Ester Reijnen

Color Channels, Not Color Appearance or Color Categories, Guide Visual Search for Desaturated Color Targets

In this article, we report that in visual search, desaturated reddish targets are much easier to find than other desaturated targets, even when perceptual differences between targets and distractors are carefully equated. Observers searched for desaturated targets among mixtures of white and saturated distractors. Reaction times were hundreds of milliseconds faster for the most effective (reddish) targets than for the least effective (purplish) targets. The advantage for desaturated reds did not reflect an advantage for the lexical category “pink,” because reaction times did not follow named color categories. Many pink stimuli were not found quickly, and many quickly found stimuli were not labeled “pink.” Other possible explanations (e.g., linear-separability effects) also failed. Instead, we propose that guidance of visual search for desaturated colors is based on a combination of low-level color-opponent signals that is different from the combinations that produce perceived color. We speculate that this guidance might reflect a specialization for human skin.

Cradling side preference is associated with lateralized processing of baby facial expressions in females

Womens cradling side preference has been related to contralateral hemispheric specialization of processing emotional signals; but not of processing babys facial expression. Therefore, 46 nulliparous female volunteers were characterized as left or non-left holders (HG) during a doll holding task. During a signal detection task they were then asked to detect the emotional baby faces in a series of baby portraits with neutral and emotional facial expressions, presented either to the left or the right visual field (VFP). ANOVA revealed a significant HG x VFP interaction on response bias data (p < .05). Response bias was lowest when emotional baby faces were presented in the visual field of cradling side preference, suggesting that womens cradling side preference may have evolved to save cognitive resources during monitoring emotional baby face signals.

Scientific Problem Solving in a Virtual Laboratory: A Comparison Between Individuals and Pairs

This study compared individuals with pairs in a scientific problem-solving task. Participants interacted with a virtual psychological laboratory called Virtue to reason about a visual search theory. To this end, they created hypotheses, designed experiments, and analyzed and interpreted the results of their experiments in order to discover which of five possible factors affected the visual search process. Before and after their interaction with Virtue, participants took a test measuring theoretical and methodological knowledge. In addition, process data reflecting participants’ experimental activities and verbal data were collected. The results showed a significant but equal increase in knowledge for both groups. We found differences between individuals and pairs in the evaluation of hypotheses in the process data, and in descriptive and explanatory statements in the verbal data. Interacting with Virtue helped all students improve their domain-specific and domain-general psychological knowledge.

Coarse guidance by numerosity in visual search

In five experiments, we examined whether the number of items can guide visual focal attention. Observers searched for the target area with the largest (or smallest) number of dots (squares in Experiment 4 and “checkerboards” in Experiment 5) among distractor areas with a smaller (or larger) number of dots. Results of Experiments 1 and 2 show that search efficiency is determined by target to distractor dot ratios. In searches where target items contained more dots than did distractor items, ratios over 1.5:1 yielded efficient search. Searches for targets where target items contained fewer dots than distractor items were harder. Here, ratios needed to be lower than 1:2 to yield efficient search. When the areas of the dots and of the squares containing them were fixed, as they were in Experiments 1 and 2, dot density and total dot area increased as dot number increased. Experiment 3 removed the density and area cues by allowing dot size and total dot area to vary. This produced a marked decline in search performance. Efficient search now required ratios of above 3:1 or below 1:3. By using more realistic and isoluminant stimuli, Experiments 4 and 5 show that guidance by numerosity is fragile. As is found with other features that guide focal attention (e.g., color, orientation, size), the numerosity differences that are able to guide attention by bottom-up signals are much coarser than the differences that can be detected in attended stimuli.

Color Similarity in Visual Search

In the present study, we investigated the role of phenomenologically perceived color differences between stimuli in determining visual search efficiency. We contrasted this with predictions based on the categorical color status, as proposed by Wolfes Guided Search 2 model. We first asked participants to rate the color similarity of each pair of stimuli (pairwise comparison). The results were combined using multidimensional scaling to produce a similarity metric, which was subsequently used to define stimulus similarities for two visual search experiments. The results demonstrate that the time required by participants to find a target is more adequately explained by the perceived similarity of colors than by color categories.