Continuous versus discrete dimensions of reinforcement schedules: An integrative analysis

An approach to reinforcement-schedule contingencies is presented that accommodates continuous as well as discrete effective dimensions of responses and reinforcers. College students' wheel turning was reinforced by projected reading material according to four schedule contingencies that incorporated either a discontinuous (count) or continuous (duration) dimension of the response and the reinforcer. The contingencies arranged a 1:1 correspondence between (a) response count and consequent stimulus count, (b) response duration and stimulus count, (c) response count and stimulus duration, and (d) response duration and stimulus duration. Contingencies incorporating response count produced moderate to high rates of very short-duration responses. Contingencies incorporating response duration produced very low-rate, long-duration responding. The dimension of the reinforcer had minimal or no additional effect. We suggest that incorporating duration and other continuous dimensions into schedule contingencies may improve our understanding of both laboratory and nonlaboratory behavior.     

Involuntary attentional capture by abrupt onsets

The extent to which brief abrupt-onset visual stimuli involuntarily capture spatial attention was examined in five experiments. The paradigm used was intended to maximize the opportunity and incentive for subjects to ignore abrupt-onset distractor stimuli in nontarget locations. Subjects made a speeded two-choice response to a target letter appearing in one of four boxes. An abrupt-onset visual stimulus, easily discriminable from the target, was flashed briefly prior to the presentation of a target. In separate blocks, the flash stimulus marked the box in which the target would subsequently appear (SAME), a different box (DIFF), fixation (CENTER), or all four boxes (ALL). Prior to each block, subjects were informed of the flash-target relationship. In all five experiments, response time was elevated in the DIFF, CENTER, and ALL conditions. The interference effect was larger for the DIFF condition and persisted for longer flash-target SOAs. These results suggest that, under appropriate conditions, spatial attention can be involuntarily drawn to abrupt-onset events despite the intention of subjects’ to ignore them.     

Can practice eliminate the psychological refractory period effect?

Can people learn to perform two tasks at the same time without interference? To answer this question, the authors trained 6 participants for 36 sessions in a Psychological Refractory Period (PRP) experiment, where Task 1 required a speeded vocal response to an auditory stimulus and Task 2 required a speeded manual response to a visual stimulus. The large PRP effect found initially (353 ms in Session 1) shrank to only about 40 ms over the course of practice, disappearing entirely for 1 of the 6 participants. This reduction in the PRP effect with practice is considerably larger than has been previously reported. The obtained pattern of factor interactions between stimulus onset asynchrony and each of three task difficulty manipulations (Task 1 judgment difficulty, Task 2 stimulus contrast, and Task 2 mapping compatibility) supports a postponement (bottleneck) account of dual-task interference, both before and after practice.     

A test of the Sophisticated Guessing Theory of word perception

Under difficult viewing conditions, a letter in a familiar word can be perceived more accurately than the same letter alone or in a string of unrelated letters. Sophisticated Guessing Theory asserts that perception is more accurate when a letter appears in a word because its identity is constrained by the identity of neighboring context letters. Experiment 1 tested the following prediction: A letter in a word should be perceived more accurately in strongly constraining word contexts than in weakly constraining word contexts. No such trend was found using a number of different measures of contextual constraint and perceptual accuracy. Experiment 2 verified that, with the same conditions used in Experiment 1 to test Sophisticated Guessing Theory, a strong perceptual advantage could be obtained for letters in words vs. letters alone or in unrelated-letter strings. Several alternative theories of word perception are discussed. The most attractive asserts that for words an additional higher-level perceptual code is formed that is more resistant to degradation than the code formed for letters.     

Adult Needs and Strengths Assessment-Abbreviated Referral Version to specify psychiatric care needed for incoming patients: exploratory analysis

The present study examined the Adult Needs and Strengths Assessment-Abbreviated Referral Version ratings for a group of 272 incoming psychiatric patients over a 2-yr. period to assess whether the rating scale was useful in predicting clinical placement for psychiatric treatment. Participants were patients (125 women) admitted to Regional Mental Health Care, St. Thomas, Canada between April 2004 and June 2006. Most participants were Euro-Canadian and ranged in age from 16 to 87 years. Clinical cutoff scores were established using observed mean differences in the patients' total scores and are expected to help guide psychiatric triage and longer term rehabilitation placement decisions. A canonical discriminant function analysis showed 85.9% of original level of care placements were correctly classified. The rating scale is a valid and reliable tool to specify level of psychiatric care needed for adults with mental disorders.