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Three experiments using human participants varied the distribution of point-gain reinforcers or point-loss punishers in two-alternative signal-detection procedures. Experiment 1 varied the distribution of point-gain reinforcers for correct responses (Group A) and point-loss punishers for errors (Group B) across conditions. Response bias varied systematically as a function of the relative reinforcer or punisher frequencies. Experiment 2 arranged two conditions--one where an unequal ratio of reinforcement (5:1 or 1:5) was presented without punishment (R-only), and another where the same reinforcer ratio was presented with an equal distribution of point-loss punishers (R+P). Response bias was significantly greater in the R-only condition than the R+P condition, supporting a subtractive model of punishment. Experiment 3 varied the distribution of point-gain reinforcers for correct responses across four unequal reinforcer ratios (5:1, 2:1, 1:2, 1:5) both without (R-only) and with (R+P) an equal distribution of point-loss punishers for errors. Response bias varied systematically with changes in relative reinforcer frequency for both R-only and R+P conditions, with 5 out of 8 participants showing increases in sensitivity estimates from R-only to R+P conditions. Overall, the results indicated that punishers have similar but opposite effects to reinforcers in detection procedures and that combined reinforcer and punisher effects might be better modeled by a subtractive punishment model than an additive punishment model, consistent with research using concurrent-schedule choice procedures. (Contains 3 tables, 7 figures, and 2 footnotes.)

The present experiment examined the effects of varying stimulus disparity and relative punisher frequencies on signal detection by humans. Participants were placed into one of two groups. Group 3 participants were presented with 1:3 and 3:1 punisher frequency ratios, while Group 11 participants were presented with 1:11 and 11:1 punisher frequency ratios. For both groups, stimulus disparity was varied across three levels (low, medium, high) for each punisher ratio. In all conditions, correct responses were intermittently reinforced (1:1 reinforcer frequency ratio). Participants were mostly biased away from the more punished alternative, with more extreme response biases found for Group 11 participants compared to Group 3. For both groups, estimates of discriminability increased systematically across the three disparity levels and were unaffected by the punisher ratios. Likewise, estimates of response bias and sensitivity to the punisher ratios were unaffected by changes in discriminability, supporting the assumption of parameter invariance in the Davison and Tustin (1978) model of signal detection. Overall, the present experiment found no relation between stimulus control and punisher control, and provided further evidence for similar but opposite effects of punishers to reinforcers in signal-detection procedures. (Contains 5 figures and 2 tables.)

Six pigeons were trained in a delayed matching-to-sample task involving bright- and dim-yellow samples on a central key, a five-peck response requirement to either sample, a constant 1.5-s delay, and the presentation of comparison stimuli composed of red on the left key and green on the right key or vice versa. Green-key responses were occasionally reinforced following the dimmer-yellow sample, and red-key responses were occasionally reinforced following the brighter-yellow sample. Reinforcer delivery was controlled such that the distribution of reinforcers across both comparison-stimulus color and comparison-stimulus location could be varied systematically and independently across conditions. Matching accuracy was high throughout. The ratio of left to right side-key responses increased as the ratio of left to right reinforcers increased, the ratio of red to green responses increased as the ratio of red to green reinforcers increased, and there was no interaction between these variables. However, side-key biases were more sensitive to the distribution of reinforcers across key location than were comparison-color biases to the distribution of reinforcers across key color. An extension of Davison and Tustin's (1978) model of DMTS performance fit the data well, but the results were also consistent with an alternative theory of conditional discrimination performance (Jones, 2003) that calls for a conceptually distinct quantitative model. (Contains 8 figures and 5 tables.)

Three pigeons discriminated between two sample stimuli (intensities of red light). The difficulty of the discrimination was varied over four levels. At each level, the relative reinforcer magnitude for the two correct responses was varied across conditions, and the reinforcer rates were equal. Within levels, discriminability between the sample stimuli did not change systematically as reinforcer magnitude varied. Across levels, the sensitivity of behavior to changes in the reinforcer-magnitude ratio decreased as the discriminability between the sample stimuli increased. Subsequent analysis showed that this relation was limited to performance following only one of the sample stimuli, the dim red light that remained constant across all conditions. Extant behavioral models of signal detection cannot easily accommodate these results. (Contains 6 figures and 2 tables.)

Quantitative analyses of stimulus control and reinforcer control in conditional discriminations and delayed matching-to-sample procedures often encounter a problem; it is not clear how to analyze data when subjects have not made errors. The present article examines two common methods for overcoming this problem. Monte Carlo simulations of performance demonstrated that both methods introduced systematic deviations into the results, and that there were genuine risks of drawing misleading conclusions concerning behavioral models of signal detection and animal short-term memory. (Contains 1 table, 7 figures and 1 footnote.)

