Asymmetries in visual search: An introduction

In visual search tasks, observers look for a target stimulus among distractor stimuli. A visual search asymmetry is said to occur when a search for stimulus A among stimulus B produces different results from a search for B among A. Anne Treisman made search asymmetries into an important tool in the study of visual attention. She argued that it was easier to find a target that was defined by the presence of a preattentive basic feature than to find a target defined by the absence of that feature. Four of the eight papers in this symposium inPerception & Psychophysics deal with the use of search asymmetries to identify stimulus attributes that behave as basic features in this context. Another two papers deal with the long-standing question of whether a novelty can be considered to be a basic feature. Asymmetries can also arise when one type of stimulus is easier to identify or classify than another. Levin and Angelone’s paper on visual search for faces of different races is an examination of an asymmetry of this variety. Finally, Previc and Naegele investigate an asymmetry based on the spatial location of the target. Taken as a whole, these papers illustrate the continuing value of the search asymmetry paradigm.     

Search for multiple targets: remember the targets, forget the search

Models of visual search performance typically assume that search proceeds by sampling without replacement. This requires memory for each deployment of attention. We tested this assumption of memory-driven search using a multiple-target search paradigm. We held total set size constant, varied the number of targets in the display, and asked subjects to report whether or not there were at least n targets present, where n was varied by block. This allowed us to measure the time to find each subsequent target. Memory-driven search predicts that reaction time should be a linear function of n. The alternative memory-free search hypothesis predicts an accelerating function. The data falsify the memory-driven hypothesis. They were consistent with the memory-free search hypothesis but would also be consistent with memory for a small number of previously attended locations.     

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.     

Hybrid value foraging: How the value of targets shapes human foraging behavior

In hybrid foraging, observers search visual displays for multiple instances of multiple target types. In previous hybrid foraging experiments, although there were multiple types of target, all instances of all targets had the same value. Under such conditions, behavior was well described by the marginal value theorem (MVT). Foragers left the current “patch” for the next patch when the instantaneous rate of collection dropped below their average rate of collection. An observer’s specific target selections were shaped by previous target selections. Observers were biased toward picking another instance of the same target. In the present work, observers forage for instances of four target types whose value and prevalence can vary. If value is kept constant and prevalence manipulated, participants consistently show a preference for the most common targets. Patch-leaving behavior follows MVT. When value is manipulated, observers favor more valuable targets, though individual foraging strategies become more diverse, with some observers favoring the most valuable target types very strongly, sometimes moving to the next patch without collecting any of the less valuable targets.

     

SCiP at 35: An idiosyncratic history of the Society for Computers in Psychology

SCiP history may be divided into three eras: the Paleozoic (1971–1982), the Mesozoic (1982–1994), and the Cenozoic (1994-present). Following a list of Secretary-Treasurers, a list of all SCiP Presidents is provided in Table 1. Next I present personal highlights, including the first symposium on psychology and the World-Wide Web; David Rumelhart’s mathematical explanation of connectionism; and Stevan Harnad’s discussion of “freeing” the journal literature. I observe that a small conference is becoming more intimate and that much of our mission involves figuring out how to conduct high-quality scientific research with consumer-grade electronics. I argue that we are an increasingly international organization, that graduate students are welcome, and that we should become more inclusive in the areas of gender and ethnicity and should make membership more meaningful. I conclude by looking ahead and attempting to predict the future.     

Punishment of shock-induced aggression

Squirrel monkeys were restrained in a chair equipped with a tail-shock apparatus and a pneumatic bite hose located in front of the subject's face. An aggressive response was recorded when the monkey bit the hose. Initial sessions in which no shocks were delivered produced some biting. When biting during these sessions stabilized at a near-zero level, regularly scheduled shocks were delivered to the monkey's tail, causing a consistently higher rate of biting. After several sessions under these conditions, a punishment phase was introduced in which the previous shock conditions were maintained, and every bite was followed immediately by another, more intense shock. Biting under these conditions was suppressed to a near-zero level. When the punishment contingency was removed, biting increased. With one subject, two additional bite-contingent stimuli were examined: (1) a milder shock that, when made contingent upon hose biting, also suppressed that response, and (2) a contingent tone that had no obvious suppressing or facilitating effect. Individual differences among subjects were extreme, but the effect of bite-contingent shock was consistent. Observations of the subjects during the punishment sessions indicated the existence of certain side effects that resulted from the use of punishment to suppress shock-induced aggression.     

