Stimulus Events Research Articles

Consistency versus compatibility: a question of levels?

Consistency can be expressed in terms of minimal components of an interaction language. However, what is taken as a unit in describing stimulus events is crucial. A particular command set may be generated by very few rules (internal consistency) but should also map on to the users' expectations (higher level consistency, or compatibility). Sixty subjects took part in a simple computer game in order to explore the relationship between internal consistency, compatibility, and mode of learning. Internal consistency was found to be related to the subjects' ability to create an explicit model of the task, and compatibility was related to enhanced performance on the task. There was evidence that properties of a consistent underlying rule structure were made more salient when the mappings were consistent with users' expectations—and only under these circumstances were performance benefits observed.

Methodological Approaches to the Study of Social Event Perception

The ecological-event-perception view of social knowing differs from the traditional cognitive approach to person perception in some fundamental ways. First, the ecological view holds that veridical information about people and their interactions is available in dynamic, ongoing stimulus events. Second, perception itself is conceptualized as a dynamic process, in which an active perceiver comes to recognize the potential of the environment through exploration and behavior These tenets provide researchers with some unique methodological challenges both when selecting stimuli for study and when assessing subjects' responses to those stimuli. This article describes a number of methodological approaches taken by researchers to deal with these problems. The advantages and disadvantages of each are discussed.

A model of synchronization of motor acts to a stimulus sequence. II. Stability analysis, error estimation and simulations.

In Part I (Mates 1994), a linear model of timing and error-corrections was constructed that aims at an explanation of the mechanisms underlying a subject's performance in an experimental paradigm, in which the task is to synchronize a sequence of motor acts to a sequence of stimuli. The model consists of two error-corrective mechanisms: (1) corrections of period (inverted frequency) of the sequence of responses; (2) corrections of phase shift of that sequence (synchronization error). In this paper, the influence of the physiologically justifiable model variables and of initial conditions on the steady-state response sequence as well as the stability of performance of the model are analyzed. The model is stable for error-correction gains in the range from 0 to 2. Comparison with known empirical data supports the assumption that reasonable values are less than 1. Furthermore, an alternative to the basic linear model is introduced in which the possible character of the process of subjective acquisition of the synchronization error is discussed. On the basis of findings from other experimental paradigms (fusion and order threshold) it can be assumed that the subjective estimate is a nonlinear function of the difference between the temporal central availability of internal representations of the stimulus and response-feedback events. Some other known synchronization data are simulated by the nonlinear modification of the model in this paper. A good fit of the simulation results achieved further justifies the model structure proposed. Finally, the possible effect of the subjective synchronization-error estimation on empirical data is discussed.

Oscillatory and non-oscillatory synchronizations in the visual cortex and their possible roles in associations of visual features

It was postulated that the perceived association of visual features is based on the synchronization of those neural signals that are activated by a coherent visual object. Two types of synchronized cortical signals were found by us in cat and monkey visual cortex, and were proposed as candidates for feature association: (1) stimulus-locked signals, evoked by transient retinal stimulation, and typically non-rhythmic; (2) oscillatory signals, induced by sustained stimuli, and typically not locked in their oscillation phases to stimulus events. Both types of signals can occur synchronously in those neurons that are activated by a common stimulus. Synchronized activities were found in paired recordings within vertical cortex columns, in separate columns of the same cortical area, and even between different cortical areas or hemispheres. The average phase difference between such common oscillatory events was typically close to zero (< 1 msec mean +/- 2 msec S.D.). For the dependence of synchronization from stimulus and receptive field properties, a preliminary 'rule' can be given: the coherence of fast oscillations in separate cortical assemblies depends inversely on the 'coding distance' between the assemblies' RF properties, but directly on the degree of overlap between the assemblies' respective coding properties and the features of a common stimulus. This means that oscillatory events in any two assemblies, in the same or in different cortical areas or hemispheres, are more closely correlated the more similar are their receptive field properties, and the better a common stimulus activates the assemblies simultaneously. Our results can explain some neural mechanisms of perceptual feature-linking, including mutual enhancement among similar, spatially and temporally dispersed features, definitions of spatial and temporal continuity, scene segmentation, and figure-ground discrimination. We further propose that mutual enhancement and synchronization of cell activities are general principles of temporal coding by assemblies, that are also used within and among other sensory modalities as well as between cortical sensory and motor systems.

