Short-term memory in the pigeon: delayed-pair-comparison procedures and some results.

A discrete-trials, delayed-pair-comparison procedure was developed to study visual short-term memory for tilted lines. In four experiments, pigeons' responses on left or right keys were reinforced with food depending on whether a comparison stimulus was or was not the same as a standard stimulus presented earlier in the same trial. In Experimental I, recall was an increasing function of the exposure time of the to-be-remembered stimulus and was a decreasing function of the retention interval. In Experiment II, retroactive interference was investigated: recall was poorer after a retention interval during which was presented either a tilted line or contextual stimuli in the form of the illuminated experimental chamber. In Experiment III, a subject was required to engage, throughout the retention interval, in one or the other of two different behaviors, depending on which of two stimuli a subject was to remember. This mnemonic strategy vastly improved recall after 15- and 20-second retention intervals. In Experiment IV, the opposite end of the performance continuum was studied: by combining the effects of a larger stimulus set and the effects of what presumably was an increased memory load, performance was reduced to approximately chance levels after retention intervals shorter than 1 second.     

A thinking aid

Writing a paper is often a process of discovering what you have to say. A small, inexpensive, "three-dimensional" outline of the paper is a help in guiding the process of discovery. New points can be accurately placed as they appear. The outline grows with the paper. The construction of such an outline is described.     

Delay-interval illumination changes interfere with pigeon short-term memory.

Pigeons acquired a successive depayed matching-to-sample task at delay intervals ranging from 2.5 to 7 seconds. Test sessions were conducted during which delay-interval illumination conditions were changed from those illumination conditions that prevailed during the baselines. Compared to baseline delayed matching performance, changing delay-interval illumination disrupted matching. This disruption occurred whether the change in delay-interval illumination represented an increase or a decrease, relative to the baseline, and whether there was or was not a change in illumination during the test session. It was concluded that illumination per se introduced during delay intervals of delayed matching tasks does not interfere with pigeon short-term memory. Rather, a change in delay-interval illumination, relative to the baseline, appears to retroactively interfere in pigeon short-term memory.     

Short-term memory in the rhesus monkey: A behavioral analysis of delayed-response performance

This study obtained quantitative data on the bodily orientations of rhesus monkeys in a delayed-response task and determined whether such orientations mediate the correct response in a choice trial. The basic task was a two-key chain schedule with the key leading to food signaled in the initial component. During the subsequent delay interval, the signal was removed, but it was necessary that one of the keys be pressed to advance the schedule to the terminal choice component. The position of the key pressed thus indicated orientation during the delay interval. When the monkeys had free access to the left and right keys, they tended to press the key leading to food throughout the chain schedule components and received food on more than 85% of the trials, even when the delay was extended to 20 seconds. However, when orientation toward the food key was disrupted by forcing the monkeys to press an extraneous center key during the delay, choice performance deteriorated. Requiring the center key presses early, rather than late, in the delay component had a strong disruptive effect. The relation of the results to the mediating coding-response hypothesis is discussed.     

The impact of balance‐focused attitudes on job stress: Gender differences evidenced in American and Chinese samples

Based on gender role expectations model, we examined how balance‐focused attitudes would affect job stress by influencing individuals' perceptions of family interference with work (FIW), and investigated whether a gender difference would exist in the relationships among balance‐focused attitudes, FIW and job stress. Using two independent samples from the United States and China, we found support for the indirect influence of balance‐focused attitudes on job stress, through FIW. Participants with balance‐focused attitudes experienced lower levels of job stress as they perceived less interference from family to work. As expected, such indirect effect was more pronounce among male participants, meaning that the male participants benefited more from having balance‐focused attitudes. Discussion, theoretical and practical implications are provided.     

