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Biomedical subjects

C F Lowe

Publications and source records attributed to C F Lowe.

At least 19 recordsLinked to original sources
PubMed2004

Reinforcer concentration effects on a fixed-interval schedule.

Four rats received training on a mixed FI 30-s FI 150-s schedule, where the different FI values were associated with different levers. During baseline, the reinforcer was a 30% concentration of condensed milk. During subsequent testing sessions, the reinforcer concentration was varied within sessions over values of 10, 30, 50, and 70%. Measures of behaviour were taken from the FI 30-s lever during trials where the reinforcer was delivered for responses on the other lever. Increasing the reinforcer concentration which began the interval (a) increased the time to start responding in the interval, and (b) increased the location of the response peak on the FI 30-s lever (often to values well above 30s). Response rate at the peak, and spread of the response rate versus time function, changed much less with reinforcer concentration. The data are discussed relative to predictions derived from Scalar Expectancy Theory, the Behavioural Theory of Timing, and the Tuned-trace model.

Animals↗
PubMed2004

Effects of a peer modelling and rewards-based intervention to increase fruit and vegetable consumption in children.

OBJECTIVE: To measure children's consumption of, and liking for, fruit and vegetables and how these are altered by a peer modelling and rewards-based intervention. DESIGN: In this initial evaluation of the programme, children's consumption of fruit and vegetables were compared within and across baseline and intervention phases. SETTING: Three primary schools in England and Wales. SUBJECTS: In total, 402 children, aged from 4 to 11 y. INTERVENTION: Over 16 days, children watched six video adventures featuring heroic peers (the Food Dudes) who enjoy eating fruit and vegetables, and received small rewards for eating these foods themselves. MAIN OUTCOME MEASURES: Fruit and vegetable consumption was measured (i) in school at lunchtime and snacktime using a five-point observation scale, with inter-rated reliability and weighed validation tests; and (ii) at home using parental recall. A questionnaire measured children's liking for fruit and vegetables before and after the intervention. RESULTS: Consumption during the intervention was significantly higher than during baseline at lunchtime and at snacktime (P<0.001 in all instances). Consumption outside school was significantly higher during the intervention on weekdays (P<0.05) but not weekend days. Following the intervention, children's liking for fruit and vegetables also showed a significant increase (P<0.001). CONCLUSIONS: The peer modelling and rewards-based intervention was shown to be effective in bringing about substantial increases in children's consumption of, and expressed liking for, fruit and vegetables. SPONSORSHIP: : Horticultural Development Council, Fresh Produce Consortium, ASDA, Co-operative Group, Safeway, Sainsbury, Somerfield, Tesco and Birds Eye Wall's.

Child↗
PubMed2004

Increasing children's fruit and vegetable consumption: a peer-modelling and rewards-based intervention.

OBJECTIVE: To evaluate a peer-modelling and rewards-based intervention designed to increase children's fruit and vegetable consumption. DESIGN: Over a 5-month period, children in an experimental and a control school were presented with fruit and vegetables at lunchtime. Children aged 5-7 y also received fruit at snacktime (mid-morning). The intervention was implemented in the experimental school and levels of fruit and vegetable consumption were measured at baseline, intervention and at 4-month follow-up. SETTING: Two inner-city London primary schools. SUBJECTS: In total, 749 children aged 5-11 y. INTERVENTION: Over 16 days children watched video adventures featuring heroic peers (the Food Dudes) who enjoy eating fruit and vegetables, and received small rewards for eating these foods themselves. After 16 days there were no videos and the rewards became more intermittent. MAIN OUTCOME MEASURES: Consumption was measured (i) at lunchtime using a five-point observation scale; (ii) at snacktime using a weighed measure; (iii) at home using parental recall. RESULTS: Compared to the control school, lunchtime consumption in the experimental school was substantially higher at intervention and follow-up than baseline (P<0.001), while snacktime consumption was higher at intervention than baseline (P<0.001). The lunchtime data showed particularly large increases among those who initially ate very little. There were also significant increases in fruit and vegetable consumption at home (P<0.05). CONCLUSIONS: The intervention was effective in bringing about substantial increases in children's consumption of fruit and vegetables.

