Note on luminous flux discrimination in monkey and man

Subjects were instructed to equate the brightness of two stimuli of different areas presented alternately to the far periphery. The results are closely describable by IA = k (Ricco's Law), indicating that the subjects equated total luminous flux. It is suggested that these results and certain other behavioural and anatomical considerations make it unnecessary to consider flux discrimination a “subcortical” or “lower” visual function as compared with brightness discrimination.     

Auditory generalization gradients for response latency in the monkey

Two monkeys were trained to press and hold a response key in the presence of a light and to release it at the onset of a pure tone. Initially, all responses with latencies shorter than 1 sec were reinforced without regard to the frequency of the pure tone, and the intensity of the pure tone that resulted in equal latencies at each frequency was determined. The second stage of the experiment consisted of discrimination training, during which releases to one pure-tone frequency (positive stimulus) were reinforced and releases to a second frequency (negative stimulus) were extinguished. Median latencies to the negative stimulus slowly increased as did the variability of the latency distribution for the negative stimulus. There was no evidence of a concurrent decrease in latencies to the positive stimulus indicative of behavioral contrast. The third part of the experiment consisted of determining maintained generalization gradients by increasing the number of nonreinforcement stimuli. The gradients that eventually resulted showed approximately equal latencies to all frequencies of the negative stimulus and shorter latencies to the positive stimulus frequency.     

Note on the invariance of response latency in shuttlebox avoidance learning

Rats trained to avoid shock by running in a shuttlebox showed an orderly increase over trials in the probability of avoidance but no corresponding change over trials in the latency of the avoidance response. Both responding in the presence of shock (escapes) and responding prior to shock onset (avoidances) appeared to be stationary in time. Latencies were found to vary with different experimental conditions but in every case to be invariant over trials.     

Additive summation following intradimensional discrimination training

Rats were exposed to intradimensional composite stimuli presented on the response lever that varied in both light intensity and flicker rate. For all subjects, pressing the lever was reinforced when it was illuminated at a high intensity and flickered at a low rate (I + f) or when it was illuminated at a low intensity and flickered at a high rate (i + F). For half the subjects, lever responding was not reinforced when it was illuminated at a low intensity and flickering at a low rate (i + f). For the remaining subjects, lever presses were not reinforced when the lever was illuminated at a high intensity and flickered at a high rate (I + F). When the composite stimulus composed of the light intensity and flicker rates that had been associated only with reinforced responding was displayed (I + F for half the subjects and i + f for the remaining subjects), it controlled the highest response rate of all stimuli (additive summation). The results demonstrated that similar attentional processes control intra- and interdimensional composite-stimulus discriminations in a manner consistent with Weiss' (1972) analysis of summation.     

Generalization gradients following two-response discrimination training

Stimulus generalization was investigated using institutionalized human retardates as subjects. A baseline was established in which two values along the stimulus dimension of auditory frequency differentially controlled responding on two bars. The insertion of the test probes disrupted the control established to the two S^Ds during training. The discrimination was recovered between each test probe and the resulting gradients were stable across 10 test sessions. These gradients, supported by other two-response generalization studies, indicate that this type of two-response discrimination training divides the stimulus dimension into two functional classes separated by a region of transition from one class to the other. Each stimulus value in a class, which extends from an S^D outward to the functional limit of the dimension, controls a similar proportion of the two responses as each other value in the class. All values on the stimulus dimension control identical response rates with an absence of the usual generalization decrement. The latency of the initial response, however, shows a bimodal gradient with the modes at the S^D values.     

Visual discrimination with a single manipulandum following temporal ablations in the monkey

The aim of this investigation was to determine what effect variation in the conditions of cue presentation and response availability has on the visual discrimination performance of monkeys with bilateral inferior temporal ablations. Six animals were trained on one of two versions of a test of successive brightness discrimination. Common to both versions of this test was the availability of a single lever, manipulation of which in the presence of the positive cue constituted the correct response. Performance on this test was compared with performance on a pattern discrimination, for which the customary simultaneous two-choice procedure was used. It was found that the temporal removals were followed by definite impairment on the pattern discrimination (as expected), but no consistent change in efficiency at brightness discrimination could be attributed to the lesions. Alternative interpretations, making reference to the amount of pre-operative training on the brightness discrimination or the lack of differentiation between the correct and alternative responses in this test, are discussed.     

