Successive Stimulus Presentations Research Articles

Pattern discrimination in the near-ultraviolet by pigeons.

Four pigeons were tested, using an operant conditioning method with successive stimulus presentation, on a pattern discrimination task to determine whether or not they could distinguish patterns that were illuminated by near-ultraviolet (UV) light. Tests at red, green, and UV wavelengths showed that they could significantly discriminate not only the chromatic stimuli that were visible to human observers but also the UV-illuminated patterns that humans could not see. In control sessions, the birds’ performance deteriorated to chance levels when these UV wavelengths were blocked by additional filters. Their discrimination of UV patterns precludes that the pigeon’s known sensitivity to UV is mediated by a preretinal fluorescence, as is probably the case in some other animals, since such a fluorescence does not permit a focused retinal image. Possible retinal mechanisms mediating their UV detection are discussed.

Inhibitory Blocking with Successive Stimulus Presentations

The possibility of a previously established inhibitor blocking the acquisition of inhibitory control by another stimulus was investigated using successive stimulus presentations rather than the simultaneous technique that has been used in most other blocking studies. Rats were first trained on a two-stimulus successive discrimination task. They were then given a second task with three stimuli, again presented in succession. The main concern was with discriminative responding to the novel S + and S- of Task 2 as a function of the nature of the third stimulus which was always an S +. When the third stimulus was the S- from Task 1, and exerted inhibitory control during Task 2, learning not to respond to the current S- was retarded relative to groups for which the third stimulus was either the S + from Task 1 or was novel. However, when the S- from Task 1 failed to exert inhibitory control during Task 2, no such retardation occurred. A second experiment ruled out the possibility that the effect was due simply to a change in status of the third stimulus from S- to S +. These results were discussed in terms of an explanation of blocking holding that surprising events produce stronger conditioning than expected events.

MEMORY FOR SEQUENCES OF STIMULI AND RESPONSES

Two experiments sought to determine if pigeons could discriminate and remember recent sequences of stimuli and responses. A variant of Konorski's short-term memory procedure involving successive presentation of sample and test stimuli was used. The samples were stimulus-response pairs of the form, (S-R)(1)-(S-R)(2). Differential test responding disclosed memory of the two-item samples, with birds showing earlier and greater control by the second item than the first (Experiment 1). When the retention interval separating the second item of the sample sequence from the test stimulus was lenghtened from .5 to 2.0 or 4.0 sec, a systematic loss of stimulus control resulted; however, when varied over the same temporal range, the interval between the two items of the sample sequence had a much smaller effect, or none at all (Experiment 2). These results support an account of response-sequence differentiation that stresses short-term memory of organized behavior patterns.

Two definitions of persistence in visual perception.

It is well known that the perception of a visual stimulus does not terminate with the offset of that stimulus, but decays with time. Although a variety of specific methods have been developed to study this phenomenon, these methods have not always yielded consistent results. We believe that some of the discrepancies in the literature on visual persistence have arisen because different researchers have based their estimates of persistence on qualitatively different features of the visual residual. Efron (1970) asked subjects to temporally align the onset of a click with the offset of a brief flash. Persistence, defined as the interval between flash offset and onset of the indexing click, was found to decrease with increasing flash intensity. Bowen, Pola, and Matin (1974) asked subjects to adjust the temporal placement of a probe flash so that it was coincident with the apparent offset of a spatially separated test flash. Persistence was defined as the interval between test flash offset and onset of the indexing flash. Again, measured persistence decreased with increasing test stimulus intensity. The same result has been reported by Hansteen (1971) using a procedure resembling that of Bowen et al. In a somewhat different approach, Haber and Standing (1969) presented a repetitive cycle in which a stimulus was followed by a blank interval. Subjects were asked to adjust the duration of the blank interval between successive stimulus presentations so as to produce a discontinuity. Once again, persistence, defined by the duration of the blank interval between successive stimuli, declined with increases in the intensity of the test stimulus. Other researchers, however, using different procedures, have reported that stimulus intensity has the opposite effect on persistence. In one of a series of experiments, Sakitt (1976) asked observers to temporally align the onset of a click with the disappearance of the residual (icon) of a briefly exposed letter array. Her measure of persistence, the temporal inter-

Changing role of stimulus intensity as a determinant of infants' attention.

When pairs of stimuli which varied in size or brightness and in pattern were presented to 6-, 9- and 24-wk.-olds, the visual attention of the younger infants appeared to be more influenced by size or brightness than by pattern, while the opposite was the case for the oldest infants. The results of another study suggested that the effects of size and brightness were additive for 9-wk.-olds. Finally, a third study using a subject-control procedure with successive stimulus presentation yielded results which were essentially the same as those of the first study. The results were interpreted as supporting the hypothesis that amount of stimulation is a major determinant of attention in the first 2 mo. and that its effectiveness decreases with age.

