Transfer after pretraining with the negative stimulus

Two groups of rats trained in the jumping stand acquired a horizontal stripes vs. vertical stripes discrimination and then learned its reversal. The groups differed in their pretraining. One group had previously learned a black vs. white discrimination; the other a discrimination in which the S- was the same as that used in the horizontal against vertical problem. S- pretraining facilitated not only acquisition but also the reversal of the orientation discrimination thereby confirming a prediction that reversal learning will be rapid when the original problem is learned chiefly in terms of the S-. It is suggested that overtraining may facilitate reversal learning, in some cases at least, by inducing animals to concentrate on the S-.     

Selective response activation can begin before stimulus recognition is complete: a psychophysiological and error analysis of continuous flow

In discussions of process models of human information processing, the continuous flow conception (Eriksen and Schultz 1979) plays a prominent role. A central prediction of this conception is that any information in a display associated with a response activates that response as soon as it becomes available in the perceptual system. If it concerns the correct response channel, then response facilitation occurs. If it concerns the incorrect response channel, then response competition occurs. To assess these mechanisms more directly, we used psychophysiological measures as well as reaction time (RT). We used the latency of the P3 component of the event related brain potential (ERP) as an index of stimulus evaluation duration, the onset of lateralized motor activity derived from the ERP as an index of selective central motor activation, and the onset of electromyographic activity as an index of the start of peripheral motor activation. Subjects were required to respond to target letters that were either flanked by letters that signalled the opposite response (incompatible arrays), by the target itself (compatible arrays), by letters not associated with a response (neutral arrays), or by no other letters (targets alone). Our results replicated the basic findings obtained in this paradigm. RTs to targets alone did not differ from RTs to compatible arrays. The latter were faster than RTs to neutral arrays, which were faster than RTs to incompatible arrays. P3 latencies were longer on incompatible than on neutral trials, and longer on compatible than on target alone trials. Incorrect central response activation on incompatible trials and correct central response activation on compatible trials, both began earlier than on target alone trials. Peripheral responding on both trial types, however, began later than on target alone trials. More incompatible but less compatible trials than neutral ones exhibited incorrect peripheral response activation. Peripheral response execution was faster and more accurate on compatible than on target alone trials, while it was slower and less accurate on incompatible than on neutral trials. These results indicate, that the flankers activated their associated response channel while display evaluation was still going on, and that response facilitation and competition occurred. After applying criteria proposed by Miller (1988), it was concluded that the set of stimulus recognition processes and the set of response activation processes cannot be regarded as independent stages of processing.     

Implicit alternatives to a stimulus,difficulty of encoding,and schema-plus-correction representation

Garner has hypothesized that a S exposed to a stimulus infers alternatives to it. Data are reviewed which establish a close correlation between the number of implicit alternatives to a stimulus and the difficulty of encoding that stimulus. This correlation provides a datum to be explained and suggests that the identification of specific implicit alternatives may provide clues to the encoding process. For dot patterns of a certain kind, it has been suggested that the rotations and reflections of a stimulus are its only alternatives, but a close examination of certain data indicates that, for many of these patterns, the alternatives also include one or more other patterns which differ from the stimulus only in the position of a single dot and which locate that dot in a position where it is more predictable from the other dots. It is suggested that the one-dot-different alternatives represent schemas used in schema-plus-correction encoding.     

The influence of the number of alternatives on the perceptual recognition threshold

A study of the recognition thresholds for nonsense syllables previously presented in lists containing from 2 to 15 syllables is reported. The threshold is found to increase in proportion to the logarithm of the number of alternatives (i.e. the length of the list from which a given test syllable is drawn). It is therefore concluded that recognition threshold is a function of the amount of information transmitted.     

Role of response imagery on stimulus recognition*

This experiment investigated the role of response imagery on recognition of stimulus terms following associative training. Ss learned to associate 12 high-imagery or low-imagery responses with trigram stimuli by the study-associative matching procedure. Half the pairs were consistently paired and half were re-paired anew on each trial. Following associative training, Ss were given a stimulus recognition and an associative matching task The results indicated that the probability of stimulus recognition, given correct associative matching, was greater when the responses were high-imagery rather than low-imagery. In contrast, no rehable response imagery effects were found for the probability of stimulus recognition, given incorrect associative matching. It was argued that the locus of the response imagery effect was primarily during retrieval rather than during encoding.     

