Signal detection and matching: analyzing choice on concurrent variable-interval schedules.

Pigeons' pecks on a red key and a green key were followed by access to grain according to pairs of concurrent independent variable-interval schedules in a combined signal detection/matching law paradigm. Pecks on the red key were reinforced by the richer variable-interval schedule if a short-duration tone had been presented; pecks on the green key were reinforced by the richer variable-interval schedule if a long-duration tone had been presented. Pecks on the green key given a short-duration tone, or on the red key given a long-duration tone, were reinforced by the leaner variable-interval schedule. The data were analyzed according to both signal detection's and the matching law's separate measures of, first, the discrimination of the choices and, second, the bias to make one response or another. Increasing the difficulty of the tone-duration discrimination decreased both methods' measures of the discrimination of the choices and did not change both methods' measures of the bias to make one response or another. Changing the leaner variable-interval schedule so that it approached the richer variable-interval schedule decreased signal detection's measure of discrimination but left its measure of response bias and the matching law measures unchanged. Data collected only until a subject's first changeover response following presentation of a long or a short tone showed higher values for both methods' measures of discrimination, no change in signal detection's measure of response bias, and lower values for the matching law's measure of response bias. Relationships between the matching law's and signal detection's methods of analyzing choice are discussed. It is concluded that a signal detection analysis is more efficient for examining changes in the difficulty of a discrimination, whereas a matching law analysis is more effective for examining the effects of changes in relative reinforcer frequency.     

Determinants of pigeons' waiting time: Effects of interreinforcement interval and food delay

Four pigeons performed on three types of schedules at short (i.e., 10, 30, or 60 s) interreinforcement intervals: (a) a delay-dependent schedule where interreinforcement interval was held constant (i.e., increases in waiting time decreased food delay), (b) an interreinforcement-interval-dependent schedule where food delay was held constant (i.e., increases in waiting time increased interreinforcement interval), and (c) a both-dependent schedule where increases in waiting time produced increases in interreinforcement interval but decreases in food delay. Waiting times were typically longer under the delay-dependent schedules than under the interreinforcement-interval-dependent schedules. Those under both-dependent schedules for 1 subject were intermediate between those under the other two schedule types, whereas for the other subjects waiting times under the both-dependent procedure were similar either to those under the delay-dependent schedule or to those under the interreinforcement-interval-dependent schedule, depending both on the subject and the interreinforcement interval. These results indicate that neither the interreinforcement interval nor food delay is the primary variable controlling waiting time, but rather that the two interact in a complex manner to determine waiting times.     

Second-order schedules: discrimination of components

Pigeons were exposed to a series of second-order schedules in which the completion of a fixed number of fixed-interval components produced food. In Experiment 1, brief (2 sec) stimulus presentations occurred as each fixed-interval component was completed. During the brief-stimulus presentation terminating the last fixed-interval component, a response was required on a second key, the brief-stimulus key, to produce food. Responses on the brief-stimulus key before the last brief-stimulus presentation had no scheduled consequences, but served as a measure of the extent to which the final component was discriminated from preceding components. Whether there were one, two, four, or eight fixed-interval components, responses on the brief-stimulus key occurred during virtually every brief-stimulus presentation. In Experiment 2, an attempt was made to punish unnecessary responses on the brief-stimulus key, i.e., responses on the brief-stimulus key that occurred before the last component. None of the pigeons learned to withhold these responses, even though they produced a 15-sec timeout and loss of primary reinforcement. In Experiment 3, different key colors were associated with each component of a second-order schedule (a chain schedule). In contrast to Experiment 1, brief-stimulus key responses were confined to the last component. It was concluded that pigeons do not discriminate well between components of second-order schedules unless a unique exteroceptive cue is provided for each component. The relative discriminability of the components may account for the observed differences in initial-component response rates between comparable brief-stimulus, tandem, and chain schedules.     

