Semantic memory retrieval: Analysis by speed accuracy tradeoff functions

Semantic memory retrieval for verifying category--example associations was tested by a speed accuracy tradeoff method: present the category for 2 s, present a correct or incorrect example followed, after a variable lag (0, 0.1, 0.2, 0.3, 0.4, 0.6, 0.8, 1, 2, or 3 s), by a signal to make a “yes-no” response in about 0.2 s. Although the strength of the category--example association is higher for high dominance examples of a category, retrieval dynamics did not vary with dominance level. Recognition for category--example associations appears to be a direct-access (parallel) retrieval process. Priming a category by repeated testing of the same category over three consecutive trials had no effect on either asymptotic strength or retrieval dynamics. Partitioning into short, medium, and long latency responses at each lag produced microtradeoff functions which did not lie on the same macrotradeoff function. Retrieval dynamics were invariant with long-term practice.     

Pattern-directed attention in uncertain-frequency detection

The role of early pattern components as cues in uncertain frequency detection was investigated in four probe-signal experiments. Listeners heard two consecutive presentations of one of two 12-tone patterns in a noise background. One presentation of the pattern was complete, whereas the other was missing the 11th (primary) tone. Listeners were required to indicate which presentation was complete. On 20% of the test trials, the 11th component of the complete pattern was replaced with one of four probe tones. The results indicated that listeners were more sensitive to the primary tone than to probe tones, and this selective sensitivity changed on a trial-by-trial basis as a function of the attentional cues provided by early pattern components. The data suggested two cue functions: (1) an “informational” function in providing information regarding which of two primary tones is likely to occur on a given trial, and (2) a “frequency” function that “automatically” directs listening to an appropriate frequency range and narrows or “fine tunes,” the listening band.     

Monotic and dichotic presentation of phonemic elements in a backward recognition-masking paradigm

Summary Auditory processing was examined in eight normal subjects using monotic and dichotic presentations of phonemic elements in an auditory backward recognition-masking paradigm. Experimental trials consisted of the presentation of one of three equiprobable consonant-vowel targets (/ba/,/da/,/ga/) followed by a vowel masker (/a/), separated by a variable silent interstimulus interval (ISI). For the dichotic condition, the mean percentage of correct recognition scores for target identification improved systematically with increases in ISIs, reaching an asymptote followed by an apparent plateau. In contrast, mean performance accuracy for the monotic condition revealed a U-shaped function for signal pairs having short temporal offsets. Although the dichotic presentations resulted in overall lower mean recognition scores, comparability between listening conditions was observed at prolonged ISIs. Observed differences in performance between the monotic and dichotic conditions at short-duration ISIs suggested the existence of different processing mechanisms, correlated with integration and interruption of phonemic pairs, for target-mask interactions occurring in close temporal succession.     

Effects of reinforcement scheduling on simultaneous discrimination performance

Pigeons were trained on a discrete-trials, simultaneous discrimination procedure, with confusable stimuli such that asymptotic performance was about 85% correct. Trials were terminated if no response occurred within 2 sec of stimulus onset, so that probability of responding was free to vary. The schedule of reinforcement for correct responses was varied, with the following results: (1) there was no relation between frequency of reinforcement and accuracy of responding. (2) In extinction, the probability of responding fell to low levels, but accuracy remained roughly constant. (3) When reinforcement was available after a fixed number of trials or after a fixed number of correct responses, the probability of responding increased with successive trials after reinforcement, but accuracy was generally constant. (4) When every fifth correct response was reinforced, accuracy decreased immediately after reinforcement if the birds were required to respond on every trial.     

Implicit word activation during pre-recognition processing influences correct recognition and estimates of presentation frequency

False recognition of new test words is higher for experimental lures (e.g., universal) with initial phonemes identical to studied words (e.g., university) than for control lures. A proposed mechanism to explain this phenomenon involves implicit activation of potential solution words during the brief period of uncertainty immediately following onset of a spoken study word. Two experiments examined whether the presumed pre-recognition processing during the stimulus discovery phase of spoken word identification increased familiarity of a studied word, thereby increasing correct recognitions and estimates of presentation frequency. Critical test words were presented a single time during study in Experiment 1, and their phonologically related words were presented one, two, or three times. Correct recognition and frequency estimates of targets were enhanced by multiple presentations of associates sharing initial phonemes. Experiment 2 provided a replication with five repetitions of phonological associates during study and two study presentations of critical test words. The results of these two experiments confirmed a necessary theoretical consequence of the implicit activation mechanism that has been invoked to explain the effects of phonological similarity on false recognition.     

