The P300 component of the event-related brain potential in a short-term memory paradigm]

In numerous investigations the P300-component of the event-related-brain-potential (ERP) has proved a valid indicator of memory activities. The present study explores the amplitude of the P300 in an isolated short term memory task with variant difficulties. In two experiments the reproduction of senseless memory material was examined using the categories "syllables" and "consonants". One syllable was thereby synonymous with the so-called "chunk" which represents a subjective unit arising from grouping of memory material. The results show a significant increase in P300-amplitude in a line with memory load in both categories. On the contrary there is no significant difference in the amplitude of P300 between the two categories. These results suggest that the costs for storing one syllable are comparable with those for one consonant.     

Relative reinforcer magnitude under a nonindependent concurrent schedule of cocaine reinforcement in rhesus monkeys.

Lever pressing by three rhesus monkeys was maintained under a two-lever concurrent schedule of cocaine reinforcement. Responding on one lever (constant-dose lever) produced a constant dose of 0.05 or 0.1 mg/kg/injection arranged according to a variable-interval 1-min schedule. Responding on the other lever (variable-dose lever) produced a comparison dose of cocaine (0.013 to 0.8 mg/kg/injection), also under a variable-interval 1-min schedule. The two variable-interval schedules were made nonindependent by arranging that the assignment of a reinforcer by one schedule inactivated the second schedule until the assigned reinforcer had been obtained. This modification ensured that the two cocaine doses were obtained with approximately equal frequency, regardless of the distribution of the subject's responding. Preference, indicated by relative response frequency on the variable-dose lever, was almost always for the larger of the doses and was a monotonic function of the comparison dose, except at the highest doses. Preferences at the highest comparison doses may have resulted from the low overall response rates exhibited at these doses. Relative response frequencies on the variable-dose lever roughly matched relative reinforcer magnitude (mg/kg/injection available on the variable-dose lever divided by the sum of mg/kg/injections available on each lever).     

The Minnesota interactive statistical system

The Minnesota Interactive Statistical System (MISS) is reviewed as a successful application of on-line minicomputing in an instructional and research context. The MISS system is described with regard to (1) the instructional and research needs which prompted its development, (2) its programming design, (3) its operating system, (4) its computer hardware requirements, and (5) the continued innovative minicomputing development that it has inspired.     

College major and career choice: A retest of Holland's theory

In an effort to examine whether the previously established relationship between vocational choice and self-ratings on Holland's personality stereotypes among college freshmen would be strengthened with a sample of male college seniors, 109 subjects, sampled on the basis of major field choice, completed a questionnaire to select career stereotypes which described them best. The relationship between self-ratings and academic major was also to be examined. Significant relationships were obtained for four stereotypes (realistic, conventional, enterprising, and artistic) on the basis of both major and vocational choice, although significant stereotypes were not identical in each. Three of these significant relationships based on vocational choice matched those obtained previously. An additional finding suggested that vocational choice was slightly more valid than major field as a basis for utilizing this technique. The more restricted class sample emphasized did not, however, produce a more substantial relationship between self-ratings and occupational choice as expected.     

Concept identification with concurrent and delayed verbalization

Concept labelling and use of complex solutions is facilitated by instructions to verbalize concurrently with initial stimulus presentation. Older subjects who delay verbalization until after task completion are less effective in using relevant stimulus dimensions for solution and more closely approximate the performance of younger concurrent verbalizers.     

A cooperative approach to the internship in school psychology

The internship program in school psychology in Ohio involves the close and continuing cooperation of the Ohio Department of Education, Ohio Inter-University Council on School Psychology, and field supervisors employed by local school districts. The roles of each are briefly discussed.     

A simple technique for delivering liquids directly to the mouth of an unrestrained rat

A simple surgical procedure is described that makes it possible to deliver liquids directly into the mouth of a freely mobile rat. Data presented show that an 8% sucrose solution delivered by this technique is an effective reinforcer in a variety of simple and discriminative schedules of reinforcement.