A comparison of bounded diffusion models for choice in time controlled tasks

The Wiener diffusion model (WDM) for 2-alternative tasks assumes that sensory information is integrated over time. Recent neurophysiological studies have found neural correlates of this integration process in certain neuronal populations. This paper analyses the properties of the WDM with two different boundary conditions in decision making tasks in which the time of response is indicated by a cue. A dual reflecting boundary mechanism is proposed and its performance is compared with a well-established absorbing boundary in the cases of the WDM, the WDM with extensions, and the WDM with prior probability. The two types of boundary influence the dynamics of the model and introduce differential weighting of evidence. Comparisons with Ornstein-Uhlenbeck models are also done, and it is shown that the WDM with both types of boundary achieves similar performance and produces similar fits to existing behavioural data. Further studies are proposed to distinguish which boundary mechanism is more consistent with experimental data.     

A theoretical framework for understanding the effects of simultaneous base-rate and payoff manipulations on decision criterion learning in perceptual categorization

Observers completed perceptual categorization tasks in which base rates and payoffs were manipulated separately or simultaneously across a range of category discriminabilities. Decision criterion estimates from the simultaneous base-rate/payoff conditions were closer to optimal than those predicted from the independence assumption, in line with predictions from the flat-maxima hypothesis. A hybrid model that instantiated the flat-maxima and competition between reward and accuracy maximization hypotheses was applied to the data as well as used in a reanalysis of C. J. Bohil and W.J. Maddox's (2001) study. The hybrid model was superior to a model that incorporated the independence assumption, suggesting that violations of the independence assumption are to be expected and are well captured by the flat-maxima hypothesis, without requiring any additional assumptions.     

A critical comparison of two random-walk models for two-choice reaction time

Two random-walk models for two-choice reaction time, being the sequential probability ratio test model initially suggested by Stone and the relative judgment theory recently proposed by Link, are here compared. The comparison shows the precise mathematical relation between the models, the predictions they have in common, and two points at which they differ. Three experiments concerned with the effect of stimulus probability on two-choice reaction time are examined with respect to three predictions from the models. In this three-way comparison the two models are more like each other than either is to the data; a greater variety of phenomena is revealed than either model can at present accommodate.     

A comparison of two models for performance under fixed interval schedules of reinforcement

Two models are proposed for responding under fixed-interval schedules of reinforcement. The first model is a Poisson model and seems suitable for situations in which responding produces a classical “FI scallop”. A second model is then developed to describe “break and run” performance, which is also known to occur under some Fixed Interval schedules. The models do not however give any indication of the circumstances under which a particular mode of responding should arise. A comparison of the models to a small set of data collected from rats performing under an FI 60 sec schedule indicates that for the data considered, the second model (a State model) produced by far the best fit.     

A comparison of two psychological treatments for bulimia nervosa: Implications for models of maintenance

In an effort to elucidate the role of cognitive factors in the maintenance of bulimia nervosa, the efficacy of two psychological treatments was examined in a randomised control trial: cognitive behaviour therapy in the absence of explicit exposure instructions was compared with exposure and response prevention treatment in the absence of cognitive restructuring procedures. In the short term both treatments were successful at effecting substantial improvement in both the specific and the non-specific psychopathology of the disorder. However, at a one year follow up, whilst improvements were well maintained for those who had received the cognitive-behavioural treatment, virtually all of those who had responded to the purely behavioural treatment had relapsed. This provides some support for the cognitive model of the maintenance of bulimia nervosa. Nevertheless, the two treatment groups could not be distinguished on post-treatment measures of cognitive disturbance and neither was it the case that residual levels of cognitive disturbance, as assessed, predicted relapse. This may suggest that the level at which the necessary cognitive change takes place may not be accessible by conventional assessment procedures.     

Characteristics of residential care for adolescent offenders: A comparison of assumptions and practices in two models

Staff assumptions and program practices in two models of residential care for male adolescent offenders were compared. Group care settings had from 6 to 15 youths in residence and used peer-mediated treatments. Treatment Foster Care settings had one youngster placed in each home and treatments were adult-mediated. Results showed that group care and Treatment Foster Care program models differed on staff assumptions about therapeutic mechanisms of change, and different patterns of daily program practices were found.     

Mathematical models of memory and the problem of stimulus variation: A comparison of Minerva 2 and Todam

MINERVA 2 Hintzman, 1983, Hintzman, 1984 and TODAM (Murdock 1982, 1983), two contemporary mathematical models of memory, are compared with regard to the way they conceptualize and formalize the processes of encoding, storage, and retrieval. Both models were applied to a set of data from an experiment involving stimulus variation and memory (Avant and Bevan 1968b). Results show that TODAM more closely simulated tha data than did MINERVA 2. These findings are discussed in terms of the relevant differences between the two models.     

