Contextual dependencies in a stimulus equivalence paradigm

Two experiments with human subjects assessed contextual dependencies in a stimulus equivalence paradigm. Subjects learned to form two sets of stimuli in a matching-to-sample training procedure. Each set was presented against one of two different background colours, the contextual cues. At test, the influence of a context change--that is, presenting each set against the other context--was measured on baseline, symmetry, and equivalence trials. These three trial types reflect a difference in task complexity. It was predicted that the magnitude of context-dependent effects would be a positive function of task complexity. In Experiment 1, the context change was realized by switching the stimulus set at test while keeping the background colour constant. In Experiment 2, the stimulus set remained constant, and the background colour was switched. In both experiments, a change in context only resulted in an increase in response latency on equivalence trials; no effect was seen on symmetry and baseline trials. Results were discussed in the framework of switch costs, habituation to contextual stimuli, and a model based on Shea and Wright (1995) that explains the differential influence of a context switch on easy versus difficult tasks.     

Event-related potentials in adolescents with combined ADHD and CD disorder: a single stimulus paradigm

Some studies of the event-related potentials demonstrated a reduction of the voluntary component P3 (P300 or P3b) in youngsters with the attention deficit/hyperactivity disorder (ADHD) or in conduct disorders (CD), and a reduction of the automatic processing component, mismatch negativity, in patients with both ADHD and CD (ADHD+CD). Recently, a passive auditory P3 potential has been elicited by a single stimulus. We therefore tried this potential study in 20 healthy subjects and 20 teenagers with ADHD+CD to search for further evidence of the altered automatic cerebral processing in the latter. Subjects also answered a self-report Dimensional Assessment of Personality Pathology (DAPP). The patient group scored significantly higher on most DAPP traits that reflect problems of emotion control, showed significantly prolonged P2, N2, and P3, and reduced P3. In all subjects Stimulus Seeking was positively correlated with P3 latencies at Fz, Cz, and Pz, and with P3 amplitude at Cz. This study suggests that youngsters with ADHD+CD had pronounced emotion dysregulation, and prominent deficit in passive attention, as reflected by the automatic processing of auditory stimuli.     

Timing in pigeons: effects of the similarity between intertrial interval and gap in a timing signal

Previous research suggests that when a fixed interval is interrupted (known as the gap procedure), pigeons tend to reset memory and start timing from 0 after the gap. However, because the ambient conditions of the gap typically have been the same as during the intertrial interval (ITI), ambiguity may have resulted. In the present experiment, the authors found that when ambient conditions during the gap were similar to the ITI, pigeons tended to reset memory, but when ambient conditions during the gap were different from the ITI, pigeons tended to stop timing, retain the duration of the stimulus in memory, and add to that time when the stimulus reappeared. Thus, when the gap was unambiguous, pigeons timed accurately.     

Age differences in switching the relevant stimulus dimensions in a speeded same-different judgment paradigm

The present study employed a same-different judgment task-switching paradigm to re-examine the effects of age on switch costs. We manipulated perceptual and conceptual dimensions to serve as the criteria for making a same-different judgment. We also manipulated a short versus long cue-stimulus interval, while keeping the response-stimulus interval constant in order to examine whether older adults can benefit from longer preparatory intervals. The results indicate that older adults exhibited larger switch costs. In contrast to this impairment, older adults maintained the ability to prepare for an upcoming task switch. Nevertheless, even with a long preparatory interval, older adults still exhibited larger switch costs than younger adults. A more detailed analysis using a mixture model technique suggests that older adults' elevated residual costs in performing perceptual-judgment switches might be attributable to an increased probabilistic failure to complete advance preparation, whereas older adults' elevated residual costs in performing conceptual-judgment switches might be attributable to an intrinsic limitation in their ability to attain a complete task-set reconfiguration during a preparatory interval.     