Planning at the Phonological Level during Sentence Production

In two picture–word interference experiments we examined whether phrase boundaries affected how far in advance speakers plan the sounds of words during sentence production. Participants produced sentences of varying lengths (short determiner + noun + verb or long determiner + adjective + noun + verb) while ignoring phonologically related and unrelated words to the verb of the sentence. Response times to begin producing both types of sentences were faster in the presence of a related versus unrelated distractor. The results suggest that the activation of phonological properties of words outside the first phrase and first and second phonological word affect onset of articulation during sentence production. The results are discussed in the light of previous evidence of phonological planning during multi-word production. Implications for the phonological facilitation effect in the picture–word interference paradigm are also discussed.The research reported in this article served as partial fulfillment of the requirements for the PhD degree at Harvard University for Tatiana T. Schnur     

Intertrial sources of stimulus control and delayed matching-to-sample performance in humans

Two experiments compared delayed matching-to-sample (DMTS) accuracy under 2 procedures in adults with mental retardation. In the trial-unique procedure, every trial in a session contained different stimuli. Thus, comparison stimuli that were correct on one trial were never incorrect on other trials in that session (or vice versa). In the 2-sample DMTS procedure, the same 2 comparison stimuli were presented on each trial, and their function changed quasi-randomly across trials conditional upon the sample stimulus. Across 2 experiments, 7 of 8 subjects showed the highest overall accuracy under the trial-unique procedure, and no subject showed consistently higher accuracy under the 2-sample procedure. Negative, exponential decay functions fit to logit p values showed that this difference was due largely to the steeper delay-mediated decline in sample control for the 2-sample procedure. Stimulus-control analyses indicated that, under the 2-sample procedure, the selection of the comparison stimulus on Trial N was often controlled by the comparison stimulus selection on Trial N-1 rather than the Trial-N sample stimulus. This source of competing stimulus control is not present in trial-unique procedures. Experiment 2 manipulated intertrial interval duration. There was a small but consistent increase in accuracy as a function of intertrial interval duration under the 2-sample procedure, but not under the trial-unique procedure.     

The effects of speech output technology in the learning of graphic symbols

The effects of auditory stimuli in the form of synthetic speech output on the learning of graphic symbols were evaluated. Three adults with severe to profound mental retardation and communication impairments were taught to point to lexigrams when presented with words under two conditions. In the first condition, participants used a voice output communication aid to receive synthetic speech as antecedent and consequent stimuli. In the second condition, with a nonelectronic communications board, participants did not receive synthetic speech. A parallel treatments design was used to evaluate the effects of the synthetic speech output as an added component of the augmentative and alternative communication system. The 3 participants reached criterion when not provided with the auditory stimuli. Although 2 participants also reached criterion when not provided with the auditory stimuli, the addition of auditory stimuli resulted in more efficient learning and a decreased error rate. Maintenance results, however, indicated no differences between conditions. Finding suggest that auditory stimuli in the form of synthetic speech contribute to the efficient acquisition of graphic communication symbols.     

The effects of reinforcement frequency and response requirements on the maintenance of behavior.

Six rats responded under fixed-interval and tandem fixed-interval fixed-ratio schedules of food reinforcement. Basic fixed-interval schedules alternated over experimental conditions with tandem fixed-interval fixed-ratio schedules with the same fixed-interval value. Fixed-interval length was varied within subjects over pairs of experimental conditions; the ratio requirement of the tandem schedules was varied across subjects. For both subjects with a ratio requirement of 10, overall response rates and running response rates typically were higher under the tandem schedules than under the corresponding basic fixed-interval schedules. For all subjects with ratio requirements of 30 or 60, overall response rates and running response rates were higher under the tandem schedules than under the corresponding basic fixed-interval schedules only with relatively short fixed intervals. At longer fixed intervals, higher overall response rates and running rates were maintained by the basic fixed-interval schedules than by the tandem schedules. These findings support Zeiler and Buchman's (1979) reinforcement-theory account of response strength as an increasing monotonic function of both the response requirement and reinforcement frequency. Small response requirements added in tandem to fixed-interval schedules have little effect on reinforcement frequency and so their net effect is to enhance responding. Larger response requirements reduce reinforcement frequency more substantially; therefore their net effect depends on the length of the fixed interval, which limits overall reinforcement frequency. At the longest fixed intervals studied in the present experiment, reinforcement frequency under the tandem schedules was sufficiently low that responding weakened or ceased altogether.