Further investigations of stimulus coding in nonlinear discrimination problems.

Two human Pavlovian SCR conditioning experiments are reported, investigating CS-coding in negative patterning (NP). In Experiment 1, NP was run with two pairs of letter stimuli (C, N, and M, J), reinforced by shock when alone but not in compound. Controls with the same paired-unpaired sequence saw two additional nonreinforced letters (X and H) instead of compounds. The NP group learned the element-compound differentiation, but the controls did not discriminate reinforced from nonreinforced letters. The availability of an abstract rule (such as stimulus number) for distinguishing between reinforced and nonreinforced CSs led to discrimination in NP, but its unavailability resulted in no discrimination in the controls. In Experiment 2, NP was run with one pair of letters (reinforced as elements but not in compound). A control group had the same paired-unpaired sequence, but their compound contained two different letters from the reinforced ones. The NP discrimination was learned, but the controls failed to differentiate the reinforced elements from the nonreinforced compound. It was concluded that the NP discrimination was not based on the number of reinforced and nonreinforced stimuli, because this dimension was available to both groups in Experiment 2. The abstract dimension of separate versus together, on the other hand, was available only in NP, suggesting that it is the SINE QUA NON for the acquisition of the kind of NP discriminations we have been studying.

Experimental manipulation of a unique cue in Pavlovian SCR conditioning with humans.

We report two experiments on positive and negative patterning in human skin conductance response (SCR) conditioning with a manipulable unique cue. In experiment 1 flashing red lights, arrayed horizontally, were used as elements and apparent movement was used as additional (unique) cue when the elements were presented in compound. Positive and negative patternings were both acquired readily, and positive patterning transferred to new stimuli (green lights, vertically arrayed). The unique cue did not influence these outcomes. Experiment 2 examined only positive patterning, using a more conventional unique cue, a visual frame that surrounded the letter stimuli on compound trials but not on element trials. The unique cue again facilitated neither acquisition nor transfer. These results do not support either the unique cue extension of the Rescorla-Wagner theory or configural theories. Human participants seem to utilize 'size' or 'number' or some other abstract feature in preference to available concrete stimuli.

Blocking and unconditioned response diminution in human classical autonomic conditioning.

Four experiments examined blocking and UR diminution in human SCR conditioning. In Experiment 1, CSX was conditioned in compound with previously conditioned CSA, in one group, or in a compound with another novel stimulus, CSN, in additional group. UR diminution occurred, but there was no post-compound difference in CRs in the two groups and no difference in responding to CSX and CSA following equal training on each, i.e., no blocking. The correlation between blocking and UR diminution was not significant. In Experiment 2, two groups received a blocking procedure, but one was tested on CSX and one on CSA. UR diminution occurred, but there were no post-compound CR or UR differences. There was again no within-subjects blocking effect. The correlation between blocking and UR diminution was not significant, but this correlation was significant when data from Experiments 1 and 2 were combined. In Experiment 3, a differential conditioning procedure was used, followed by reinforcement of two compounds, one with CSA+ and one with CSA-. One subgroup was tested on CSA+ and CSA- with reinforcement; another was tested without reinforcement. UR diminution occurred, and there was significant blocking, but only after two nonreinforced tests. Blocking and UR diminution were significantly correlated. In Experiment 4, four groups received compound conditioning after initial training with CSA. The compound contained CSX and CSA for three groups and two novel CSs for the fourth. Ten nonreinforced test trials were run. The three blocking groups received two CSAs plus eight CSXs four CSAs plus six CSXs, or all CSXs. The fourth group received ten nonblocked CSXs. CR magnitude to blocked CSX was significantly smaller than to nonblocked CSX during the last six test trials, but not initially. Blocking and UR diminution were not correlated, in disagreement with the first three studies. The results indicated that repeated nonreinforced test trails are needed for blocking to be observed in this preparation. The proposition that blocking and UR diminution are both due to reduced processing of the US received only partial support.

Extinction instead of incubation following classical aversive conditioning in dogs.

Two dogs received a single paired classical conditioning trial, with tone CS and 12 mA shock US. Both dogs then showed a conditioned blood pressure increase in response to the nonreinforced CS, which extinguished with additional nonreinforced presentations. The CR showed spontaneous recovery four days later, but reextinguished with additional nonreinforced presentations. The results were interpreted as not supporting Eysenck's theory of "incubation" following one-trial aversive conditioning.

Extending the Rescorla-Wagner theory to account for transswitching.