A comparison of two response time models applied to perceptual matching

Two models, a Poisson race model and a diffusion model, are fit to data from a perceptual matching task. In each model, information about the similarity or the difference between two stimuli accumulates toward thresholds for either response. Stimulus variables are assumed to influence the rate at which information accumulates, and response variables are assumed to influence the level of the response thresholds. Three experiments were conducted to assess the performance of each model. In Experiment 1, observers performed under different response deadlines; in Experiment 2, response bias was manipulated by changing the relative frequency ofsame anddifferent stimuli. In Experiment 3, stimulus pairs were presented at three eccentricities: foveal, parafoveal, and peripheral. We examined whether the race and diffusion models could fit the response time and accuracy data through changes only in response parameters (for Experiments 1 and 2) or stimulus parameters (for Experiment 3). Comparisons between the two models suggest that the race model, which has not been studied extensively, can account for perceptual matching data at least as well as the diffusion model. Furthermore, without the constraints on the parameters provided by the experimental conditions, the diffusion and the race models are indistinguishable. This finding emphasizes the importance of fitting models across several conditions and imposing logical psychological constraints on the parameters of models.     

A comparison of verbal and tangible stimulus preference assessments

Tangible preference assessments were compared with verbal preference assessments for 6 individuals with mental retardation, behavior disorders, or both. In the tangible assessment, items were placed in front of the participant. In the verbal assessment, participants were asked, “Do you want X or Y?” and the items were not present. The two assessments yielded similar high‐preference items for 4 of the 6 participants. The verbal assessment was typically completed in less time than the tangible assessment.     

A further test of sequential-sampling models that account for payoff effects on response bias in perceptual decision tasks

Recently, Diederich and Busemeyer (2006) evaluated three hypotheses formulated as particular versions of a sequential-sampling model to account for the effects of payoffs in a perceptual decision task with time constraints. The bound-change hypothesis states that payoffs affect the distance of the starting position of the decision process to each decision bound. The drift-rate-change hypothesis states that payoffs affect the drift rate of the decision process. The two-stage-processing hypothesis assumes two processes, one for processing payoffs and another for processing stimulus information, and that on a given trial, attention switches from one process to the other. The latter hypothesis gave the best account of their data. The present study investigated two questions: (1) Does the experimental setting influence decisions, and consequently affect the fits of the hypotheses? A task was conducted in two experimental settings--either the time limit or the payoff matrix was held constant within a given block of trials, using three different payoff matrices and four different time limits--in order to answer this question. (2) Could it be that participants neglect payoffs on some trials and stimulus information on others? To investigate this idea, a further hypothesis was considered, the mixture-of-processes hypothesis. Like the two-stage-processing hypothesis, it postulates two processes, one for payoffs and another for stimulus information. However, it differs from the previous hypothesis in assuming that on a given trial exactly one of the processes operates, never both. The present design had no effect on choice probability but may have affected choice response times (RTs). Overall, the two-stage-processing hypothesis gave the best account, with respect both to choice probabilities and to observed mean RTs and mean RT patterns within a choice pair.     

Expectancy and stimulus frequency: A comparative analysis in rats and humans

We examined whether expectancy, one of several factors influencing attention, is similarly affected in rats and humans by manipulation of relative stimulus frequency, A two-choice reaction time (RT) task was developed for rats, and an analogous task was used for humans. Errors, RTs, discriminability, and response bias were measured. Both rats and humans shifted their response bias to the more frequent stimulus, with no change in overall discriminability. As stimulus probability or stimulus repetition increased, RTs and errors decreased. These results illustrate the similarity of expectancy in rats and humans. This two-choice RT task for rats can be used in future studies to examine the neuronal mechanisms of expectancy and attention.     