Human symbolic matching-to-sample performance: Effects of reinforcer and sample-stimulus probabilities

Four experiments, each with 6 human subjects, varied the distribution of reinforcers for correct responses and the probability of sample-stimulus presentation in symbolic matching-to-sample procedures. Experiment 1 held the sample-stimulus probability constant and varied the ratio of reinforcers obtained for correct responses on the two alternatives across conditions. There was a positive relation between measures of response bias and the ratio of reinforcers. Experiment 2 held the ratio of reinforcers constant and varied the sample-stimulus probability across conditions. Unlike previous studies that used pigeons as subjects, there was a negative relation between bias and the ratio of sample-stimulus presentations. In Experiment 3, the sample-stimulus probability and the reinforcer ratio covaried across conditions. Response bias did not vary systematically across conditions. In Experiments 1 to 3, correct responses were reinforced intermittently. Experiment 4 used the same procedure as Experiment 3, but all correct responses now produced some scheduled consequence. There was a positive relation between response bias and the ratio of reinforcers. The results suggest that human performance in these tasks was controlled by both the relative frequency of reinforced responses and the relative frequency of nonreinforced responses.     

Response latency and accuracy in visual word recogniton

In a single visual word recognition experiment, the effects of (1) eccentricity of presentation, (2) word length, and (3) word frequency were investigated. The stimuli used were Dutch nouns in two frequency classes of about 15 and 150.10^-6; word length varied from 1 to 10; eccentricity varied from ?4 to +4 deg. The response quality and response latency of 11 subjects were measured. For the correct responses, recognition scores decreased and response latencies increased with eccentricity; both showed asymmetrical curves in the visual field. It is argued that word length proper affects neither the probability of correct responses nor latency. A clear word frequency effect was established. The eccentricity of presentation is considered as the determinant of the amount of available information, thus directly influencing accuracy and latency. The linear relationship between accuracy and latency is a major finding. A word recognition scheme is offered which incorporates (1) activation, (2) decision, and (3) speech. The time relations between incoming retinal information and response decision, leading to an extra 400 msec for incorrect as compared with correct responses, are discussed. Word recognition in reading is examined, together with the impact of the present experimental results on information flow in successive eye fixations, eye movement control, and eye-voice span.     

Delayed signal detection, differential reinforcement, and short-term memory in the pigeon.

In two discrete-trial delayed-detection experiments, six pigeons were trained on dependent concurrent variable-interval schedules. Pecking a red side key was reinforced when the brighter of two white lights (S1) had been presented on the center key, and pecking a green side key was reinforced when the duller of two white lights (S2) had been presented on the center key. Incorrect responses were red side-key pecks following S2 presentations and green side-key pecks following S1 presentations; these resulted in three-second blackouts. In Experiment 1, the time between presentation of S1 or S2 on the center key and the onset of the red and green side keys was varied nonsystematically from 0.06 seconds to 19.69 seconds across experimental conditions. Stimulus discriminability decreased as the stimulus-choice delay increased. A rectangular-hyperbolic function better described this decrease in discriminability over time than did a negative-exponential function. In Experiment 2, at each of three stimulus-choice delays (0.06, 3.85, and 10.36 seconds), relative reinforcer frequency for correct responses to the red and green side keys was varied by changing the values of the dependent concurrent variable-interval schedules. The sensitivity of choice to relative reinforcer frequency was independent of the decrease in stimulus discriminability with increasing stimulus-choice delay.     