Evidence of rapid recovery from perceptual odor adaptation using a new stimulus paradigm

By attenuating neural and perceptual responses to sustained stimulation, adaptation enhances the detection of new, transient stimuli. Disadaptation serves a similarly important role as a temporal filter for chemoreceptor cells, producing rapid recovery of sensitivity upon termination of the adapting odorant. Previous research from our laboratory indicated that a rapid form of odor adaptation can be measured using a novel, simultaneous-odorant paradigm. In the present study, we extended the earlier method by measuring recovery from adaptation. Perceptual odor adaptation was measured by estimating psychophysical detection thresholds in a group of college-aged student volunteers (N = 20; 12 females, eight males) for a self-adapting odorant, vanilla extract. To induce adaptation, the time between the onset of the adapting odorant and the onset of the target odorant was systematically varied. By first quantifying adaptation, recovery of sensitivity could therefore be investigated by using different time points following the termination of the adapting odorant. Consistent with our previous work, thresholds estimated in the presence of the simultaneous adapting odorant were significantly increased, reflecting a decrease in sensitivity due to adaptation. Conversely, approximately 100 ms following termination of the adapting stimulus (the briefest delay tested), sensitivity began to rapidly recover. Nevertheless, some residual adaptation was evident at the longest offset delay of 500 ms. These findings suggest that the recovery from adaptation proceeds at least as rapidly as the onset of adaptation, a finding that is consistent with physiological evidence from olfactory receptors. These data also suggest the effectiveness of this new odorant paradigm in characterizing the temporal characteristics underlying these critical olfactory mechanisms.     

Aversive stimulus properties of morphine: evaluation using the drug preexposure conditioned taste aversion paradigm

Interpretation of the finding that positive-reinforcing drugs such as morphine also possess possible aversive properties, as revealed by their ability to induce a conditioned taste aversion (CTA), remains problematic. This issue was addressed in the present study using the drug preexposure CTA paradigm. Water-deprived rats were given noncontingent preexposure to one of three doses of morphine (2.5, 5.0, or 15.0 mg/kg) or drug vehicle. Subsequently, animals in each of these preexposure groups were presented with a novel 0.1% saccharin-flavored solution followed immediately by injection with one of the same three morphine doses or drug vehicle. This procedure was repeated at 5-day intervals until six saccharin presentations had been performed. Results indicated that while the three morphine doses were differentially potent as taste aversion-conditioning agents, they were equipotent as preexposure agents serving to disrupt CTA. These data suggest that preexposure to morphine's predominantly positive-reinforcing (and non-CTA-inducing) properties is sufficient for preexposure disruption of subsequent morphine CTA. A second experiment indicated that the minimal effective preexposure dose is between 0.3 and 1.25 mg/kg of morphine. It is suggested that an important commonality may exist between the discriminative stimulus properties of morphine as a CTA-inducing agent and as a positive reinforcer.     

Unconscious perception: the need for a paradigm shift

According to Snodgrass, Bernat, and Shevrin (2004), unconscious perception can be demonstrated convincingly only at the objective detection threshold, provided that the conditions of their objective detection/strategic model are met, whereas both the subjective threshold model of Cheesman and Merikle (1984, 1986) and the objective threshold/rapid decay model of Greenwald, Draine, and Abrams (1996) are inconclusive. We argue on theoretical, metatheoretical, and empirical grounds that all three dual-process models, which are based on both conscious and unconscious perception, should be rejected in favor of the single-process conscious perception model.     