Concurrent schedules: Effects of time- and response-allocation constraints

Five pigeons were trained on concurrent variable-interval schedules arranged on two keys. In Part 1 of the experiment, the subjects responded under no constraints, and the ratios of reinforcers obtainable were varied over five levels. In Part 2, the conditions of the experiment were changed such that the time spent responding on the left key before a subsequent changeover to the right key determined the minimum time that must be spent responding on the right key before a changeover to the left key could occur. When the left key provided a higher reinforcer rate than the right key, this procedure ensured that the time allocated to the two keys was approximately equal. The data showed that such a time-allocation constraint only marginally constrained response allocation. In Part 3, the numbers of responses emitted on the left key before a changeover to the right key determined the minimum number of responses that had to be emitted on the right key before a changeover to the left key could occur. This response constraint completely constrained time allocation. These data are consistent with the view that response allocation is a fundamental process (and time allocation a derivative process), or that response and time allocation are independently controlled, in concurrent-schedule performance.     

Performances on ratio and interval schedules of reinforcement: Data and theory

Two differences between ratio and interval performance are well known: (a) Higher rates occur on ratio schedules, and (b) ratio schedules are unable to maintain responding at low rates of reinforcement (ratio “strain”). A third phenomenon, a downturn in response rate at the highest rates of reinforcement, is well documented for ratio schedules and is predicted for interval schedules. Pigeons were exposed to multiple variable-ratio variable-interval schedules in which the intervals generated in the variable-ratio component were programmed in the variable-interval component, thereby “yoking” or approximately matching reinforcement in the two components. The full range of ratio performances was studied, from strained to continuous reinforcement. In addition to the expected phenomena, a new phenomenon was observed: an upturn in variable-interval response rate in the midrange of rates of reinforcement that brought response rates on the two schedules to equality before the downturn at the highest rates of reinforcement. When the average response rate was corrected by eliminating pausing after reinforcement, the downturn in response rate vanished, leaving a strictly monotonic performance curve. This apparent functional independence of the postreinforcement pause and the qualitative shift in response implied by the upturn in variable-interval response rate suggest that theoretical accounts will require thinking of behavior as partitioned among at least three categories, and probably four: postreinforcement activity, other unprogrammed activity, ratio-typical operant behavior, and interval-typical operant behavior.     

Stochastic choice models: A comparison between Bush-Mosteller and a source-independent reward-following model

Horner and Staddon (1987) argued that a class of reward-following processes defined by a property they termed ratio invariance is a better model for the probabilistic choice performance of pigeons than competing molecular accounts such as momentary maximizing, melioration, and the Bush-Mosteller model. The critical data were provided by choice distributions-distributions of a variable S, the proportion of Right choices, defined on a moving window typically 32 choices long-obtained under a frequency-dependent schedule. The schedule prescribed equal payoff probabilities, p(S), for both choices. p(S) was a maximum when S = 0.5 and declined linearly for S values above and below 0.5. Pigeons showed generally bimodal choice distributions with the modes at equal p(S) values. These data do not follow easily from melioration or momentary maximizing and are inconsistent with molar maximizing, but they may be consistent with Bush-Mosteller. We present here the results of computer simulations showing that the ratio-invariance model studied yields, as expected, choice modes at equal p(S) values, but that Bush-Mosteller, although capable of generating bimodal choice distributions, does not have choice modes at equal p(S) values.     

More on concurrent interval-ratio schedules: a replication and review.

It has been suggested that the failure to maximize reinforcement on concurrent variable-interval, variable-ratio schedules may be misleading. Inasmuch as response costs are not directly measured, it is possible that subjects are optimally balancing the benefits of reinforcement against the costs of responding. To evaluate this hypothesis, pigeons were tested in a procedure in which interval and ratio schedules had equal response costs. On a concurrent variable time (VT), variable ratio-time (VRT) schedule, the VT schedule runs throughout the session and the VRT schedule is controlled by responses to a changeover key that switches from one schedule to the other. Reinforcement is presented independent of response. This schedule retains the essential features of concurrent VI VR, but eliminates differential response costs for the two alternatives. It therefore also eliminates at least one significant ambiguity about the reinforcement maximizing performance. Pigeons did not maximize rate of reinforcement on this procedure. Instead, their times spent on the alternative schedules matched the relative rates of reinforcement, even when schedule parameters were such that matching earned the lowest possible overall rate of reinforcement. It was further shown that the observed matching was not a procedural artifact arising from the constraints built into the schedule.     

