Marylou Cheal

Central and peripheral precuing of forced-choice discrimination

There are suggestions in the literature that spatial precuing of attention with peripheral and central cues may be mediated by different mechanisms. To investigate this issue, data from two previous papers were reanalysed to investigate the complete time course of precuing target location with either: (1) a peripheral cue that may draw attention reflexively, or (2) a central, symbolic cue that may require attention to be directed voluntarily. This analysis led to predictions that were tested in another experiment. The main result of this experiment was that a peripheral cue produced its largest effects on discrimination performance within 100 msec, whereas a central cue required approximately 300 msec to achieve maximum effects. In conjunction with previous findings, the present evidence for time differences between the two cuing conditions suggests that more than one process is involved in the spatial precuing of attention.

Scopolamine disrupts maintenance of attention rather than memory processes.

Memory of a novel stimulus was demonstrated in scopolamine-treated gerbils following a 60-sec, nonreinforced exposure. On a second trial, 60 sec or 24 hr later, gerbils that received 0.01–10 mg/kg scopolamine showed shorter durations of investigation, indicating normal habituation. The frequency of approaching an object, however, did not decrease significantly in gerbils given 0.1–10 mg/kg. The duration per approach was shorter in scopolamine-treated gerbils suggesting a deficit in maintenance of attention. The loss of habituation of frequency, but not duration, occurred in the same animals during the same responses to novel objects or odors, and also occurred in gerbils habituated to the object before drug treatment. This effect was not present in physostigmine-treated gerbils or in gerbils given methylscopolamine. The data indicate the inadequacy of hypotheses that scopolamine disrupts memory, disinhibits responses, or prevents appropriate selection of stimuli. It is proposed that acetylcholine pathways are present in neural areas strategic for modulation of the interaction of sensory, limbic, and motor systems.

Social olfaction: a review of the ontogeny of olfactory influences on vertebrate behavior

Research on the postnatal development of behavior involving olfaction is reviewed. Included are investigations of olfactory responses of human neonates and young children, the development of preferences in various mammals, the ontogeny of the fright reaction in fish and amphibia, and the attraction of maternal odors for small mammals. The effects of early exposure and conditioning to olfactory stimuli on adult behavior in mammals and fish are reported including a survey of the status of the olfactory hypothesis in fish migration. Deprivation experiments suggest disruption of later behavior. Limitations of the present knowledge and directions for future research are presented.

A framework for understanding the allocation of attention in location-precued discrimination

The effects of attention on visual perception are assessed in the location-precuing paradigm. First, we present a review of some current metaphors for attention and relevant data. Then, a framework is suggested that provides an interpretation of the temporal sequence of external and assumed internal processes within a location-cuing trial. Cases when a precue correctly indicates the target location (valid trials) are compared to cases when the precue directs attention to the wrong location (invalid trials) with the cue location either at fixation or peripheral to the target location. Several specific hypotheses are suggested; these concern decrements in performance on invalid trials and effects of the location of a precue. For the most part, these hypotheses are supported by data in the literature and in some new studies. A gradient-filter metaphor for attention, which includes a synthesis of ideas from the gradient model and the attention gate model, is more consistent with the data than is a spotlight metaphor.

Social Olfaction: A Review of the Role of Olfaction in a Variety of Animal Behaviors

Behavioral olfactory experiments were reviewed, relating the behavioral effects of pheromones to the psychophysical work in olfaction. Short descriptions of various experiments were used to show the importance of olfaction to the social behavior of animals by tracing the history of the experimental evidence and viewing the behavioral data pertaining to the discharge of pheromones and their effects and to look at the psychophysical evidence for olfactory acuity and the behavioral implications for the role of the physiological structures in olfaction.

Attention Effects on Form Discrimination at Different Eccentricities

Considerable disagreement exists in the visual attention literature about how attention is allocated over the visual field. One frequently expressed metaphor is that attention moves like a spotlight, and in some variants it is assumed that attention takes longer to shift to targets further from fixation. In order to test this metaphor, five experiments were conducted in which target location was precued and form discrimination accuracy was assessed. By varying the interval between the precue and the target (stimulus onset asynchrony, SOA), a time course of attention effects was obtained for targets at 2°, 6°, and 10° eccentricity. In the first three experiments, precueing effects were found, but there were no differences in performance as a function of eccentricity for very short SOAs, with either a peripheral cue or a foveal arrow cue. For long SOAs, however, performance was better for targets that were closer to fixation. In Experiments 4 (peripheral cue) and 5 (foveal cue), the targets were scaled to make them equally discriminable at all eccentricities. Again precueing effects were found, but there were no differences in accuracy as a function of eccentricity for most SOAs. These results suggest that attention shifting is not analogous to a constant-velocity moving spotlight.