Judging interevent relations: From cause to effect and from effect to cause

Stimulus competition was studied in college students' correlational judgments in a medical decision-making setting. In accord with prior findings, subjects making cause-to-effect (predictive) judgments discounted a stimulus event that was moderately correlated with a target event when rival stimuli were more highly correlated with the effect. However, subjects making effect-to-cause (diagnostic) judgments were not at all disposed to discount a stimulus event which was moderately correlated with a target event when rival stimuli were more highly correlated with the cause. The theoretical implications of these results are considered in connection with associative and mentalistic models of causal attribution.

Primate frontal cortex: neuronal activity following attentional versus intentional cues.

We examined neuronal activity in three parts of the primate frontal cortex: the dorsal (PMd) and ventral (PMv) premotor cortex and a ventrolateral part of the dorsolateral prefrontal (PF) cortex. Two monkeys fixated a 0.2 degrees white square in the center of a video display while depressing a switch located between two touch pads. On each trial, a spatial-attentional/mnemonic (SAM) cue was presented first. The SAM cue consisted of one 2 degrees x 2 degrees square, usually red or green, and its location indicated where a conditional motor instruction would appear after a delay period. The stimulus event containing the motor instruction, termed the motor instructional/conditional (MIC) cue, could be of two general types. It might consist of a single 2 degrees x 2 degrees square stimulus identical to one of the SAM cues presented at the same location as the SAM cue on that trial. When the MIC cue was a single square, it instructed the monkey to move its forelimb to one of the two touch pads according to the following conditional rule: a green MIC cue meant that contact with the right touch pad would be rewarded on that trial and a red MIC cue instructed a movement to the left touch pad. Alternatively, the MIC cue might consist of two 2 degrees x 2 degrees squares, only one of which was at the SAM-cue location: in those cases, one square was red and the other was green. The colored square at the SAM cue location for that trial was the instructing stimulus, and the other part of the MIC cue was irrelevant. When, after a variable delay period, the MIC cue disappeared, the monkey had to touch the appropriate target within 1 s to receive a reward and could break visual fixation. The experimental design allowed comparison of frontal cortical activity when one stimulus, identical in retinocentric, craniocentric, and allocentric spatial location as well as all other stimulus parameters, had two different meanings for the animal's behavior. When a stimulus was the SAM cue, it led to either a reorientation of spatial attention to its location, or the storage of its location in spatial memory. By contrast, when it was the MIC cue, the same stimulus instructed a motor act to be executed after a delay period. For the majority of PMd neurons (55%), post-MIC cue activity exceeded post-SAM cue activity.(ABSTRACT TRUNCATED AT 400 WORDS)

The RF-cinematogram. A cross-correlation technique for mapping several visual receptive fields at once.