Return of fear in a human differential conditioning paradigm caused by a stimulus change after extinction

In a human fear conditioning experiment, 32 participants were trained in a differential conditioning procedure with geometrical shapes as CS+ and CS- (four presentations each), and an electric shock as US. Measures of conditioned responding were skin conductance response (SCR) and retrospective US-expectancy ratings. For half of the participants (Generalization Group, GG), the subsequent extinction phase consisted of four nonreinforced presentations of generalization stimuli (GS+ and GS-). Participants from the Extinction control Group received an equal amount of nonreinforced presentations of the CSs. Finally, all participants were tested with the original CSs. The results from both measures clearly show an increase in the size of the discrimination upon the stimulus change after extinction in the GG. Because this pattern is not observed in the Extinction control Group, extinction performance appears to be somehow restricted to the perceptual characteristics of the extinction stimulus. Interestingly, the size of the conditioned SCR discrimination in the GG is not influenced by the stimulus change after acquisition. This observation points to a differential impact of stimulus change after acquisition vs. extinction treatment. The findings are discussed from the theoretical perspective of renewal and the clinical perspective of Return of Fear.     

On the interaction between linguistic and pictorial systems in the absence of semantic mediation: Evidence from a priming paradigm

Use of the letter search task in the context of the priming paradigm has proved to be an invaluable tool for the investigation of the strategic control of processes involved in word recognition. In particular, previous findings that letter search on a prime word interferes with the priming of semantically/associatively related targets, but not with the priming of either identical or morphologically related targets, suggests that letter search may selectively interfere with semantic processing, leaving other levels of processing intact. In the present experiments, this investigation was extended by exploring the priming of pictures following letter search of either a same-concept word (repetition priming) or a semantically/associatively related word (semantic priming). There was significant repetition priming of picture categorization following both silent reading and letter search of the prime word (Experiments 1 and 2). In contrast, semantic priming of pictures was found only following silent reading of the prime; there was no semantic priming following letter search of the prime (Experiment 2). This pattern of results suggests that focusing attention at the letter level during prime processing selectively attenuates activation of the semantic system by the prime. It does not prevent the spread of activation between the lexical and pictogen levels of representation of a given concept.     

Infants' fast saccades in the gap paradigm and development of visual attention

The saccadic reaction times (SRTs) in the overlap, no-overlap, and gap conditions of 2.5- to 12-month-old infants and adults were measured. In the overlap condition, the SRTs of younger infants were over 600 ms longer than those of older infants, whereas the SRTs in the gap condition of the younger infants were 300–350 ms, much faster than reported hitherto, and were shortened only by about 100 ms. The results indicate that the oculo-motor system and attention process for disengagement in the gap condition mature earlier than the attention process for disengagement in the overlap condition.     

提取-消退范式中复合刺激对恐惧消退的影响

情绪障碍治疗的关键在于消退条件性恐惧记忆,研究证明基于记忆再巩固的提取-消退范式能有效消除或改写原有的恐惧记忆。本研究将提取-消退范式应用到更复杂的恐惧记忆中,采用多感官复合刺激(声音+图片)作为条件刺激,以皮电反应作为恐惧反应指标,考察采用单个线索(声音或图片)、复合线索(声音+图片)进行提取-消退对条件性恐惧记忆的消退效果有何差异。结果表明:声音线索提取-消退组出现了自发恢复和重建效应,图片提取-消退组只出现了重建效应,复合刺激提取-消退组未出现自发恢复和重建效应。说明由复合刺激线索引发的条件性恐惧,采用复合刺激中的单个较强线索或原有完整线索进行提取-消退,对恐惧记忆的消退效果最好。     

Choice-induced preferences in the absence of choice: Evidence from a blind two choice paradigm with young children and capuchin monkeys

In two studies, we provide a test of the revealed-preferences account of choice-induced preferences. To do so, we introduce a blind two-choice task in which preferences cannot guide choices. Children chose between two similar objects while ignorant of the objects’ identities, and then chose between the rejected alternative and a third similar object. Monkeys were given an illusion of choice between two similar objects, and then chose between the rejected object and a third similar object. Both children and monkeys preferred the third object, indicating that they devalued the rejected object. This response pattern did not occur when the children and monkeys were not given the opportunity to choose between the two initial items. These results provide evidence against a revealed-preferences account of choice-induced preferences and demonstrate that the process of making a choice itself induces preferences.     

