potentiated startle response paradigm, a startle stimulus and a light conditioned stimulus (CS) were paired. A startle stimulus then was tested alone or following the CS. Freezing behavior was measured to index conditioned fear. The startle response was potentiated on CS trials, and rats froze more in CS than in non-CS periods. In Experiment 1, response to a previously habituated, weak startle stimulus was potentiated. In Experiment 2, response to the same stimulus used as the unconditioned stimulus (US) in training was potentiated. This CS-potentiated response retarded the course of response decrements over training sessions as compared with an explictly unpaired control group. Conditioned fear is a standard feature of this habituation paradigm, serves to potentiate the startle response, and provides an associative dimension lacking in the habituation process per se.     

Pavlovian second-order conditioned analgesia

Three experiments with rat subjects assessed conditioned analgesia in a Pavlovian second-order conditioning procedure by using inhibition of responding to thermal stimulation as an index of pain sensitivity. In Experiment 1, rats receiving second-order conditioning showed longer response latencies during a test of pain sensitivity in the presence of the second-order conditioned stimulus (CS) than rats receiving appropriate control procedures. Experiment 2 found that extinction of the first-order CS had no effect on established second-order conditioned analgesia. Experiment 3 evaluated the effects of post second-order conditioning pairings of morphine and the shock unconditioned stimulus (US). Rats receiving paired morphine-shock presentations showed significantly shorter response latencies during a hot-plate test of pain sensitivity in the presence of the second-order CS than did groups of rats receiving various control procedures; second-order analgesia was attenuated. These data extend the associative account of conditioned analgesia to second-order conditioning situations and are discussed in terms of the mediation of both first- and second-order analgesia by an association between the CS and a representation or expectancy of the US, which may directly activate endogenous pain inhibition systems.     

An analysis of second-order autoshaping

Three mechanisms can explain second-order conditioning: (1) The second-order conditioned stimulus (CS2) could activate a representation of the first-order conditioned stimulus (CS1), thereby provoking the conditioned response (CR); The CS2 could enter into an excitatory association with either (2) the representation governing the CR, or (3) with a representation of the reinforcer evoked by the CS1. A series of experiments using second-order autoshaping with birds was performed to examine these possibilities. Following second-order autoshaping, birds’ responding to the CS2 was found to be unaffected by extinction of the CS1, a result interpreted as showing mechanism (1) to be unimportant and implicating either one or both of the other mechanisms. The CS2 was also shown to provide the birds with specific sensory information about the reinforcer, a pattern of results uniquely predicted by mechanism (3). Implications for the understanding of second-order conditioning and for the SOP model (Wagner, 1981) of associative learning are discussed.     

Goal-tracking behavior in the pond snail, Lymnaea stagnalis

The occurrence of goal-tracking, an unconditioned stimulus (US)-directed autoshaping behavior, was studied in open-field tests with control and classically conditioned pond snails, Lymnaea stagnalis. In an appetitive classical conditioning paradigm with a tactile stimulus as conditioned stimulus (CS) and a localized food stimulus as US a conditioned feeding response built up in the experimental but not in the control animals. In the post-training open-field tests the experimental group alone showed an enhanced attraction toward the source of water current in the environment which previously signalled the arrival of the US but did not act as CS in the classical conditioning procedure. We suggest that this stimulus-directed goal-tracking behavior in Lymnaea is the result of a classical-operant interaction, described so far only in vertebrate animals, and that neurophysiological analysis of this behavior is possible in this snail.     

Skin conductance response conditioning with CS intensities equal to and greater than UCS intensity

With .2-sec bursts of white noise as both conditioned stimulus (CS) and unconditioned stimulus (UCS), conditioning of first-interval skin conductance responses was obtained when the intensity of the CS equaled and exceeded that of the UCS. There was no evidence that second-interval response conditioning occurred. Nonspecific response frequencies were also affected by the variations in stimulus intensity, this raising some question about typical controls employed in SCR conditioning. There was some evidence that second interval responses were suppressed by the intense CS values. It was concluded that the existence of simple conditioning with a CS/UCS intensity ratio equal to or greater than unity was contrary to the Pavlovian proposition that a CS must be biologically less salient than the UCS in order for conditioning to occur. It was noted, however, that the suppression of second-interval responses might indicate that anticipatory CRs which are not confounded with orienting reflexes are prevented from exhibiting a conditioning effect when a high CS/UCS intensity ratio is employed.     

The Relation of the Galvanic Skin Reflex Recovery Curve to Reactivity,Resistance Level,and Perspiration

The effect of stimulus compounding in classical conditioning was investigated by conditioning one group of rats to a compound CS consisting of a buzzer and light and then conditioning separate groups of rats to the individual elements of the compound CS. On hurdle-jump test trials, the group of Ss conditioned to the compound CS performed better than Ss conditioned to the elements of the compound. Strength of conditioning to each of the elements of the compound CS was about equal. There was some evidence of a summation effect resulting from conditioning to the compound CS. Strength of conditioning to the compound CS was somewhat greater than the sum of the response strengths conditioned to the elements of the compound CS.     