We present a spike-triggered averaging method capable of mapping the visual receptive fields of several neurons simultaneously. The stimulation is general and the mapping proceeds automatically without the need to match the stimulation to the cells' preference for position, orientation, direction, etc. The maps are spatiotemporal; receptive field (RF) structures are quantitatively determined in three dimensions: the two dimensions of visuotopic space, and time. The method presented is one of a family of "reverse correlation" or "spike-triggered averaging" techniques (DeBoer and Kuyper 1968) capable of revealing linear aspects of stimulus-response coupling. The formal relationship of these methods to stimulus-response cross-correlation is shown. The analysis is extended to provide some second-order axis-of-motion information ("direction marks"). The stimulus is a constantly illuminated, randomly jumping bright or dark spot, not an elongated bar. Spot diameters between one-third to 1 x RF width are effective. The method ascertains for each recorded action potential or "spike" the prior visual field position of the spot. The average or most probable spot positions define the receptive field spatially. Repeating the process for a succession of times prior to observed spikes defines the field temporally, presented here as a succession of spatial maps. We term this portrayal a receptive field cinematogram, RFc or ciné. The RFc reveals and economically portrays the spread of excitability and suppression across the receptive field, culminating in the generation of a spike. RFcs for LGN neurons and for simple cells recorded in cat cortical areas 17 and 18 are presented and interpreted in terms of classic ON/OFF regions. The availability of temporal information permits the separation of an excitatory exit response, generated when a moving bright spot leaves an OFF region, from an excitatory entrance response occurring when a bright spot enters an ON region, because these responses occur at different times (exit responses earlier). Spike emission remains coupled to (cross-correlated with) stimulus events over time periods as long as 96 ms, implying that some stimulus drive or afferent visual input is delayed by as much as 96 ms more than other input. This is a striking instance of temporal dispersion in the visual system. In some cells, said to be "spatiotemporally inseparable", the delay (latency) varies systematically across the visual field; i.e., the place for optimal stimulation varies with the time prior to spike emission. In these cells, the RFc shows receptive field structures which move across the visual field over trajectories equal to approximately twice the total conventional RF width.(ABSTRACT TRUNCATED AT 400 WORDS)

Cognitive aspects of classical conditioning

Cognitive processes have been increasingly implicated in Pavlovian conditioning. Research in the past year has focused on questions of stimulus selection and the internal representation of events and the relations between them. Recent data support negative feedback models of selection that assume conditioning-dependent changes in processing of conditioned and unconditioned stimulus events, and suggest potential neural mechanisms that may underlie these processes. New models of conditioning propose a more detailed representation of individual conditioning episodes than traditionally assumed. The results of investigations into conditional discrimination learning imply a hierarchical organization of event representations, and illustrate the importance of conditioned modulatory processes as distinct from response elicitation.

Effect of prior stimulation on modulation detection interference

Thresholds were measured for detecting amplitude modulation of a 2049-Hz probe carrier in the presence of a two-tone masker complex (909 and 4186 Hz). The probe and masker were modulated in-phase at 10 Hz. The effect of prior stimulation on masked probe AM detection was evaluated by either preceding the probe with a 200-ms, 2049-Hz tone burst (precursor) or adding an unmodulated carrier fringe preceding the onset of probe modulation. Precursor and masker onsets were synchronous, with the interval between precursor offset and probe onset (Δt) either 0, 40, or 160 ms. The precursor was either unmodulated, modulated at 10 Hz in-phase with the masker, modulated at 10 Hz antiphasic to the masker, or modulated at 20 Hz. With a Δt of 160 ms, precursor modulation characteristics had little effect. For Δt’s of 0 and 40 ms, modulation of the precursor lowered probe AM detection thresholds with performance generally best with 10-Hz precursor AM. In the fringe conditions, the unmodulated probe carrier preceded the masker onset, with the probe- and masker-modulation onsets synchronous. Fringe duration was either 50, 100, or 200 ms. The addition of the fringe improved performance only with the 50-ms fringe. Results will be discussed in terms of perceptual grouping of stimulus events. [Work supported by NSF.]

Newborn infants' memory for speech sounds retained over 24 hours.

