Effects of processing speed on intelligence may be underestimated: Comment on Demetriou et al. (2013)

This commentary suggests ways to extend research by Demetriou et al. (2013), who may have underestimated the effects of processing speed on the development of intelligence. It argues that future research should consider variability in processing speed, complexity in speed tasks, and reaction times excluded from speed estimates.     

Executive function and intelligence in the resolution of temporary syntactic ambiguity: an individual differences investigation

In the current study, we examined the role of intelligence and executive functions in the resolution of temporary syntactic ambiguity using an individual differences approach. Data were collected from 174 adolescents and adults who completed a battery of cognitive tests as well as a sentence comprehension task. The critical items for the comprehension task consisted of object/subject garden paths (e.g., While Anna dressed the baby that was small and cute played in the crib), and participants answered a comprehension question (e.g., Did Anna dress the baby?) following each one. Previous studies have shown that garden-path misinterpretations tend to persist into final interpretations. Results showed that both intelligence and processing speed interacted with ambiguity. Individuals with higher intelligence and faster processing were more likely to answer the comprehension questions correctly and, specifically, following ambiguous as opposed to unambiguous sentences. Inhibition produced a marginal effect, but the variance in inhibition was largely shared with intelligence. Conclusions focus on the role of individual differences in cognitive ability and their impact on syntactic ambiguity resolution.     

Self-organizing individual differences in brain development

Brain development is self-organizing in that the unique structure of each brain evolves in unpredictable ways through recursive modifications of synaptic networks. In this article, I review mechanisms of neural change in real time and over development, and I argue that change at each of these time scales embodies principles of self-organizing systems. I demonstrate how corticolimbic configurations that emerge within occasions lay down synaptic structure across occasions, giving rise to individual trajectories that become entrenched with age. Emotions have a powerful influence on this process.This is because the neural processes mediating emotion consolidate patterns of activation across the brain, through their enhancement of inter-regional coordination in real time and their contribution to synaptic shaping over development. The loss of corticolimbic plasticity with age is an unfortunate fact of development, but it is compensated in part by transitional phases and individual learning experiences through which habits are modified or replaced. I emphasize variations in inter-systemic coupling as a key mediator of developing individual differences, and I discuss the acquisition of anxious/depressive appraisals as an example.     

Evidence for mental ability related individual differences in the attentional blink obtained by an analysis of the P300 component

Attentional blink (AB) refers to impaired identification of a target (T2) when this target follows a preceding target (T1) after about 150-450 ms within a stream of rapidly presented stimuli. Previous research on a possible relation between AB and mental ability (MA) turned out to be highly ambiguous. The present study investigated MA-related individual differences in consolidation of T2 in working memory during the AB as indicated by the P300 component of the event-related potential. Thirty high (HA) and 30 low MA (LA) female participants performed an AB task while their brain activity was recorded. The AB did not differ between the two groups. HA individuals exhibited a larger P300 amplitude and longer P300 latencies during the AB suggesting higher mental effort. This higher mental effort, however, did not result in better performance presumably because of more competition between target and distractor stimuli in HA than LA individuals.     

Understanding causal conditionals: A study of individual differences

Previous studies have suggested that a minority of university students, of lower cognitive ability, are inclined to interpret abstract conditional statements, if p then q, as if they were conjunctions: p and q. In the present study we administered the conditional truth table task to a large sample of students (n = 160), but using realistic, everyday causal conditionals. We also measured their general intelligence. While individual differences were found, these were not consistent with some participants adopting a conjunctive interpretation of such statements. Rather, it appears that students of lower cognitive ability are rather likely to assume that a conditional implies its converse, so that it means also if q then p. The results are discussed with reference to the suppositional theory of conditionals and our more general account of hypothetical thinking.     

Domain-specificity and individual differences in worry

Worrying is generally perceived to be an undesirable mental state. An evolutionary approach suggests, however, despite the potential distress, worry may function to focus individuals’ attention on evolutionarily-relevant tasks. In the current study (N = 193), we demonstrated that participants’ primary worries were focused within domains central to reproductive success and mate-value. Furthermore, mating strategy predicted worries in the domains of social status and mating. Neuroticism, as an individual difference reflecting vigilance to threats, was correlated with worry about fitness-relevant but not fitness-irrelevant domains. The current study documents the first domain-specific assessment of worries and complements this analysis with intriguing individual difference predictors of worry.     