Altered motivational processing is purported to contribute to ADHD symptoms. A stronger preference for immediate over delayed reward is well documented in ADHD. However, little attention has been paid to children's capacity to withhold responding until a "better" reward becomes available, and their actions while waiting. Using a novel computer task, we examine the ability of children with and without ADHD to wait to collect a large reward in the presence of a small available reward. The effects of a reward-predicting cue on response times and response choices are also explored. Data from 136 children (6–12 years), 90 with ADHD and 46 typically developing (TD) children, are included. The children could collect a small immediately available reward or wait to access a larger reward after a variable delay, its imminent availability sometimes signaled by a cue. Subsequent probe trials explored the effects of longer waiting times and disruption of the cue-reward association. As expected, children with ADHD collected the small immediately available reward more often than TD children. Importantly, they were more likely to terminate waiting once commenced, collecting the small reward or attempting to collect the large reward early. The cue decreased their response time but disrupted their waiting when it no longer consistently predicted reward. Children with ADHD were more likely to abandon efforts to wait, especially when wait times were extended and when expected rewards failed to appear. Behavioral interventions for ADHD should take into account reduced waiting capacity that extends beyond children's preference for immediate reward. [ABSTRACT FROM AUTHOR]

Detection performance for humans can be seen, similar to research in pigeon behavior, as discriminated operants. Manipulated stimulus and response disparity reduced discrimination although the former often reduced bias while the latter did not.

Research presented concerns psychophysical judgements, choice behavior and response bias in humans. An analysis of signal detection and stimulus response suggests methods for examining bias in research groups.

Four standard two-choice signal-detection experiments involving varied signal presentation probability as well as a constant and equal reinforcement distribution are conducted, with college students participating in one experiment. In three of the experiments, a systematic response bias for reporting the stimulus presented least often was noted among the students. This result runs contrary to current theories on stimulus detection.

The generalized matching law describes one kind of choice behavior. An experiment was designed to investigate this and the signal-detection theory. A two-alternative forced-choice procedure, used to train four pigeons to discriminate between two line orientations, showed that discriminability among stimuli failed to vary as a function of choice latency. Response-bias and discriminability measures were calculated for the overall performance and faster and slower choice responses in each condition. Larger response biases were produced for the faster responses by varying the reinforcer distributions.

The responses of pigeons show an increase in time allocation over response-allocation sensitivity in concurrent exponential and arithmetic variable-interval schedules. The exponential-schedule sensitivity is also greater than arithmetic-schedule sensitivity for both measures of choice. The correlation of the shortest interval of the Hybrid 6 schedule with the mean interval, produce response and time sensitivities is lower than the changes variedly with overall reinforcer rates.

A study of the effects of altering reinforcer distribution for correct responses and the probability of sample-stimulus presentation in symbolic matching-to-sample experiments reveals that response bias measures and reinforcer ratio are positively correlated when the sample-stimulus probability is held constant. Varying sample-stimulus probability at constant reinforcer ratio leads to an inverse relationship between response bias measures and sample-stimulus probability. Covarying both parameters leads to a positive correlation between reinforcer ratio and response bias, indicating that the relative frequencies of both reinforced responses and nonreinforced responses influence human performance in matching tasks.

Two experiments involving adult white Carneau pigeons subjected to concurrent-chains schedule training to examine the uncued and cued terminal links in the schedules show that cued terminal links induced an inclination for short terminal-link schedule among the pigeons. Uncued terminal links induced a preference for shorter initial-link schedule. Under cued and uncued conditions the two terminal-link schedules have different and similar center-key color signals, respectively. The terminal-link cues reduce the sensitivity to the initial-link contingencies.

Background: Most research on motivational processes in attention deficit hyperactivity disorder (ADHD) has been undertaken in Western Europe and North America. The extent to which these findings apply to other cultural groups is unclear. The current study evaluated the behavioral sensitivity of Japanese children with and without ADHD to changing reward availability. Forty-one school-aged children, 19 diagnosed with DSM-IV ADHD, completed a signaldetection task in which correct discriminations between two stimuli were associated with different reinforcement frequencies. The response alternative associated with the higher rate of reinforcement switched twice during the task without warning. Findings: Both groups of children developed an initial bias toward the more frequently reinforced response alternative. When the reward contingencies switched the response allocation (bias) of the control group children followed suit. The response bias scores of the children with ADHD did not, suggesting impaired tracking of reward availability over time. Conclusions: Japanese children with ADHD adjust their behavioral responses to changing reinforcer availability less than their typically developing peers. This is not explained by poor attention to task or a lack of sensitivity to reward. The current results are consistent with altered sensitivity to changing reward contingencies identified in non-Japanese samples of children with ADHD. Irrespective of their country of origin, children with ADHD will likely benefit from behavioral expectations and reinforcement contingencies being made explicit together with high rates of reinforcement for appropriate behaviors. [ABSTRACT FROM AUTHOR]

A study was conducted to determine the effects of signal-detection theory. Three pigeons were used for the experiment. These birds were trained to peck certain keys as signalled by a magazine light. The signal-detection theory describes choice performance within a given task as a function of either discriminability or bias. Discriminability is believed to be influenced by physical differences in stimuli, while bias is believed to be influenced by personal preference.