Newborn infants were exposed to speech sounds in 2 sessions separated by 24 hr. Their habituation and recovery to these sounds were assessed by spontaneous head orienting toward the sound's location. Thirty-six neonates were assigned to 1 of 3 groups: a no-change group that heard the same word both days; a change group that heard a different word each day; and a Day 2 age-control group that heard 1 of the 2 words for the 1st time on Day 2. Both groups habituated to the sound on Day 1 and recovered head turning after the 24-hr delay, but infants who heard the same word again responded less than did age controls. In addition, these infants also began turning away from the sound, unlike the other 2 groups. Following habituation, all groups displayed comparable levels of recovery by turning toward a novel posttest stimulus. Neonates appeared to retain memory for a specific sound over a 24-hr period when presented with the same sound over both days. The extent to which the newborn infant retains information has been difficult to establish. Numerous studies of habituation (for review, see Clifton & Nelson, 1976; Zelazo, Weiss, & Tarquinio, 1991) and conditioning (for review, see Rovee-Collier & Lipsitt, 1982) attest to the newborn's ability to retain sensory information about specific stimuli and contingencies between stimulus events. This large body of work has examined the limits of retention over short periods, usually within single sessions lasting 1 hr or less. Much less information is available on memory for stimuli or events over longer periods. One of the earliest efforts to extend habituation was successful in showing retention of an habituated heart-rate response to repeated auditory stimuli after 24 hr (Keen, Chase, & Graham, 1965). Newborns who were presented with the same sound over 2 consecutive days responded less to the stimulus on the second day compared with a control group of the same age tested for the first time. A subsequent study in the same laboratory that tested newborns over 5 consecutive days failed to replicate the

Selective sensitivity of schedule-induced activity to an operant suppression contingency.

The sensitivity of pigeons' schedule-induced activity to operant consequences was studied in two experiments. During a 30-s interval between food presentations, a keylight stimulus brightened incrementally. Stable terminal key pecking and interim locomotor activity developed. An operant "setback" contingency was applied to activity. The contingency arranged for locomotor movements (detected by a nine-panel floorboard) to be followed by a resetting of the keylight brightness to a dimmer value and a 1-s delay of reinforcement (for individual responses). Experiment 1 showed that activity patterns were highly sensitive to their operant consequences. Accompanying key-peck rates were only transiently affected. In Experiment 2, the setback contingency was imposed during restricted portions of the trial, and differential operant control of activity was demonstrated. However, birds in this study produced higher rates of key pecking as activity rates were reduced. These results suggest that although schedule-induced activity arises in response to the temporal arrangement of stimulus events, this behavior may retain considerable sensitivity to response-consequence relations.

Reenacting the route to interpretation: Enhanced perceptual identification without prior perception.

Memory for processing a stimulus event may be expressed indirectly through more fluent processing of that stimulus on a later occasion. In 11 experiments, enhanced identification of words presented under visual masking was measured following events that involved reading target words or generating them from semantic cues. Amount of enhancement was related not to whether a word was actually seen on its first presentation, but to the degree to which it was integrated with its encoding context—integration led to less enhancement. It is proposed that 2 sets of operations are carried out during encoding. Interpretive encoding operations construct a context-sensitive interpretation of the stimulus and are optionally followed by elaborative encoding operations. Enhanced word identification due to memory for a prior episode is determined by the fluent reenactment of interpretive encoding operations applied during that episode. In their everyday use of the word, people usually think of remembering as a single act. This is evident in the frequent analogy to locating a book on a library shelf: The routine is done essentially the same way every time. But cognitive psychologists have shown over and over that, as appealing as the library analogy may be, it is not appropriate for describing memory. Remembering is not a single routine; it is a family of skills that we learn to use alone or in combination to meet the demands placed on us by our contexts. To understand memory, then, a key step will involve categorizing different types of remembering, finding commonalities among superficially different acts of remembering. In the past decade, this enterprise has focused particularly on a distinction between two ways of remembering—the deliberate recollection of specific episodes and the fluent application of memory for past experience to current task performance. Situations in which we deliberately attempt to remember have been called direct or explicit tests of memory (Richardson