Evidence of limited capacity and noise reduction with single-element displays in the location-cuing paradigm.

Precuing a location facilitates accuracy of identification of a target at that location and reduces noise from other nontarget characters in a multicharacter field. In 5 experiments, evidence for facilitation included higher accuracy with long precue-target intervals than with short intervals and higher accuracy when a precue indicated the correct location than with short intervals and higher accuracy when a precue indicated the correct location than when it indicated the wrong location. These results were found for each target-mask condition used (1 target with 1 mask, 1 target with 4 masks, or 1 target and 3 nontargets with 4 masks) in experienced and inexperienced observers. Evidence for noise reduction was found because accuracy was higher in the 1 target-1 mask condition than in the other conditions on correctly cued trials with short-cue-target intervals and on incorrectly cued trials. Data are related to methodological factors that are important to obtaining these effects and to capacity and noise reduction models.

Attention in visual search: Multiple search classes

Data from visual-search tasks are typically interpreted to mean that searching for targets defined by feature differences does not require attention and thus can be performed in parallel, whereas searching for other targets requires serial allocation of attention. The question addressed here was whether a parallel-serial dichotomy would be obtained if data were collected using a variety of targets representing each of several kinds of defining features. Data analyses included several computations in addition to search rate: (1) target-absent to target-present slope ratios; (2) two separate data transformations to control for errors; (3) minimum reaction time; and (4) slopes of standard deviation as a function of set size. Some targets showed strongly parallel or strongly serial search, but there was evidence for several intermediate search classes. Sometimes, for a given target-distractor pair, the results depended strongly on which character was the target and which was the distractor. Implications from theories of visual search are discussed.

Does attention have different effects on line orientation and line arrangement discrimination

Visual search and texture segregation studies have led to the inference that stimuli differing in the orientation of their component line segments can be distinguished without focal attention, whereas stimuli that differ only in the arrangement of line segments cannot. In most of this research, the locus of attention has not been explicitly manipulated. In the first experiment presented here, attention was directed to a relevant peripheral target by a cue presented near the target location or at the fovea. Effects of attention on orientation discrimination were assessed in a two-alternative forced-choice task with targets that were either: (1) lines that slanted obliquely to the right or left, or were horizontal or vertical, or (2) Y-like targets that had a short arm leading obliquely right or left of a vertical line. In some groups, a four-alternative forced-choice test with lines at 0°, 45°, 90°, and 135° orientations was used. Discrimination of these targets (i.e. targets that differ in the orientation of component line segments) was only minimally facilitated as the time between the onset of the valid cue and the onset of the target (cue-target stimulus onset asynchrony, SOA) was increased from 0 or 17 msec to 267 msec. In contrast, discrimination of targets that did not differ in the orientation of component line segments but differed in line arrangement (T-like characters), was greatly facilitated by longer cue-target SOAs. In Experiment 2, a cue misdirected attention on 20% of the trials. A decrement occurred on incorrectly cued trials in comparison to correctly cued trials for both types of stimuli used (lines and Ts). The results from these experiments suggest that discrimination of line orientation benefits less from focal attention than does discrimination of line arrangement, but that both discriminations suffer when attention must be disengaged from an irrelevant spatial location.

Importance of precue location in directing attention

In location-precuing experiments, accuracy in discrimination of T-like characters improves with increasing time between the precue and the target. In this experiment, two central and two peripheral cue locations were examined using 13 different cue-target intervals from 0 to 234 msec. Accuracy was the same when trials were cued from the two peripheral locations (two thirds distance between fixation and target or distal to the target location). Centrally cued trials (cues at fixation or next to fixation) resulted in slower onset of attentional effects than peripherally cued trials, but there was greater accuracy at long cue-target intervals for central than for peripheral cues. Data are compared to previously published research.