Implicit word activation during pre‐recognition processing influences correct recognition and estimates of presentation frequency

False recognition of new test words is higher for experimental lures (e.g., universal) with initial phonemes identical to studied words (e.g., university) than for control lures. A proposed mechanism to explain this phenomenon involves implicit activation of potential solution words during the brief period of uncertainty immediately following onset of a spoken study word. Two experiments examined whether the presumed pre‐recognition processing during the stimulus discovery phase of spoken word identification increased familiarity of a studied word, thereby increasing correct recognitions and estimates of presentation frequency. Critical test words were presented a single time during study in Experiment 1, and their phonologically related words were presented one, two, or three times. Correct recognition and frequency estimates of targets were enhanced by multiple presentations of associates sharing initial phonemes. Experiment 2 provided a replication with five repetitions of phonological associates during study and two study presentations of critical test words. The results of these two experiments confirmed a necessary theoretical consequence of the implicit activation mechanism that has been invoked to explain the effects of phonological similarity on false recognition.     

Increasing mentally retarded adolescents' verbalizations about current events

The effects of antecedent and consequent events on the verbal behavior of three institutionalized mentally retarded adolescents were examined. Verbal statements, related to current national and international events, were recorded after exposures to television news programs. The study examined the accuracy of verbalizations as a function of: (1) exposures to television news presentations in massed (i.e., viewing the entire news program before an opportunity to describe it) versus distributed from (i.e., viewing each news item separately with each followed by an opportunity to describe it), and (2) contingent tokens and social praise for correct verbal responses (i.e., statements corresponding to news items presented). Both the temporal distribution of news presentations and the reinforcement procedures improved the accuracy of verbal statements emitted by the subjects.     

Effects of morphine, clonidine, and intensity change on electric-shock discrimination.

The effects of morphine, clonidine, and changes in stimulus intensity were examined in squirrel monkeys responding on one of two levers following brief presentations of one of two electric-shock intensities (0.1 and 0.5 mA). Responses were designated as correct or incorrect depending on which shock intensity had been presented and which lever was pressed. Morphine (0.42 to 1.80 mg/kg) and clonidine (0.075 to 0.18 mg/kg) decreased percentage correct responding. Morphine and clonidine also increased response latency and the number of shock presentations that were not followed by responses. Changes in shock intensity also decreased percentage correct responding but had no effect on response latency or on the number of shock presentations not followed by responses.     

The role of feedback and dot presentation format in younger and older adults’ number estimation

Numerosity estimation, the rapid assessment of the number of items in a visual scene, is historically inaccurate. We assessed whether providing feedback regarding the correct numerosity on either 0%, 50%, or 100% of the trials would affect younger and older adults’ estimation accuracy for randomized, clustered (i.e., groups of 3 or 7 dots), and stacked (i.e., column) dot formats. Participants provided estimates and confidence ratings in six blocks, each containing 48 trials (16 numerosities shown in each format). Feedback frequency was manipulated between participants during blocks 1–4; no feedback was provided during blocks 5 and 6, which contained old and new numerosities and previously estimated presentations rotated 90°. Estimation accuracy was age equivalent across blocks despite younger adults initially being more accurate than older adults. Feedback improved both age groups’ accuracy. Stacked presentations were most accurately estimated but were more likely to be over-estimated than clustered and randomized presentations. Older adults gave lower confidence ratings than younger adults despite both age groups showing increased confidence across blocks, for more structured presentation formats, and as feedback frequency increased. These results expand our understanding of the role of presentation format and feedback in producing age equivalence or age-related differences in numerosity estimation.     

Divided stimulus control: Which key did you peck,or what color was it?

Responding on concurrent schedules produced a conditional discrimination (Phases 1 and 2), asking either which peck produced the event, or which color the keys were when the event was produced. In Phases 3 and 4, reinforcer delivery or a delay in blackout was interpolated between responding and the conditional discrimination. In Phase 1, location versus color discrimination accuracy was controlled by the relative reinforcer frequency for correct responses to these questions (divided stimulus control). In Phases 2 to 4, relative reinforcer frequency for correct responses to these questions was .5, and the relative frequency with which concurrent‐schedule responses produced the questions was varied. This variation had no clear effect on the accuracy of reporting Location or Color. These results are consistent with the model of divided control suggested by Davison and Elliffe (2010). Arranging a 3‐s reinforcer between responding and choice decreased both color and location accuracy, but a 3‐s delay only decreased location accuracy. Thus, in concurrent‐schedule performance, both ambient stimuli prior to a reinforcer and the location of the just‐reinforced response are available as discriminative stimuli following the reinforcer. Control of postreinforcer responding is divided between these according to their association with the relative frequency of subsequent reinforcers.     

