On the form of the forgetting function: the effects of arithmetic and logarithmic distributions of delays

Forgetting functions with 18 delay intervals were generated for delayed matching-to-sample performance in pigeons. Delay interval variation was achieved by arranging five different sets of five delays across daily sessions. In different conditions, the delays were distributed in arithmetic or logarithmic series. There was no convincing evidence for different effects on discriminability of the distributions of different delays. The mean data were better fitted by some mathematical functions than by others, but the best-fitting functions depended on the distribution of delays. In further conditions with a fixed set of five delays, discriminability was higher with a logarithmic distribution of delays than with an arithmetic distribution. This result is consistent with the treatment of the forgetting function in terms of generalization decrement.     

Effects of methylphenidate and morphine on delay-discount functions obtained within sessions

Four rats responded under a "self-control" procedure designed to obtain delay-discount functions within sessions. Each session consisted of seven blocks, with seven trials within each block. Each block consisted of two initial forced-choice trials followed by five free-choice trials. On choice trials, the rats could press either of two retractable levers. A press on one lever was followed by presentation of a smaller reinforcer (a single dipper presentation of a sucrose solution); a press on the other lever was followed by presentation of a larger reinforcer (four consecutive dipper presentations). The delay associated with the smaller reinforcer always was 0 s, whereas the signaled delay associated with the larger reinforcer increased across blocks (from 0 to 50 s). Under these conditions, the percentage of choices of the larger reinforcer decreased across blocks, and relatively reliable delay-discount functions were obtained within sessions. Doses of methylphenidate (1.0 to 17.0 mg/kg) and morphine (0.3 to 17.0 mg/kg) were then administered prior to selected sessions. Typically, intermediate doses of methylphenidate shifted the discount functions to the right (increased choices of the larger reinforcer). For 2 of the rats, this effect was pronounced; for the other 2 rats, this effect occurred after the range of delays for the larger reinforcer was decreased (0 to 20 s). On the other hand, in most cases morphine produced a slight leftward shift in the discount function (decreased choices of the larger reinforcer). The present procedure appears to be a useful and efficient method to characterize drug effects on an entire delay-discount function. As with many procedures used to study self-control choices, however, sources of control other than reinforcement delay and amount may have been operating in the present study, and these sources must be considered when interpreting drug effects.     

Three predictions of the economic concept of unit price in a choice context

Economic theory makes three predictions about consumption and response output in a choice situation: (a) When plotted on logarithmic coordinates, total consumption (i.e., summed across concurrent sources of reinforcement) should be a positively decelerating function, and total response output should be a bitonic function of unit price increases; (b) total consumption and response output should be determined by the value of the unit price ratio, independent of its cost and benefit components; and (c) when a reinforcer is available at the same unit price across all sources of reinforcement, consumption should be equal between these sources. These predictions were assessed in human cigarette smokers who earned cigarette puffs in a two-choice situation at a range of unit prices. In some sessions, smokers chose between different amounts of puffs, both available at identical unit prices. Individual subjects' data supported the first two predictions but failed to support the third. Instead, at low unit prices, the relatively larger reinforcer (and larger response requirement) was preferred, whereas at high unit prices, the smaller reinforcer (and smaller response requirement) was preferred. An expansion of unit price is proposed in which handling costs and the discounted value of reinforcers available according to ratio schedules are incorporated.     

Effects of television exposure on developmental skills among young children

BackgroundLiterature addressing the effects of television exposure on developmental skills of young children less than 36 months of age is scarce. This study explored how much time young children spend viewing television and investigated its effects on cognitive, language, and motor developmental skills.MethodsData were collected from the Pediatric Clinics at University Medical Center in Southern Taiwan. The participants comprised 75 children who were frequently exposed to television and 75 children who were not or infrequently exposed to television between 15 and 35 months old. The age and sex were matched in the two groups. The Bayley Scales of Infant Development-second edition and Peabody Developmental Motor Scales-second edition were used to identify developmental skills. Independent t-tests, χ² tests, and logistic regression models were conducted.ResultsAmong 75 children who were frequently exposed to television, young children watched a daily average of 67.4 min of television before age 2, which was excessive according to the American Academy of Pediatrics. Viewing television increased the risk of delayed cognitive, language, and motor development in children who were frequently exposed to television. Cognitive, language, and motor delays in young children were significantly associated with how much time they spent viewing television. The type of care providers was critical in determining the television-viewing time of children.ConclusionWe recommend that pediatric practitioners explain the impacts of television exposure to parents and caregivers to ensure cognitive, language, and motor development in young children. Advocacy efforts must address the fact that allowing young children to spend excessive time viewing television can be developmentally detrimental.     

An evaluation of toy quality for increasing self‐control in typically developing preschool children

Children often make impulsive choices, and previous research has shown that access to activities during the delay may enhance self‐control (e.g., Newquist, Dozier, & Neidert, 2012). The purpose of the current study was to extend the results of Newquist et al. (2012) by comparing the effects of access to low‐preference, moderate‐preference, and high‐preference toys during delays. Results showed that (a) all toys increased self‐control for 2 participants when toys were available for all choice options and (b) high‐preference toys (and sometimes moderate‐preference toys) increased self‐control for 3 participants when the toys were available only for large delayed choices.     

Periodic change in phase relationship between target and hand motion during visuo-manual tracking task: Behavioral evidence for intermittent control

When one performs visuo-manual tracking tasks, velocity profile of hand movements shows discontinuous patterns even if the target moves smoothly. A crucial factor of this “intermittency” is considerable delay in the sensorimotor feedback loop, and several researchers have suggested that the cause is intermittent correction of motor commands. However, when and how the brain monitors task performance and updates motor commands in a continuous motor task is uncertain. We examined how tracking error was affected by the timing of target disappearance during a tracking task. Results showed that tracking error, defined as the average phase difference between target and hand, varied periodically in all conditions. Hand preceded target at one specific phase but followed it at another, implying that motor control was not performed in a temporally uniform manner. Tracking stability was evaluated by the variance in phase difference, and changed depending on the timing of target-removal. The variability was larger when target disappeared around turning points than that when it disappeared around the center of motion. This shows that visual information at turning points is more effectively exploited for motor control of sinusoidal target tracking, suggesting that our brain controls hand movements with intermittent reference to visual information.     

情绪、职业数量对不同职业生涯延迟满足大学生职业决策过程的影响

为探究情绪与职业数量对不同职业生涯延迟满足个体职业决策过程的可能潜在影响,分别对40名高、低职业生涯延迟满足倾向的大学生被试诱发正、负性情绪并完成信息板技术模拟的职业决策任务。结果显示:1)高延迟满足个体的搜索深度和搜索模式显著大于低延迟满足个体;2)不同延迟满足的个体在正性情绪或低职业数量条件下都表现出更好的搜索深度和搜索模式;3)在不同情绪及职业数量条件下,高延迟满足个体在不同职业属性间的搜索更多。职业生涯延迟满足倾向作为与未来规划密切联系的概念,揭示了个体职业生涯规划对其职业决策过程可能存在的影响。