Search PubMed⌕ Search

Biomedical subjects

H Lachnit

Publications and source records attributed to H Lachnit.

At least 19 recordsLinked to original sources
PubMed2001

What is learned in patterning discriminations? Further tests of configural accounts of associative learning in human electrodermal conditioning.

Two Pavlovian SCR conditioning experiments investigated positive and negative patterning discriminations in humans by means of transfer tests. In Experiment 1, positive patterning (A-,B-,AB+) was trained interleaved with non-reinforced presentations of an additional stimulus (C-). Then responding to new compounds consisting of either already trained elements (AC,BC) or new elements (DE) was examined. In Experiment 2, negative patterning (A+,B+,AB-) was trained interleaved with reinforced presentations of an additional stimulus (C+). Again, we examined responding to new compounds consisting of either already trained elements (AC,BC) or new elements (DE). In both experiments the initial patterning discrimination was solved successfully. The response patterns to the test compounds in both experiments were in contradiction to configural accounts of associative learning. In positive patterning human participants seemed to utilize 'number' or some other abstract feature in preference to available concrete stimuli. In negative patterning the abstract dimension of 'separate-versus-together' or 'opposite' was used.

Adult↗
PubMed2001

Evidence for the application of rules in Pavlovian electrodermal conditioning with humans.

Two Pavlovian SCR conditioning experiments investigated interference effects in sequential training of positive and negative patterning discriminations in humans. In Experiment 1, positive patterning (A-, B-, AB+) was trained in Phase 1, immediately followed by a negative patterning schedule (C+, D+, CD-). We predicted that human participants would learn a specific numerosity rule in positive patterning, which interferes with the subsequent negative patterning schedule. In Experiment 2, negative patterning (C+, D+, CD-) was trained in Phase 1, followed by a positive patterning schedule (A-, B-, AB+) in Phase 2. Because human participants would learn an abstract 'separate-versus-together'- or 'opposite'-rule to solve the negative patterning discrimination in Phase 1, there should be less interference in positive patterning in Phase 2 where the separate/together-rule could be applied, too. In both experiments, the initial patterning discriminations were acquired successfully. In Experiment 1, human participants totally failed to solve the Phase 2 discrimination, while in Experiment 2 appropriate response differentiation developed in Phase 2. Thus, without pre-experience human participants seem to utilize a specific numerosity-rule in positive patterning and a separate/together-rule in negative patterning.

Adult↗
PubMed2000

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.

Adult↗
PubMed2000

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.

Adult↗
PubMed2000

Costs or benefits of emotional conditioning on cognitive processing?

We report on two experiments using a transfer-of-control procedure in evaluating costs or benefits of emotionally relevant stimuli on the processing of a cognitive task. In differential conditioning the impact of Pavlovian conditioning usually is examined by contrasting instrumental responses in the presence of an excitatory conditioned stimulus (CS+) and an inhibitory conditioned stimulus (CS-). We expanded this comparison by introducing a neutral third condition. This additional neutral condition served as a within subject control for evaluating whether the CS+ increased responding and/or the CS- decreased responding. Both experiments yielded the same result; the CS- slowed down cognitive processing while the CS+ had no impact. Thus, the proposed transfer-of-control procedure may serve as a reliable and valid research tool in the evaluation of motivation and emotion in humans.

Adult↗
PubMed2000

Stimulus representations in human Pavlovian conditioning: implications of missing negative transfer across response systems.

Three Pavlovian conditioning experiments with human participants are reported, which investigated whether common or separate stimulus representations are involved in solving nonlinear discrimination tasks in different response systems. In our experiments we made use of a negative transfer effect between positive and negative patterning. Experiment 1 specified the conditions under which such a negative transfer effect occurs in human eyelid conditioning. Experiments 2 and 3 investigated whether a similar effect also occurs if two response systems--the eyelid and the skin conductance response system--are trained with trials of both types being randomly interleaved. The presence or absence of a negative transfer effect indicates whether or not the stimulus representations involved in the two conditioning processes overlap. The findings are discussed within the framework of a neuropsychological model of hippocampal function. The results suggest that the representations are distinct and thus support the idea of acquired equivalence and distinctiveness of stimulus representations.

Adult↗
PubMed1996

[Are there differences in processing times of variously complex rules in differential eyelid conditioning?].

Two logical relations, conjunction (AND) and exclusive disjunction (XOR) differ in formal complexity as well as in observable difficulties. AND results in less errors, fewer trials to criterion, and shorter processing time per trial than XOR. Two paradigms of differential classical conditioning are based on these rules. Negative patterning (A+, B+, AB-) equals XOR, and positive patterning (A-, B-, AB+) equals AND. We studied experimentally whether or not differences in processing time per trial are reflected in different optimal interstimulus intervals in human eyelid conditioning. Results of four groups (AND/XOR x 400/1200 ms; each group n = 10) suggest that differential conditioning could be observed in positive patterning (800-1000 ms) earlier than in negative patterning (1000-1200 ms).

Adult↗
PubMed1994

[Inductive versus associative processes in stimulus discrimination].