Child↗
PubMed2003

Multiple-interval timing in rats: Performance on two-valued mixed fixed-interval schedules.

Three experiments studied timing in rats on 2-valued mixed-fixed-interval schedules, with equally probable components, Fixed-Interval S and Fixed-Interval L (FI S and FI L, respectively). When the L:S ratio was greater than 4, 2 distinct response peaks appeared close to FI S and FI L, and data could be well fitted by the sum of 2 Gaussian curves. When the L:S ratio was less than 4, only 1 response peak was usually visible, but nonlinear regression often identified separate sources of behavioral control, by FI S and FI L, although control by FI L dominated. Data were used to test ideas derived from scalar expectancy theory, the behavioral theory of timing, and learning to time.

Animals↗
PubMed2000

Testing for symmetry in the conditional discriminations of language-trained chimpanzees.

If subjects are taught to match Stimulus A to B and then, without further training, match B to A, they have passed a test of symmetry. It has been suggested that non-humans' lack of success on symmetry tests might be overcome by giving them a history of symmetry exemplar training, that is, by directly teaching a large number of conditional relations (e.g., AB, CD, EF,...) and also directly training the "reverse" of these relations (e.g., BA, DC, FE,...). The chimpanzee subjects of the present study, Sherman, Austin, and Lana, had already received extensive symmetry exemplar training as a result of attempts to teach a selection-based language system of lexigrams. The present study systematically subjected 2 of these chimps (Sherman and Lana), for the first time, to standard symmetry tests in controlled conditions. Both chimps failed the tests, even when their correct responses on test trials were reinforced. The findings do not support the exemplar training hypothesis, and cast doubt upon whether the chimps can pass tests of stimulus equivalence.

Animal Communication↗
PubMed1996

Delusional phenomenology--dimensions of change.

Although the application of cognitive techniques to both the measurement and modification of delusional beliefs has recently been developed in more theoretical detail (e.g. Chadwick & Lowe, 1994, Behaviour Research and Therapy, 32, 355-367) there has not been an effort to examine the variability of delusional phenomenology across time. In the present study we report on the treatment of 6 individuals who fulfilled DSM-III-R (American Psychiatric Association, 1987) criteria for Delusional Disorder and who received cognitive therapy targeted specifically on the single symptom of their delusional belief(s). Single-case time-series methodology was used to examine the associations between different aspects of delusional phenomenology through baseline and intervention study phases. Belief maintenance factors were found to be significantly associated with conviction in all 3 individuals who responded to the intervention. Negative behaviours, affect associated with the belief, preparedness to talk to others about the belief and insight were associated with conviction in some individuals but not others. Preoccupation and acting on the belief were aspects of delusional phenomenology that were found to systematically vary independent of belief conviction. The results support a multidimensional view of delusional phenomenology and the process of change during cognitive intervention.

Adult↗
PubMed1996

On the origins of naming and other symbolic behavior.

We identify naming as the basic unit of verbal behavior, describe the conditions under which it is learned, and outline its crucial role in the development of stimulus classes and, hence, of symbolic behavior. Drawing upon B. F. Skinner's functional analysis and the theoretical work of G. H. Mead and L. S. Vygotsky, we chart how a child, through learning listener behavior and then echoic responding, learns bidirectional relations between classes of objects or events and his or her own speaker-listener behavior, thus acquiring naming-a higher order behavioral relation. Once established, the bidirectionality incorporated in naming extends across behavior classes such as those identified by Skinner as the mand, tact, and intraverbal so that each becomes a variant of the name relation. We indicate how our account informs the specification of rule-governed behavior and provides the basis for an experimental analysis of symbolic behavior. Furthermore, because naming is both evoked by, and itself evokes, classes of events it brings about new or emergent behavior such as that reported in studies of stimulus equivalence. This account is supported by data from a wide range of match-to-sample studies that also provide evidence that stimulus equivalence in humans is not a unitary phenomenon but the outcome of a number of different types of naming behavior.