Effects of relative reinforcer frequency on complex color detection

Pigeons were trained under a discrete-trials detection procedure in which one of a set of color stimuli was presented on the center key and a single response turned off the stimulus and illuminated two side keys. Single responses to one or the other side key produced occasional reinforcers depending on the value of the color stimulus. In Experiment 1, one color-stimulus set comprised 559, 564, 569, and 574 nm, and right-key pecks were occasionally reinforced following presentations of members of this set. The other stimulus set comprised 579, 584, 589, and 594 nm, and left-key pecks were occasionally reinforced following presentations of members of this set. Across seven experimental conditions, the left/(left + right) relative reinforcer frequency was varied from .1 to .9. In Experiment 2, one stimulus set contained only one member, 574 nm, and right-key responses were occasionally reinforced following its presentation. Over 12 experimental conditions, two manipulations were carried out. First, the number of stimuli comprising the other stimulus set was increased from one (579 nm) to two (579 and 584 nm) to three (579, 584, and 589 nm) and to four (579, 584, 589, and 594 nm), and left-key responses were reinforced occasionally following center-key presentations of members of this set. Second, for each stimulus combination, the left/(left + right) relative reinforcer frequency was varied from .1 to .5 to .9 across three experimental conditions. The principal finding of Experiments 1 and 2 was that reinforcers and stimuli interacted in their effects on behavior. In Experiment 3, pairs of adjacent stimuli (5 nm apart) in the range 559 to 594 nm were presented in each experimental condition, and the left/(left + right) relative reinforcer frequency was held constant at .5. The data from all three experiments were analyzed according to a detection model describing performance in multiple-stimulus two-response procedures. This model provided independent measures of stimulus discriminability, contingency discriminability, and bias. The analysis showed that (a) consistent with the color-naming function, pigeons were better able to discriminate between higher nanometer values than lower nanometer values; (b) their ability to discriminate between the stimuli was independent of the number of wavelengths comprising each stimulus set; (c) they allocated delivered reinforcers very accurately to the previously emitted response; and (d) no consistent biases emerged.     

Auditory detection and optimal response biases

Rats were trained to detect a signal consisting of an increment in the intensity of a random noise. The procedure was analogous to the yes-no method of human psychophysics, in that one response was defined as correct and reinforced with brain stimulation if the signal was presented, and another response was correct and reinforced if the noise alone was presented. Incorrect responses produced periods of time-out. Bias functions showing how the animals’ response probabilities varied as the signal intensity was reduced were obtained in two ways. In Experiment 1, the probability of presenting the signal was varied over four values between 0.4 and 0.6. In Experiment 2, the number of brain stimulations consequent upon a correct response in the presence of the signal was varied over four values between 3:1 and 1:2. Differences of 0.10 and 0.05 in the signal probability, and unit differences in the ratio of brain stimulations, resulted in distinctly different bias functions. Accuracy of detection increased with the signal intensity, and was independent of the animals’ response biases. When the signal probability was varied, the animals optimized the number of correct trials, and hence the number of brain stimulations obtained. When the ratio of brain stimulations was varied, the animals compromised between optimizing the number of correct trials and optimizing the number of brain stimulations obtained.     