Differential acquisition,extinction, and reinstatement of conditioned suppression in mice

In animals, the reappearance of conditioned fear responses after extinction has been primarily investigated using single-cue conditioning paradigms. However, a differential paradigm can overcome several of the disadvantages associated with a single-cue procedure. In the present study, the reinstatement phenomenon was assessed in mice using a differential conditioned suppression paradigm. In a first phase, one conditioned stimulus (CS + ) was consistently paired with an unconditioned stimulus (US; footshock) while another CS (CS–) was not, resulting in selective suppression of previously trained instrumental behaviour during the CS + . After the extinction phase, half of the animals (reinstatement group) were presented with unsignalled USs, while the other half were not (control group). A differential return of conditioned responding was observed in the reinstatement group, but not in the control group. The implications of these findings for future conditioning research are discussed.     

Conditioning the unconditioned response: modification of the rabbit's (Oryctolagus cuniculus) unconditioned nictitating membrane response

Conditioning-specific reflex modification (CRM) occurs when classical conditioning modifies responding to an unconditioned stimulus (US) in the absence of a conditioned stimulus (CS). Three experiments monitored rabbit nictitating (Oryctolagus cuniculus) membrane unconditioned responses to 5 intensities and 4 durations of periorbital electrical stimulation before and after CS or US manipulation. CRM occurred after 12 days of CS-US pairings but not following unpaired CS/US presentations or restraint. CRM survived CS-alone and CS/US-unpaired extinction of the conditioned response (CR) but not presentations of the US alone, although CRs remained intact. Thus, CRs could be weakened without eliminating CRM and CRM could be weakened without eliminating CRs. Data indicate CRM is a reliable, associative effect that is more than a generalized CR and may not be explained by habituation, stimulus generalization, contextual conditioning, or bidirectional conditioning.     

Attenuation of age-related conditioning deficits in humans by extension of the interstimulus interval

Young (17-22 years) and older (61-86 years) persons underwent classical conditioning of the eye-blink response to a tone conditioned stimulus (CS) and an airpuff unconditioned stimulus (UCS) at 1 of 3 interstimulus intervals (ISIs; 400, 650, and 900 ms). As in a previous study, older subjects conditioned more slowly and emitted fewer conditioned responses at the optimal 400-ms ISI. At longer ISIs, however, this age-related disruption of classical conditioning was attenuated. These differences in conditioning were not due to nonassociative factors, such as sensitivity to the tone CS or airpuff UCS or to differences in spontaneous blink rate, nor were they due to differences in general cognitive abilities. The results are discussed in terms of the role of temporal relationships between stimuli in conditioning across the life span.     

Simultaneous conditioning in honeybees (Apis mellifera).

Honeybees (Apis mellifera) were classically conditioned with odor as conditioned stimulus (CS), sucrose as unconditioned stimulus (US), and proboscis extension as response. The purpose of Experiment 1 (Ns = 26 and 27) was to look for facilitation of forward conditioning by CS-US overlap, but rapid conditioning without overlap left little room for improvement. In 2 further experiments, CS and US were simultaneous, and response to odor alone was measured in subsequent tests. In Experiment 2, a Simultaneous group (N = 25) responded more to the training odor than did an Unpaired control group (N = 25). In Experiment 3, a differentially conditioned Simultaneous group (N = 29) responded more to an odor paired with sucrose in training (S+) than to an odor presented alone (S-). The implications of the results for the problem of the role of amount of reward in honeybee learning are considered.     

Differential acquisition, extinction, and reinstatement of conditioned suppression in mice

In animals, the reappearance of conditioned fear responses after extinction has been primarily investigated using single-cue conditioning paradigms. However, a differential paradigm can overcome several of the disadvantages associated with a single-cue procedure. In the present study, the reinstatement phenomenon was assessed in mice using a differential conditioned suppression paradigm. In a first phase, one conditioned stimulus (CS + ) was consistently paired with an unconditioned stimulus (US; footshock) while another CS (CS-) was not, resulting in selective suppression of previously trained instrumental behaviour during the CS + . After the extinction phase, half of the animals (reinstatement group) were presented with unsignalled USs, while the other half were not (control group). A differential return of conditioned responding was observed in the reinstatement group, but not in the control group. The implications of these findings for future conditioning research are discussed.     

The comparator hypothesis of conditioned response generation: manifest conditioned excitation and inhibition as a function of relative excitatory strengths of CS and conditioning context at the time of testing

In the present research water-deprived rats were used in a conditioned lick suppression paradigm to test and further develop Rescorla's (1968) contingency theory, which posits that excitatory associations are formed when a conditioned stimulus (CS) signals an increase in unconditioned stimulus (US) likelihood and that inhibitory associations develop when the CS signals a decrease in US likelihood. In Experiment 1 we found that responding to a CS varied inversely with the associative status of the context in which the CS was trained and that this response was unaltered when testing occurred in a distinctively dissimilar context with a different conditioning history, provided associative summation with the test context was minimized. These results suggest that manifest excitatory and inhibitory conditioned responding is modulated by the associative value of the training context rather than that of the test context. In Experiment 2 it was demonstrated that postconditioning decreases in the associative value of the CS training context reduced the effective inhibitory value of the CS even when testing occurred outside of the training context. Moreover, this contextual deflation effect was specific to the CS training context as opposed to any other excitatory context. Collectively, these studies support the comparator hypothesis, which states that conditioned responding is determined by a comparison of the associative strengths of the CS and its training context that occurs at the time of testing rather than at the time of conditioning. This implies that all associations are excitatory and that responding indicative of conditioned inhibition reflects a CS-US association that is below (or near) the associative strength of its comparator stimulus. It is suggested that response rules which go beyond a monotonic relation between associative value and response strength can partially relieve learning theories of their explanatory burdens, thereby allowing for simpler models of acquisition.     

