Differences in temporal appearance associated with activity in the chromatic and achromatic systems

The temporal appearances of spatially coincident increments that activate the chromatic or achromatic system are different. Whereas near-threshold stimuli that are detected by the chromatic system appear to come on gradually, increments detected by the achromatic system appear to flash or step on. This difference in perception is consistent with previous reports that show differences in the temporal properties of the two systems.     

Preparing dichotic tapes using a digital music synthesizer

Digital music synthesizers represent audio signals in the form of binary coded numbers. These binary coded numbers can be manipulated by the operator, thereby altering the audio signal in a variety of ways. The present article describes how these capabilities can be used to produce perfectly aligned dichotic tapes in which the stimulus items are matched on all extraneous (timbre, amplitude, duration) factors.     

Out-of-home placement of children: Selected issues and prospects for the future

This paper describes the recent trends in the child welfare and children's mental health systems and their implications for public policy. Despite the rhetoric calling for preserving families and treating children and youth in their own homes, the best available evidence indicates that the rates of out-of-home placement are increasing at an alarming rate. More concerted and comprehensive efforts are needed if this trend is to be reversed in the near future.     

The effects of parental alcoholism on perception of control and imposter phenomenon

The present study examined the differences in internal and external locus of control and imposter phenomenon among persons with alcoholic and non-alcoholic parents. The subjects were 48 college students and 21 members of local Adult Children of Alcoholic groups. The students were further divided into those with alcoholic parents and non-alcoholic parents. The subjects were administered the following three instruments: the Nowicki-Strickland Internal-External Control Scale for Adults (Nowicki & Duke, 1973), the Imposter Test (Chance & O’Toole, 1987), and a family history survey. Analysis of locus of control scores revealed a highly significant (p<.01) difference for externality, with Adult Children being most external and students with non-alcoholic parents least external. Similarly, internality scores differed significantly (p<.0001), with Adult Children being least, and the non-alcoholic group being most internally oriented. Analysis of variance for imposter phenomenon revealed a significant (p<.05) difference among the three groups, with the Adult Children of Alcoholics group having the highest scores and students with non-alcoholic parents having the lowest. These findings are consistent with the idea that parental alcoholism interferes with nurturing and consistent reinforcement, and with the development of personal adaptability.     

Interval and ratio reinforcement of a complex sequential operant in pigeons

Pigeons were required to produce exactly four pecks on each of two keys in any order for reinforcement. Correct response sequences were reinforced on either fixed-interval two-minute or fixed-ratio four schedules, with each correct sequence treated as a single response. Each pigeon developed a particular dominant sequence that accounted for more than 80% of all sequences. Sequence stereotypy was relatively unaffected by the temporal properties of the fixed-interval and fixed-ratio schedules. Response time (time from the first response in each sequence to the last) was also relatively unaffected by the temporal properties of the schedules. In contrast, response latency (time from end of one sequence to the beginning of the next) was markedly affected by the schedules. Latencies were long early in the interreinforcement interval and got shorter as the interreinforcement interval progressed. These data suggest that stereotyped response sequences become functional behavioral units, resistant to disruption or alteration by reinforcement variables that ordinarily influence the temporal spacing of individual responses.     

Verbal ability and mental processing speed

The notion that verbal ability is related to mental processing speed was examined using tasks that systematically varied in semantic content. Subjects' reaction times were measured in five tasks involving arrow matching, physical identity word matching, or taxonomic identity word matching. The findings indicated that matching tasks using different decision rules and different stimuli were all related to verbal ability. In fact, reaction time for subjects required to judge whether two arrows pointed in the same direction was the best predictor of verbal ability. One explanation of the results is that speed of information processing (a general factor) may be the important component of verbal ability which is measured by seemingly different matching tasks.     

Chunking in recall of symbolic drawings

Three experiments explored memory for symbolic circuit drawings using skilled electronics technicians and novice subjects. In the first experiment a skilled technician reconstructed circuit diagrams from memory. Recall showed marked “chunking”, or grouping, by functional units similar to Chess Masters’ recall of chess positions. In the second experiment skilled technicians were able to recall more than were novice subjects following a brief exposure of the drawings. This advantage did not hold for randomly arranged symbols. In the third experiment the size of chunks retrieved systematically increased with additional study time. Supplementary analyses suggested that the chunking by skilled subjects was not an artifact of spatial proximity and chunk statistics, and that severe constraints are placed on any explanation of the data based on guessing. It is proposed that skilled subjects identify the conceptual category for an entire drawing, and retrieve elements using a generate-and-test process.     

Two types of pigeon key pecking: suppression of long- but not short-duration key pecks by duration-dependent shock

The key pecking of eight pigeons was maintained on a variable-interval 1-minute schedule of food reinforcement. Sometimes, all responses between 35 and 50 milliseconds in duration produced a shock; sometimes, all responses between 10 and 25 milliseconds produced a shock; sometimes, shocks were produced by pecks without regard to duration (nondifferential punishment), and sometimes shocks were delivered independently of responding. Punishment of 35- to 50-millisecond responses selectively suppressed those responses, while punishment of 10- to 25-millisecond responses and nondifferential punishment suppressed responding overall but did not suppress responses of particular duration. Punishment of 35- to 50-millisecond responses suppressed key pecking slightly less than did nondifferential punishment. Punishment of 10- to 25-millisecond responses and response-independent shock produced roughly equal amounts of suppression, substantially less than the other punishment procedures. The data support the view that there are at least two kinds of key peck, identifiable on the basis of duration, one of which (short duration) is insensitive to its consequences.     

Further examinations of the category-recall function

Subjects were assigned to use either three or six categories and were given either 5 or 10 trials in a word-sorting task. Subsequent to sorting, they recalled as many words as they could. A measure of sorting consistency showed that the six-category sort was a more difficult task than was the three-category sort. Number of categories did not have a significant effect on recall performance regardless of whether 5 or 10 sorting trials were used. A correlational analysis raised questions about the relationship of the sorting tasks to recall performance and clustering.