Storage mode of geometrical dimensions in a two-stimulus matching paradigm.

In a two-stimulus matching paradigm requiring “same” and “different” responses to simple geometric dimensions, the successive stimulus presentation mode with several retention intervals was compared to a simultaneous stimulus presentation mode. For the simultaneous condition, the data suggested a wholistic template matching process, but in none of the successive conditions was template matching indicated. The retention interval of the successive condition allows the subject to analyze out the target dimension from the first two-dimensional stimulus. The ability to anticipate the value of the target dimension in the second stimulus could also influence the representation of the first stimulus. The findings shed some light upon the perceptual interactions between dimensions that constitute the stimulus. In particular, an outside-to-inside order of iconic scanning appeared to be supported by the data.

A measure of extracellular unit responses to repeated stimulation applied to observations of the time course of olfactory responses

A technique for measurement of small samples of unit behavior during regularly repeated stimulation is described. A correlation-based measure was computed over two successive stimulus presentations by summing the products of spike counts for corresponding time bins and normalizing to the number of bins and the numbers of spike counts during the two stimulus presentations. This measure was combined with the mean frequency of spike occurrence during the stimulus presentation to give a characterization of neuronal activity sensitive to changes in both strength of temporal pattern and mean frequency. Examples are given of olfactory responsive neurons with comparison of measurement techniques. The time course of the response to odor of neurons recorded under urethane anesthesia from the olfactory bulb and the lateral hypothalamus was studied. By both simple mean frequency measures and the measures proposed in this study, the neurons recorded from the lateral hypothalamus underwent more rapid temporal decrements in the odor response.

Neural Correlates of Habituation of the Cardiac Component of the Orienting Response

Amplitudes of multiple unit activity (MUA) responses to an auditory stimulus decrease with stimulus repetition. Correlations between neural response decrements and the time course of other indices of habituation [e.g., orienting response (OR) habituation] are not known. We explored the relationship between habituation of the cardiac OR and response changes in the lateral midbrain reticular formation (LMRF), inferior colliculus (IC), and medial geniculate (MG) over successive stimulus presentations. Intracranial electrodes and subcutaneous EKG electrodes were chronically implanted in 16 rats. Subsequently, they were curarized and respirated in a chamber equipped with an overhead speaker. At mean intervals of 90 sec, a 5-sec tone was presented. Twenty successive presentations were made at each of two frequencies. Cardiac rates during the five successive tone seconds were compared with rates for five successive pretone seconds. Most rats showed initial deceleratory responses, which habituated. Others gave acceleratory responses, which were also decremental over trials. The response-generated MUA was analyzed for changes in spike frequency. Amplitudes of MLRF responses either decreased over the 20 trials or showed an initial increment, then a decrement. Smaller decrements occurred in MG responses and occasionally we saw an initial sensitization. IC responses also tended to decrease over trials. [Supported by a grant from SUNY Research Foundation.]

Effects of simultaneous and successive stimulus presentation on visual discriminations by aphasic patients.

In order to determine whether aphasic and nonaphasic subjects would perform differentially in simultaneous and successive discrimination tasks, 10 aphasic and 10 nonaphasic hospital patients performed in a successive and a simultaneous discrimination task in which 2 stimuli were presented on each trial, and in a successive discrimination with a single stimulus presented on each trial. Aphasic and nonaphasic subjects learned the successive discrimination task with a single stimulus faster than the other two discriminations. When the discrimination involved two stimuli, simultaneous presentation of stimuli resulted in faster learning by aphasic subjects than did successive presentation. Learning of visual discriminations by aphasic and nonaphasic subjects appeared to occur all at once, rather than as gradual improvement over trials. The hypothesis that aphasic subjects would have difficulty with inhibition of responses to negative discriminative stimuli was not supported.

Adaptation: Central or Peripheral?

Adaptation was measured using successive and simultaneous presentation of heterophonic stimuli in order to determine if adaptation is more a central than a peripheral phenomena. The first of the two studies reported compared the method of delayed balance, method of simultaneous dichotic balances (SDB) involving tracking for 15-sec periods, and a modification of the SDB utilizing 1-sec tones. Only the homophonic SDB involving tracking produced noticeable adaptation. In the second experiment several procedural variations of the heterophonic tracking SDB method were studied. None of the variations produced the intensity decrement customarily associated with adaptation. It was concluded that, when binaural interactions (loudness and/or lateralization) are reduced or eliminated by test procedures, the adapted ear shows little if any shift. Thus, the decrements observed with the typical SDB procedure probably reflect slowly developing changes in binaural interactions—and, consequently, are central rather than peripheral changes. Judgments obtained with simultaneous stimulation, therefore, are not procedures that should be utilized for the study of peripheral adaptation effects.

Hemispheric differences in evoked potentials to verbal and nonverbal stimuli in the left and right visual fields.