Reinforcement and punishment effects in concurrent schedules: A test of two models

The joint effects of punishment and reinforcement on the pigeon's key-peck response were examined in three choice experiments conducted to compare predictions of Farley and Fantino's (1978) subtractive model with those made by Deluty's (1976) and Deluty and Church's (1978) model of punishment. In Experiment 1, the addition of equal punishment schedules to both alternatives of a concurrent reinforcement schedule enhanced the preference exhibited for the more frequent reinforcement alternative. Experiment 2 demonstrated decreases in the absolute response rate for each member of a concurrent reinforcement schedule when increasing frequencies of punishment were added to each alternative. Experiment 3 found that preference for the denser of two reinforcement schedules diminished when the absolute frequencies of reinforcement were increased by a constant factor and conditions of punishment for both alternatives were held constant. Diminished preferences were obtained regardless of whether the frequency of punishment associated with the denser reinforcement schedule was greater or less than that associated with the lean reinforcement alternative. The results from all three experiments uniquely supported Farley and Fantino's (1978) subtractive model of punishment and reinforcement.     

The effect of foreperiod duration on reaction time and its relation to interval schedules of reinforcement

Two groups of pigeons were exposed to a simple reaction-time procedure in which mean foreperiod duration was 5, 10, or 20 seconds. For one group, the foreperiods had an arithmetic, or rectangular, distribution; for the second group, they had a constant-probability, or Bernoulli, distribution. Under both distributions, mean response latency was an increasing, negatively accelerated function of mean foreperiod duration. On a given trial, response latency was a function of its associated foreperiod duration: latency was a decreasing function of foreperiod duration in the arithmetic distribution, and an increasing function of foreperiod duration in the constant-probability distribution. Examination of the distribution of latencies revealed a harmonic structure reminiscent of distributions of interresponse times under variable-interval schedules of reinforcement. Taken together, the results confirm and extend previous findings with human subjects, and also suggest numerous similarities to behavior maintained by variable-interval schedules.     

Concurrent schedules: Effects of reinforcement rate and changeover delay on time allocation in a three-alternative procedure

Pigeons were exposed to a continuous choice procedure where three alternatives alternated in a fixed, recycling order (ABCABC, etc.). Responses were reinforced according to independent variable-interval schedules. For three birds, the reinforcement rate for responses on alternative C was varied. For three other birds, the duration of the changeover delay after the changeover to C was varied. For both groups, the reinforcement rates and changeover delay durations associated with A and B were constant throughout the experiment. The time proportion at A relative to B increased as a function of the reinforcement rate for responses on C and decreased as a function of the duration of the changeover delay during C. The results show that the proportion of time spent at a variable-interval alternative of a continuous choice procedure is not completely determined by the reinforcement rates provided by the alternatives. The results support the assumption that time allocation is governed by delayed reinforcement of changeover behaviour.     

Temporal constraint on choice: Sensitivity and bias in multiple schedules

In multiple schedules of reinforcement, ratios of responses in successive components are relatively insensitive to ratios of obtained reinforcers. An analysis is proposed that attributes changes in absolute response rates to concurrent interactions between programmed reinforcement and extraneous reinforcement in other components. The analysis predicts that ratios of responses in successive components vary with reinforcer ratios, qualified by a term describing the reinforcement context, that is, programmed and extraneous reinforcers. Two main predictions from the analysis were confirmed in an experiment in which pigeons' responses were reinforced in the components of a multiple schedule and analog extraneous reinforcement was scheduled for an alternative response in each component. Sensitivity of response and time ratios to reinforcer ratios in the multiple schedules varied as a function of the rate of extraneous reinforcers. Bias towards responding in one component of the multiple schedule varied as an inverse function of the ratios of extraneous reinforcer rate in the two components. The data from this and previous studies of multiple-concurrent performance were accurately predicted by our analysis and supported our contention that the allocation of behavior in multiple-schedule components depends on the relative values of concurrently-available reinforcers within each component.     

