Location dominance in attending to color and shape.

Investigated in 4 experiments whether Ss direct attention to stimulus location when attempting to attend to its color or shape. In the 1st 2 experiments, a given property (location, color, or shape) of a letter cue instructed Ss whether to report any letters from a subsequent display. Regardless of which property was relevant, Ss reported letters adjacent to the cue and not those similar to its color or shape. In the last 2 experiments, the varied location of a cue was irrelevant to the task, whereas its varied color instructed Ss to report a letter in a given location or of a given shape. Targets adjacent to the cue were reported faster than those remote from the cue. The results suggest that attempting to attend to any aspect of a stimulus entails directing attention to location. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of pre-cues on voluntary and reflexive saccade generation. II. Pro-cues for anti-saccades

The reaction times of saccades (SRT) to a suddenly presented visual stimulus (pro-saccade) can be decreased and a separate mode of express saccades can occur when a gap paradigm is used (i.e. fixation-point offset precedes target onset by 200 ms). A valid peripheral cue, presented briefly (100 ms) before target onset, has been found to facilitate the generation of saccades to the target, thereby increasing the frequency of express saccades and decreasing the mean latency. This facilitation occurs only for cues that correctly indicate the direction of the subsequent target presentation (valid cues). The present study investigates the effects of valid cues on SRTs and error rate in the anti-saccade task (saccades in the direction opposite to the stimulus) by systematically varying the cue lead time (CLT) and using the gap and overlap conditions, i.e. fixation point remains on throughout the trial. For a CLT of 100 ms, both reaction times and error rates were significantly increased. With increasing CLT (200-500 ms), both the reaction times of the anti-saccades and the error rates returned to approximately control level, with CLT more than 200 ms in both the gap and the overlap condition. Additional experiments using non-informative cues in the overlap task showed that the reaction times of correct anti-saccades and the error rate were decreased when cue and stimulus appeared at the same side. Analysis of the erratic pro-saccades revealed that almost all of them were corrected, i.e. they were followed by a second saccade towards the required location. It is found that the correction times were usually very short, with intersaccadic intervals between 0 and 150 ms. We suggest that the orienting mechanism, elicited by a transient peripheral cue, relates to the command and the decision to make a pro- rather than an anti-saccade. The cue elicits pro-orienting towards its position when a pro-saccade is required, and anti-orienting when an anti-saccade is required. The orienting effect is transient and decays with CLTs of more than 200 ms; this result holds for both anti-saccades and pro-saccades. Since subjects reported that they could not prevent the erratic pro-saccades or were often not aware of them, we conclude that this orienting mechanism occurs automatically, beyond voluntary control.     

Active inhibition of a distractor word: The distractor precue benefit in the Stroop color-naming task.

The current study investigated attentional control through active inhibition of the identity of the distractor. Adapting a Stroop paradigm, the distractor word was presented in advance and made to disappear, followed by the presentation of a Stroop stimulus. Participants were instructed to inhibit the distractor in order to reduce its interference. Experiments 1 and 2 demonstrated that the distractor precue facilitated Stroop color naming by reducing Stroop interference. Experiment 3 demonstrated beneficial effects of the distractor precue when congruent trials were introduced. Experiment 4 showed that the distractor precue benefit was observed when the cue and target were in different forms. Experiment 5 indicated that if the item used as the cue became the target, naming it took longer in order to overcome the inhibitory effect. Experiment 6 demonstrated that the benefit of the distractor precue was not observed when the cue was uninformative. Finally, Experiment 7 demonstrated that active inhibition required working-memory resources to operate. This study suggests that the best explanation for the distractor precue benefit is the active inhibition account. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Eliminating inhibition of return by changing salient nonspatial attributes in a complex environment.