The role of stimulus familiarity in context-dependent recognition

Memory & Cognition - Investigations of context-dependent recognition, a phenomenon in which recognition is better for items studied and tested with the same rather than different context, have...     

Tactile letter recognition under different modes of stimulus presentation

Block capital letters were displayed to experienced and inexperienced Ss, using a 20 x 20 matrix of vibratory tactors placed against the back. In two separate experiments, a total of five modes of stimulus presentation, three of them employing a linear scanning slit, were studied. The poorest method, stationary flashing of the letter, allows performance that is well above chance, implying that a purely spatial presentation does convey information. Performance is improved when the letter is moved horizontally across the display. The best performance is achieved when the amount of simultaneous stimulation is limited by using a linear scanning slit. In one method, the letter moves behind a stationary slit, with the result that its horizontal dimension is portrayed only in time. In the other two methods, the scanning slit moves across the stationary letter, portraying the letter both in time and in space. The results of all five display modes indicate that Ss can use whichever representation, spatial or temporal, is available, although patternings which most closely approximate sequential tracing by a single moving point lead to the highest recognition accuracy. We interpret these results in terms of the limited spatial resolution of the cutaneous sense. While the perception of a letter presented in either full-field condition is limited by the spatial resolution, the best measure being the two-point limen, the perception of a letter traced sequentially is limited by the localization acuity of the cutaneous sense, the best measure being the “error of localization,” which is known to be considerably smaller than the two-point limen. Inasmuch as the slit methods of presentation are a compromise between simultaneous and sequential display, letter-recognition accuracy is better with slit presentation than with the corresponding full-field mode of display.     

Cerebral lateralization of visual stimulus recognition in stutterers and fluent speakers

Cerebral lateralization of stutterers and nonstutterers was assessed in terms of choice reaction times to stimuli presented to either the left or right visual hemifield on letter recognition and figure recognition tasks. Reaction times on both tasks were determined before and after a behavioral speech therapy program. Stutterers demonstrated a significant reduction in mean reaction times in the letter recognition task over the course of the therapy program. This change differed significantly from that obtained from stutterers in the figure recognition task. The stutterers' responses were in contrast to the responses of the nonstutterers, who showed no reduction in mean reaction times for the letter or figure recognition tasks. The results were discussed in terms of alterations in aspects of central nervous system processing as a result of participation in the behavioral speech therapy.     

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.     

Sensory and meaning features in stimulus recognition and associative retrieval.

Three experiments addressed the problem of isolating the effects of sensory similarity on subprocesses involved in coding paired associates. In the first, the standard recognition-recall procedure was used and stimulus similarity, concreteness, and frequency were varied. However, because of concern with the validity of this recognition procedure as a measure of functional stimulus contact, an alternative was developed. This alternative led to the second study in which only stimulus similarity was manipulated. In the third experiment, similarity was varied, and the pairs were either associatively compatible, unrelated, or incompatible. The results using the new procedure indicated that similarity consistently disrupted functional stimulus contact but not associative retrieval. By contrast, associative relatedness facilitated both subprocesses.     

Accuracy of recognition for speech presented to the right and left ears

Earlier reports by other authors had shown that recall of dichotically presented speech was better for words arriving at the right ear, while recognition of passages of music was better for music presented to the left ear. It seemed desirable to test recognition for speech, in order to show that the difference between materials rather than the difference in testing techniques was responsible for this disparity between ears.

Accordingly 18 men were presented with dichotic lists of digits, and then tested for recognition of the digits. There was no indication of an advantage for the left ear, but rather of the advantage for the right already established for recall of speech materials.     