Social cues, cognitive style, error magnitude, and male performance on the Felt Figure Replacement Technique.

A series of studies was undertaken to determine possible factors contributing to low predictive utility for Felt Figure Replacement Technique (FFRT) scores from normal, adult males. It was first postulated that normal adult males, compared to normal adult females, are less sensitive to social cues present in the FFRT task. Twenty-six undergraduate males and the same number of undergraduate females were asked to replace both a) department store manikins, thought to be less abstract, and then b) felt figures. While task differences were obtained, these were not dependent on gender, nor did any overall gender differences occur for three types of replacement error. The second study involved 31 college males and 33 college females replacing both felt figures and a male and female confederate. It was assumed that differential attention to social cues would be more visible in this comparison. The general results were identical to the first study.     

Effects of Self-Monitoring on the On-Task Behavior and Written Language Performance of Elementary Students with Learning Disabilities

The present study was conducted to determine the effects of self-monitoring and a changing criterion with public posting phase on student on-task behavior and written language performance. Four elementary school boys participated and were enrolled in an urban-based, elementary-level resource room for students with learning disabilities. Self-monitoring procedures for on-task behavior included the students listening to a tone recorded at 60-s intervals and responding to the question, “Am I on-task?” Written language performance involved the students writing for a 10-min. session and counting and graphing the number of words written. During baseline conditions, student on-task behavior and written language performance were collected. During the self-monitoring conditions, the students monitored their on-task behavior and written language performance simultaneously. In the changing criterion with public posting condition, the students received their goal for the day's session prior to writing, wrote, and recorded whether they met their goal. While the results show a functional relationship between self-monitoring and on-task behavior, the data for the relationship between self-monitoring and written language performance were less compelling. A greater increase occurred when the changing criterion with public posting condition was introduced. Results suggest that self-monitoring changed on-task behavior; however, further research needs to be conducted to determine the conditions that would produce comparable effects for written language performance. Several implications for students and teachers and parent training were discussed.     

Inhibition of the LH Surge by Restraint Stress in Cyclic Rats: Studies on the Role of GABAA and GABAB Receptors

There is evidence that stress can alter the activity in the brain of gamma-aminobutyricacid (GABA), a neurotransmitter that has been implicated in the regulation of LH secretion. In the present study the role of GABA in the restraint stress-induced inhibition of the LH surge was investigated in the intact cyclic rat. Intracerebroventricular (icv) administration of the GABAA receptor agonist muscimol (0.1, 0.5 or 1 μg) 5 min before the presumed onset of the pro-oestrous LH surge (at 0900 h) caused a dose dependent suppression of the surge. A single dose of the GABAB receptor agonist baclofen (1 μg; icv) injected at 0855 h postponed the onset of the LH surge, and repeated injections at 0855 and 1130 h suppressed the surge. These data indicate that GABA-ergic activity in the brain can inhibit the LH surge in the cyclic rat via GABAA and GABAB receptors. Pro-oestrous rats were subjected to 5 hrs of restraint starting at 0855 h. Pretreatment with the GABAA receptor antagonist bicuculine (1 μg; icv) at 0840, 0940 and 1040 h or pretreatment with the GABAB receptor antagonist phaclofen (10 μg; icv) at 0840 h were ineffective in preventing the restraint-induced inhibition of the LH surge. The results suggest that GABAA and GABAB receptors are not involved in the inhibitory effect of restraint stress on the LH surge.