Inhibition of return (IOR) occurs when a target is preceded by an irrelevant stimulus (cue) at the same location: Target detection is slowed, relative to uncued locations. In the present study, we used relatively complex displays to examine the effect of repetition of nonspatial attributes. For both color and shape, attribute repetition produced a robust inhibitory effect that followed a time course similar to that for location-based IOR. However, the effect only occurred when the target shared both the feature (i.e., color or shape) and location with the cue; this constraint implicates a primary role for location. The data are consistent with the idea that the system integrates consecutive stimuli into a single object file when attributes repeat, hindering detection of the second stimulus. The results are also consistent with an interpretation of IOR as a form of habituation, with greater habituation occurring with increasing featural overlap of a repeated stimulus. Critically, both of these interpretations bring the IOR effect within more general approaches to attention and perception, rather than requiring a specialized process with a limited function. In this view, there is no process specifically designed to inhibit return, suggesting that IOR may be the wrong framing of inhibitory repetition effects. Instead, we suggest that repetition of stimulus properties can interfere with the ability to focus attention on the aspects of a complex display that are needed to detect the occurrence of the target stimulus; this is a failure of activation, not an inhibition of processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus and temporal cues in classical conditioning.

In 2 experiments, separate groups of rats were given stimulus conditioning, temporal conditioning, untreated control and (in Experiment 2) learned irrelevance control procedures followed by a compound with both stimulus and temporal cues. Stimulus conditioning consisted of a random 15-s duration conditioned stimulus (CS) followed by food; temporal conditioning consisted of food–food intervals of fixed 90 s (Experiment 1) or fixed 75?+?random 15 s (Experiment 2). The stimulus group abruptly increased responding after CS onset, and the temporal group gradually increased responding over the food–food interval. When the food–food interval was fixed 90 s, the temporal cue exerted stronger control in the compound, whereas when the food–food interval was fixed 75?+?random 15 s, the stimulus cue exerted stronger control. The strength of conditioning, temporal gradients of responding, and cue competition effects appear to reflect simultaneous timing of multiple intervals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Does attention affect visual feature integration?

Investigated whether (1) the integration of color and shape information is affected by attending to the stimulus location and (2) attending to a stimulus location enhances the perceptual representation of the stimulus or merely affects decision processes. In 3 experiments with 39 Ss (aged 16–38 yrs), Ss were briefly presented with colored letters. On most trials, Ss were precued to the stimulus location (valid cue); on some trials, a nonstimulus location was cued (invalid cue). Ss were less likely to combine colors and letter shapes incorrectly following a valid cue. The attentional facilitation afforded by the cue was not limited to feature integration but also affected the registration of features; however, when the amount of feature information was strictly controlled, attention still affected feature integration. It is suggested that orienting attention to the location of the cue affects the quality of the perceptual representation for features and their integration. (31 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Time course of the blindness to response-compatible stimuli.

This article examines the time course of a deficit in identifying a stimulus sharing a compatible feature with a response that is executed in parallel ("blindness to response-compatible stimuli," J. Müsseler & B. Hommel, 1997a). In 5 experiments, participants performed a timed response, and the presentation point of time of a to-be-identified stimulus was varied in respect to response execution. A blindness effect was observed when the stimulus was presented between response cue offset and response execution. In contrast, the identification of a stimulus presented before the response cue or after response execution was not affected by stimulus-response compatibility—a finding that rules out a retention-based explanation. These results support an explanation that states that the perceptual processing of a stimulus feature is impaired as long as the shared perception–action feature code is integrated into the representation of a to-be-executed response. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Simon Effect in Pigeons.

Pigeons pecked left versus right keys contingent upon the color presented at 1 of those locations. Spatial-response latencies were shorter when the color appeared at the same location as the required response than at the opposite location. This Simon effect occurred when the stimulus on the alternative key was constant, varied from trial to trial, or changed when the color cue appeared and when the reinforcement probability for correct responses was the same on corresponding as on noncorresponding trials. Humans performing the same task by touching the keys also showed the Simon effect. These findings demonstrate that for pigeons, too, a relevant symbolic cue activates a spatial code that produces faster responses at the location corresponding with the activated code. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus-response compatibility and automatic response activation: evidence from psychophysiological studies

Effects of dimensional overlap between stimuli and responses on partial response activation were investigated within a priming paradigm with the help of event-related potentials. The likely position of a target stimulus (requiring a left or a right reaction) was indicated by an arrow precue. To test whether automatic response activation processes are triggered by the cue, the lateralized readiness potential was computed. It was found that responses congruent to the direction of the cue were activated about 200 ms after cue onset. This early process was unaffected by specific cue-response contingencies and was completely missing when a nonspatial (color) cue was used. A second response activation phase was observed, which was partially controlled by specific response instructions and subjective expectancies. It is concluded that when stimuli and responses overlap with respect to spatial attributes, automatic response activation process are triggered, which may later be replaced by the activation of an expected response.     

