Drug discrimination under a concurrent fixed-ratio fixed-ratio schedule.

Pigeons were trained to discriminate 5.0 mg/kg pentobarbital from saline under a two-key concurrent fixed-ratio 10 fixed-ratio 40 schedule of food presentation, in which the fixed-ratio component with the lower response requirement was programmed to reinforce responding on one key after drug administration (pentobarbital-biased key) and on the other key after saline administration (saline-biased key). After responding stabilized, pigeons averaged 98% of their responses on the pentobarbital-biased key during training sessions preceded by pentobarbital, and they averaged 90% of their responses on the saline-biased key during training sessions preceded by saline. In test sessions preceded by doses of pentobarbital, chlordiazepoxide, or ethanol, pigeons switched from responding on the saline-biased key at low doses to responding on the pentobarbital-biased key at higher doses (the dose-response curve was quantal). High doses of phencyclidine produced responding on both keys, whereas pigeons responded almost exclusively on the saline-biased key after all doses of methamphetamine. These and previous experiments using concurrent reinforcement schedules to study drug discrimination illustrate that the schedule of reinforcement is an important determinant of the shape of dose-effect curves in drug-discrimination experiments.     

Support for a theory of memory for event duration must distinguish between test-trial ambiguity and actual memory loss

Staddon and Higa's (1999) trace-strength theory of timing and memory for event duration can account for pigeons' bias to "choose short" when retention intervals are introduced and to "choose long" when, following training with a fixed retention interval, retention intervals are shortened. However, it does not account for the failure of pigeons to choose short when the intertrial interval is distinct from the retention interval. That finding suggests that stimulus generalization (or ambiguity) between the intertrial interval and the retention interval may result in an effect that has been attributed to memory loss. Such artifacts must be eliminated before a theory of memory for event duration can be adequately tested.     

Equivalence class establishment, expansion, and modification in preschool children

Preschool children were taught four two-choice match-to-sample conditional discriminations with 10 arbitrary visual stimuli. For 6 participants, 2 of the 10 stimuli served as the sample, or conditional, stimuli in all discriminations. For 5 additional participants, the same pair of stimuli served as the discriminative, or comparison, stimuli in all discriminations. Equivalence classes were established with more participants in the latter group, replicating prior research with participants with retardation. Four participants, in whom equivalence classes were established and who were available for further participation, were exposed to new conditional discriminations without trial-by-trial feedback and involving some novel and some familiar stimuli. Consistent conditional responding was observed, and tests for inclusion of the novel stimuli in the original classes showed class expansion. Training to reverse the unreinforced conditional performances produced a reversal of class membership in 3 of 4 participants, an outcome not consistent with other studies. The results are discussed with respect to the interaction of class structure and size.     

A discrimination analysis of training-structure effects on stimulus equivalence outcomes.

Experiments designed to establish stimulus equivalence classes frequently produce differential outcomes that may be attributable to training structure, defined as the order and arrangement of baseline conditional discrimination training trials. Several possible explanations for these differences have been suggested. Here we develop a hypothesis based on an analysis of the simple simultaneous and successive discriminations embedded in conditional discrimination training and testing within each of the training structures that are typically used in stimulus equivalence experiments. Our analysis shows that only the comparison-as-node (many-to-one) structure presents all the simple discriminations in training that are subsequently required for consistently positive outcomes on all tests for the properties of equivalence. The sample-as-node (one-to-many) training structure does not present all the simple discriminations required for positive outcomes on either the symmetry or combined transitivity and symmetry (equivalence) tests. The linear-series training structure presents all the simple discriminations required for consistently positive outcomes on tests for symmetry, but not for symmetry and transitivity combined (equivalence) or transitivity alone. Further, the difference in the number of simple discriminations presented in comparison-as-node training versus the other training structures is larger when the intended class size is greater than three or the number of classes is larger than two. We discuss the relevance of this analysis to interpretations of stimulus equivalence research, as well as some methodological and theoretical implications.     

Eternity in an hour: experiences of time related to psychotherapy sessions

In this paper I consider the individual nature of the way a person develops senses of time. I suggest that something of a patient's early, unvoiced, experience is revealed through the temporal rhythms of interaction with the therapist. I refer to development, cycles of experience, metabolism, transgenerational emotions, experiences of beginnings and endings, early interactions with (m)other, together with narrative and its relation to unconscious processes. Experiences of time within the session indicate the nature of the feelings that are being lived, or refused life. I consider the paradox of living in the present and its relation to chronology. Lastly I give an example of the difficulty of timing comments when there is no flow of feeling, which is, itself, a communication.     

Full statistical mediation of the relationship between trauma and depressive symptoms

Owing to the potentially devastating effects of trauma‐induced depression, explaining the relationship between trauma and depressive symptoms is important. In this study, we measured lifelong exposure to potentially traumatic events and depressive symptoms in 370‐female undergraduates. We also measured anxiety, past negative time perspective and dissociation as potential mediators. Trauma exposure and depressive symptoms were related with a small but significant effect size (r = .16). Trauma was not associated with dissociation. We found that past negative time perspective and anxiety were full statistical mediators of this trauma‐depressive symptoms relationship. These two mediators combined accounted for all of the variance in that association. Anxiety accounted for more of the variance than past negative time perspective. A proposed explanation is that trauma both affectively elevates anxiety and cognitively creates an enduring focus on the events. Chronic anxiety and a past negative time perspective may lead to depression over time. The clinical implications are possible explanations as to why some treatments work.     

Time perspective and environmental engagement: A meta-analysis

Environmental issues entail both a social conflict (private vs. public interests) and a temporal conflict (short- vs. long-term interests). This paper focuses on the role temporal concerns play in influencing environmental engagement by quantitatively integrating results of studies that assessed the associations between time perspective and proenvironmental attitudes and behaviors. The meta-analysis included a total of 19 independent samples and 6,301 participants from seven countries (Australia, Brazil, Germany, Mexico, New Zealand, Norway, and the United States). Results showed that the associations between time perspective and proenvironmental behaviors were higher than those for proenvironmental attitudes. Supporting predictions, the associations between future time perspective and proenvironmental behaviors were strong and nontrivial compared to those for the combined past-present time perspective. The findings indicate that future time perspective seems to play an important role in influencing individuals' attitudes and behaviors towards the environment. Implications of the findings for theory and practice are discussed.     

Individual differences in vulnerability to subjective time distortion1

Time duration is perceived to be longer when accompanied by dynamic sensory stimulation than when accompanied by static stimulation. This distortion of time perception is thought to be due to the acceleration of an internal pacemaker that has been assumed to be the main component of temporal judgments. In order to investigate whether the function of the internal pacemaker is modality dependent or independent, we examined the correlation of visual flicker and auditory flutter effects on a temporal production task. While seeing a 10‐Hz visual flicker or hearing a 10‐Hz auditory flutter, participants estimated a duration of 2500 ms as accurately as possible by pressing a button. The results showed a significant within‐individual correlation between the time distortion due to visual flicker and that due to auditory flutter. Additionally, we found that time distortion due to auditory flutter tended to be larger in female participants than in male participants. These results suggest that the mechanisms underlying subjective time dilation are similar between vision and audition within individuals, but that they vary across individuals.