Journal Article↗
PubMed1994

A cognitive approach to measuring and modifying delusions.

The present paper summarizes and integrates with the existing literature the results of three studies we have conducted on the measurement and modification of delusions. The findings of two of these studies have been presented previously; the third is briefly reported here. A total of 12 people with delusions took part. Ten participated in two investigations that used between-subject multiple-baseline designs; the remaining two, each of whom held three distinct delusions, took part in a study using an across-beliefs multiple-baseline design. A variety of dimensions of delusional experience were monitored over baseline periods of at least 4 weeks, and two distinct cognitive interventions were used: a structured verbal challenge and a planned empirical test. Our focus in the present article is on intervention and the process of change as people come to question and sometimes reject their delusions. We also address related issues, including problems of measurement (i.e. demand characteristics, independent validation), the connection between depression and delusions and the prediction of treatment response. We conclude with specific recommendations for cognitive therapy for delusions.

Adult↗
PubMed1993

Determinants of human performance on concurrent schedules.

Six experiments, each with 5 human adults, were conducted to investigate the determinants of human performance on multiple concurrent variable-interval schedules. A two-key procedure was employed in which subjects' key presses produced points exchangeable for money. Variables manipulated across experiments were (a) changeover delay (Experiments 2, 4, and 6), (b) ordinal cues related to scheduled reinforcement frequencies (Experiments 3 and 4), and (c) instructions describing the ordinal relations between schedule-correlated stimuli and scheduled reinforcement frequency (Experiments 5 and 6). The performances of only 13 of the 30 subjects could be described by the generalized matching equation and were within a range of values typical of those reported in the animal literature. Eight subjects showed indifference, 9 undermatched, 7 approximated matching, 3 overmatched, and a further 3 responded exclusively to the richer component of the concurrent schedules. These differing modes of responding were closely related to the different types of performance rules reported by subjects in postexperimental questionnaires. The results are in good agreement with those from studies of human performance on single schedules, suggesting that rule-governed behavior, in interaction with contingencies, may be an important determinant of human choice.

Adolescent↗
PubMed1990

Measurement and modification of delusional beliefs.

It has been proposed that delusional thinking may be on a continuum with normal behavior and can be assessed by taking account of factors such as the client's degree of belief conviction or the extent of preoccupation with the belief. In our research a number of measures were used to assess the delusional thinking of people diagnosed as schizophrenic. Two interventions were used: (a) a structured verbal challenge and (b) a reality test in which the belief was subject to an empirical test. We used a multiple-baseline, across-subjects design. Of the 6 clients, 2 completely rejected their beliefs, and 3 others significantly reduced their belief conviction. Maintenance was good, and there was evidence that the intervention had enabled 5 of the 6 clients to effectively regulate their delusional thinking.

Adult↗
PubMed1987

The role of verbal behavior in human learning: III. Instructional effects in children.

Lever pressing of children from three age groups (2(1/2) to 4, 5 to 6(1/2), and 7(1/2) to 9 years) could produce reinforcers according to a fixed-interval 40-s schedule: (1) Some were instructed to respond at a high rate, others at a low rate, and (2) they were subsequently taught to provide their own spoken self-instructions consonant with the earlier, experimenter-supplied instructions. All subjects who received high-rate instructions responded at a steady, high rate, which was maintained following self-instructional training. The effects of low-rate instructions were directly related to the age of the children. The two older groups produced low-rate patterns, with the oldest children responding at very low rates; effects were least noticeable in the youngest age group. Following self-instructional training, all three groups showed adult-like low-rate behavior and the oldest children showed an improved ability to estimate the interval length. The results provide further evidence of the importance of language as a determinant of human behavior.