Abstract Successive presentation of verbal and nonsense stimuli to right and left visual fields produced dissimilar evoked responses from the left and right occipital cortex in man. Stimulation of a dominant left hemiretina-hemisphere route yielded greater differences in evoked response waveform for the two classes of stimuli than the corresponding system on the right. Transmission of information via the direct visual pathways to each hemisphere also showed greater stability in evoked response activity than that from secondary or indirect pathways.

Sort Board for Random Access of Auditory Stimuli

An apparatus is described that allows subjects to initiate presentation of auditory stimuli at random and to sort, rank, or otherwise arrange the stimuli in a two-dimensional array. The system consists of (1) a square board with 256 holes; (2) a set of up to 36 freely movable control pegs; (3) a general-purpose DDP-516 computer; (4) a random rapid-access disk. When a subject presses down on a peg placed in any of the holes, the computer identifies the peg and presents an auditory stimulus. In a pilot study using this system, subjects were asked to arrange two-parameter complex tones so that proximity of pegs on the board reflected similarity. The tones were stored on disk in digital form. The computer identified the peg, retrived from disk the stimulus assigned to that peg, and updated a CRT display containing an image of the board and the location of each peg at last operation. A chronological history of the subject's performance, including the sequence of stimulus presentation, location of the peg at each operation, and the interval between successive stimulus presentations, was recorded on digital tape.

The ‘peck/no-peck decision-maker’ in the black-headed gull chick

1. 1. In companion papers a model called the Choice Threshold Model was described, and its applicability to percentage preference data tested. The present paper extends the treatment to absolute numbers of responses in a choice situation. 2. 2. It is postulated that while the Choice Threshold Model functions as a ‘directing’ decision-maker, determining how choices are to be directed, the determination of when and how often such choices shall occur may be the function of a separate ‘go/no-go decision-making mechanism’, the rate of whose activity is represented by the symbol K. 3. 3. Data on rates of pecking at coloured stimuli by black-headed gull chicks Larus ridibundus, are used to determine the relationship between K and the stimulus situation. 4. 4. It is found that K is determined only by the most preferred stimulus available. 5. 5. Thus a stimulus affects the animal in two different ways. By influencing the ‘directing decision-maker’ (the Choice Threshold Model), it affects the relative number of times it is chosen compared with other simultaneously available stimuli. By influencing the ‘go/no-go decision-maker’, which it only does when it is the most preferred of the available stimuli, it affects the absolute rate of choosing regardless of which stimulus is chosen. This dichotomy is reminiscent of that of classical ethology between ‘directing’ and ‘releasing’ roles of stimuli. 6. 6. Paradoxically it is found that stimuli which are preferred with respect to their ‘directing’ function tend to have low ‘releasing’ value and vice versa. 7. 7. A quantitatively precise prediction concerning the relative merits of two methods of studying selective responsiveness, simultaneous or successive presentation of stimuli, can be derived from the model if it is assumed that K is constant. In the light of the findings about the dependence of K on the stimulus situation, this prediction has to be modified. The present data are used in an indirect way to verify the modified prediction. 8. 8. The actual values of K (i.e. ‘releasing’ value) for each colour are estimated from the data, and are plotted graphically against the corresponding threshold values (i.e. ‘directing’ value). The inverse relationship appears to be a regular one, for the points all fall on a smooth curve. 9. 9. These findings can all be explained by a Lorenzian hydraulic type of model. Various versions of the model have been simulated, and the parameters of one version adjusted to achieve a precise fit to the gull data.

Eye movements and the perception of rectilinear dot progressions

Three groups of high school students were tested on a task requiring “straight” or “crooked” judgments of rectilinear dot progressions generated by sequentially illuminated lights. Each group was tested under one of three conditions, which differed in the amount of eye movement occasioned by successive stimulus presentations. There were no significant, differences between the numbers of “straight” judgments for the three groups. In all groups the number of “straight” judgments increased with faster presentation rates.

TRANSPOSITION IN ADULTS WITH SIMULTANEOUS AND SUCCESSIVE STIMULUS PRESENTATION.

TRANSPOSITION IN ADULTS WITH SIMULTANEOUS AND SUCCESSIVE STIMULUS PRESENTATION.

Brightness Discrimination Learning under Conditions of Simultaneous and Successive Presentation of Stimuli with Punishment

Under relational conditions with electric shock punishment for incorrect responses, all 9 rats learned to choose the dimmer of two stimuli; no Ss in a parallel group of rats ( N = 6) given equivalent training under absolute conditions reached the learning criterion. Results are interpreted as supporting the Gestalt theory of discrimination learning rather than the theory of Spence.

Human discrimination learning with simultaneous and successive presentation of stimuli.

Human discrimination learning with simultaneous and successive presentation of stimuli.

Visual discrimination learning with simultaneous and successive presentation of stimuli.

Visual discrimination learning with simultaneous and successive presentation of stimuli.