This article is a brief response to commentaries made by Bond and Siddle (1988) and Lovibond (1988) to our article (Kimmel & Lachnit, 1988) outlining some of the difficulties encountered by the Rescorla-Wagner theory in predicting the outcome of transswitching experiments. We show that Bond and Siddle's assertion that increasing the value of beta would "bring the model into line with the empirical data" (p. 186) is incorrect. Increasing beta in simulated transswitching experiments causes the theory to predict a more rapid increase in associative values, to higher levels, but does not change the degree of predicted phasic switching. We agree with Lovibond's observation that the Rescorla-Wagner theory can predict phasic switching more effectively if it is assumed that an unobserved additional stimulus is present whenever the phasic stimulus occurs in positive tonic segments and a different unobserved additional stimulus is present whenever the phasic stimulus occurs in negative tonic segments. But this kind of usage of the "unique cue hypothesis" does little more then immunize a theory against problematic empirical findings. When the salience of the unique cue is increased relative to that of the stimuli that are actually physically present, simulated transswitching experiments show greater and greater phasic switching. But, unless there is a good a priori reason to postulate such unique cues, or unless the unique cue hypothesis leads to empirically testable new hypotheses, it does not provide a scientifically useful solution to the theory's problem with transswitching.

Blocking and unconditioned response diminution in human classical autonomic conditioning.

This paper summarizes the results of three experiments on blocking and unconditioned response diminution in human SCR conditioning. Recent theories of conditioning propose that reduced processing of the unconditioned stimulus due to conditioning results in reduced unconditioned response magnitude and in blocking of conditioning of a second conditioned stimulus when it is in compound with the previously conditioned stimulus. In these experiments, clear evidence of diminution of the unconditioned response was obtained in all three studies, but blocking was found only in the third study, which employed a within-subject design and in which the blocking was observed only after at least one extinction trial on both the blocked and nonblocked stimuli. Order of testing was not a factor in this delayed blocking effect. These results do not support the view that blocking occurs because of reduced processing of the unconditioned stimulus in the unconditioned response diminution sense.

Acquisition of a unique cue in positive and negative patterning?

Forty college students received a classical differential conditioning procedure involving both positive and negative patterning, each of these being associated with a different pair of stimuli. In positive patterning, elemental stimuli, A and B, were presented without an unconditioned stimulus while their compound, AB, was paired with electric shock. In negative patterning, elemental stimuli, C and D, were paired with shock while their compound, CD, remained unpaired. Thirty of these subjects then received a negative patterning transfer test on new stimuli, while ten subjects received a positive patterning transfer test. First interval response (FIR) and second interval response (SIR) were measured. During initial acquisition, positive patterning occurred in both dependent measures, but negative patterning was present only in the SIR. The transfer tests showed almost significant transfer of positive patterning in FIR and SIR. Negative patterning showed significant transfer neither in FIR nor SIR. It was concluded that, although elementary models of conditioning can explain positive patterning on the basis of summation of excitation from the elements to the compound, the occurrence of negative patterning in the SIR and the almost significant transfer of positive patterning in FIR and SIR appear to require the additional assumption of a unique cue.

Contextual conditioning. A comparison of eastern and western views.

Eastern and Western interpretations of contextual control of phasic conditional responses (transswitching) are contrasted. The Eastern (Asratyan, 1965) approach emphasizes the role of the tonic conditional stimulus and the (hypothetical) tonic response it evokes. The Western (Lachnit, 1986) approach emphasizes the role of compound conditional stimuli. Although Lachnit showed that transswitching-like results can be obtained without a tonic stimulus, attempts to simulate transswitching experiments using a computer model of the Rescorla-Wagner theory (Kimmel and Lachnit, 1988) have shown that predictions from the theory approximate empirical results in human classical conditioning only when the tonic stimulus is given far greater weight than the phasic stimulus. In other words, only when the Rescorla-Wagner theory is made more like Asratyan's theory, can the compound conditional stimulus approach account for real empirical transswitching data.

Persistent effects of a serotonin depletor (p-chlorophenylalanine) in regenerated planaria (Dugesia dorotocephala).

p-Chlorophenylalanine (pCPA) caused an increase in looping and locomotion speed in planaria (Dugesia dorotocephala). These effects dissipated quickly after treatment, except in animals that regenerated from worms surgically sectioned after treatment. Planaria that regenerated from head sections showed more looping 6 and 11 days later than tail regenerates, regenerates from untreated worms, and uncut worms. After the initial acceleration, pCPA animals, especially regenerates from tail sections, slowed down compared with untreated controls. Tail regenerates showed reduced speed 6 and 11 days later in comparison with head regenerates, regenerates from untreated animals, and uncut animals. The speed effect may have been due to pathogenesis in the eye spots in pCPA animals. The looping effect, however, may have been due to persisting serotonin depletion in the head regenerates. It is suggested that research on this problem might profitably be pursued with sexually reproducing planaria, to examine the possibility of genetic recoding due to serotonin depletion.