Impact of individual differences upon emotion-induced memory trade-offs

After seeing a scene containing an emotional component (e.g., a snake in a forest) people often demonstrate a “trade-off” in memory, where memory for the emotional component (e.g., the snake) is good, but memory for the non-emotional elements (e.g., the forest) is poor. The result is an incomplete memory retaining central emotional information at the expense of neutral background information. Though almost everyone demonstrates the trade-off, there may be individual differences in the magnitude of the effect. We investigated whether differences in the strength of the trade-off would correlate with anxiety levels, working memory capacity, and executive functioning abilities. Sixty-four participants studied scenes comprised of a negative or neutral item placed on a neutral background, and memory was later tested for items and backgrounds separately. The magnitude of the trade-off correlated positively with anxiety and negatively with visuospatial working memory and executive function. These results suggest that greater anxiety, poor visuospatial working memory, and poor executive function may inhibit formation of complete mental representations of these complex emotional scenes.     

Sustained attention in language production: An individual differences investigation

Whereas it has long been assumed that most linguistic processes underlying language production happen automatically, accumulating evidence suggests that these processes do require some form of attention. Here we investigated the contribution of sustained attention: the ability to maintain alertness over time. In Experiment 1, participants’ sustained attention ability was measured using auditory and visual continuous performance tasks. Subsequently, employing a dual-task procedure, participants described pictures using simple noun phrases and performed an arrow-discrimination task while their vocal and manual response times (RTs) and the durations of their gazes to the pictures were measured. Earlier research has demonstrated that gaze duration reflects language planning processes up to and including phonological encoding. The speakers’ sustained attention ability correlated with the magnitude of the tail of the vocal RT distribution, reflecting the proportion of very slow responses, but not with individual differences in gaze duration. This suggests that sustained attention was most important after phonological encoding. Experiment 2 showed that the involvement of sustained attention was significantly stronger in a dual-task situation (picture naming and arrow discrimination) than in simple naming. Thus, individual differences in maintaining attention on the production processes become especially apparent when a simultaneous second task also requires attentional resources.     

Assessing individual differences in the degree to which people are committed to following their beliefs

The authors developed a new dispositional measure of Commitment to Beliefs (CTB)—the degree to which people feel it is important to follow their value-expressive beliefs—across three phases of research. In Phases 1 and 2 (Studies 1-4), the CTB scale demonstrated strong internal consistency, and convergent and discriminant validity. Phase 3 demonstrated the scale’s predictive validity: high-CTB individuals were more likely to report engaging in activities during the past month and year that followed directly from their beliefs (Study 5), act on their beliefs when given the opportunity (Study 6), and show more polarized attitudes toward ideologically-relevant groups (Study 7). These findings illustrate the utility of a dispositional approach for examining the extent to which people follow their beliefs.     

The factorial structure of individual differences in visual perception

Although at first glance the way we perceive the world is similar for most individuals and resembles a veridical interpretation of the environment, the persistent individual differences found in many perceptual processes continue to inspire and confuse researchers. Despite numerous attempts to map out the reliable factors and correlates of individual variance in perception, the factorial structure of vision has remained elusive. The current article reviews recent developments in the study of individual differences in perception with a focus on work that has applied latent variable techniques for analysing performance across multiple visual paradigms. As this overview reveals, studies that have attempted to answer the question whether one general or several specific factors best describe vision tend to reject the monolithic view. Some general notes are also provided regarding pitfalls that should be taken into account when designing such research in the future.     

Sex differences in brain activity related to general and emotional intelligence

The study investigated gender differences in resting EEG (in three individually determined narrow alpha frequency bands) related to the level of general and emotional intelligence. Brain activity of males decreased with the level of general intelligence, whereas an opposite pattern of brain activity was observed in females. This difference was most pronounced in the upper-alpha band which is related to semantic memory processes. It was further found that highly intelligent males displayed greater decoupling of frontal brain areas, whereas highly intelligent females showed more coupling between frontal and parietal/occipital brain areas. Similar, but less significant differences were observed for the two area scores of strategic and experiential emotional intelligence. It appears that males and females have different resting EEG correlates of IQ.     

Executive functions in decision making: An individual differences approach

This individual differences study examined the relationships between three executive functions (updating, shifting, and inhibition), measured as latent variables, and performance on two cognitively demanding subtests of the Adult Decision Making Competence battery: Applying Decision Rules and Consistency in Risk Perception. Structural equation modelling showed that executive functions contribute differentially to performance in these two tasks, with Applying Decision Rules being mainly related to inhibition and Consistency in Risk Perception mainly associated to shifting. The results suggest that the successful application of decision rules requires the capacity to selectively focus attention and inhibit irrelevant (or no more relevant) stimuli. They also suggest that consistency in risk perception depends on the ability to shift between judgement contexts.     

