Temporal processing capabilities in repetition conduction aphasia

This study investigates the temporal resolution capacities of the central-auditory system in a subject (NP) suffering from repetition conduction aphasia. More specifically, the patient was asked to detect brief gaps between two stretches of broadband noise (gap detection task) and to evaluate the duration of two biphasic (WN-3) continuous noise elements, starting with white noise (WN) followed by 3 kHz bandpass-filtered noise (duration discrimination task). During the gap detection task, the two portions of each stimulus were either identical (“intra-channel condition”) or differed (“inter-channel condition”) in the spectral characteristics of the leading and trailing acoustic segments. NP did not exhibit any deficits in the intra-channel condition of the gap detection task, indicating intact auditory temporal resolution across intervals of 1–3 ms. By contrast, the inter-channel condition yielded increased threshold values. Based upon the “multiple-looks” model of central-auditory processing, this profile points at a defective integration window operating across a few tens of milliseconds – a temporal range associated with critical features of the acoustic speech signal such as voice onset time and formant transitions. Additionally, NP was found impaired during a duration discrimination task addressing longer integration windows (ca. 150 ms). Concerning speech, this latter time domain approximately corresponds to the duration of stationary segmental units such as fricatives and long vowels. On the basis of our results we suggest, that the patient’s auditory timing deficits in non-speech tasks may account, at least partially, for his impairments in speech processing.     

An evaluation of the value of choice-making opportunities in single-operant arrangements: simple fixed- and progressive-ratio schedules

The current study compared the effects of choice and no-choice reinforcement conditions on the task responding of 3 children with autism across 2 single-operant paradigm reinforcer assessments. The first assessment employed simple fixed-ratio (FR) schedules; the second used progressive-ratio (PR) schedules. The latter assessment identified the differential strength of choice-making conditions in promoting task responding relative to no-choice conditions for 2 participants; no differential findings were obtained during the FR assessment.     

Further examination of video‐based preference assessments without contingent access

The first purpose of this study was to attempt to replicate previous findings that video‐based preference assessments without access to selected stimuli may accurately predict relative reinforcing efficacy of stimuli. To do this, we conducted a concurrent operant reinforcer assessment in which we evaluated the relative reinforcing value of highly preferred and less preferred items identified in a video‐based preference assessment. The second purpose of this study was to begin to evaluate the potential behavioral mechanisms responsible for the validity of this assessment. To conduct this analysis, we evaluated the relative reinforcing value of those same stimuli depicted in video format and then compared results to results obtained during the reinforcer assessment for tangible stimuli. For all five participants, stimuli identified as highly preferred functioned as reinforcers, and four of five participants, responding during the reinforcer assessment was similar in the presence of tangible stimuli and videos depicting those stimuli.     

Assessing preference for types of social interaction

To date, few researchers have evaluated methods for assessing preference for social interactions. Due to concerns that commonly used stimulus preference assessment methods may be inappropriate, or at least cumbersome, for the assessment of social reinforcers, we developed and evaluated a new method of assessing preference for social interactions. A social interaction preference assessment (SIPA) and a concurrent operant reinforcer assessment were conducted with five participants diagnosed with autism spectrum disorder. A differentially preferred and reinforcing social interaction was identified for all five participants. The SIPA procedures, results, and the implications of these results are discussed.     

Relative reinforcer rates and magnitudes do not control concurrent choice independently

One assumption of the matching approach to choice is that different independent variables control choice independently of each other. We tested this assumption for reinforcer rate and magnitude in an extensive parametric experiment. Five pigeons responded for food reinforcement on switching-key concurrent variable-interval variable-interval schedules. Across conditions, the ratios of reinforcer rates and of reinforcer magnitudes on the two alternatives were both manipulated. Control by each independent variable, as measured by generalized-matching sensitivity, changed significantly with the ratio of the other independent variable. Analyses taking the model-comparison approach, which weighs improvement in goodness-of-fit against increasing number of free parameters, were inconclusive. These analyses compared a model assuming constant sensitivity to magnitude across all reinforcer-rate ratios with two alternative models. One of those alternatives allowed sensitivity to magnitude to vary freely across reinforcer-rate ratios, and was less efficient than the common-sensitivity model for all pigeons, according to the Schwarz-Bayes information criterion. The second alternative model constrained sensitivity to magnitude to be equal for pairs of reinforcer-rate ratios that deviated from unity by proportionately equal amounts but in opposite directions. This model was more efficient than the common-magnitude-sensitivity model for 2 of the pigeons, but not for the other 3. An analysis of variance, carried out independently of the generalized-matching analysis, also showed a significant interaction between the effects of reinforcer rate and reinforcer magnitude on choice. On balance, these results suggest that the assumption of independence inherent in the matching approach cannot be maintained. Relative reinforcer rates and magnitudes do not control choice independently.     