[The effect of temporal distribution in relation to constant frequency of stimuli on habituation of the orienting reaction]. / Der Einfluss von zeitlicher Verteilung bei konstanter Häufigkeit der Reize auf die Habituation der Orientierungsreaktion.

The lack of empirical evidence for faster habituation with the regular presentation of stimuli suggests that it is not the constancy of presentation of stimuli, but rather the rate of stimulation--defined as the reciprocal of the harmonic mean of the interstimulus intervals--that determines the speed of habituation. Using alternation of 10-70 and 30-50 sec and a constant sequence of 40 sec, three different rates of stimulation were realized. The hypothesis of faster habituation of skin conductance reactions with higher rates of stimulation was not confirmed. However, a consistent pattern of skin conductance reactions, with an increase in reaction after long intervals and a decrease after short intervals, was found, especially in the group with alternating intervals of 10 and 70 sec. The analysis of an additional group with a random sequence of intervals showed that the response pattern did not result simply from the expired time since last stimulus, i.e., a simple mechanical effect. The possibility of anticipating the stimuli and differing information content of the stimuli are discussed as possible determining factors.

Pavlovian conditional stimuli cannot always be defined solely in physical terms.

Twenty-four university students received differential Pavlovian conditioning with two colored stimuli separately accompanied by shock, and two other colored stimuli separately presented without shock. The reinforced and nonreinforced pairs of stimuli both contained complementary elements. After differentiation between the reinforced and nonreinforced elements was established, the complementary pairs were each additively mixed, (i.e., presented at the same time and in the same locus), producing two identical white compounds (established by pilot study). The subjects' skin-conductance responses to the two compounds showed that their different conditioning histories did not result in different responses. Rather, a simple declining function was obtained, resembling habituation or extinction. It was concluded that the definition of the conditional stimulus as a physical event is inappropriate in studies in which physically different stimuli may result in identical internal processes (or phenomenologic experiences)--for example, in additive color mixture.

The Rescorla-Wagner theory does not predict contextual control of phasic responses in transswitching.

Theoretical predictions regarding differential phasic responding to the same phasic conditioned stimulus in two different tonic contexts, generated by a computer simulation of the Rescorla-Wagner theory of classical conditioning, were compared to empirical evidence of phasic switching in two studies of transswitching of the skin conductance response in humans. Significant phasic switching was found in both studies, but the Rescorla-Wagner theory substantially underestimated the obtained differences. It was shown that the theory predicts phasic differences that are more in accord with empirical data when the salience (alpha) of the contextual stimuli is assumed to be much greater than the salience (alpha) of the phasic conditioned stimulus. This modification in salience relationships, however, makes the Rescorla-Wagner theory more like Asratyan's theory of transswitching. Analysis of both tonic and phasic differentiation in experimental groups run with two different phasic stimuli AND two different tonic stimuli or with two phasic stimuli and only one tonic stimulus provided support for the conclusion that tonic response differentiation is a necessary precondition for obtaining phasic switching. It is suggested that the Rescorla-Wagner theory fails to account for phasic switching because it treats tonic and phasic stimuli as essentially equivalent, ignoring the fact that the tonic stimulus is present prior to the time that phasic stimuli occur and that responses to the tonic stimuli can occur during the period following tonic stimulus onset and preceding the administration of phasic stimuli.

Determinants of tonic and phasic reactions in transswitching.

Forty-eight college students were assigned randomly to four groups in a 2 X 2 factorial arrangement of phasic conditional stimuli (same vs. different) and tonic conditional stimuli (same vs. different) to receive 2 days of classical conditioning with a transswitching procedure. Tonic stimuli were a 5-minute projected white triangle or circle; phasic stimuli were a 5-second red or green square superimposed over the tonic stimuli. There were six tonic stimulus segments each day, separated by 20-second periods of no stimulus, three containing six trials of the phasic stimulus paired with shock and three containing six trials of the phasic stimulus alone, in the counterbalanced order. Tonic responding at the onset of the tonic stimuli or during brief periods following its onset were recorded, along with phasic responses to the phasic stimuli. Responses included magnitude of skin conductance responses, frequency of unelicited skin conductance responses, and tonic heart rate. Both skin conductance measures of responding to the tonic stimuli differentiated significantly between positive and negative tonic segments during Day 2, but only in the group with two different tonic stimuli and one phasic stimulus ("standard" transswitching). This supported the hypothesis that tonic stimulus differentiation would be absent when two different phasic stimuli were present. The heart rate data did not support this hypothesis, showing tonic differentiation in both groups with two tonic stimuli. Phasic differentiation controlled by the different phasic stimuli was observed on Day 1; on Day 2, phasic differentiation was present only in the group with two tonic and one phasic stimuli and the group with one tonic and two phasic stimuli.(ABSTRACT TRUNCATED AT 250 WORDS)