Journal Article↗
PubMed1985

The role of verbal behavior in human learning: II. Developmental differences.

When children in four different age ranges operated a response device, reinforcers were presented according to fixed-interval schedules ranging in value from 10 to 70 seconds. Only the behavior of the subjects in the youngest of the four groups, the preverbal infants, resembled that of other animal species. The children in age ranges 5 to 6(1/2) and 7(1/2) to 9 years exhibited either the low-rate or high-rate response patterns typical of human adults. Those who showed the low-rate pattern reported a time-based formulation of the contingencies and some of them were observed to occasionally count out the interval before responding. The performance of children aged 2(1/2) to 4 years differed from that of both infants and older children, though containing some patterning elements similar to those produced by the older and younger subjects. The predominant response pattern of the infants consisted of a pause after reinforcement followed by an accelerated rate of responding that terminated when the next reinforcer was delivered. Analysis of postreinforcement-pause duration and response rate showed that infant performance, but not that of the older children, consistently exhibited the same kinds of schedule sensitivity observed in animal behavior. The evidence supports the suggestion that the development of verbal behavior greatly alters human operant performance and may account for many of the differences found between human and animal learning.

Journal Article↗
PubMed1983

The role of verbal behavior in human learning: infant performance on fixed-interval schedules.

The performances of two infants less than one year old were investigated on fixed-interval schedules. When the infants touched a cylinder either music or food was presented according to fixed-interval schedules ranging in value from 10 to 50 seconds. With respect to two principal criteria, namely, pattern of responding and sensitivity to the schedule parameter, the subjects' behavior closely resembled that of animals but differed markedly from that of older children and adults. Negatively accelerated responding in the course of the fixed interval in the early sessions gave way to a scalloped pattern, consisting of a pause after reinforcement followed by an accelerated response rate. This scalloped pattern was the final form of responding on all schedule values. Analysis of data after performance had stabilized showed that postreinforcement pause was a negatively accelerated increasing function, and running rate (calculated after excluding the postreinforcement pause) was a declining function, of schedule value. On each schedule, the durations of mean successive interresponse times declined in the course of the fixed interval and were directly related to schedule value. The results supported Lowe's (1979) suggestion that verbal behavior may be responsible for major differences in the schedule performance of older humans and animals.

Age Factors↗
PubMed1983

Fixed-interval performance: The dynamics of behavior and the interval length.

Postreinforcement pauses from successive intervals under various fixed-interval schedules (ranging from 15 seconds to 480 seconds in length) were subjected to lag-1 autocorrelation analysis. Results from both rats and pigeons suggested that there was a consistent tendency for pause values in successive intervals to be weakly positively related. This tendency did not appear to change systematically with interval length and was exhibited both when the reinforcer magnitude was constant and when it was variable at different interval values. The findings do not support suggestions that the dynamic properties of performance under fixed-interval schedules vary systematically with interval length, and are in the opposite direction from some previous findings suggesting that measures of behavior (such as post-reinforcement pause length or number of responses) in successive intervals are inversely related.

Journal Article↗
PubMed1979

Temporal control of behavior and the power law.

The performance of rats and pigeons under fixed-interval schedules was studied in two experiments. The duration of postreinforcement pause was a declining proportion of fixed-interval duration. For pigeons this was true both when the duration of the reinforcer was fixed and when it was increased in direct proportion to increases in fixed-interval duration; the longer reinforcer durations did, however, lengthen the postreinforcement pause at higher schedule values. A quantitative analysis of data from Experiments 1 and 2 and from other studies showed that fractional exponent power functions described the relationship between postreinforcement pause and fixed-interval value; similar functions have previously been observed in studies of temporal differentiation. It was concluded that power functions reflect a direct causal, rather than artifactual, relationship between performance and the temporal requirements of reinforcement schedules.

Journal Article↗