David A. T. Siddle

Human Blink Startle During Aversive and Nonaversive Pavlovian Conditioning

Potentiation of blink startle during aversive and nonaversive Pavlovian single-cue conditioning was assessed in human Ss. In Experiment 1 (N = 89), the conditioning group received paired presentations of a visual conditioned stimulus (CS) and an unconditioned stimulus (US), whereas the control group was presented with a random sequence. The US was an electric shock for half the Ss and a nonaversive reaction time task for the other half. Electrodermal conditioning was evident regardless of the nature of the US, but blink potentiation was found only in the conditioning group that had been trained with the aversive US. These results were replicated in Experiment 2 (N = 65), in which a nonaversive US of increased motivational significance was used. Thus, only aversive conditioning seems to affect the affective valence of the CS, at least as reflected by changes in a skeletal reflex.

Latent inhibition in humans : single-cue conditioning revisited

Latent inhibition in human Pavlovian conditioning was assessed by way of autonomic responses. In Experiment 1 (N = 72), three pairs of conditioning and control groups were preexposed to 0, 10, or 20 to-be-conditioned stimuli (to-be-CSs), respectively. Acquisition of electrodermal first-interval and heart rate response conditioning were detectable only in the zero preexposure condition. However, 20 preexposures were needed for latent inhibition of vasomotor response conditioning. In Experiment 2 (N = 48), preexposure to the to-be-CS was compared with preexposure to a stimulus that was not presented during subsequent acquisition. CS preexposure completely abolished electrodermal first-interval and heart rate response conditioning. Although vasomotor conditioning was not affected by preexposure, latent inhibition of second-interval electrodermal response conditioning was obtained. Taken together, the data from both experiments provide clear evidence for latent inhibition in human Pavlovian conditioning.

PSYCHOSIS PRONENESS IN A NON-CLINICAL SAMPLE I: A PSYCHOMETRIC STUDY

Previous experimental research that has investigated differences in performance between psychosis prone and not-prone healthy subjects has utilized a variety of different measures of psychosis proneness. The present work investigated the relationship between these measures and provided reliability data for each of them. Ten scales that have been employed to measure different aspects of psychosis proneness were administered to 537 undergraduate students (371 females) together with measures of extraversion and neuroticism. Internal consistency and retest reliabilities were calculated and gender differences were analysed. To investigate the structure of psychosis proneness, factor analyses were performed both with and without the measures of extraversion and neuroticism. These analyses yielded two factors, one representing cognitive/perceptual aspects of psychosis proneness and a second consisting of measures of anhedonia and psychoticism. If extraversion and neuroticism were included, three factor solutions were obtained. The present results confirm earlier findings that psychosis proneness consists of two separate components. Based on the reliability scores, suitable measures for each component are suggested for use in future experimental research.

The effect of warning stimulus modality on blink startle modification in reaction time tasks

The present study investigated the effects of lead stimulus modality on modification of the acoustic startle reflex during three reaction time tasks. In Experiment 1, participants (N = 48) were required to press a button at the offset of one stimulus (task relevant) and to ignore presentations of a second (task irrelevant). Two tones that differed in pitch or two lights served as signal stimuli. Blink startle was elicited during some of the stimuli and during interstimulus intervals. Skin conductance responses were larger during task-relevant stimuli in both groups. Larger blink facilitation during task-relevant stimuli was found only in the group presented with auditory stimuli, whereas larger blink latency shortening during task-relevant stimuli was found in both groups. Experiment 2 (N = 32) used only a task-relevant stimulus. Blink magnitude facilitation was significant only in the group presented with tones, whereas blink latency shortening was significant in both groups. Experiment 3 (N = 80) used a go/nogo task that required participants to press a button if one element of a compound stimulus ended before the second, but not if the asynchrony was reversed. The offset asynchrony was varied between groups as a manipulation of task difficulty. Startle magnitude facilitation was larger during acoustic than during visual stimuli and larger in the easy condition. The present data indicate that startle facilitation in a reaction time task is affected by stimulus modality and by task demands. The effects of the task demands seem to be independent of lead stimulus modality.

Effects of stimulus modality and task condition on blink startle modification and on electrodermal responses

Participants in Experiments 1 and 2 performed a discrimination and counting task to assess the effect of lead stimulus modality on attentional modification of the acoustic startle reflex. Modality of the discrimination stimuli was changed across subjects. Electrodermal responses were larger during task-relevant stimuli than during task-irrelevant stimuli in all conditions. Larger blink magnitude facilitation was found during auditory and visual task-relevant stimuli, but not for tactile stimuli. Experiment 3 used acoustic, visual, and tactile conditioned stimuli (CSs) in differential conditioning with an aversive unconditioned stimulus (US). Startle magnitude facilitation and electrodermal responses were larger during a CS that preceded the US than during a CS that was presented alone regardless of lead stimulus modality. Although not unequivocal, the present data pose problems for attentional accounts of blink modification that emphasize the importance of lead stimulus modality.

