The Effects of Intermittent Illumination on a Visual Inspection Task

Two experiments are described in which eye movements were monitored as subjects performed a simple target-spotting task under conditions of intermittent illumination produced by varying the display-screen frame rate on a computer VDU. In Experiment 1, subjects executed a saccade from a fixation point to a target which appeared randomly at a fixed eccentricity of 14 character positions to the left or right. Saccade latency did not differ reliably as a function of screen refresh rate, but average saccade extent at 70 Hz and 110 Hz was reliably shorter than at 90 Hz and 100 Hz. Experiment 2 examined the same task using a range of target eccentricities (7, 14, and 28 character positions to the left and right) and across a wider range of screen refresh rates. The results confirmed the curvilinear relationship obtained in Experiment 1, with average saccade extent reliably shorter at refresh rates of 50 Hz and 125 Hz than at 75 Hz and 100 Hz. While the effect was greater for remote targets, analyses of the proportional target error failed to show a reliable interaction between target eccentricity and display refresh rate. In contrast to Experiment 1, there was a pronounced effect of refresh rate on saccade latency (corrected for time to write the screen frame), with shorter latencies at higher refresh rates. It may be concluded that pulsation at frequencies above fusion disrupts saccade control. However, the curvilinear functional relationship between screen refresh rate and saccade extent obtained in these studies differs from previously reported effects of intermittent illumination on the average size of 'entry saccades' (the first saccade to enter a given word) in a task involving word identification (Kennedy & Murray, 1993a, 1996). This conflict of data may arise in part because withinword adjustments in viewing position, which are typical of normal reading, influence measures of average saccade extent.     

Self-efficacy as a mediator of children's achievement motivation and in-class physical activity

The present study was designed to examine the mediating effect of self-efficacy on relations of middle school students' four achievement goals with their perceptions of two motivational climates and in-class physical activity in physical education. The four achievement goals (mastery-approach, mastery-avoidance, performance-approach, and performance-avoidance), perceptions of the motivational climate (mastery- and performance-involving climates), and self-efficacy were measured in a sample of 194 students (93 boys, 101 girls) in a public school. Students' in-class physical activity was assessed using Actical Accelerometers. A series of multiple-regression analyses supported the mediating effect of self-efficacy on the relationships among students' mastery-approach goal, perceived mastery-involving climate, and physical activity.     

The dark side of comprehensive soldier fitness

Comprehensive Soldier Fitness (CSF), the focus of the January 2011 special issue of the American Psychologist, is a $125 million resilience training initiative designed to reduce and prevent the adverse psychological consequences of combat for soldiers and veterans. These are worthy goals. Soldiers and veterans deserve the best care possible, and military psychologists have critically important roles to play. But the special issue is troubling in several important respects. Elsewhere, we have offered a detailed review (Eidelson, Pilisuk, & Soldz, 2011). Here we offer only a summary of our concerns. The CSF program is a massive research project launched without pilot testing to determine, first, the effectiveness of the training in a military environment. This is highly irregular and obviously worrisome considering the stakes. No evidence was provided indicating that CSF received preliminary review by an independent ethics review board. There are other ethically fraught possibilities.This special issue reveals much about current moral challenges facing the profession of psychology.     

Perception of object-context relations: eye-movement analyses in infants and adults

Twenty-eight 4-month-olds' and twenty-two 20-year-olds' attention to object-context relations was investigated using a common eye-movement paradigm. Infants and adults scanned both objects and contexts. Infants showed equivalent preferences for animals and vehicles and for congruent and incongruent object-context relations overall, more fixations of objects in congruent object-context relations, more fixations of contexts in incongruent object-context relations, more fixations of objects than contexts in vehicle scenes, and more fixation shifts in incongruent than congruent vehicle scenes. Adults showed more fixations of congruent than incongruent scenes, vehicles than animals, and objects than contexts; equal fixations of animals and their contexts but more fixations of vehicles than their contexts; and more shifts of fixation when inspecting animals in context than vehicles in context. These findings for location, number, and order of eye movements indicate that object-context relations play a dynamic role in the development and allocation of attention.     

