Biomedical subjects

Phil Reed

Publications and source records attributed to Phil Reed.

15 recordsLinked to original sources

PubMed2006

Brief report: relative effectiveness of different home-based behavioral approaches to early teaching intervention.

The effectiveness of home-based early behavioral interventions for children (2:6-4:0 years old) with autistic spectrum disorders was studied over 9-10 months. Measures of autistic severity, intellectual, educational, and adaptive behavioral functioning were taken. There was no evidence of recovery from autism. High-intensity behavioral approaches (mean 30 h/week) produced greater gains than low-intensity programs (mean 12 h/week). Lovaas- and complete application of behavior analysis to schools approach-type interventions produced largest gains [similar to gains produced by longer-term clinic-based applied behavior analysis (ABA) programs]. Within the high-intensity groups, increased temporal input on the program was not associated with increased gains in the children. The results from clinic-based ABA trials were partially replicated on a home-based sample, using children with greater autistic and intellectual impairments.

Age Factors↗

PubMed2006

The effect of retention interval on stimulus over-selectivity using a matching-to-sample paradigm.

The conditions under which stimulus over-selectivity occurred were studied using a matching-to-sample procedure with non-autistic adults. A matching-to-sample discrimination learning task with a number of sample-comparison retention intervals was used. The results demonstrated that an increase in retention interval increased the degree of stimulus overselectivity displayed. In addition, it was shown that the matching-to-sample procedure is suitable for eliciting overselectivity in a non-autistic adult sample.

Adult↗

PubMed2006

Resurgence of response sequences during extinction in rats shows a primacy effect.

Rats were trained to emit a series of three-response sequences to a criterion (i.e., more than 80% of all emitted sequences correct over five successive sessions). Each rat was trained on a series of different, three-response sequences. After the final three-response sequence was acquired, two extinction tests were administered, and the three-response sequences that re-emerged during these extinction tests were noted. Resurgence effects during extinction were observed; that is, the previously trained sequences were emitted. These resurgence effects followed an orderly pattern, which involved a primacy effect. The rats initially emitted the immediately previously trained response, but then started to emit the response sequence they first were trained to emit. Thus, resurgence behavior during extinction can be an orderly function of previous training history. These results replicate those previously obtained with human subjects.

Animals↗

PubMed2005

The effect of concurrent task load on stimulus over-selectivity.

Stimulus over-selectivity is a phenomenon displayed by individuals with autism, and has been implicated as a basis for many autistic-spectrum symptoms. In four experiments, non-autistic adult participants were required to learn a simple discrimination using picture cards, and then were tested for the emergence of stimulus over-selectivity, both with and without a concurrent task. Greater stimulus over-selectivity was noted when participants completed the concurrent task. The results are discussed in relation to the implications for the development of a model of memory deficits in autism.

Adult↗

PubMed2005

Stimulus over-selectivity in rats.

The present study explored whether a similar phenomenon to stimulus over-selectivity occurred in rats, in the hope of establishing a non-human model for the autism. Rats were serially presented with two-15 seconds, two-element compound stimuli prior to the delivery of food, in an appetitive classical conditioning procedure. Each compound stimulus consisted of two lights. Once the rats had acquired a conditioned response (CR) to the stimuli, they were presented with each of the component elements separately in extinction. The rats demonstrated greater conditioning to components of the compound presented just prior to reinforcement than to the components of the temporally distant compound. However, there was a smaller difference between CRs to the components of the compound presented just prior to reinforcement (i.e. less overshadowing) than between the components of the temporally distant compound. It is suggested that rats demonstrated a form of stimulus over-selectivity, resulting in greater overshadowing of one cue by another. Such results may form the basis of a viable non-human model of this symptom of autistic spectrum disorder.

Animals↗

PubMed2005

Do positive schizotypal symptoms predict false perceptual experiences in nonclinical populations?

We examined whether positive schizotypy (i.e., reports of hallucinatory and delusional-like experiences) in nonclinical participants could predict false perceptual experiences during detection of fast-moving words beyond a possible response bias. The participants (N = 160) were assigned to one of two conditions: they were asked either to make presence/absence judgments (loose criterion) or to read aloud every detected word (strict criterion). Regression analysis showed that high levels of positive schizotypy predicted false alarms in the loose condition and false perceptions of words in the strict condition. The obtained effects were independent of detection accuracy, task order, impulsivity, and social desirability. We discuss the results in the context of information processing biases linked to the positive symptomatology of schizophrenia. Clinical and theoretical implications are also considered.