The experiment reported here was an attempt to demonstrate that the solution of specific discrimination problems is based on rules rather than on differences in associative strengths. With positive and negative patterning as examples, we examined whether or not the solution of the discrimination problem depends on the number of reinforcements for each individual stimulus when the total number of reinforcements is kept constant. This was achieved by manipulating the number of stimuli used. We also examined the transfer to new stimuli. Forty subjects took part in a 2 x 2-factorial experiment with anticipatory skin conductance responses as the dependent variable. All the results were in accordance with the assumption of rule based problem solution. The amount of discrimination was independent of the number of reinforcements for each stimulus. Furthermore, according to results of concept formation studies, an asymmetry in transferring the solution to new stimuli was observed.

Adult↗
PubMed1994

[Is there a feature-positive effect in classical conditioning in humans?].

Jenkins and Sainsbury (1969, 1979) first described an asymmetry in pigeon's operant discrimination learning which they called a feature-positive effect. Subsequent studies demonstrated that other animals as well as humans also show a similar asymmetry. The effect is often explained as being caused by a bias in information processing which results from the neglect of negative information as a discriminative cue. The effect has also been observed in classical conditioning experiments, but not yet with human subjects. Sometimes, however, a reversal of the asymmetry, i.e., a feature-negative effect, has been observed. The experiment reported here primarily intended to demonstrate a feature-positive effect in a classical conditioning procedure with human subjects. Secondly, we also wanted to test an alternative explanation of the feature-positive effect. We found that a substantial feature-positive effect does indeed occur during classical conditioning in human subjects. Our results, however, did not fully support the alternative explanation based on rule learning.

Adult↗
PubMed1994

[Skin conduction as an indicator of cognitive and emotional processes].

Classical conditioning experiments can be used to study both cognition and emotions. In studies involving human subjects two different scores based on the human skin conductance response are generally used: the "first interval responses" (FIR) and the "second interval responses" (SIR). The SIR is thought to reflect cognitive but not emotional processes, while the FIR is assumed to reflect both. An experiment with two groups of subjects (n = 20 each) was run in order to demonstrate that the SIR indeed is able to reflect emotional processes. Each group was trained with five different conditioned stimuli, each of which was paired with a specific unconditioned stimulus. These unconditioned stimuli varied in aversiveness. Immediately after training, skin conductance responses to combinations of already trained conditioned stimuli were examined. The sequence of testing was varied across groups. Our results clearly showed that the SIR reflected aversiveness, while the FIR was confounded by orienting responses under these experimental conditions.

Adult↗
PubMed1992

Mobilization of cognitive resources and the generation effect.

The generation effect refers to the memory advantage of words that have been generated rather than read. Such a read-generate comparison confounds qualitative task differences and raises methodological problems. A revised methodology is proposed circumventing these problems in that the encoding task is held constant and all stimuli have to be generated, but the degree of generativeness (i.e. the amount of cueing) is varied. In Experiment 1, 1, the (refined version of the) generation effect is demonstrated in a within-subjects design; with increasing generation activity left to the subject, free recall performance increases. No effect is obtained for degree of target masking. The same finding is replicated and shown to be independent of self-paced study time when generative activity is manipulated between subjects (Experiment 2) or within subjects (Experiment 3). As all learning trials involve generation, encoding time is controlled statistically, and free recall is used as a measure of memory, this refined generation effect cannot be explained as an artifact of selective attention or elaboration. Rather, generative activity seems to increase the mobilization of cognitive resources. This motivational account is supported by Experiment 4 showing an enhanced generation effect for positive mood.

Adult↗
PubMed1990

Speed and accuracy effects of fingers and dexterity in 5-choice reaction tasks.

In two experiments we studied the influence of dexterity (controls, typists, pianists) and of differences between the five fingers of the dominant hand on speed and accuracy in a 5-choice reaction task. We used five coloured squares (Blue, Green, Yellow, Red, White) as stimuli, randomly varying foreperiods (3-10s) and an intermediate stimulus-response-compatibility. The results reported here were independent of sex, foreperiods, and colour of stimuli. In Experiment 1 (N = 168) with three groups (controls, typists, pianists) thumb and little finger showed significantly shorter reaction times than did index, middle, and ring finger. This difference did not interact with dexterity. Averaged across all the fingers typists and controls did not differ. Pianists showed significantly shorter reaction times than these two groups. Experiment 2 (N = 40) replicated all these findings. In both experiments groups did not differ in speed-accuracy-trade-off. The accuracy of the fingers was independent of dexterity. In all three groups the little finger showed the lowest rate of false alarms and the highest degree of reliability. The frequency distribution of finger confusions in all groups was in accordance with the spatial proximity of fingers: the closer their proximity the higher were the rates of confusion. In addition, these distributions showed an asymmetry across all three groups. The finger next to the 'correct' finger in direction towards the thumb showed the highest false alarm rate in each case.

Adolescent↗
PubMed1988

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.

Arousal↗
PubMedDate not supplied

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.

Adult↗
PubMedDate not supplied

Simultaneous classical conditioning of two effector systems.

The experiment reported here was an attempt to develop an experimental procedure for independent classical conditioning of two different response systems, the skin conductance response (SCR) and the eyelid response. In a differential conditioning design with human subjects (N = 50) two different unconditioned stimuli were used, a white noise (US1) and airpuff (US2). Two conditioned stimuli (CS11 and CS12) were paired with US1, and two other CSs (CS21 and CS22) were paired with US2. A special trial architecture was used to accomplish measurement of both anticipatory SCR and eyelid responses during each trial. Significant eyelid differentiation as well as significant SCR (especially second interval responses) differentiation developed.

Adult↗