Electrophysiological responses to coarticulatory and word level miscues

The influence of coarticulation cues on spoken word recognition is not yet well understood. This acoustic/phonetic variation may be processed early and recognized as sensory noise to be stripped away, or it may influence processing at a later prelexical stage. The present study used event-related potentials (ERPs) in a picture/spoken word matching paradigm to examine the temporal dynamics of stimuli systematically violating expectations at three levels: entire word (lexical), initial phoneme (phonemic), or in coarticulation cues contained in the initial phoneme (subphonemic). We found that both coarticulatory and phonemic mismatches resulted in increased negativity in the N280, interpreted as indexing prelexical processing of subphonemic information. Further analyses revealed that the point of uniqueness differentially modulated subsequent early or late negativity depending on whether the first or second segment matched expectations, respectively. Finally, it was found that word-level but not coarticulatory mismatches modulated the later-going N400 component, indicating that subphonemic information does not influence word-level selection provided no lexical change has occurred. The results indicate that acoustic/phonetic variation resulting from coarticulation is preserved in and influences spoken word recognition as it becomes available, particularly during prelexical processing.     

Assessing categorization performance at the individual level: a comparison of Monte Carlo simulation and probability estimate model procedures

Two analytical procedures for identifying young children as categorizers, the Monte Carlo Simulation and the Probability Estimate Model, were compared. Using a sequential touching method, children aged 12, 18, 24, and 30 months were given seven object sets representing different levels of categorical classification. From their touching performance, the probability that children were categorizing was then determined independently using Monte Carlo Simulation and the Probability Estimate Model. The two analytical procedures resulted in different percentages of children being classified as categorizers. Results using the Monte Carlo Simulation were more consistent with group-level analyses than results using the Probability Estimate Model. These findings recommend using the Monte Carlo Simulation for determining individual categorizer classification.     

Metacognition in monkeys during an oculomotor task

This study investigated whether rhesus monkeys show evidence of metacognition in a reduced, visual oculomotor task that is particularly suitable for use in fMRI and electrophysiology. The 2-stage task involved punctate visual stimulation and saccadic eye movement responses. In each trial, monkeys made a decision and then made a bet. To earn maximum reward, they had to monitor their decision and use that information to bet advantageously. Two monkeys learned to base their bets on their decisions within a few weeks. We implemented an operational definition of metacognitive behavior that relied on trial-by-trial analyses and signal detection theory. Both monkeys exhibited metacognition according to these quantitative criteria. Neither external visual cues nor potential reaction time cues explained the betting behavior; the animals seemed to rely exclusively on internal traces of their decisions. We documented the learning process of one monkey. During a 10-session transition phase, betting switched from random to a decision-based strategy. The results reinforce previous findings of metacognitive ability in monkeys and may facilitate the neurophysiological investigation of metacognitive functions.     

Small samples do not cause greater accuracy--but clear data may cause small samples: comment on Fiedler and Kareev (2006)

Fiedler and Kareev (2006) have claimed that taking a small sample of information (as opposed to a large one) can, in certain specific situations, lead to greater accuracy--beyond that gained by avoiding fatigue or overload. Specifically, they have argued that the propensity of small samples to provide more extreme evidence is sufficient to create an accuracy advantage in situations of high caution and uncertainty. However, a close examination of Fiedler and Kareev's experimental results does not reveal any strong reason to conclude that small samples can cause greater accuracy. We argue that the negative correlation between sample size and accuracy that they reported (found only for the second half of Experiment 1) is also consistent with mental fatigue and that their data in general are consistent with the causal structure opposite to the one they suggest: Rather than small samples causing clear data, early clear data may cause participants to stop sampling. More importantly, Experiment 2 provides unequivocal evidence that large samples result in greater accuracy; Fiedler and Kareev only found a small sample advantage here when they artificially reduced the data set. Finally, we examine the model that Fiedler and Kareev used; they surmised that decision makers operate with a fixed threshold independent of sample size. We discuss evidence for an alternative (better performing) model that incorporates a dynamic threshold that lowers with sample size. We conclude that there is no evidence currently to suggest that humans benefit from taking a small sample, other than as a tactic for avoiding fatigue, overload, and/or opportunity cost-that is, there is no accuracy advantage inherent to small samples.