Hormones and personality: Testosterone as a marker of individual differences

Recently, testosterone (T) has been linked to behaviors that are conceptually related to dominance as a personality characteristic. Although evidence for this association is growing, the psychometric properties of T as an individual difference variable have been largely neglected. For T to be considered a biological marker of dispositional dominance it is critical that it demonstrates high test–retest reliability and good convergent and discriminant validity. Two studies tested the temporal stability of salivary T in humans and the relationship between T and traditional measures of personality. Across both studies, test–retest reliability for T was high and comparable to the short-term stability of questionnaire-based and implicitly assessed personality assessment instruments. In being modestly correlated with self-reported dominance, T showed some evidence of convergent validity. In being statistically independent from conceptually unrelated personality constructs (such as Emotional Stability and Openness to Experience) it showed good evidence of discriminant validity. The findings strengthen the psychometric foundation for using T as a hormonal marker of individual differences.     

Routine cognitive errors: A trait-like predictor of individual differences in anxiety and distress

Five studies (N=361) sought to model a class of errors—namely, those in routine tasks—that several literatures have suggested may predispose individuals to higher levels of emotional distress. Individual differences in error frequency were assessed in choice reaction-time tasks of a routine cognitive type. In Study 1, it was found that tendencies toward error in such tasks exhibit trait-like stability over time. In Study 3, it was found that tendencies toward error exhibit trait-like consistency across different tasks. Higher error frequency, in turn, predicted higher levels of negative affect, general distress symptoms, displayed levels of negative emotion during an interview, and momentary experiences of negative emotion in daily life (Studies 2–5). In all cases, such predictive relations remained significant with individual differences in neuroticism controlled. The results thus converge on the idea that error frequency in simple cognitive tasks is a significant and consequential predictor of emotional distress in everyday life. The results are novel, but discussed within the context of the wider literatures that informed them.     

Common and distinct factors in decision making under ambiguity and risk: A psychometric study of individual differences

The relation between decision making under ambiguity and risky decision making was examined. In Studies 1 and 2, choices under ambiguity were measured for a large sample receiving an Ellsberg-type Ambiguity-Probability Tradeoff Task. Participants with extreme scores were recruited for Part 2 of each study which consisted of a risky decision making task (Study 1) or a series of decisions under ambiguity in “real life” scenarios (Study 2). Despite a time gap of up to 2 months, individual differences in scores on Part 1 predicted scores on Part 2. In Study 3 participants received in a single session several risky decision making tasks, several measures of decision making under ambiguity, and several personality scales related to uncertainty and decision making style. Taken together, the findings support the existence of a stable dispositional trait to reduce uncertainty in decision making but also task-specific differences related to gains and losses.     

Beta-MPT: Multinomial processing tree models for addressing individual differences

Traditionally, multinomial processing tree (MPT) models are applied to groups of homogeneous participants, where all participants within a group are assumed to have identical MPT model parameter values. This assumption is unreasonable when MPT models are used for clinical assessment, and it often may be suspect for applications to ordinary psychological experiments. One method for dealing with parameter variability is to incorporate random effects assumptions into a model. This is achieved by assuming that participants’ parameters are drawn independently from some specified multivariate hyperdistribution. In this paper we explore the assumption that the hyperdistribution consists of independent beta distributions, one for each MPT model parameter. These beta-MPT models are ‘hierarchical models’, and their statistical inference is different from the usual approaches based on data aggregated over participants. The paper provides both classical (frequentist) and hierarchical Bayesian approaches to statistical inference for beta-MPT models. In simple cases the likelihood function can be obtained analytically; however, for more complex cases, Markov Chain Monte Carlo algorithms are constructed to assist both approaches to inference. Examples based on clinical assessment studies are provided to demonstrate the advantages of hierarchical MPT models over aggregate analysis in the presence of individual differences.     

Factors contributing to individual differences in facial expression categorisation

Individuals vary in perceptual accuracy when categorising facial expressions, yet it is unclear how these individual differences in non-clinical population are related to cognitive processing stages at facial information acquisition and interpretation. We tested 104 healthy adults in a facial expression categorisation task, and correlated their categorisation accuracy with face-viewing gaze allocation and personal traits assessed with Autism Quotient, anxiety inventory and Self-Monitoring Scale. The gaze allocation had limited but emotion-specific impact on categorising expressions. Specifically, longer gaze at the eyes and nose regions were coupled with more accurate categorisation of disgust and sad expressions, respectively. Regarding trait measurements, higher autistic score was coupled with better recognition of sad but worse recognition of anger expressions, and contributed to categorisation bias towards sad expressions; whereas higher anxiety level was associated with greater categorisation accuracy across all expressions and with increased tendency of gazing at the nose region. It seems that both anxiety and autistic-like traits were associated with individual variation in expression categorisation, but this association is not necessarily mediated by variation in gaze allocation at expression-specific local facial regions. The results suggest that both facial information acquisition and interpretation capabilities contribute to individual differences in expression categorisation within non-clinical populations.