Blocking observed in human eyelid conditioning

The status of blocking in human eyelid conditioning was examined in a series of four experiments modelled on rabbit nictitating membrane (NMR) procedures to ensure comparability with the animal literature. The first three employed Tones and Lights as CSs and a preliminary experiment established equivalent salience of these stimuli. The fourth employed all light conditioned stimuli (CSs). Each of the experiments balanced order of presentation of blocked and non-blocked stimuli in extinction; each yielded reliable evidence of blocking tested in extinction. However, the blocking effects were attenuated or abolished in those groups receiving the to-be-blocked stimulus on the first trial in extinction. The results show blocking to be a relatively weak, easily disrupted phenomenon compared with rabbit studies. They suggest that rapid re-appraisal of stimulus significance plays a more important role in human subjects than has been observed in animal studies.     

Blocking observed in human eyelid conditioning

Four eyelid conditioning experiments designed to be comparable to rabbit nictitating membrane (NMR) studies examined the blocking phenomenon in humans. All experiments utilized a within-subjects design, with Stage 1 of discrimination, Stage 2 of compound training, and a final test stage comparing responding to the blocked and non-blocked CSs. In two of the experiments (1 and 4) the comparison was made within subjects over all extinction trials. In Experiment 3 the test phase consisted of further reinforced training of the blocked and non-blocked CSs. These three experiments produced evidence of blocking when all extinction trials were entered into the analysis. Experiment 2, which involved a between-subjects comparison, failed to demonstrate the blocking effect. Wide variability both between and within subjects obscured the experimental effects. Post-experimental questionnaires designed to assess awareness of stimulus relations failed to identify a subjective blocking effect and showed no relationship to conditioned eyelid responding     

An electrode hookup for eyelid conditioning

A method for recording eyelid CRs, using skin electrodes rather than the usual mechanical connection to the S’s eyelid, is described. Data are presented to show the comparability of the two recording systems.     

Manipulation of response-contingent unconditioned-stimulus intensity in human eyelid conditioning: A two-phase model analysis

Four groups of human subjects were given 360 classical eyeblink conditioning trials. All groups received the same UCS (unconditioned stimulus) intensity on[Formula: see text] (nonconditioned response) trials but differed in the intensity presented on CR trials. Response probability increased as a positive function of UCS intensity on CR trials. Phase 1 of the two-phase model was longer when no UCS was presented on CR trials, but did not differ in duration among the remaining three groups. Most subjects could be described with a single operator in Phase 2, the operator limit increasing as a positive function of CR-contingent UCS intensity. For subjects requiring different operator limits on CR and[Formula: see text] trials, the latter was lower with high CR-trial intensities but higher with low CR-trialintensities. The results were interpreted to be more consistent with drive theory than with "law-of-effect" or two-factor theories.     

The orienting reaction during human eyelid conditioning following preconditioning exposures to the CS

Summary Two experiments on latent inhibition are described in which the electrodermal and alpha blocking components of the orienting reaction (OR) were measured during human eyelid conditioning. In the first experiment the 16 Ss in the experimental group received 20 CS pre-exposure trials. The OR habituated on those trials but reappeared fully after the first conditioning trial. Therefore, after that trial there was no difference in OR amplitude with a no pre-exposure control group. The two groups did not differ in conditioning performance either. In the second experiment two groups of 25 Ss received an equal number of CS pre-exposures but one group was conditioned during the performance of a masking task. This time the reappearance of the OR was only observed in the no-task group. The results of both experiments are discussed in relation to Sokolov's theory on the facilitative effect of the OR on conditioning.The author wishes to thank Ernest van Lieshout and Ad van Oirschot for running the experiments and for help in the data analysis     

A comparison of classical eyelid conditioning in adults and infants

In a classical conditioning procedure an eyeblink-eliciting tap to the glabella (the flat region of skin between the eyebrows) was presented 500 ms after the onset of a mild l-kHz tone. As tone-tap presentations proceeded, the probability of an eyeblink during the latter part of the tone increased in both infants (median age 8 months) and adults, but the infants were slower to condition than the adults and were more variable. Overall, the latency of the conditioned response to tone was significantly longer for infants than for adults, but the latency of the unconditioned response to tap was significantly shorter for infants than for adults.     

Component summation or configuration in human eyelid conditioning depends upon stimulus properties

The experiment reviewed here merges Garner’s (1974) distinction of separable and integral stimulus properties with the field of Pavlovian eyelid conditioning with human subjects. According to one rule, two sets of stimuli (separable vs integral) were constructed. A differential compound conditioning procedure was used with one group of subjects being trained with a subset of the separable material and then tested with a new subset. The same procedure was used with a second group but with integral material. The experiment showed a reversal of conditioning effects, depending on the properties of stimuli. Separable compounds showed results as predicted by elementistic conditioning theories: the associative values of the elements summed up. With integral compounds, the associative values of the elements were irrelevant. Instead, integral compounds were processed and classified primarily on the basis of similarity.     

Component summation or configuration in human eyelid conditioning depends upon stimulus properties

The experiment reviewed here merges Garner's (1974) distinction of separable and integral stimulus properties with the field of Pavlovian eyelid conditioning with human subjects. According to one rule, two sets of stimuli (separable vs integral) were constructed. A differential compound conditioning procedure was used with one group of subjects being trained with a subset of the separable material and then tested with a new subset. The same procedure was used with a second group but with integral material. The experiment showed a reversal of conditioning effects, depending on the properties of stimuli. Separable compounds showed results as predicted by elementistic conditioning theories: the associative values of the elements summed up. With integral compounds, the associative values of the elements were irrelevant. Instead, integral compounds were processed and classified primarily on the basis of similarity.