Visual P3-like potentials in squirrel monkey: Effects of a noradrenergic agonist

Event-related potentials (ERPs) were recorded from squirrel monkeys ( Saimiri sciureus) in a 90-10 visual “oddball” paradigm. A small, blue rectangle was presented every 2 s on 90% of the trials (background), whereas a yellow rectangle occurred on 10% on the trials (oddball). Electrical activity time-locked to these stimulus events was recorded from epidural electrodes before and following systemic administration of the alpha-2 noradrenergic agonist clonidine (0.1 mg/kg intramuscularly, IM). Baseline data in response to oddball stimuli showed a large, P3-like potential exhibiting a fronto-central maximum along midline electrodes and a parietal maximum along lateral electrodes. A frontally dominant, long-latency, negative slow wave (SN) consistently followed this P3-like potential. Amplitudes for P3 were larger following 10% than 50% probable oddball events. These results suggest that monkeys exhibit large, probability-sensitive P3-like potentials similar to the visual potentials reported in humans. Administration of clonidine had no effect on the amplitude, area, or latency of the monkey P3 component. This contrasts with our previous findings that the same dose of clonidine significantly decreases auditory P3s in these monkeys. Such differences may reflect distinct functional roles for norepinephrine in the processing of low-probability acoustic versus visual signals and argues against the hypothesis that norepinephrine is a common neurotransmitter substrate for auditory and visual P3-like potentials.

IS BACK TO NATURE ALWAYS BEST?

Comunidad Los Horcones mounts a compelling argument for the use of in the schools, offering the strategy as a way to improve education. No person concerned with educational effectiveness can take issue with the notion that the most enjoyable and enduring learning is that which is an automatic product of, that is, reinforced by its function (i.e., the natural as defined in the Los Horcones paper). Natural or functional reinforcers, the stimulus events produced by the instrumental (learning) responses, are integral to the behavior, follow it everywhere, and support its continued maintenance. They require no time from educators, nor can society, educators, parents, or students take issue with their use on philosophical or ethical grounds. Indeed, is best and the way to go, provided (a) that the learning objective does produce a reinforcer and (b) that the reinforcer is more powerful than any competing punishers inherent in the task or reinforcers for competing responses. Let us examine each of these provisos separately. Do all learning tasks automatically produce reinforcers? Often, but not always. Many function to enable more advanced or complex objectives, frequently set a long time into the future. Learning to discriminate a b from a d contributes toward the student's ultimate skill as a reader, but in and of itself provides little in the way of reinforcement. Learning a definition of a concept such as negative reinforcement is essential to understanding, talking about, experimenting with, and so on, the behavior of organisms, but acquiring the verbal chain accomplishes little for the person (other than the limited some find inherent in meeting a challenge). Were it not for the fact that someone in the verbal community indicated the

A theory of humor elicitation.

This article presents a general theory of humor elicitation that specifies the conditions in which humor is experienced in both social and nonsocial situations. The theory takes into account the interpretation of a stimulus event that is necessary to elicit humor, the difficulty of identifying the humor-eliciting features of this interpretation, and the cognitive elaboration of implications of the event. The influence of these factors is postulated to depend on subjects' information-processing objectives at the time a stimulus event occurs. The theory is used to conceptualize the humor elicited by jokes, witticisms, and social events that are neither intended nor expected to be humorous. Particular attention is given to the cognitive underpinnings of responses to ethnic humor and to the humor that is elicited by one's own behavior in social situations.

The Ecology of Automaticity: Toward Establishing the Conditions Needed to Produce Automatic Processing Effects

In the past 15 years, the single term automatic has been applied to a diversity of laboratory phenomena that differ as to the preconditions necessary for their occurrence. Several major strains of automaticity are distinguished, based on the experimental conditions under which they are obtained: preconscious automatic processes, requiring only the proximal stimulus event; postconscious automatic processes, similar to preconscious effects but needing a recent activation or "priming" event for their operation; and goal-dependent automatic processes, which occur only when a specific, intentional processing goal is in place. It is argued that to more accurately specify the conditions under which an automatic effect will occur in the natural environment, greater attention needs to be given to aspects of the experimental paradigm (e.g., subjects' task goal, questionnaire administrations, previous tasks) that might be necessary to produce the effect.

Implicit versus explicit learning processes in a probabilistic, continuous fine-motor catching task.