Adolescent↗

PubMed2005

Seeing words that are not there: detection biases in schizotypy.

OBJECTIVE: The present study introduced a novel word-detection paradigm to examine detection biases as a function of different schizotypy dimensions in a sample of undergraduate students. METHOD: The participants (N = 80) were asked to detect fast moving (8 frames/second) words among simultaneously moving non-words. RESULTS: Positive schizotypy was associated with a tendency to report words that never appeared in the trials. This effect was independent of task order, impulsivity and social desirability. None of the schizotypy measures were associated with correct words (detection accuracy). CONCLUSIONS: A bias to report events in the absence of corresponding events may constitute a cross-modal mechanism responsible for translating internally generated experiences into perceptual experiences.

Adolescent↗

PubMed2005

Within-subject testing of the signaled-reinforcement effect on operant responding as measured by response rate and resistance to change.

Response rates under random-interval schedules are lower when a brief (500 ms) signal accompanies reinforcement than when there is no signal. The present study examined this signaled-reinforcement effect and its relation to resistance to change. In Experiment 1, rats responded on a multiple random-interval 60-s random-interval 60-s schedule, with signaled reinforcement in only one component. Response resistance to alternative reinforcement, prefeeding, and extinction was compared between these components. Lower response rates, and greater resistance to change, occurred in the component with the reinforcement signal. In Experiment 2, response rates and resistance to change were compared after training on a multiple random-interval 60-s random-interval 60-s schedule in which reinforcer delivery was unsignaled in one component and a response-produced uncorrelated stimulus was presented in the other component. Higher response rates and greater resistance to change occurred with the uncorrelated stimulus. These results highlight the significance of considering the effects of an uncorrelated signal when used as a control condition, and challenge accounts of resistance to change that depend solely on reinforcer rate.

Animals↗

PubMed2004

Dimensional approaches to experimental psychopathology of schizophrenia: shift learning and report of psychotic-like experiences in college students.

Adopting a dimensional approach to experimental psychopathology, and taking into account inconsistencies in the previous literature, we examined whether reports of psychotic-like experiences in undergraduate students were associated with shift-learning deficits, akin to those seen in schizophrenia. The participants (N=72) were tested on a new compound stimulus discrimination task before and after a target shift, and were administered a multi-dimensional schizotypy inventory (O-LIFE). Performance impairment following a target shift was associated with the negative (introvertive anhedonia) and the impulsive (impulsive non-conformity) dimension of schizotypy, but not with the positive (unusual experiences), nor the disorganised (cognitive disorganisation) dimension. None of the schizotypy measures were associated with performance on discrimination learning before the target shift. The obtained results are in line with past evidence that shift learning is associated with the severity of the negative symptomatology of schizophrenia. The possibility that psychotic-like features may contribute differentially to performance deficits across successive stages of learning is considered.

Adolescent↗

PubMed2004

Differential reinstatement predicted by preextinction response rate.

Reinstatement refers to the recovery of previously extinguished responding by the response-independent delivery of a stimulus that was a reinforcer in training. Two experiments were conducted to examine relative reinstatement following the training of differential preextinction response rates, either with equal (Experiment 1) or unequal (Experiment 2) preextinction reinforcement rates. In Experiment 1, each of 3 pigeons first pecked at relatively high rates in the tandem variable-time 117-sec fixed-interval 3-sec component of a multiple schedule and at lower rates in a separate tandem variable-interval 117-sec fixed-time 3-sec component. Reinforcement rates were equal between components. Pecking then was extinguished in each component, before being reinstated under a multiple variable-time 120-sec variable-time 120-sec schedule. Greater reinstatement occurred in the component previously correlated with higher rates of pecking. In Experiment 2, in an initial condition, the mean rate of lever pressing for one group of 8 rats was significantly higher under a fixed-ratio 3 schedule than for another group of 8 rats under a fixed-ratio 1 schedule. Mean reinforcement rate was significantly higher for the group exposed to the fixed-ratio 1 schedule. For each group, lever pressing then was extinguished, before being reinstated under a variable-time 30-sec schedule. Significantly greater mean reinstatement occurred for the group previously exposed to the fixed-ratio 3 schedule. These results suggest that differential reinstatement may be predicted by preextinction response rate, perhaps independently of preextinction reinforcement rate.

Animals↗

PubMed2003

Rats' performance on variable-interval schedules with a linear feedback loop between response rate and reinforcement rate.