Blink startle modulation during anticipation of pleasant and unpleasant stimuli

The present research investigated blink startle modulation during the anticipation of pleasant, unpleasant, or neutral pictures. In Experiment 1 (N = 18), participants were presented with three different tone-picture pairings. Tones differed in pitch and were followed by pleasant, neutral or unpleasant pictures. Acoustic blink reflexes were elicited during some tones and during stimulus free intervals. Blink facilitation during tones that preceded pleasant and unpleasant pictures was larger than during the tone that preceded neutral pictures. Experiment 2 (N = 10) assessed whether this difference was due to a difference in the presentation frequency of the three conditions. No difference in blink facilitation between the conditions was found when pictures of flowers and mushrooms replaced the pleasant and unpleasant pictures, indicating that picture content was instrumental in causing the differential blink facilitation in Experiment 1. The results from Experiment 1 seem to indicate that startle modulation during the anticipation of pictorial material reflects the interest in or the arousal associated with the pictures rather than picture valence.

The effects of threat and nonthreat word lead stimuli on blink modification

Two experiments examined the effects of visually presented threat and nonthreat word lead stimuli on blink modification among unselected young adults (Experiment 1, N = 35) and participants selected for low and high trait anxiety (Experiment 2, N = 60). The blink reflex was elicited by a white noise probe of 105 dB. Lead stimulus intervals of 60, 120, 240, and 2000 ms were used in both experiments. Prepulse inhibition was observed at the 240-ms interval and prepulse facilitation was observed at the 60-ms interval in both experiments. Also, greater facilitation was found in both experiments during threat words at the 60-ms interval and greater inhibition during threat words at the 240-ms interval. Experiment 2 provided some evidence that the greater facilitation during threat words than during nonthreat words at the 60-ms probe interval may be found in high trait anxious participants, but not in low trait anxious participants. The results are discussed in relation to contemporary information processing theories of anxiety.

The effects of unconditional stimulus valence and conditioning paradigm on verbal, skeleto-motor, and autonomic indices of human Pavlovian conditioning

The effects of unconditional stimulus (US) valence (aversive electro-tactile stimulus vs. non-aversive imperative stimulus of a RT task) and conditioning paradigm (delay vs. trace) on affective learning as indexed by verbal ratings of conditional stimulus (CS) pleasantness and blink startle modulation and on relational learning as indexed by electrodermal responses were investigated. Affective learning was not affected by the conditioning paradigm; however, electrodermal responses and blink latency shortening indicated delayed learning in the trace procedure. Changes in rated CS pleasantness were found with the aversive US, but not with the non-aversive US. Differential conditioning as indexed by electrodermal responses and startle modulation was found regardless of US valence. The finding of significant differential blink modulation and electrodermal responding in the absence of a change in rated CS pleasantness as a result of conditioning with a non-aversive US was replicated in a second experiment. These results seem to indicate that startle modulation during conditioning is mediated by the arousal level of the anticipated US, rather than by the valence of the CS.

Effects of miscuing on Pavlovian conditioned responding and on probe reaction time.

Two experiments examined the effect of the miscuing of an unconditioned stimulus on Pavlovian conditioned responding. In Experiment 1 (N = 32), subjects received 12 CS+-US and 12 CS- presentations followed, in the experimental group, by a CS--US pairing (miscuing) on Trial 25 and a CS+-US pairing on Trial 26. For the control group, Trial 25 consisted of a CS--alone presentation and Trial 26 consisted of a CS+-US pairing. Visual stimuli (geometric shapes) of 8-s duration served as CSs, and a 1-s burst of white noise (100 dBA) was used as the US. Both electrodermal activity and a continuous measure of US expectancy were obtained. Expectancy of the US was significantly lower in the experimental group than in the control on the CS+-US trial which followed miscuing, whereas electrodermal responses to the US were significantly larger. However, first- and second-interval responses during CS+ on this trial were not influenced by miscuing. Experiment 2 (N = 64) employed the same stimuli and procedures as used in Experiment 1, but the dependent measure was reaction time to a probe stimulus presented either early (300 ms) or late (7500 ms) during some CSs+ and some CSs-. During the acquisition phase, probe reaction time was slower during CS+ than during CS- regardless of probe position. Moreover, reaction time to probes presented during CS+ on the trial which followed miscuing was slower in the experimental group than in the control irrespective of probe position. Although not all findings were as predicted, the present results suggest that a CS-US pairing disrupted the association between CS+ and the US. This effect of US miscuing is difficult to interpret within the framework of current theories of Pavlovian conditioning.

The effects of change in lead stimulus modality on the modulation of acoustic blink startle

In two experiments we investigated the effect of generalized orienting induced by changing the modality of the lead stimulus on the modulation of blink reflexes elicited by acoustic stimuli. In Experiment 1 (n = 32), participants were presented with acoustic or visual change stimuli after habituation training with tactile lead stimuli. In Experiment 2 (n = 64), modality of the lead stimulus (acoustic vs. visual) was crossed with experimental condition (change vs. no change). Lead stimulus change resulted in increased electrodermal orienting in both experiments. Blink latency shortening and blink magnitude facilitation increased from habituation to change trials regardless of whether the change stimulus was presented in the same or in a different modality as the reflex-eliciting stimulus. These results are not consistent with modality-specific accounts of attentional startle modulation.