An Investigation of the Perruchet Effect

The single versus dual processing systems debate is one that has taken centre stage in the human learning literature. The existence of a propositional reasoning system is not disputed in this thesis, but whether a secondary processing system is required is. This is specifically tackled by investigating the mechanisms which underlie the Perruchet effect, an effect which is used widely to support a dual processing systems stance. During the Perruchet paradigm a single conditioned stimulus (CS) is partially reinforced by an unconditioned stimulus (US). Conditioned responding is found to dissociate from conscious expectation of the US across runs of reinforced (CS-US) and non-reinforced (CS-noUS) trials. US expectancy ratings typically fluctuate in accordance with the gambler’s fallacy. Conversely associative mechanisms are postulated to govern the variable strength of the conditioned response (CR). The associative nature of the CR is the subject of this thesis as it is queried whether a non-associative mechanism might explain this result. Three different methodological strands of the Perruchet effect are studied in this thesis: autonomic conditioning (Chapters 2 and 3), eyeblink conditioning (Chapter 3) and reaction time (RT) studies (Chapters 4 and 5). Additionally transcranial magnetic stimulation (Chapter 5) and computational modelling (Chapter 6) are used as tools to investigate the CR. It is concluded in this thesis that the associative explanation of the CR in the Perruchet effect cannot be dismissed, although the strength of such an effect has perhaps been overstated in previous research. Evidence from autonomic conditioning provides the strongest evidence for an influence of CS-US association in the Perruchet effect as removal of the CS abolishes the CR in this thesis (Chapters 2 and 3). However, evidence from the eyeblink (Chapter 3) and RT (Chapters 4 and 5) variants of the effect suggest that there is undoubtedly a non-associative contribution to these effects. Although the exact mechanistic nature of this non-associative mechanism is unknown, priming is given as a possible explanation, and it is confirmed that such effects cannot be explained propositionally (Chapter 5). Overall a single processing system explanation of learning is not sufficient to explain the Perruchet effect.ESR

An Investigation of the Perruchet Effect

The single versus dual processing systems debate is one that has taken centre stage in the human learning literature. The existence of a propositional reasoning system is not disputed in this thesis, but whether a secondary processing system is required is. This is specifically tackled by investigating the mechanisms which underlie the Perruchet effect, an effect which is used widely to support a dual processing systems stance. During the Perruchet paradigm a single conditioned stimulus (CS) is partially reinforced by an unconditioned stimulus (US). Conditioned responding is found to dissociate from conscious expectation of the US across runs of reinforced (CS-US) and non-reinforced (CS-noUS) trials. US expectancy ratings typically fluctuate in accordance with the gambler’s fallacy. Conversely associative mechanisms are postulated to govern the variable strength of the conditioned response (CR). The associative nature of the CR is the subject of this thesis as it is queried whether a non-associative mechanism might explain this result. Three different methodological strands of the Perruchet effect are studied in this thesis: autonomic conditioning (Chapters 2 and 3), eyeblink conditioning (Chapter 3) and reaction time (RT) studies (Chapters 4 and 5). Additionally transcranial magnetic stimulation (Chapter 5) and computational modelling (Chapter 6) are used as tools to investigate the CR. It is concluded in this thesis that the associative explanation of the CR in the Perruchet effect cannot be dismissed, although the strength of such an effect has perhaps been overstated in previous research. Evidence from autonomic conditioning provides the strongest evidence for an influence of CS-US association in the Perruchet effect as removal of the CS abolishes the CR in this thesis (Chapters 2 and 3). However, evidence from the eyeblink (Chapter 3) and RT (Chapters 4 and 5) variants of the effect suggest that there is undoubtedly a non-associative contribution to these effects. Although the exact mechanistic nature of this non-associative mechanism is unknown, priming is given as a possible explanation, and it is confirmed that such effects cannot be explained propositionally (Chapter 5). Overall a single processing system explanation of learning is not sufficient to explain the Perruchet effect.ESR

Can US sensitization account for the electrodermal variant of the Perruchet effect?