Cues that hippocampal place cells encode: dynamic and hierarchical representation of local and distal stimuli

Hippocampal place fields were recorded as rats explored a four-arm radial maze surrounded by curtains holding distal stimuli and with distinct local tactile, olfactory, and visual cues covering each arm. Systematic manipulations of the individual cues and their interrelationships showed that different hippocampal neurons encoded individual local and distal cues, relationships among cues within a stimulus set, and the relationship between the local and distal cues. Double rotation trials, which maintained stimulus relationships within distal and local cue sets, but altered the relationship between them, often changed the responses of the sampled neural population and produced new representations. After repeated double rotation trials, the incidence of new representations increased, and the likelihood of a simple rotation with one of the cue sets diminished. Cue scrambling trials, which altered the topological relationship within the local or distal stimulus set, showed that the cells that followed one set of controlled stimuli responded as often to a single cue as to the constellation. These cells followed the single cue when the stimulus constellation was scrambled, but often continued firing in the same place when the stimulus was removed or switched to respond to other cues. When the maze was surrounded by a new stimulus configuration, all of the cells either developed new place fields or stopped firing, showing that the controlled stimuli had persistent and profound influence over hippocampal neurons. Together, the results show that hippocampal neurons encode a hierarchical representation of environmental information.     

Evidence of visual processing negativity with attention to orientation and color in central space

The aim of this study was to determine whether the visual frontal processing negativity reported in our earlier paper (Karayanidis, F. and Michie, P.T. Electroenceph. clin. Neurophysiol., 1996, 99: 38-56) is related to selection of spatial location, or occurs regardless of the stimulus features used to define the target. Subjects were instructed to respond to infrequent target stimuli of a particular combination of orientation, color and size. All stimuli were presented at central fixation. Posteriorly, orientation selection enhanced P125 amplitude over the right hemisphere but neither orientation nor color selection had an effect on N190. Posterior selection negativities emerged for orientation, color and their conjunction. At anterior sites, widespread effects of orientation and color processing were evident. The effect of location selection on the anterior N1 seen in our previous study was not evident with orientation selection. Instead, selection of orientation, color and their conjunction resulted in P145-250 frontally. Two later anterior negativities emerged. The early negativity (vPNe) was affected independently by orientation and color selection while the late negativity (vPNl) was affected only by selection of feature conjunction. Thus, the present results show that, like its auditory counterpart, the visual processing negativity occurs with a variety of stimulus classification features and is not exclusively related to spatial selection.     

Aging and the Strategic Control of the Fixation Offset Effect.

A study was conducted to examine potential age-related differences in the strategic control of exogenous and endogenous saccades within the context of the fixation offset effect (FOE; i.e., faster saccades when a fixation point is removed than when it is left on throughout a trial). Subjects were instructed to make rapid saccades either on the basis of a suddenly appearing peripheral visual stimulus (exogenous saccade) or in response to a tone (endogenous saccade). On half of the trials the fixation point was removed simultaneously with the occurrence of the cue stimulus. Subjects' preparatory set was varied by manipulating the proportion of saccades generated to a visual and auditory stimulus within a trial block. Young and old adults both produced FOEs, and the FOEs were strategically modulated by preparatory set. The data are discussed in terms of aging and oculomotor control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characteristics of perceptual grouping in rats

Parametric analysis was made of the characteristics by which proximity and alignment serve as cues for perceptual grouping in rats. Rats were initially conditioned to discriminate a series of horizontal lines from vertical lines. Following training, rats were presented with test stimuli that consisted of bistable arrays of disjunct dots. A grouping cue (greater proximity, greater alignment, or both) was randomly assigned to either the horizontal or vertical orientation. The effectiveness of the cues was based on behavioral responses to the cued orientation. Results indicated that proximity served as a cue for perceptual grouping. The effectiveness of the proximity cue was less for rats than found previously in humans and, unlike humans, diminished with increased stimulus scale. Rats did not respond to alignment cues when used in isolation, although alignment facilitated grouping when used in conjunction with proximity cues. Diminished effectiveness of grouping cues likely reduces object recognition abilities, particularly for complex visual stimuli.     

Reconfiguration of processing mode prior to task performance.