Effects of varying stimulus size on object recognition in pigeons

The authors investigated the pigeon's ability to generalize object discrimination performance to smaller and larger versions of trained objects. In Experiment 1, they taught pigeons with line drawings of multipart objects and later tested the birds with both larger and smaller drawings. The pigeons exhibited significant generalization to new sizes, although they did show systematic performance decrements as the new size deviated from the original. In Experiment 2, the authors tested both linear and exponential size changes of computer-rendered basic shapes to determine which size transformation produced equivalent performance for size increases and decreases. Performance was more consistent with logarithmic than with linear scaling of size. This finding was supported in Experiment 3. Overall, the experiments suggest that the pigeon encodes size as a feature of objects and that the representation of size is most likely logarithmic.     

Kin recognition in Rana cascadae tadpoles: effects of rearing with nonsiblings and varying the strength of the stimulus cues

Experiments with two clutches of Rana cascadae tadpoles were undertaken to determine if (1) rearing tadpoles exclusively with nonkin affects sibling recognition behavior and (2) if tadpoles are capable of distinguishing between groups of varying sibling/nonsibling composition. Individual tadpoles reared from embryonic stages with 12 nonsiblings behaved as tadpoles reared with siblings by exhibiting a preference for siblings over nonsiblings in choice tests. This suggests that experience with siblings is not a necessary prerequisite for the development of sibling recognition in this species. Tadpoles reared with siblings preferred to associate with a group composed of 50% siblings and 50% nonsiblings over a group of 100% nonsiblings, but exhibited no preference for a group composed of 25% siblings and 75% nonsiblings versus one composed of nonsiblings only. Thus tadpoles are capable of discriminating between mixed groups of siblings and nonsiblings, but probably require some minimum proportion of siblings to do so.     

Comparison of the effects of scopolamine administered before and after acquisition in a test of visual recognition memory in monkeys

The effect of scopolamine on visual recognition memory in rhesus monkeys was assessed with a delayed nonmatching-to-sample task employing trial-unique stimuli. During the acquisition phase, 40 sample stimuli were presented sequentially. During the test phase, these same stimuli were presented in the reverse order, each paired with a novel stimulus. The animal was rewarded for choosing the novel stimulus in each pair. Two versions of this design were used. In Task 1, scopolamine (10.0 or 17.8 micrograms/kg) was administered 20 min prior to acquisition, which was followed immediately by the test phase. In Task 2, the drug was administered immediately after acquisition, which was followed 20 min later by the test phase. Performance was impaired in a dose-related manner in Task 1, but not at all in Task 2, indicating that the effects of scopolamine on performance cannot be attributed to an impairment either in the retrieval of stored information or in the attentive or perceptual discriminative processes needed for such retrieval, or, by implication, for storage. In addition, the forgetting curves for scopolamine in Task 1 were parallel to those of the control sessions; i.e., the curves did not diverge with increasing delay intervals, indicating that scopolamine did not increase the rate of forgetting. Taken together, the results suggest that scopolamine interferes selectively with the initial storage of the information to be remembered.     

Hemispheric differences in tactile and visual recognition of braille-like stimulus patterns with static and dynamic modes of inspection

Summary Braille-like patterns were presented unilaterally to both tactual and visual modalities. The subject's task was to identify the location of three dots in a 2 × 3 six-dot pattern. Specifically, tactual versus visual presentation, dynamic versus static presentation of tactual stimuli, learning, and gender were examined in relation to cerebral hemisheric differences. Data were analyzed in terms of both the number of individual stimulus dots and the number of complete three-dot patterns correctly identified with regard to their spatial location. Although no reliable laterality differences were obtained with the tactual-static condition, owing to a significant interaction between learning and side of stimulus presentation, dot positions were reported reliably more accurately when presented in a dynamic fashion, i. e., scanned by the subject, to the right hand. For the visual modality, both correct reports of individual dot positions as well as correct reports of the entire patterns were reliably more accurate for stimulus presentations to the right visual field. Increased familiarity with the task, i. e., learning accross trials, generally increased report accuracy, particularly for static presentations to the left hand. The effect of gender was negligible. The results are dicussed in terms of their theoretical implications for differential cerebral hemispheric specializations in terms of differential processing strategies.The research reported here was supported by a Grant (A8621) from the Natural Sciences and Engineering Research Council of Canada to the second author. Offprint requests should be sent to Eugene C. Lechelt, Department of Psychology, University of Alberta, Edmonton, Alberta, Canada T6G 2E9