Copyright © 2013 Cognitive Science SocietyDuring experiments employing Perruchet's (1985) paradigm there are runs of reinforced (CS-US) trials and non-reinforced (CS-noUS) trials. Conditioned responding (CR) is measured, for example, using eyeblink responses (Perruchet, 1985), reaction times (Perruchet, Cleeremans, & Destrebeceqz, 2006), or changes in skin conductance (SCR; McAndrew, Jones, McLaren, & McLaren, 2012), as well as an online measure of expectancy for the unconditioned stimulus (US). A double dissociation between CR and conscious expectancy of the US is typically found, whereby expectancy of the US decreases while the CR increases across runs of successively reinforced trials. A gambler’s fallacy explanation can be offered for the expectancy data, whereas an associative explanation can be used to explain variations in the CR (consistent with the dual processing theory of McLaren, Green, & Mackintosh, 1994). However, skeptics of this effect have proposed nonassociative explanations of the CR data seen in these experiments. They note that every CS-US pairing is confounded by the presence of the US. Therefore, it is possible that US sensitization, the phenomenon whereby repeated US presentations leads to stronger unconditioned responding to the US, could produce the increasing CR pattern with successive reinforcements (Weidemann, Tangen, Lovibond, & Mitchell, 2009). Two experiments are presented investigating whether US sensitization can explain the recently published electrodermal version of the Perruchet effect.ESR

Why decision making may not require awareness.

CommentJournal ArticleCopyright © Cambridge University Press 2014Newell & Shanks (N&S) argue against the idea that any significant role for unconscious influences on decision making has been established by research to date. Inasmuch as this conclusion applies to the idea of an "intelligent cognitive unconscious," we would agree. Our concern is that the article could lead the unwary to conclude that there are no unconscious influences on decision making - and never could be. We give reasons why this may not be the case

Genetic Approaches To The Analysis of Body Colouration in Nile Tilapia (Oreochromis niloticus)

Body colouration in tilapia is an important trait affecting consumer preference. In the Nile tilapia (Oreochromis niloticus), there are three colour variants which are normal (wild type), red and blond. In some countries, the red variant is important and reaches higher prices in the market. However, one major problem regarding red tilapia culture is their body colouration which is often associated with blotching (mainly black but also red) which is undesirable for the consumer. The overall aim of this work was to expand knowledge on various aspects of body colouration in Nile tilapia using genetic approaches. The results of this research are presented as four different manuscripts. The manuscripts (here referred as Papers) have either been published (Paper IV) or are to be submitted (Paper I, II and III) in relevant peer reviewed journals. Paper I and II investigated the inheritance of black blotching and other body colour components of the red body colour. Specifically, Paper I consisted of two preliminary trials (Trial 1 and 2), to look at the ontogeny of black blotching and body colour components over a period of six months. Trial 1 investigated the effect of tank background colour (light vs dark) on black blotching and other body colour components and was carried out using a fully inbred (all female) clonal red line. Trial 2 was carried out using mixed sex fish and was aimed to investigate the association of black blotching with the sex of the fish. The results from this study were used to guide the experiment described in Paper II. Sixteen red sires with various levels of black and red blotching were crossed to clonal females and the inheritance of blotching and other body colour components were investigated using parent-offspring regressions. The results showed no significant heritability for black blotching and body redness, but a significant correlation for body redness and black blotching was found in female offspring at one sampling point suggesting that attempts to increase body redness may increase black blotching, as had been hypothesized. Paper III was divided into two parts. The first objective was to map the blond locus onto the tilapia linkage map and the second was to investigate the interaction of the blond and red genes on black blotching using the blond-linked markers to distinguish different blond genotypes in heterozygous red fish (i.e. RrBlbl or Rrblbl). In the blond fish, the formation of melanin is almost blocked via much reduced melanophores and this feature may be able to help reducing the black blotching in red tilapia. Two intraspecific families (O. niloticus) and one interspecific family (O. aureus and O. niloticus) were used as mapping families and the blond locus was located in LG5. Four out of eight markers were successfully used to assess the interaction of blond on red blotched fish. The blond gene did not significantly reduce the area of blotching but did reduce the saturation (paler blotching) and enhanced the redness of body colour in the Rrblbl fish compared to the RrBlbl group. Finally, Paper IV aimed to find out the effect of male colouration on reproductive success in Nile tilapia. A choice of one wild type male and one red male was presented to red or wild type females and these fish were allowed to spawn under semi-natural spawning conditions. Eggs were collected from the female’s mouth after spawning and paternity was assessed using microsatellite genotyping and phenotype scoring. No significant departures from equal mating success were observed between the red and wild type males, however there was a significant difference between the red and wild type females in the frequency of secondary paternal contribution to egg batches. The results suggest that mating success of wild type and red tilapia is approximately equal. The results from this research help to broaden our knowledge and understanding on the aspects of body colouration in Nile tilapia and provide fundamental information for further research