List length and the time course of recognition in immediate memory

The response signal method of Reed (1973) was used to study the time-course of list membership recognition after 2 sec of uncontrolled rehearsal, with lists of one, two, and four consonants. Fourteen specific hypotheses about the time course of this process were derived from various theories (Anderson, 1973; Anderson & Bower, 1973; Baddeley & Ecob, 1973; Corballis, Kirby, & Miller, 1972; Kirsner, 1972; Murdock, 1971; Sternberg, 1966, 1969; Theios, Smith, Haviland, Traupmann, & Moy, 1973; etc.) and additional assumptions about the effect of the response signal. When members of the to-be-learned lists are drawn from a small population of highly confusable items, as in the current experiment, list membership recognition appears to follow the model of Theios et al. (1973). Latency functions of signal lag appear to be particularly useful in differentiating among hypotheses which predict similar speed-accuracy tradeoff functions. The lag by positive-negative interaction for latencies of correct responses is highly significant for lists of one consonant, a result predicted by the hypothesis derived from the model of Theios et al. and incompatible with hypotheses derived from exhaustive search and single-threshold strength models.     

Rapid acquisition of bias in signal detection: dynamics of effective reinforcement allocation

We investigated changes in bias (preference for one response alternative) in signal detection when relative reinforcer frequency for correct responses varied across sessions. In Experiment 1, 4 rats responded in a two-stimulus, two-response identification procedure employing temporal stimuli (short vs. long houselight presentations). Relative reinforcer frequency varied according to a 31-step pseudorandom binary sequence and stimulus duration difference varied over two values across conditions. In Experiment 2, 3 rats responded in a five-stimulus, two-response classification procedure employing temporal stimuli. Relative reinforcer frequency was varied according to a 36-step pseudorandom ternary sequence. Results of both experiments were analyzed according to a behavioral model of detection. The model was extended to incorporate the effects of current and previous session reinforcer frequency ratios on current-session performance. Similar to findings with concurrent schedules, effects on bias of relative reinforcer frequency were highest for the current session. However, carryover from reinforcer ratios of previous sessions was evident. Generally, the results indicate that bias can come under control of frequent changes in relative reinforcer frequency in both identification and classification procedures.     

The emergence of symmetry in a conditional discrimination task using different responses as propioceptive samples in pigeons

In Experiment 1, 10 pigeons were exposed to a successive symbolic matching-to-sample procedure in which the sample was generated by the pigeons' own behavior. Each trial began with both response keys illuminated white, one being the "correct" key and the other the "incorrect" key. The pigeons had no way of discriminating which key was correct and which incorrect, since these roles were assigned on a random basis with the same probability of 0.5 for each key. A fixed ratio of five responses was required on the correct key. However, each time the pigeon pecked the incorrect key, the correct key response counter reset. Five consecutive pecks on the correct key was the only way to end this component, and switch off both key lights. Two seconds later, these same keys were illuminated again, one green and the other red (comparison stimuli). Now, if the correct white key had been on the left, a peck at one color produced food, and if the correct white key had been on the right, a peck at the other color produced food. When the pigeons had learned this discrimination, they were exposed to several symmetry tests (simultaneous presentations of both keys illuminated the same color-i.e., both red or both green), in order to interchange the sample with the comparison stimuli. In Experiment 2, the importance of requiring discrimination between the samples and between the comparisons was analyzed. In Experiment 3, we compared the results of Experiment 1 with a slightly different experiment, which resulted in discrimination of key position, an exteroceptive stimulus. The results showed that symmetry emerged only when different responses were used as samples.     

Discrimination of auditory intensities by rats

Rats were trained to press one of two keys when a standard intensity value of a 4.0-kHz sine tone (70 or 100 db re 2 x 10(-4) microbar) was presented from a centrally located loudspeaker. Pressing the other key was reinforced when comparison intensity values (as much as 30 db less than the standard value) were presented. The animals initiated tone presentations by breaking a light beam at the rear of the chamber. Correct choices produced brain-stimulation reinforcement, and errors produced a timeout. A procedure designed by Jenkins was used to partial out choice data under potential control of sequential cues in the stimulus series. When the standard-comparison intensity difference was varied, the rats showed similar psychometric functions despite wide differences in response bias (relative position preference). A signal detection analysis showed that response biases for individual animals remained fairly consistent during psychophysical testing. The trend of decreasing choice accuracy at small intensity differences was described by the cumulative normal probability function. The similarity of psychometric functions obtained with 70- and 100-db standards supported Weber's law. There was some evidence that response latencies were controlled by intensity differences even when choice behavior was undifferentiated.