Categorical perception of emotional facial expressions in preschoolers

Adults perceive emotional facial expressions categorically. In this study, we explored categorical perception in 3.5-year-olds by creating a morphed continuum of emotional faces and tested preschoolers’ discrimination and identification of them. In the discrimination task, participants indicated whether two examples from the continuum “felt the same” or “felt different.” In the identification task, images were presented individually and participants were asked to label the emotion displayed on the face (e.g., “Does she look happy or sad?”). Results suggest that 3.5-year-olds have the same category boundary as adults. They were more likely to report that the image pairs felt “different” at the image pair that crossed the category boundary. These results suggest that 3.5-year-olds perceive happy and sad emotional facial expressions categorically as adults do. Categorizing emotional expressions is advantageous for children if it allows them to use social information faster and more efficiently.     

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.     

Attention effects of abrupt-onset precues with central, single-element, and multiple-element precues

Endogenous and exogenous processes of attention have been inferred with different types of precues used in allocation of attention to a target location. In the present research, a comparison was made between the typical peripheral single-element precue (SEP), a central precue, and a multiple-element precue (MEP) in order to further understanding of the processes involved in allocation of attention. Two precues were used on each trial in these experiments. An abrupt-onset precue appeared with an SEP, an MEP, or a central precue and was followed 50 or 300 ms later by a screen containing a target and two distractor characters. The abrupt-onset precue and the other precue each could be valid or invalid in indicating the location of the target, as in the study by Juola, Koshino, and Warner (1995). Response times to the targets showed that validity effects of the abrupt-onset precue and the MEP or central precue were additive, whereas those of the abrupt-onset precue and the SEP were interactive. These data suggest that, like a central precue, an MEP is an endogenous precue that guides conscious control of attention and has its attentional effects at a different processing level from an SEP, which is an exogenous precue and may compete for attentional resources with an abrupt-onset precue.     

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.     

Attention effects of moving and stationary single-element and multiple-element precues: Limits of automaticity

A multiple-element precue (MEP), in which one unique element defines the actual precue, results in efficient precuing for identification of a target. The time course for identification in this case is similar to that for a central precue, even though it is presented peripherally (Chastain, 1996; Chastain & Cheal, in press). Five experiments were conducted to gain further information on the function of MEPs and to question what advantage prior knowledge of the precue may give. In Experiments 1 and 2, it was shown that for “pop-out” features, accuracy of identification of a target was higher if the precue type was known in advance. In contrast, as shown in Experiments 3, 4, and 5, when the precue was defined by apparent motion, there was no difference in accuracy due to advanced knowledge of the precue. Further, accuracy was considerably better for motion precues than for stationary precues.     

Mapping emotion category boundaries using a visual expectation paradigm

Past research showing categorical perception of emotional facial expressions has relied on identification and discrimination tasks that require an explicit response via keypress. Here we report a new paradigm for investigating the category boundary of emotional facial expressions that, instead, relies on an implicit response--eye direction. Participants were trained to expect a target stimulus on a particular side of the monitor, predicted by an emotional expression on a face image. An eye-tracker then recorded eye movements of participants as they viewed novel intermediate facial-expression stimuli. Anticipatory eye movement was taken as evidence of categorisation. Results from two experiments suggest that this implicit method can be used to determine category boundaries, and that the boundaries found with this method are similar to those found with the keypress response.     

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.     

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.