Dissociation of sensory facilitation and decision bias in statistical learning

ABSTRACT

The detection of regularities in the sensory environment, known as statistical learning, is an important brain function that has been observed in many experimental contexts. In these experiments, statistical learning of patterned sensory stimulation leads to improvements in the speed and/or accuracy with which subsequent stimuli are recognized. That is, statistical learning facilitates the transformation of sensory stimuli into motor responses, but the mechanism by which this occurs is unclear. Statistical learning could improve the efficiency of sensory processing, or it could bias responses toward particular outcomes. The distinction is important, as these different hypotheses imply different functions and different neural substrates for statistical learning. Here we address this problem by studying statistical learning as a decision-making process, which allows us to leverage the extensive computational literature on this topic. Specifically we describe a method for applying the Diffusion Decision Model (DDM) to isolate different sensory and cognitive processes associated with decision-making. The results indicate that statistical learning improves performance on a visual learning task in two distinct ways: by altering the efficiency of sensory processing and by introducing biases in the decision-making process. By fitting the parameters of the DDM to data from individual subjects, we find that the prominence of these two factors differed substantially across the population, and that these differences were predictive of individual performance on the psychophysical task. Overall, these results indicate that different cognitive processes can be recruited by statistical learning, and that the DDM is a powerful framework for detecting these influences.     

Goal-driven reasoning overcomes cell D neglect in contingency judgements

Research on contingency judgement typically shows cell weight inequality such that the information in cell A of a contingency table is considered more relevant than the information in cell D, even though both kinds of information have the same confirmatory meaning. Two studies tested whether goal-driven reasoning can lead people to realise the value of the information in cell D. Participants' goal to defend a particular conclusion for which the information in cell D was helpful was manipulated. Whereas participants who did not have that goal displayed the usual cell D neglect, goal-driven participants for whom cell D contained goal-relevant information considered it important. More importantly, in subsequent tasks with different contents where participants were no longer driven by any goal, they continued to consider information in cell D relevant (Study 1), and they were more likely to make correct contingency judgements, which depended on considering cell D (Study 2).     

Social priming of hemispatial neglect affects spatial coding: Evidence from the Simon task

In the Simon effect (SE), choice reactions are fast if the location of the stimulus and the response correspond when stimulus location is task-irrelevant; therefore, the SE reflects the automatic processing of space. Priming of social concepts was found to affect automatic processing in the Stroop effect. We investigated whether spatial coding measured by the SE can be affected by the observer’s mental state. We used two social priming manipulations of impairments: one involving spatial processing - hemispatial neglect (HN) and another involving color perception - achromatopsia (ACHM). In two experiments the SE was reduced in the “neglected” visual field (VF) under the HN, but not under the ACHM manipulation. Our results show that spatial coding is sensitive to spatial representations that are not derived from task-relevant parameters, but from the observer’s cognitive state. These findings dispute stimulus-response interference models grounded on the idea of the automaticity of spatial processing.     

Weigh(t)ing for Awareness

We wished to learn if weight perception can be extinguished by studying two patients with right hemisphere brain damage. When lifting weights simultaneously, a patient with right frontal damage was not biased in her judgments of which weight was heavier. By contrast, a patient with right parietal damage reported left-sided weights as being lighter than those on the right. Psychophysical power functions revealed that her awareness of increasing weights on the left was dampened compared to the right when lifting weights individually on each side. Strikingly, her awareness of weight changes on the left was completely abolished when she lifted weights in both hands simultaneously. She demonstrated an unusual split in awareness, being motorically aware of and actively engaged with left-sided weights while being unaware of their incremental changes.     

Is Physical Abuse,Neglect, or a Combination of Both More Predictive of Delinquent Behavior in a High-Risk Population?

This study explored early abuse type and severity in relation to delinquency utilizing an archival longitudinal data set. These data were collected every 2 years, starting at age 4, from the individuals, caregivers, and teachers. Mean differences tests were conducted to determine how delinquency scores varied by abuse type and severity. These analyses used Child Protective Services reports of the type and severity of abuse as independent measures and the behavior problem scale from the Child Behavior Checklist, Youth Self Report, and Teacher Report Form as independent measures. Follow-up analyses of variance and post-hoc tests were conducted as necessary to clarify the relationship between abuse and delinquency. Although results did not reach significance, a relatively small mean difference was discovered between severity types (more severe maltreatment history demonstrating higher levels of delinquency) for teacher ratings of delinquency.     

Creating Brand Meaning: A Review and Research Agenda

In this paper I review, from the perspective of experimental research, studies that have examined how brands acquire cultural meaning, and suggest future research directions. McCracken's (Journal of Consumer Research, 13 , 1986 and 71) model of the meaning transfer process gained influence about thirty years ago, but experimental studies of the processes it posited have been limited in their scope. The review is organized around three questions. First, what should be the dependent variables: the types of meanings that can adhere to brands? Second, what have we learned from studies on the types of visual, sensory, and human cues that are the sources of particular types of brand meaning—our independent variables? Third, what do we know, and need to know, about the inferential and other processes through which consumers “take possession” of these brand meanings from these cues? The review concludes with a research agenda.     

The caregiving relationship under stress: foster carers’ experience of loss of the sense of self

This paper is an account of a piece of research which involved interviewing six foster carers who had ended a placement with a child under the age of five with an early experience of abuse and neglect. The paper describes one of the themes that emerged from the data analysis, the loss of the sense of self in the foster carers, and argues that the experience of attempting to provide care for these children led to internal shifts in the carers that reverberated throughout the network around the child. The paper suggests that knowing about the external reasons for placement breakdown is not enough without taking into account the impact on the internal world of the foster carers and the emotional impact of attempting to provide care for a child who has experienced abuse and neglect.