We compared the influences of explicit instruction and uninstructed implicit learning of correlations among visual events, in a fine-motor task. The task required visual tracking of a small "ball" of light and "catching" it by means of joystick manipulation. A general pattern of improvement with practice for instructed and "noninstructed" conditions was found. Additionally, both instructed and noninstructed conditions evidenced use of the predictive relationships among stimulus events. The improvement in overall performance caused by explicit verbal instructions was less than the improvement seen with the implicit learning condition. Further, instructed and noninstructed conditions showed different patterns of joystick activity. These findings suggest a qualitatively different approach to visual information processing and task performance for the instructional conditions

Serial spatial reversal learning in rats: Comparison of instrumental and automaintenance procedures

Serial reversals of a spatial discrimination were trained in rats under automaintenance conditions, in which food reward occurred regardless of responding. This automaintained reversal learning was compared to instrumental reversal learning in other rats trained under a similar procedure which required responding for reward. In the automaintenance (AU) procedure, rats received food after every retraction of a “positive” response lever (S +); retraction of a second, “neutral” lever (S°) was not paired with food delivery. Responses to the S + were elicited at fairly constant rates during daily 100-trial conditioning sessions. Responses to the S° occurred early in each session but rapidly diminished across trials. When the valences of the levers were reversed, responding shifted to the new S + and diminished on the new S°. Criterion for reversal was defined as a discrimination ratio (DR) of at least 90% responding to the S + in two consecutive 10-trial blocks. With repeated reversals, acquisition of criterion performance occurred with increasing rapidity, reaching an asymptote below that required for the original discrimination. A second group of rats was trained on a similar instrumental schedule, in which at least one response to the S + was required for food delivery. Response rates in this instrumental (IN) group were approximately double those of the AU group. However, ratios of S + to S° response rates were similar to those of the AU group, and the serial reversal curves generated were qualitatively similar. Thus rats can show improvement across serial reversals of a spatial discrimination based entirely on pairings of stimulus events (automaintenance), in a manner similar to that observed in instrumental procedures, in which reward is contingent upon correct responding.

Visible persistence following a brief increment in stimulus luminance

In previous studies, it has been demonstrated that visible persistence--the period for which the perceived duration of a stimulus exceeds its physical duration--can be extended by briefly incrementing the luminance of the stimulus immediately prior to offset. Using a two-component pattern integration task, we show that this effect is not an artifact of change in the total luminous flux within the stimulus. Visible persistence was unaffected by overall luminance of the stimulus. It was also time-locked to the luminance increment. Visible persistence is seen to result from a process that is initiated by stimulus onset and that can be either wholly or partially reinitiated by the onset of the luminance increment. The duration of this process (which determines the duration of stimulus visibility) can be modified in a graded fashion by stimulus events that occur after its initiation. We outline a single-process inhibitory feedback model of the persistence mechanism that accounts for the present findings.

Orienting, Habituation, and Resource Allocation: An Associative Analysis

This paper addresses the question of the most appropriate theoretical account of the phenomena of orienting and habituation. Several lines of evidence are reviewed. First, it is argued that the effects of stimulus omission require a comparator theory in which it is asserted that responses to iterated events result from a comparison between predicted and actual stimulus input. Second, the data from studies in which paired stimulus events are employed seem, at least at first sight, to be best explained in terms of a comparator theory in which a key role is ascribed to associative processes. Third, secondary task probe reaction time data indicate that events that elicit orienting also command processing resources, and that habituation involves changes in the manner in which events are processed. Finally, recent data on the effects of intermodality change indicate that electrodermal responses are larger on the change trial than on the first habituation training trial; these results seem problematical for noncomparator theories. However, other data on the context-specificity of habituation and on the effects of stimulus miscuing cast doubt on the usefulness of an associative analysis as a general account of habituation phenomena. Nevertheless, the weight of evidence seems to indicate that an adequate theory of human habituation must include a comparison process and must acknowledge that orienting and habituation involve a re-allocation of attentional resources.