SENSITIVITY OF CONDITIONAL-DISCRIMINATION PERFORMANCE TO WITHIN-SESSION VARIATION OF REINFORCER FREQUENCY

The present experiment developed a methodology for assessing sensitivity of conditional-discrimination performance to within-session variation of reinforcer frequency. Four pigeons responded under a multiple schedule of matching-to-sample components in which the ratio of reinforcers for correct S₁ and S₂ responses was varied across components within session. Initially, five components, each arranging a different reinforcer-frequency ratio (from 19 to 91), were presented randomly within a session. Under this condition, sensitivity to reinforcer frequency was low. Sensitivity failed to improve after extended exposure to this condition, and under a condition in which only three reinforcer-frequency ratios were varied within session. In a later condition, three reinforcer-frequency ratios were varied within session, but the reinforcer-frequency ratio in effect was differentially signaled within each component. Under this condition, values of sensitivity were similar to those traditionally obtained when reinforcer-frequency ratios for correct responses are varied across conditions. The effects of signaled vs. unsignaled reinforcer-frequency ratios were replicated in two subsequent conditions. The present procedure could provide a practical alternative to parametric variation of reinforcer frequency across conditions and may be useful in characterizing the effects of a variety of manipulations on steady-state sensitivity to reinforcer frequency.     

浅谈病理尸检的思维方法

尸体剖验是病理学研究的主要方法之一.为了准确而全面地作出尸检诊断,必须遵循科学的思维方法,即重视分析生前临床材料,密切关注结构和功能间的变化联系,以发展运动的观点分析尸检所见,无疑是值得倡导的思维方法.     

EVALUATION OF THE MULTIPLE-STIMULUS WITHOUT REPLACEMENT PREFERENCE ASSESSMENT METHOD USING ACTIVITIES AS STIMULI

The current study examined the accuracy of the multiple-stimulus without replacement (MSWO) preference assessment for identifying preferred common classroom activities as reinforcers with children with behavioral disorders. The accuracy of predictions from the MSWO regarding high, medium, and low stimulus preference was tested by providing contingent access to activities for completing math problems within an independent seatwork format. Overall, there was an interaction effect between preference ranking (high, medium, or low) and number of problems completed. The results confirm and extend previous findings regarding the accuracy of predictions with the MSWO. The findings also reveal, however, some individual differences that may account for instances in which student behavior did not conform to predictions of stimulus preference assessments.     

THE EFFECTS OF VARIED VERSUS CONSTANT HIGH‐, MEDIUM‐, AND LOW‐PREFERENCE STIMULI ON PERFORMANCE

The purpose of the current study was to compare the delivery of varied versus constant high‐, medium‐, and low‐preference stimuli on performance of 2 adults on a computer‐based task in an analogue employment setting. For both participants, constant delivery of the high‐preference stimulus produced the greatest increases in performance over baseline; the varied presentation produced performance comparable to constant delivery of medium‐preference stimuli. Results are discussed in terms of their implications for the selection and delivery of stimuli as part of employee performance‐improvement programs in the field of organizational behavior management.     

ISOLATING BEHAVIORAL MECHANISMS OF INTERTEMPORAL CHOICE: NICOTINE EFFECT ON DELAY DISCOUNTING AND AMOUNT SENSITIVITY

Many drugs of abuse produce changes in impulsive choice, that is, choice for a smaller—sooner reinforcer over a larger—later reinforcer. Because the alternatives differ in both delay and amount, it is not clear whether these drug effects are due to the differences in reinforcer delay or amount. To isolate the effects of delay, we used a titrating delay procedure. In phase 1, 9 rats made discrete choices between variable delays (1 or 19 s, equal probability of each) and a delay to a single food pellet. The computer titrated the delay to a single food pellet until the rats were indifferent between the two options. This indifference delay was used as the starting value for the titrating delay for all future sessions. We next evaluated the acute effects of nicotine (subcutaneous 1.0, 0.3, 0.1, and 0.03 mg/kg) on choice. If nicotine increases delay discounting, it should have increased preference for the variable delay. Instead, nicotine had very little effect on choice. In a second phase, the titrated delay alternative produced three food pellets instead of one, which was again produced by the variable delay (1 s or 19 s) alternative. Under this procedure, nicotine increased preference for the one pellet alternative. Nicotine‐induced changes in impulsive choice are therefore likely due to differences in reinforcer amount rather than differences in reinforcer delay. In addition, it may be necessary to include an amount sensitivity parameter in any mathematical model of choice when the alternatives differ in reinforcer amount.