Giving context emotional significance by administration of aversive pictures.

Repeated presentation of a picture of an autopsy during a particular auditory context during two experimental sessions resulted in habituation of the unconditioned skin conductance response to the picture and in acquisition of conditioned emotional properties by the auditory context. An emotionally neutral picture, presented in a different auditory context provided a control condition for comparison with the aversive condition. The onset of the aversive auditory context evoked significantly larger skin conductance responses in Session 2 than were evoked by the neutral context. Furthermore, significantly more frequent unelicited skin conductance responses occurred during the aversive context than during the neutral one. These differences between the contexts were observed equally in subjects high in trait anxiety as in subjects low in trait anxiety. The high and low anxiety groups different in frequency of unelicited skin conductance responses, regardless of context. It was concluded that context can acquire conditioned tonic emotional properties as a result of the occurrence of phasic aversive events, even while the reactions to the phasic events are themselves habituating. This phenomenon does not interact with the subject's trait anxiety level.

The myth and the symbol of biofeedback.

This paper argues that biofeedback suffers from misrepresentation of its historical background and early development, false claims about its effects (e.g. mind-expansion) and that it now symbolizes political and social positions with which it has no connection. The myth that biofeedback arose as a revolutionary break from established science is shown to be false. The symbolization of biofeedback as antifascist and libertarian is also debunked. Unfair demands on biofeedback for miracle cures and excessive profiteering from the biofeedback technology are also criticized. It is urged that scientists and clinicians who know better about the real history and applicability of biofeedback should speak out whenever possible against these misrepresentations.

Contextual stimulus control of conditional vasomotor and electrodermal reactions to angry and friendly faces. Transswitching--yes! Preparedness--No!

An experiment with 42 human Ss used the transswitching procedure to examine tonic stimulus control of phasic and tonic conditioned vasomotor heart rate, and electrodermal reactions. The conditional stimulus (CSs) were photos of angry and friendly human faces, and the unconditional stimulus (US) was a human scream. In one tonic context (blue light), the CSs were paired with the US, in the other context (yellow light), the CSs were presented unpaired. Following acquisition, an extinction series was run with the US omitted during both tonic contexts. Phasic vasomotor and skin conductance reactions differed in the positive and negative tonic segments (stronger in positive). The skin conductance responses also differed during extinction, but the vasomotor responses did not. Tonic differences (following onset of the tonic stimuli) in unelicited skin conductance response frequency, finger pulse volume, and heart rate were also found, although these developed more slowly than the phasic differences. The finger pulse volume tonic difference was greater in extinction than the skin conductance response frequency. There was no effect of the angry-friendly facial expressions, either directly or in interaction with the transswitching effects. The results were interpreted to mean that the transswitching phenomenon is not limited to one another autonomic effector, but is more generalized across the ANS (sympathetic branch). The absence of influence of the facial expressions indicates the relative weakness of the "preparedness" hypothesis in comparison with more influential contextual factors.

Conditional tonic stimulus control of nonspecific arousal.

Subjects performed a reaction time (RT) task in the presence of colored indirect lighting which had previously been associated with either sporadic electric shock (Unsafe context) or no shock (Safe context). Autonomic and cortical processes were influenced by the visual context in two ways. Nonspecific arousal was elevated in the Unsafe context as compared with the Safe context (larger SCR and more accelerative HR change elicited by the RT warning stimulus, and retarded habituation of the middle component of the slow cortical potential during the warning stimulus). In addition, information processing may have been impaired in the Unsafe as compared to the Safe context, since the earliest component of the SCR and the N100 component of the auditory evoked potential were both reduced. Higher frequency of unelicited SCR was observed following changes from a Safe to an Unsafe context than with reverse changes, during the association of these contexts with shock, but this was the only evidence of direct tonic conditioning. In general, the results demonstrate the degree to which psychophysiological processes may be influenced by tonic environmental conditions.