Participants performed choice reaction time (RT) tasks on 2-dimensional stimuli such that each task was based on 1 stimulus dimension. A cue preceded the target stimulus and instructed the participant about which (randomly selected) task to perform. Shifting between tasks was associated with an RT cost, which was larger when the (randomly varying) cue–target interval was short as opposed to when it was long. Cue–target interval was not confounded with the remoteness from the previous trial. Hence, it affected the task-shift cost through preparation rather than by allowing carryover effects to dissipate. Similar results were obtained for 2 location tasks and for the object-based tasks (color and shape discrimination). They indicate a time-effort consuming process that operates after a task shift, precedes task execution, and presumably reflects the advance reconfiguration of processing mode. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention, exposure duration, and gaze shifting in naming performance.

Two experiments are reported in which the role of attribute exposure duration in naming performance was examined by tracking eye movements. Participants were presented with color-word Stroop stimuli and left- or right-pointing arrows on different sides of a computer screen. They named the color attribute and shifted their gaze to the arrow to manually indicate its direction. The color attribute (Experiment 1) or the complete color-word stimulus (Experiment 2) was removed from the screen 100 ms after stimulus onset. Compared with presentation until trial offset, removing the color attribute diminished Stroop interference, as well as facilitation effects in color naming latencies, whereas removing the complete stimulus diminished interference only. Attribute and stimulus removal reduced the latency of gaze shifting, which suggests decreased rather than increased attentional demand. These results provide evidence that limiting exposure duration contributes to attribute naming performance by diminishing the extent to which irrelevant attributes are processed, which reduces attentional demand. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Measuring the search image: Expectation, detection and recognition in pigeon visual search.

Pigeons searched computer screens for a grating target that varied in spatial frequency and orientation. In Experiment 1, a pretrial cue signaled that a particular target would appear. The cue speeded response to this primed target and to targets of the same orientation and similar spatial frequency to the primed target. However, the cue slowed search for targets differing from the primed target in orientation. In Experiment 2, pecks to a single target were reinforced. Responding generalized somewhat to targets of spatial frequency similar to the primed target and to targets of either orientation. Thus, stimulus aspects that affect detection may differ from those that affect recognition; if a common representation serves both, it functions differently in the 2 cases. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of motivation and orientation in sensory preconditioning.

Explored the effect of hunger on sensory preconditioning. Ss were 17 male cats. An appetitive task was used to test for sensory preconditioning effects in order to avoid complications arising from differences of drive state during preconditioning and testing for preconditioning. It was found that hunger facilitated the association between paired auditory and visual stimuli, but not between stimuli presented separately and in random order. Examination of the orientation responses of Ss during preconditioning indicate that the auditory stimulus becomes an arousing cue that signals the onset of the visual stimulus. It is suggested that the orientation responses produced as a consequence of this cue function are responsible for the association of the auditory and visual stimuli. (French summary) (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interactive Activation in Visual Word Recognition: Constraints Imposed by the Joint Effects of Spatial Attention and Semantics.

Two lexical-decision experiments investigated the effects of semantic priming and stimulus intensity when target location varied and was cued by an abrupt onset. In Experiment 1, the spatial cue was a good predictor of target location, and in Experiment 2 it was not. The results indicate that word recognition processes were postponed until spatial attention was focused on the target and that whether attention further affected word recognition depended on cue validity. The joint effects of cue validity and priming interacted when cue validity was high but were additive when cue validity was low. The joint effects of stimulus intensity and semantic priming also varied according to cue validity (i.e., interactive when high and additive when low). The results are discussed in terms of their implications for visual word recognition, the distinction between exogenous and endogenous spatial attention, and how attention is affected by visual word recognition processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Form preferences in successive discrimination learning of young chicks.

In 4 experiments the effects of form and orientation pecking preferences of a total of 100 1- and 3-day old Vantress X Arbor Acre chicks on successive discrimination learning were determined using heat reinforcement. Results indicate that (a) the young chick has both circle and vertical orientation pecking preferences that are present during at least the 1st 3 days after hatching; (b) when either of these preferred cues is the nonreinforced cue, the young chick has difficulty in learning not to respond to it but learns quickly not to respond to an unpreferred cue; and (c) these pecking preferences can be modified by heat reinforcement, and the effects of this conditioning is evident in subsequent extinction and retention tests. It is concluded that form and orientation preferences, like brightness and color preferences, are important developmental constraints on conditioning of the young chick. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)