时间顺序与时间距离对语言理解的影响:进一步的证据

探讨时间顺序和时间距离对语言理解的影响,包括2个实验.实验采用关系再认范式(relation-recognition paradigm)和句子-探测再认范式(sentence-probe-recognition paradigm).实验一探讨探讨在简单句条件下,时间顺序对不同频率事件理解的作用;实验二探讨在复句条件下时间顺序与时间距离对语言理解的影响.2个实验结果一致表明,在语言理解过程中,存在对将来取向(顺时序)的事件进行优先加工处理.时间距离对语言理解的影响取决于不同时距的事件能否整合成情景模型.     

Flexible work schedules and family time allocation: Assessment of a system change on individual behavior using self-report logs

This study assessed the effects of a flexible work schedule ("flextime") on time allocated to children and spouse by federal workers. Direct behavioral observations of family, home, and work functions were precluded because of the cost involved in observing many people for long periods of time. In order to obtain detailed individual data, participants completed hour-by-hour activity logs a mean of twice per week for 35 weeks. Participants received prior training on log completion, initial feedback on the detail of their log entries, and were prompted to complete the forms. Four different procedures assessing reliability indicated a corroboration rate of 80% with other sources. Log data were reliably reduced to nine categories such as "PM time with children" and 37 subcategories such as "time at dinner." The log data were presented in time-series form and the use of a quasi-experimental design showed that participants who altered their work schedule were able to spend more PM time with their families. The log data demonstrated that the capacity exists to assess closely the effects of large-scale changes at a micro-behavioral level, but other methods are needed to make complex self-reporting systems less expensive and more capable of immediate monitoring of the intervention's effects.     

Effects of diet on early stage cortical perception and discrimination of syllables differing in voice-onset time: a longitudinal ERP study in 3 and 6 month old infants

The influence of diet on cortical processing of syllables was examined at 3 and 6 months in 239 infants who were breastfed or fed milk or soy-based formula. Event-related potentials to syllables differing in voice-onset-time were recorded from placements overlying brain areas specialized for language processing. P1 component amplitude and latency measures indicated that at both ages infants in all groups could extract and discriminate categorical information from syllables. Between-syllable amplitude differences—present across groups—were generally greater for SF infants. Responses peaked earlier over left hemisphere speech-perception than speech-production areas. Encoding was faster in BF than formula-fed infants. The results show that in preverbal infants: (1) discrimination of phonetic information occurs in early stages of cortical processing; (2) areas overlying brain regions of speech perception are activated earlier than those involved in speech production; and (3) these processes are differentially modulated by infant diet and environmental factors.     

Reaction times of younger and older men: effects of compound samples and a prechoice signal on delayed matching-to-sample performances.

Five younger (18 to 23 yrs) and five older (65 to 73 yrs) men were exposed to a series of immediate and delayed (0 to 15 seconds) matching-to-sample problems. Presentation of the pairs of delayed comparison stimuli was either signaled or unsignaled, and the sample contained either 1, 2, or 3 elements, one of which appeared as the positive stimulus. During initial sessions, unlimited time was available to respond. Subsequently, correct responses were reinforced only if they occurred within a specified time limit. A general finding was slower responding with increased delay and with increased number of sample elements. These effects were reduced when the comparison stimuli were signaled and when time limits were in effect. Errors increased as a function of the manipulations of sample complexity and time limits, but did not change systematically when the delay between sample and comparison stimuli was varied. Although the younger men generally responded more quickly than the older ones, men of both ages showed increased speeds when limits were placed on response time, and these changes were maintained when the temporal contingencies were removed.     

Bridging the gap between theory and model: a reflection on the balance scale task

At first glance, the two lead articles in this issue share little except the balance scale task, yet we view them as complementary rather than unrelated or contradictory. Our Reflection focuses on the individual strengths of the two lead articles and, to a greater extent, the potential power of their combined perspectives. Our general approach is to allow psychological theory to suggest a model of performance that can both evaluate specific theoretical claims and reveal important features of the data that had been previously obscured using conventional statistical analyses. Our guiding principle is that model, theory, and data all should be connected.