Conserved Genes Act as Modifiers of Invertebrate SMN Loss of Function Defects

Spinal Muscular Atrophy (SMA) is caused by diminished function of the Survival of Motor Neuron (SMN) protein, but the molecular pathways critical for SMA pathology remain elusive. We have used genetic approaches in invertebrate models to identify conserved SMN loss of function modifier genes. Drosophila melanogaster and Caenorhabditis elegans each have a single gene encoding a protein orthologous to human SMN; diminished function of these invertebrate genes causes lethality and neuromuscular defects. To find genes that modulate SMN function defects across species, two approaches were used. First, a genome-wide RNAi screen for C. elegans SMN modifier genes was undertaken, yielding four genes. Second, we tested the conservation of modifier gene function across species; genes identified in one invertebrate model were tested for function in the other invertebrate model. Drosophila orthologs of two genes, which were identified originally in C. elegans, modified Drosophila SMN loss of function defects. C. elegans orthologs of twelve genes, which were originally identified in a previous Drosophila screen, modified C. elegans SMN loss of function defects. Bioinformatic analysis of the conserved, cross-species, modifier genes suggests that conserved cellular pathways, specifically endocytosis and mRNA regulation, act as critical genetic modifiers of SMN loss of function defects across species

A RT investigation of the Perruchet effect (2)

Human dataset from a go/nogo reaction time psychology experiment. This data was collected as part of the doctoral studies of the thesis "An investigation of the Perruchet effect".Within the reaction time (RT) version of the Perruchet effect a single stimulus (the conditioned stimulus, CS) is paired with a second stimulus (the unconditioned stimulus, US) on half the trials and on the other half the trials the US is not presented. Conditioned responding to the CS is typically found to dissociate from conscious expectancy for the US. This experiment is a basic replication of this effect using modified recording procedures. In this experiment there were two USs, one requiring participants to make a speeded reaction time response (goUS trials) and another the withholding of said response (nogoUS trials). Participants were required to make expectancy ratings on every trial about the likelihood of the nogoUS being presented.ESRC +3 fundin

A SCR investigation of the Perruchet effect (3)

Human dataset from an electrodermal psychology experiment. This data was collected as part of the doctoral studies of the thesis "An investigation of the Perruchet effect".This study aimed to determine whether the conditioned stimulus (CS) in the electrodermal version of the Perruchet effect is instrumental to the production of said effect. In the Perruchet effect a single stimulus (the CS) is paired with a second stimulus (the unconditioned stimulus, US) on half the trials and on the other half of the trials the US is not presented. Conditioned responding to the CS is typically found to dissociate from conscious expectancy for the US. In this experiment the US is an electric shock and the conditioned response is change in skin conductance response (SCR). Importantly there is only a discrete CS in this experiment. If the CS is important in the production of the Perruchet effect then manipulation of the CS-US relationship in this experiment should distort SCR, whereas if the CS-US relationship is not important then a similar SCR pattern should be produced to that seen in previous Perruchet experiments.ESRC +3 fundin