Central mechanisms in the perception of reward

The perception of reward is crucial in many psychological processes. Wise (1982) has suggested that the neurotransmitter dopamine is involved in producing 'hedonic' responses to rewards. Dopamine is also involved in the control of movement and hunger. Testing dopamine's role in reward perception is therefore complicated by these other actions; the effects of manipulations can often be interpreted as actions on hunger or motor control, rather than on reward. Two methods are described in this thesis which isolate reward effects. The effects of dopaminergic drugs on the rewarding impact of exploration were investigated. The use of exploration eliminates the influence of hunger, while the impact of motor deficits was reduced by using choice measures. Control experiments assessed effects on activity and emotionality. Results indicated that dopamine was involved in exploratory reinforcement independently of its roles in hunger or simple motor control. Tests of whether dopamine is involved in hedonia, or merely in engaging responses to reinforcers, used the 'behavioural contrast' paradigm. Contrast occurs when animals over-react to unexpected changes in reinforcement and allow response elicitation effects to be dissociated from effects on hedonia. Although the dopamine anatagonist a-flupenthixol did not affect contrast induced by changes in reinforcement value, the introduction or withdrawal of the drug could, itself, induce contrast effects. It is concluded that dopamine is involved in hedonia independently of any involvement in response elicitation. A speculative model of the nature of dopamine’s involvement in hedonia is proposed and its implications for our understanding of Parkinson’s disease and schizophrenia, in which dopamine dysfunctions are implicated, are discussed

The deep past in the virtual present: developing an interdisciplinary approach towards understanding the psychological foundations of palaeolithic cave art

Virtual Reality (VR) has vast potential for developing systematic, interdisciplinary studies to understand ephemeral behaviours in the archaeological record, such as the emergence and development of visual culture. Upper Palaeolithic cave art forms the most robust record for investigating this and the methods of its production, themes, and temporal and spatial changes have been researched extensively, but without consensus over its functions or meanings. More compelling arguments draw from visual psychology and posit that the immersive, dark conditions of caves elicited particular psychological responses, resulting in the perception—and depiction—of animals on suggestive features of cave walls. Our research developed and piloted a novel VR experiment that allowed participants to perceive 3D models of cave walls, with the Palaeolithic art digitally removed, from El Castillo cave (Cantabria, Spain). Results indicate that modern participants’ visual attention corresponded to the same topographic features of cave walls utilised by Palaeolithic artists, and that they perceived such features as resembling animals. Although preliminary, our results support the hypothesis that pareidolia—a product of our cognitive evolution—was a key mechanism in Palaeolithic art making, and demonstrates the potential of interdisciplinary VR research for understanding the evolution of art, and demonstrate the potential efficacy of the methodology

Object-based attention without awareness

Attention and awareness are often considered to be related. Some forms of attention can, however, facilitate the processing of stimuli that remain unseen. It is unclear whether this dissociation extends beyond selection on the basis of primitive properties, such as spatial location, to situations in which there are more complex bases for attentional selection. The experiment described here shows that attentional selection at the level of objects can take place without giving rise to awareness of those objects. Pairs of objects were continually masked, which rendered them invisible to participants performing a cued-target-discrimination task. When the cue and target appeared within the same object, discrimination was faster than when they appeared in different objects at the same spatial separation. Participants reported no awareness of the objects and were unable to detect them in a signal-detection task. Object-based attention, therefore, is not sufficient for object awareness

Does unconscious perception really exist? Continuing the ASSC20 debate

In our ASSC20 symposium, “Does unconscious perception really exist?”, the four of us asked some difficult questions about the purported phenomenon of unconscious perception, disagreeing on a number of points. This disagreement reflected the objective of the symposium: not only to come together to discuss a single topic of keen interest to the ASSC community, but to do so in a way that would fairly and comprehensively represent the heterogeneity of ideas, opinions, and evidence that exists concerning this contentious topic. The crux of this controversy rests in no small part on disagreement about what is meant by the terms of the debate and how to determine empirically whether a state is unconscious or not. These are issues that directly concern all of us who study consciousness, so it seems it would be in our best interest to strive for consensus. Given the conversation at ASSC20, we are pleased to have the opportunity to address some of the nuanced topics that arose more formally, and share some of the thinking we have done since the meeting. To reflect the heterogeneity of ideas and opinions surrounding this topic, we have organized this discussion into four distinct contributions

Alice in Wonderland: The effects of body size and movement on children’s size perception and body representation in virtual reality