The effect of on‐ or off‐line extinction of a first‐order conditioned stimulus on a second‐order conditioned response in rats

In a water‐licking experiment with rats, the effects of the extinction of a first‐order conditioned stimulus (CS1) on the suppression of licking established for a second‐order conditioned stimulus (CS2) were explored. Extinction of the first‐order conditioned response (CR1) attenuated the conditioned suppression induced by CS2 when the rats had been allowed to lick water during the CR1 extinction phase. However, if water had been unavailable during the CR1 extinction phase, suppression by CS2 was not affected. The latter result is consistent with other studies of rats' conditioned suppression and suggests that the underlying mechanism of second‐order conditioning in this experiment is a connection between CS2 and the response elicited by CS1 rather than a CS2‐CS1 connection. The former result was interpreted as the CR1 extinction phase encouraging the rats to lick water despite the fear elicited by CS1, and thus, in testing, they licked despite the fear elicited by CS2.     

THE “WHERE IS IT?” REFLEX: AUTOSHAPING THE ORIENTING RESPONSE

The goal of this review is to compare two divergent lines of research on signal-centered behavior: the orienting reflex (OR) and autoshaping. A review of conditioning experiments in animals and humans suggests that the novelty hypothesis of the OR is no longer tenable. Only stimuli that represent biological “relevance” elicit ORs. A stimulus may be relevant a priori (i.e., unconditioned) or as a result of conditioning. Exposure to a conditioned stimulus (CS) that predicts a positive reinforcer causes the animal to orient to it throughout conditioning. Within the CS-US interval, the initial CS-directed orienting response is followed by US-directed tendencies. Experimental evidence is shown that the development and maintenance of the conditioned OR occur in a similar fashion both in response-independent (classical) and response-dependent (instrumental) paradigms. It is proposed that the conditioned OR and the signal-directed autoshaped response are identical. Signals predicting aversive events repel the subject from the source of the CS. It is suggested that the function of the CS is not only to signal the probability of US occurrence, but also to serve as a spatial cue to guide the animal in the environment.     

Time Cues Block the CS, but the CS Does Not Block Time Cues

Analysis of conditioned defensive freezing in rats revealed that prior pairings of a tone conditioned stimulus (CS) and footshock in Context 1 at Time 1 failed to give that tone CS the power to block conditioning to Context 2 at Time 2. This failure of an excitatory CS to block conditioning of time cues was not reciprocal. When the stimulus roles were reversed, excitatory time cues blocked conditioning to the tone CS. This asymmetry in blocking is best explained by the notion that time cues have special access to the association-formation mechanism.     

Conditioned taste aversion with sucrose and tactile stimuli in the pond snail Lymnaea stagnalis

A new form of taste aversion conditioning was established in the pond snail Lymnaea stagnalis. An associative memory, lasting 24h, was produced in the pond snail with 20 pairings of 100 mM sucrose as the conditioned stimulus (CS) and mechanical stimulation to the head as the unconditioned stimulus (UCS). Animals exposed to reverse pairings of the CS and UCS failed to learn the association. The learning was characterized by a shift in the response to the UCS from a whole-body withdrawal response to the cessation of feeding behavior.     

Conditioned inhibition of fear: Evidence for a competing response mechanism

In two experiments, inhibitory conditioning was attempted by presenting a discrete CS in a neutral stimulus environment shortly following the termination of either shock (Experiment 1) or a second discrete CS which had been paired in a forward manner with shock (Experiment 2). Evidence of successful inhibitory conditioning was mixed in Experiment 1, where the properties of the CS were assessed within an escape-from-fear procedure. Postresponse presentations of the CS enhanced performance, whereas the presentation of the CS prior to responding did not have the expected degrading effect on performance. In Experiment 2, the inhibitory properties of the CS were assessed by combining this stimulus with an excitatory CS and presenting the compound to rats engaged in a water-reinforced licking response. Less response suppression was found in reaction to this compound relative to three separate comparison conditions, thus witnessing the success of the inhibitory-conditioning procedure used. The common assumption that inhibitory conditioning results from the nonreinforcement of a CS in a situation where reinforcement is expected, i.e., one which contains previously reinforced cues, is not supported by these data, for no previously reinforced cues were simultaneously presented with the CS during inhibitory training. The data are in agreement with a conditioned antagonistic-response interpretation of inhibitory conditioning.