Conditioned reinforcement as a function of duration of stimulus

Pigeons were provided with three keys. Pecking the center key produced grain on a schedule that alternated at unpredictable times between a variable-interval component and extinction. On concurrent variable-interval schedules, pecking either side key produced a stimulus associated with the variable-interval component on the center key provided that said schedule was currently in effect. The independent variable was the length of time this stimulus remained on the keys. Pecking one side key produced the stimulus for 27 seconds, whereas the duration produced by pecking the other key varied for successive blocks of sessions. For the first four birds, the values tested were 3, 9, 27, and 81 seconds. For the second group, numbering three birds, the values tested were 1, 3, 9, and 27 seconds. The dependent variable was the proportion of total side key pecks that occurred on the variable key. For all birds, the function was positive in slope and negative in acceleration. This finding supports a formulation that ascribes the maintenance of observing responses in a normal setting to the fact that the subject exposes itself to the positive discriminative stimulus for a longer mean duration than it does to the negative stimulus.     

Color name as a function of surround luminance and stimulus duration

A color-naming experiment was performed in which both surround luminance and exposure duration were varied. The data showed substantial effects from these changes; however, none could be interpreted to indicate the presence of a Bezold-Brucke shift or tritanopia.     

Visual recognition as a function of stimulus offset asynchrony and duration

The stimuli consisted of two complementary dot patterns that formed a bigram when they were flashed simultaneously; impairment of letter recognition developed when one of the patterns was briefly extended beyond the termination of the other (stimulus offset asynchrony). However, if the ratio of stimulus offset asynchrony to bigram duration remained constant, the probability of a correct recognition response also remained constant as duration varied over a 50- to 100-msec interval. When percent stimulus asynchrony increased, the impairment increased. An interaction between bigram letter position and each of bigram duration and percent stimulus asynchrony was observed with recognition accuracy greater in general for the letter in the left half of the field.     

Avoidance responding as a function of stimulus duration and relation to free shock

Response-independent pairings of a tone and a brief shock were superimposed on uncued avoidance responding in four groups of rhesus monkeys. For one group, tone presentations were immediately followed by an unavoidable electric shock; for the remaining groups, gaps of 5, 20, and 80 sec intervened between tone termination and shock delivery. These temporal values subsume paradigms usually treated as discrete procedures; the conditioned emotional response procedure (0-sec gap between tone and shock), trace procedure (5-sec gap) and safety-signal training (80-sec gap). Within each group, tone durations of 10, 20, 40, and 80 sec were examined. A response pattern marked by maximum response rate in the initial 5 sec of the tone followed by deceleration before shock was observed when shock immediately followed the tone, but not when gaps were interposed between the tone and shock. Response rates in the first 5 sec of the tone were a function of both tone duration and duration of the gap. When the gap was 0 to 5 sec, initial response rates were highest in longer duration tones; this relationship between tone duration and initial tone response rate was not observed for longer gaps.     

Hemispheric asymmetries for global and local processing as a function of stimulus exposure duration

The experiments assess the relationship between stimulus exposure duration and hemispheric asymmetries for global and local processing. Six durations (27, 40, 53, 67, 80, and 147 ms) were tested in a selective attention task in which hierarchical letterforms were presented unilaterally to the left or right visual field. The results indicated that left hemisphere-local asymmetries were demonstrated more often than right hemisphere-global asymmetries and that asymmetries were most commonly found in the middle range of durations tested. The pattern of results emphasizes the importance of further study into those conditions under which the predicted asymmetries can be reliably demonstrated in healthy individuals.     

Behavioral engineering: stuttering as a function of stimulus duration during speech synchronization

Past studies have shown that stuttering is eliminated when speech is synchronized with a metronomic beat, but the speech sounds artificial. The present study investigated the effect of increasing the duration of these individual stimulus beats with the stimulus-off period constant at 1 sec. When subjects were instructed to speak during the stimulus-on period, stuttering was an inverse function of stimulus duration, indicating that the known metronome effect on stuttering is one point on a continuum of effective rhythm procedures. The "naturalness" of speech increased as the stimulus duration increased up to durations of about 2 sec, and then decreased. At optimal values, stuttering was greatly reduced and naturalness and rapidity of speech were retained. These optimal values effectively controlled stuttering in a field test that used two types of specially designed portable instruments, one of which produced a tactual stimulus and the other an auditory stimulus.     

Stimulus duration as a measure of stimulus generalization

Four pigeons in the line-positive group were trained with a vertical line on a green background that signalled intermittent reinforcement while a plain green field signalled extinction. Four pigeons in the line-negative group were trained with the opposite discrimination. Response to a control key terminated any trial and initiated the next trial. The birds also used the control key during generalization tests to control the durations of trials in which various line orientations were presented. These durations were summed to provide generalization gradients of stimulus duration that were positive or negative in accordance with the trained discriminations. In Experiment 2, birds from the line-positive group were tested with a procedure in which the control key was not available on some trials. This provided an independent assessment of response rates to the test stimuli. These rates were used to predict the stimulus durations obtained when the control key was available. The findings supported a general model for the prediction of response distributions among concurrent stimuli from rates observed with single stimuli.