An experimental and theoretical investigation of the constant-ratio rule and other models of visual letter confusion

The constant-ratio rule (CRR) and four interpretations of R. D. Luce's (In R. D. Luce, R. R. Bush, & E. Galanter (Eds.), Handbook of mathematical psychology (Vol. 1). New York: Wiley, 1963) similarity choice model (SCM) were tested using an alphabetic confusion paradigm. Four stimulus conditions were employed that varied in set size (three, four or five stimulus elements) and set constituency (block letters: A, E, X; F, H, X; A, E, F, H; A, E, F, H, X), and were presented to each subject in independent blocks. The four interpretations of the SCM were generated by constraining one, both, or neither of its similarity and bias parameter sets to be invariant in across-stimulus set model predictions. The strictest interpretation of the SCM (both the similarity and bias parameters constrained), shown to be a special case of the CRR, and the CRR produced nearly equivalent across-set predictions that provided a reasonable first approximation to the data. However, they proved inferior to the least strict SCM (neither the similarity nor bias parameters were constrained; the common interpretation of the SCM in visual confusion). Additionally, the least strict SCM was compared to J. T. Townsend's (Perception and Psychophysics, 1971, 9, 40–50, 449–454) overlap model, the all-or-none model (J. T. Townsend, Journal of Mathematical Psychology, 1978, 18, 25–38), and a modified version of L. H. Nakatani's (Journal of Mathematical Psychology, 1972, 9, 104–127) confusion-choice model. Both the least strict SCM and confusion-choice models produced nearly equivalent within stimulus set predictions that were superior to the overlap and all-or-none within-set predictions. Measurement conditions related to model structure and equivalence relations among the models, many of them new, were examined and compared with the statistical fit results of the investigation.     

Cued recall in anterograde amnesia

After a single presentation of a word list, normal subjects exhibited better retention when prompted with semantic cues than with rhyme or letter cues. Alcoholic Korsakoff patients, patients receiving electroconvulsive therapy (ECT), and the patient N.A. exhibited impaired retention and, unlike control subjects, did not exhibit an advantage of semantic cues over letter and rhyme cues. Two experimental manipulations designed to equate the level of performance of amnesics and controls indicated that these amnesias could be understood as a reflection of weak memory strength that results from deficiencies in initial learning and retention. In addition, alcoholic Korsakoff patients appeared to have greater difficulty utilizing semantic cues than patients receiving ECT or patient N.A.     

Anxiety management and applied relaxation in reducing general anxiety

Sixty-three generally anxious subjects were assigned to anxiety management training, applied relaxation training, relaxation-only, placebo and untreated control conditions. After 6 weeks of treatment, anxiety management training led to reductions on a variety of self-report measures of state and trait anxiety and decreases in maladaptive cognitions during a laboratory stress procedure. On several measures, subjects in anxiety management training differed from relaxation-only and placebo subjects as well as untreated controls. However, treatment effects did not extend to performance and physiological measures of anxiety. Applied relaxation training, which in contrast to anxiety management training lacks structured rehearsal involving the recognition and reduction of tension cues during the treatment sessions, resulted in less consistent decreases in measures of general anxiety.     

Attributed influence: The importance of observing change

The presence of a target's unexpected change in behavior following an influence attempt was hypothesized to be a critical variable for attributing influence to a particular agent. Observers read a brief story in which an agent's intervention was followed by the target's compliance, noncompliance, or countercompliance to the request. The results indicated that influence was attributed to the agent in the conditions demonstrating change, i.e., compliance and countercompliance, regardless of the direction of that change. Additional findings indicated that influence attributed to an agent decreased if the target delayed final compliance with the intervention.     

Sign-tracking in aversive conditioning

Two experiments were conducted to determine if rats tend to avoid contact with a stimulus that signals the occurrence of shock and contact a stimulus that signals the nonoccurrence of shock. The conditioned stimulus was a 60-sec platform presentation, and the unconditioned stimulus was a 2-sec inescapable shock. In each experiment, the emphasis was on two types of Pavlovian pairings: forward pairing in which each platform presentation was followed by shock, and backward pairing in which each platform presentation was preceded by shock and followed by a lengthy shock-free interval. Experiment 1 showed that in comparison with Random and CS-only procedures, the backward procedure produced a significant increase in approach and contact with the platform, but the forward procedure failed to produce a significant decrease in contact with the platform. Experiment 2, in which all groups were roughly equated for baseline levels of platform preference, demonstrated strong effects of both forward and backward conditioning. The experiments provide evidence for an aversive sign-tracking system in which animals' tendencies to withdraw from or approach and contact a platform CS are determined by the Pavlovian contingencies which render it a reliable signal for the occurrence or nonoccurrence of shock.     

Within-compound associations in a variety of compound conditioning procedures

Three experiments used a flavor-aversion preparation to demonstrate the occurrence of within-compound associations in various conditioning procedures. In Experiment 1 rats first received two separate two-flavor compounds, each followed by a mild US. They then received one element from one compound paired with a strong US and one element from the other compound nonreinforced. A subsequent choice test of the other two flavors from the compounds revealed that the consumption of each test flavor reflected the conditioning history of the element with which it had been paired. Rats drank less of the flavor whose associate had been paired with the strong US than of the flavor whose associate had been nonreinforced. In Experiment 2 within-compound associations were observed using a similar design in a blocking procedure in which one element from each of the two compounds was conditioned previously. Experiment 3 identified within-compound associations in a procedure where reinforced single element presentations were intermixed with nonreinforced compound presentations, as in a conditioned inhibition paradigm. These results suggest that within-compound associations occur in several important conditioning procedures which use multiple CS presentations.     

Differential forgetting of prototypes and old instances: Simulation by an exemplar-based classification model

A common finding in studies of classification learning is that ability to classify the prototype of a category declines much less over a retention interval than does the ability to classify the previously seen exemplars themselves. We demonstrate here that this finding does not necessarily indicate the existence, in memory, of a representation of the prototype. MINERVA, a computer-simulation model that encodes memory traces only of presented exemplars, was tested on an appropriate task. Differential forgetting of prototypes and old instances was shown by a version of the model that assumed that (1) classification is based on the exemplar trace most similar to the test stimulus and (2) individual properties are lost from the traces over time in an all-or-none fashion. It is suggested that, in general, the key to the prediction of differential forgetting may be the concomitance of forgetting and generalization.     

The University of South Florida homograph norms

Norms were collected to determine the relative dominance of different meanings of homo-graphic words. Forty-six subjects wrote down the first word that came to mind for each of 320 homographs. Each homograph, the number of times each meaning was given, and the specific associates are made available. In addition, correlations with other norms are presented.