Contrast and stimulus generalization following prolonged discrimination training

Different groups of pigeons received discrimination training in which the reinforcement-associated and extinction-associated stimuli were respectively either (a) a line tilt vs a blank key, (b) a blank key vs a line tilt, or (c) two different line tilts. The high response rates that developed to the positive stimulus in all groups during discrimination learning were maintained over 64 sessions of training. After these sessions, all subjects were tested for stimulus generalization along the line-tilt dimension. Gradients of relative (per cent) generalization around the stimulus associated with reinforcement (so-called excitatory gradients) and around the stimulus associated with extinction (so-called inhibitory gradients) were as steep as they typically are after much briefer training periods. These results do not support several of Terrace's predictions on the basis of the hypothesis that emotional responses develop to the stimulus associated with extinction during discrimination learning with errors, but eventually dissipate after extended training.     

Another dimension for assessment of speech-sound discrimination: latency of response.

The relationship of speech-sound-discrimination skills and speed of responding was investigated by presenting monosyllabic nouns in three different listening conditions to a total of 72 nursery, kindergarten, and first-grad children divided into three equal-sized groups. Speed of responding was related to the age of subjects, accuracy of responding, and context of presentation of stimulus items. There was a consistent decrease in latency of responding as age increased. Error responses had greater response latencies than correct responses. Response latencies for different contexts of presentation of stimulus items were longest for the paired-comparison context and shortest for the carrier-phrase context. Speed of responding could be considered as an additional parameter when evaluating speech-sound-discrimination skills.     

Transfer of training following discrimination learning with two reinforced responses

Pigeons were given errorless discrimination training between chromatic stimuli with a specific reinforced response associated with each discriminative stimulus. These Ss subsequently acquired a successive go/no-go auditory discrimination (utilizing one response class) faster than Ss given single stimulus training. These results are more compatible with an explanation of transfer of training in successive operant discrimination learning based on general attention than one based on withholding responses.     

Race-specific perceptual discrimination improvement following short individuation training with faces

This study explores the effect of individuation training on the acquisition of race-specific expertise. First, we investigated whether practice individuating other-race faces yields improvement in perceptual discrimination for novel faces of that race. Second, we asked whether there was similar improvement for novel faces of a different race for which participants received equal practice, but in an orthogonal task that did not require individuation. Caucasian participants were trained to individuate faces of one race (African American or Hispanic) and to make difficult eye-luminance judgments on faces of the other race. By equating these tasks we are able to rule out raw experience, visual attention, or performance/success-induced positivity as the critical factors that produce race-specific improvements. These results indicate that individuation practice is one mechanism through which cognitive, perceptual, and/or social processes promote growth of the own-race face recognition advantage.     

A further study of stimulus generalization following three-stimulus discrimination training

A group of pigeons was trained in a Skinner box to peck for VI reinforcement when the key was illuminated by a monochromatic light of 540 or 580 mμ but were non-reinforced for responding to 560 mμ. Two control groups, differing in amount of training, received only the two positive stimuli. At the completion of training all Ss received generalization tests under extinction. Both control groups produced bi-modal generalization gradients with the peaks of responding at the S+ values. The post-discrimination gradient revealed peaks displaced from the S+ values in the direction away from the S−, low responding and increased steepness in the region of S− and a general elevation of the gradient.     

Interocular generalization: a study of mirror-image reversal following monocular discrimination training in the pigeon

Generalization gradients along a continuum of angular orientation were obtained from four pigeons, following monocular training on a discrimination between a 45° oblique line (S+) and a 135° oblique line (S−). All pigeons were trained on a chain DRO VI 1 schedule of reinforcement. Generalization gradients obtained with the trained and untrained eye were compared. All pigeons responded maximally to the 45° line (S+) when tested with only the trained eye open. During generalization tests of interocular transfer with only the untrained eye open, three pigeons responded maximally to S− (135°), the mirror-image of the stimulus associated with reinforcement during training (45°). The other pigeon failed to show interocular transfer of the discrimination. Interocular reversal of left-right mirror-image stimuli has not been reported for any other species.     

Effects of punishment on response latency in extraverts

Previous findings indicate that in comparison to introverts, extraverts are prone to form responses that are resistant to interruption by punishment. Because the tendency to stop and reflect following punishment may be crucial for subsequent learning, the present study was designed to examine differences between introverts' and extraverts' reactions to punishment using response latency on the trial following punishment as the dependent variable. Sixty-six extraverted and 66 introverted male undergraduates performed a pattern-matching task in which they received noncontingent 50% success and 50% failure feedback under three incentive conditions including reward only, punishment only, or both. As predicted, a significant interaction was found in the both condition, reflecting the tendency of extraverts to respond more quickly and introverts more slowly following punishment feedback than following reward feedback. No significant effects were found in the other two conditions; however, a tendency was noted for extraverts to respond more quickly overall when only reward was given. A second experiment using reward-only and punishment-only feedback replicated this finding and yielded a significant interaction of Group X Condition. The results indicate that in contrast to introverts, extraverts are activated by the availability of reward and, paradoxically, that punishment may facilitate rather than interrupt extraverts' reward seeking behavior.