Modality effects in memory for basic stimulus attributes: A temporal and nontemporal comparison

Previous research suggests that there are significant differences in the operation of reference memory for stimuli of different modalities, with visual temporal entries appearing to be more durable than auditory entries (Ogden, Wearden, & Jones, 2008 Ogden, R. S., Wearden, J. H. and Jones, L. A. 2008. The remembrance of times past: Interference in temporal reference memory. Journal of Experimental Psychology: Human Perception and Performance, 34: 1524–1544. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar], 2010). Ogden et al. (2008 Ogden, R. S., Wearden, J. H. and Jones, L. A. 2008. The remembrance of times past: Interference in temporal reference memory. Journal of Experimental Psychology: Human Perception and Performance, 34: 1524–1544. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar], 2010 Ogden, R. S., Wearden, J. H. and Jones, L. A. 2010. Are memories for duration modality specific?. Quarterly Journal of Experimental Psychology, 63: 65–80. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) demonstrated that when participants were required to store multiple auditory temporal standards over a period of delay there was significant systematic interference to the representation of the standard characterized by shifts in the location of peak responding. No such performance deterioration was observed when multiple visually presented durations were encoded and maintained. The current article explored whether this apparent modality-based difference in reference memory operation is unique to temporal stimuli or whether similar characteristics are also apparent when nontemporal stimuli are encoded and maintained. The modified temporal generalization method developed in Ogden et al. (2008) Ogden, R. S., Wearden, J. H. and Jones, L. A. 2008. The remembrance of times past: Interference in temporal reference memory. Journal of Experimental Psychology: Human Perception and Performance, 34: 1524–1544. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar] was employed; however, standards and comparisons varied by pitch (auditory) and physical line length (visual) rather than duration. Pitch and line length generalization results indicated that increasing memory load led to more variable responding and reduced recognition of the standard; however, there was no systematic shift in the location of peak responding. Comparison of the results of this study with those of Ogden et al. (2008 Ogden, R. S., Wearden, J. H. and Jones, L. A. 2008. The remembrance of times past: Interference in temporal reference memory. Journal of Experimental Psychology: Human Perception and Performance, 34: 1524–1544. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar], 2010 Ogden, R. S., Wearden, J. H. and Jones, L. A. 2010. Are memories for duration modality specific?. Quarterly Journal of Experimental Psychology, 63: 65–80. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) suggests that although performance deterioration as a consequence of increases in memory load is common to auditory temporal and nontemporal stimuli and visual nontemporal stimuli, systematic interference is unique to auditory temporal processing.     

Physical and cognitive dimensions in stimulus comparison

Two experiments were carried out using a same-different task with sets of four stimuli varying orthogonally in three dimensions. Sameness was defined by each of the three dimensions in turn, as well as by physical identity. Two types of dimensions, physical and cognitive, were studied. In Experiment 1, the numerals 6, 10, VI, and X, which vary in Length, System, and Name, were used. With simultaneous presentation, order of difficulty was from the physical dimension of Length to the cognitive dimension of Name. While overall difficulty was related to dimensional discriminability, internal evidence suggested that Name was not a dimension in the same sense as Length is, and that some stimulus pairs were simply easier to process than others, regardless of the response required (e.g., short stimulus pairs and Arabic numerals). With sequential presentation, Name was processed as fast as System, due largely to the fact that much faster responding occurred when an Arabic numeral was the second stimulus. Thus, with sequential presentation, Name provides a processing mechanism not provided by physical dimensions. In Experiment 2, the numerals 3, 4, 6, and 7, which vary in Magnitude, Oddness, and Curvilinearity, were used. The cognitive dimension of Magnitude was pro cessed most rapidly, and numerical distance between pairs of numbers dominated the results for “same” responses, regardless of the sameness rule used. Again, evidence was found for fast processing of some stimulus pairs (e.g., 3 4), regardless of the response required. Overall, these experiments are interpreted as indicating that cognitive factors such as stimulus familiarity may override aspects of physical discriminability with many dimensions and stimuli, that, even though a cognitive dimension can be used to generate a logically proper set of stimuli, it does not necessarily act as other, more physical dimensions do, and that clarification of the functional role of a dimension is more important than attempts to locate stages.     

Adaptation-level and theory of signal detection: an examination and integration of two judgment models for voluntary stimulus generalization

An examination of two judgement models, adaptation-level (AL) theory and the theory of signal detection (TSD), was made in terms of their ability to handle data from several voluntary generalization studies. Both models were found to be somewhat inadequate, though in different ways. AL theory was found to be unable to predict amount or slope of the generalization gradient, while TSD was seen to be unable to account for shifts in judgment due to context and frequency effects. A combined AL-TSD model was presented which combines the advantages of each model and offers a good account of both choice and latency data in voluntary generalization     

Antecedent manipulations in a tangible condition: effects of stimulus preference on aggression.

After a functional analysis indicated that aggression of an 8‐year‐old boy with autism was maintained by access to preferred items, antecedent manipulations involving the relative preference of restricted and noncontingently available stimuli were conducted. Restricting highly preferred items evoked the highest rates of aggression regardless of the preference level of the noncontingently available alternative items. Restricting less preferred stimuli was associated with moderate rates of aggression even when the alternative items were more preferred.