Three experiments investigated whether rats are sensitive to the molar properties of a variable-interval (VI) schedule with a positive relation between response rate and reinforcement rate (i.e., a VI+ schedule). In Experiment 1, rats responded faster on a variable ratio (VR) schedule than on a VI+ schedule with an equivalent feedback function. Reinforced interresponse times (IRTs) were shorter on the VR as compared to the VI+ schedule. In Experiments 2 and 3, there was no systematic difference in response rates maintained by a VI+ schedule and a VI schedule yoked in terms of reinforcement rate. This was found both when the yoking procedure was between-subject (Experiment 2) and within-subject (Experiment 3). Mean reinforced IRTs were similar on both the VI+ and yoked VI schedules, but these values were more variable on the VI+ schedule. These results provided no evidence that rats are sensitive to the feedback function relating response rate to reinforcement rate on a VI+ schedule.

Animals↗

PubMed2003

The effect of signaled reinforcement on rats' fixed-interval responding.

Four experiments examined the effect on rats' response rate of presenting a brief (500 ms) stimulus simultaneously with the delivery of food on fixed-interval (FI) schedules. In Experiment 1, reinforcement signals that were spatially diffuse (both tones and lights) elevated rates of responding, but responding was attenuated by localized visual stimuli. The remaining experiments examined the signal-induced potentiation of responding. In Experiment 2, a tone reinforcement signal potentiated response rates on an FI schedule, but attenuated response rates on a variable-interval (VI) schedule. This difference was obtained even though the overall rate of responding was equated on the two schedules before the introduction of the signal. Signal-induced potentiation of responding occurred over a range of FI values employed in Experiment 3. In Experiment 4, presenting a reinforcement signal when high local rates of response had occurred immediately before reinforcement resulted in potentiated rates of responding on an FI schedule. The opposite effect on response rate occurred when the reinforcement signal followed only low local rates of response. These results indicate that a variety of factors influence the effects of a reinforcement signal. They imply, however, that the local rate of response at the time of reinforcement is a key factor in establishing the nature of the signaling effect.

Animals↗

PubMed2003

Speech perception in rats: use of duration and rise time cues in labeling of affricate/fricative sounds.

The voiceless affricate/fricative contrast has played an important role in developing auditory theories of speech perception. This type of theory draws some of its support from experimental data on animals. However, nothing is known about differential responding of affricate/fricative continua by animals. In the current study, the ability of hooded rats to "label" an affricate/fricative continuum was tested. Transfer (without retraining) to analogous nonspeech continua was also tested. The nonspeech continua were chosen so that if transfer occurred, it would indicate whether the animals had learned to use rise time or duration cues to differentiate affricates from fricatives. The data from 9 of 10 rats indicated that rats can discriminate between these cues and do so in a similar manner to human subjects. The data from 9 of 10 rats also demonstrated that the rise time of the stimulus was the basis of the discrimination; the remaining rat appeared to use duration.

Animals↗

PubMed2003

Human causality judgments and response rates on DRL and DRH schedules of reinforcement.

The effect of various relationships between a response (an investment made in the context of a game) and an outcome (a return on the investment) on judgments of the causal effectiveness of the response was examined. In Experiment 1, response rates and causal judgments were higher for a differential-reinforcement-of-high-rate (DRH) schedule relative to a variable-ratio (VR) schedule with the same probability of outcome following a response. Response rates were also higher for a DRH than for a variable-interval schedule matched for reinforcement rate. In Experiment 2, response rates and causal judgments were lower for a differential-reinforcement-of-low-rate schedule relative to a VR schedule with the same probability of outcome following a response. These results corroborate the view that schedules are a determinant of both response rates and causal judgments, and that few current theories of causal judgment explicitly predict this pattern of results.

Adolescent↗

PubMed2002

The influence of a distractor during compound preexposure on latent inhibition.

Nonreinforced exposure to a nontarget stimulus that was followed by nonreinforced exposure to a target/nontarget simultaneous compound stimulus resulted in enhanced latent inhibition of the target. Conditioning was slower after this treatment than after nonreinforced exposure to the target stimulus alone (Experiment 1). However, a salient auditory stimulus presented immediately after the compound in the second phase reduced levels of latent inhibition, relative to the enhanced latent inhibition produced when no such extracompound stimulus was presented (Experiments 2 and 3). This effect was not noted if the salient auditory cue was presented 10 sec after the termination of the compound stimulus (Experiment 4). In Experiment 5, there was no disruption of simple latent inhibition produced by a salient stimulus. These results are consistent with enhanced latent inhibition's being produced by the formation of within-compound associations, which are disrupted by the salient extracompound stimuli.

Animals↗