Previous work shows that in adults, illusory embodiment of a virtual avatar can be induced using congruent visuomotor cues. Furthermore, embodying different-sized avatars influences adults’ perception of their environment’s size. This study (N = 92) investigated whether children are also susceptible to such embodiment and size illusions. Adults and 5-year-old children viewed a first-person perspective of different-sized avatars moving either congruently or incongruently with their own body. Participants rated their feelings of embodiment over the avatar and also estimated the sizes of their body and objects in the environment. Unlike adults, children embodied the avatar regardless of visuomotor congruency. Both adults and children freely embodied different-sized avatars, and this affected their size perception in the surrounding virtual environment; they felt that objects were larger in a small body and vice versa in a large body. In addition, children felt that their body had grown in the large body condition. These findings have important implications for both our theoretical understanding of own-body representation, and our knowledge of perception in virtual environments

An Upper Palaeolithic Proto-writing System and Phenological Calendar

In at least 400 European caves such as Lascaux, Chauvet and Altamira, Upper Palaeolithic Homo sapiens groups drew, painted and engraved non-figurative signs from at least ~42,000 BP and figurative images (notably animals) from at least 37,000 BP. Since their discovery ~150 years ago, the purpose or meaning of European Upper Palaeolithic non-figurative signs has eluded researchers. Despite this, specialists assume that they were notational in some way. Using a database of images spanning the European Upper Palaeolithic, we suggest how three of the most frequently occurring signs—the line , the dot , and the —functioned as units of communication. We demonstrate that when found in close association with images of animals the line and dot constitute numbers denoting months, and form constituent parts of a local phenological/meteorological calendar beginning in spring and recording time from this point in lunar months. We also demonstrate that the sign, one of the most frequently occurring signs in Palaeolithic non-figurative art, has the meaning . The position of the within a sequence of marks denotes month of parturition, an ordinal representation of number in contrast to the cardinal representation used in tallies. Our data indicate that the purpose of this system of associating animals with calendar information was to record and convey seasonal behavioural information about specific prey taxa in the geographical regions of concern. We suggest a specific way in which the pairing of numbers with animal subjects constituted a complete unit of meaning—a notational system combined with its subject—that provides us with a specific insight into what one set of notational marks means. It gives us our first specific reading of European Upper Palaeolithic communication, the first known writing in the history of Homo sapiens

My body until proven otherwise: Exploring the time course of the full body illusion

Evidence from the Full Body Illusion (FBI) has shown that adults can embody full bodies which are not their own when they move synchronously with their own body or are viewed from a first-person perspective. However, there is currently no consensus regarding the time course of the illusion. Here, for the first time, we examined the effect of visuomotor synchrony (synchronous/asynchronous/no movement) on the FBI over time. Surprisingly, we found evidence of embodiment over a virtual body after five seconds in all conditions. Embodiment decreased with increased exposure to asynchronous movement, but remained high in synchronous and no movement conditions. We suggest that embodiment of a body seen from a first-person perspective is felt by default, and that embodiment can then be lost in the face of contradictory cues. These results have significant implications for our understanding of how multisensory cues contribute to embodiment

Developmental changes in colour constancy in a naturalistic object selection task

When the illumination falling on a surface change, so does the reflected light. Despite this, adult observers are good at perceiving surfaces as relatively unchanging-an ability termed colour constancy. Very few studies have investigated colour constancy in infants, and even fewer in children. Here we asked whether there is a difference in colour constancy between children and adults; what the developmental trajectory is between six and 11 years; and whether the pattern of constancy across illuminations and reflectances differs between adults and children. To this end, we developed a novel, child-friendly computer-based object selection task. In this, observers saw a dragon's favourite sweet under a neutral illumination and picked the matching sweet from an array of eight seen under a different illumination (blue, yellow, red, or green). This set contained a reflectance match (colour constant; perfect performance) and a tristimulus match (colour inconstant). We ran two experiments, with two-dimensional scenes in one and three-dimensional renderings in the other. Twenty-six adults and 33 children took part in the first experiment; 26 adults and 40 children took part in the second. Children performed better than adults on this task, and their performance decreased with age in both experiments. We found differences across illuminations and sweets, but a similar pattern across both age groups. This unexpected finding might reflect a real decrease in colour constancy from childhood to adulthood, explained by developmental changes in the perceptual and cognitive mechanisms underpinning colour constancy, or differences in task strategies between children and adults. Highlights Six- to 11-year-old children demonstrated better performance than adults on a colour constancy object selection task. Performance decreased with age over childhood. These findings may indicate development of cognitive strategies used to overcome automatic colour constancy mechanisms.Peer reviewe