Perceptual Categorization: Connectionist Modelling and Decision Rules

Although it is currently popular to model human associative learning using connectionist networks, the mechanism by which their output activations are converted to probabilities of response has received relatively little attention. Several possible models of this decision process are considered here, including a simple ratio rule, a simple difference rule, their exponential versions, and a winner-take-all network. Two categorization experiments that attempt to dissociate these models are reported. Analogues of the experiments were presented to a single-layer, feed-forward, delta-rule network. Only the exponential ratio rule and the winner-take-all architecture, acting on the networks' output activations that corresponded to responses available on test, were capable of fully predicting the mean response results. In addition, unlike the exponential ratio rule, the winner-take-all model has the potential to predict latencies. Further studies will be required to determine whether latencies produced under more stringent conditions conform to the model's predictions.     

Victim and Perpetrator Accounts of Hurtful Messages: An Actor–Partner Interdependence Model

This study examined how message characteristics and relational turbulence correspond with victim and perpetrator experiences of hurtful messages. Romantic partners described 2 events: one where each of them was a victim of the partner's hurtful message. Trained judges evaluated qualities of hurtful messages and participants reported relationship qualities, intensity of hurt experienced as a victim, and the partner's hurt feelings when the respondent was the perpetrator. Third‐party ratings of hurtfulness were associated with victims' intensity of hurt. For females, relational turbulence was associated with their intensity of hurt as victims. For males, relational turbulence was associated with their perception of the female victims' hurt. The authors discuss the implications for the work on hurtful messages and relational turbulence.     

Associative learning and elemental representation: II. Generalization and discrimination

This paper follows on from an earlier companion paper (McLaren & Mackintosh, 2000), in which we further developed the elemental associative theory put forward in McLaren, Kaye, and Mackintosh (1989). Here, we begin by explicating the idea that stimuli can be represented as patterns of activation distributed across a set of units and that different stimuli activate partially overlapping sets (the degree of overlap being proportional to the similarity of the stimuli). A consequence of this view is that the overall level of activity of some of the units representing a stimulus may be dependent on the nature of the other stimuli present at the same time. This allows an elemental analysis in which provision for the representation of configurations of stimuli is made. A selective review of studies of generalization and discrimination learning, including peak shift, transfer along a continuum, configural discrimination, and summation, suggests that the principles embodied in this class of theory deserve careful consideration and will form part of any successful model of associative learning in humans or animals. There are some phenomena that require an elemental/associative explanation.     

State‐Trace Analysis: Dissociable Processes in a Connectionist Network?

Some argue the common practice of inferring multiple processes or systems from a dissociation is flawed (Dunn, 2003). One proposed solution is state‐trace analysis (Bamber, 1979), which involves plotting, across two or more conditions of interest, performance measured by either two dependent variables, or two conditions of the same dependent measure. The resulting analysis is considered to provide evidence that either (a) a single process underlies performance (one function is produced) or (b) there is evidence for more than one process (more than one function is produced). This article reports simulations using the simple recurrent network (SRN; Elman, 1990) in which changes to the learning rate produced state‐trace plots with multiple functions. We also report simulations using a single‐layer error‐correcting network that generate plots with a single function. We argue that the presence of different functions on a state‐trace plot does not necessarily support a dual‐system account, at least as typically defined (e.g. two separate autonomous systems competing to control responding); it can also indicate variation in a single parameter within theories generally considered to be single‐system accounts.     

Learned associability and associative change in human causal learning.

The Mackintosh (1975) model of associative learning specifies that processing of both the cues presented on a trial and the outcome of that trial will interact to determine the amount of associative change undergone by a given cue. Experiments looking at the distribution of associative change among the elements of a reinforced compound in animal conditioning studies indicate that processing of the outcome of a trial does indeed influence associative change. The work reported here investigates the distribution of associative change among the elements of a reinforced compound in a human causal judgement paradigm, and it indicates that processing of the cues presented on a trial also plays a role in determining associative change (in terms of changes in the associability of cues as a result of experience). Taken in combination, these results provide good support for Mackintosh (1975) and the characterizations of both cue and outcome processing that it offers.     