Methodology for motor learning: a paradigm for kinematic feedback

Knowledge of results (KR)--information feedback about goal achievement--has been one of the most extensively examined variables in motor learning. In most natural movement learning situations, however, instructors more common]y provide augmented information regarding various kinematic or kinetic aspects of the movement pattern itself (sometimes termed knowledge of performance, KP). But despite the inherent interest in kinematic feedback, several factors reviewed here have operated to inhibit its study, the most important of which has been the lack of a suitable laboratory task and paradigm. The limitations of earlier paradigms have concerned (a) the use of overly simple motor behaviors, probably to minimize the problems in kinematic measurement, (b) the tendency for the environmental goal or the task to be isomorphic with the kinematic pattern, and (c) thc failure to use transfer or retention tests as measures of learning effects of the feedback manipulations. In this article, we describe our efforts to create a new paradigm for kinematic feedback, the rationale for its development, and the details of its operation. Finally, we provide evidence that the task and paradigm are sensitive to manipulations of kinematic feedback, providing some assurance that the paradigm can potentially answer future research questions about the role of kinematic feedback for learning.     

Operant hoarding: a new paradigm for the study of self-control.

In the first of four experiments, rats were exposed to a modified multiple continuous reinforcement-extinction schedule during 15-min daily sessions. In one condition (saves condition) with the cuelight on, a single lever press produced a food pellet, briefly extinguished the cuelight, and started a clock. Saves (additional lever presses with interresponse times less than 1 s) produced an additional food pellet, briefly extinguished the cuelight, and restarted the interresponse time clock. The cuelight was extinguished 1 s after the last lever press and remained off during a 10-s period of extinction, during which no food pellets were delivered. In the other condition (savings account condition), the contingencies were the same except that the cuelight was extinguished and was not reilluminated after the initial lever press, and the delivery of all food pellets in the reinforcement component was delayed until the onset of extinction. In both conditions, rats made saves, but mean saves (total saves divided by the number of reinforcement components) were slightly reduced in the savings account condition. In Experiment 2, using six equally spaced 15-min sessions per day on alternate days, saves were either followed immediately with food and brief cuelight offset (saves condition) or were not reinforced at all. Mean saves were much greater when saves were reinforced. In Experiment 3, during 5-min daily sessions, saves earned a single pellet (savings account condition) or a number of pellets equal to the ordinal number of the lever press (interest condition). Rats made fewer mean saves, with little change in the food rate, when saves earned interest. In Experiment 4, the rats earned all their food in the operant situation during 24 daily 5-min sessions, these separated by 55-min intersession intervals during which no food was available; otherwise, the conditions were the same as in Experiment 3. In Experiment 4, the shift to interest for saves led to an increase in mean daily mean saves (total daily mean saves divided by the number of daily sessions) as well as to an increase in the number of food pellets delivered in each session. The results are discussed in terms of self-control and behavioral economics.     

Metaphor: a paradigm for practice-based research into 'career'

This article describes the development of a practice-based methodology for researching 'career' in constructive and critical terms. It begins by suggesting that 'career' theories, both new and old, continue to be confounded by the dualism of human agency and social structure. An argument is then presented to suggest that metaphor provides a means of understanding the reflexive relationship between human actions and social systems. Based on a synthesis of constructivist and critical theory perspectives, a detailed exposition of metaphor as a paradigm for practice-based research is then provided. The emerging methodological implications for researching 'career' are then considered and an example is given of constructive and critical research in action. The article concludes by relating the methodology to careers guidance practice.     

Faith development theory: a case for paradigm change

Despite its influence, James Fowler's theory of faith development is in need of fundamental reappraisal. Doubts over Fowler's use of a structural model of human development and the adequacy of his research techniques have been added to in recent years by his inadequate response to the challenge of post‐modern thought. It is suggested that, despite Fowler's position, key elements of the theory are very much in tune with post‐modern thought and if the abandonment of the theory's underlying structuralism were to be allowed, these might be taken to point a constructive way forward.