The Interrelations of Agency,Depression, and Suicidal Ideation Among Older Adults

The high rates of suicide among older men are cause for concern, and have prompted the investigation of factors that might explain these elevated rates. The current research examined whether the gender role construct agency was associated with depression and suicidal ideation among older adults. The results, based on self‐report data from a sample of older Australian men (n = 69) and women (n = 90), indicated that depression mediated the relation between agency and suicidal ideation. In addition, for older men only, agency moderated the depression‐suicidal ideation relation. The results suggest that older adults, and particularly men, with low levels of agency should be the targets for interventions aimed at increasing levels of agency and improving mental health.     

Latent inhibition, context specificity, and context familiarity

In two appetitive licking experiments, thirsty rats were pre-exposed to two stimuli prior to conditioning sessions in which one or both of these stimuli were paired with water. Consistent with other results, latent inhibition was disrupted when conditioning took place in a context different from that in which stimulus pre-exposure had occurred. But in animals given prior exposure to the context of stimulus pre-exposure before the start of stimulus pre-exposure, substantial and equivalent latent inhibition was evident whether or not there was a change of context between stimulus pre-exposure and conditioning. These results are discussed in terms of current theories of latent inhibition.     

Generalization in Human Category Learning: A Connectionist Account of Differences in Gradient after Discriminative and Non discriminative Training

Two experiments are reported that investigate the difference in gradient of generalization observed between one-category (non-discriminative) and two-category (discriminative) training. Extrapolating from the results of a number of animal learning studies, it was predicted that the gradient should be steeper under discriminative training. The first experiment confirms this basic prediction for the stimuli used, which were novel, prototype-structured, and constructed from 12 symbols positioned on a grid. An explanation for the effect, based on the Rescorla-Wagner theory of Pavlovian conditioning (Rescorla & Wagner, 1972), is that under non-discriminative training 'incidental stimuli' have significant control over responding,whereas under discriminative training they do not. Incidental stimuli are those aspects of the stimulus, or the surrounding context, that are not differentially reinforced under discriminative training. This explanation leads to the prediction that a comparable effect of blocked versus intermixed discriminative training should also be found. This prediction is disconfirmed by the second experiment. An alternative model, still based on the RescorlaWagner theory but with the addition of a decision mechanism comprising a threshold unit and a competitive network system, is proposed, and its ability to predict both the choice probabilities and the pattern of response times found is evaluated via simulation.     

Attention-Deficit Hyperactivity Disorder: The Medicalization of Misbehavior

During the past decade, there has been an increase in the diagnosis and treatment of Attention-Deficit Hyperactivity Disorder (ADHD). This syndrome, typically diagnosed in childhood, is characterized by inattention, hyperactive motor behavior, and distractibility. Current prevalence rates obtained in various countries generally exceed the 3–5% reported by DSM-IV. Reasons for increased ADHD prevalence include changes in diagnostic standards, overlap between ADHD and other externalizing disorders, nonspecific behavioral criteria, and the rapid effects of stimulant medication on cognitive functioning. However, social, cultural, and economic factors may also contribute to increased diagnosis. ADHD has become a common topic in the lay media. Popular discussions of ADHD may serve as a metaphoric expression of social anxieties, particularly with respect to children. At the same time, ADHD has rapidly become incorporated into a medical model, with emphasis on pharmacological treatment. Reductions in mental health and educational services, as well as economic pressures of managed care, may also contribute to medicalization of behavioral problems. Collaboration between psychologists and primary care physicians can lead to more accurate diagnosis and appropriate treatment of ADHD and related disorders.     

The association of depression and sense of belonging with suicidal ideation among older adults: applicability of resiliency models

Suicide among older people, especially men, is a significant problem. In this study the applicability of the compensatory, the risk-protective, the challenge, and the protective-protective models of resiliency for the prediction of suicidal ideation from depression (the risk factor) and sense of belonging to the community (the protective factor) was investigated. A total of 351 retired Australians (130 males and 221 females), with a mean age of 71.31 years (SD = 7.99), completed the Zung Depression Scale, the suicide subscale of the General Health Questionnaire, and the Sense of Belonging Instrument. When sense of belonging (psychological) was the protective factor, results indicated support for the risk-protective model for men and women, and for the compensatory model for women only. In contrast, when sense of belonging (antecedents) was the protective factor, support was evident for the compensatory model for men and women, and for the challenge model for women only. Results indicate that interventions should be developed to enhance sense of belonging among aging adults.