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Thesis Format

Integrated Article

Degree

Master of Science

Program

Neuroscience

Supervisor

Mitchell, Derek

Abstract

For decades researchers have used 2D stimuli under the assumption that they accurately represent real objects. This assumption has been challenged by recent vision and neuroeconomics research which has found that 2D images can evoke different neural and behavioural responses than real objects. The current study continues this line of research in the field of affective cognitive neuroscience; a field where small effect sizes are common and rapid habituation to affective stimuli used in the lab often occurs. The present study uses realistic 2D and 3D emotional images to determine the impact of visual dimension on affective responding. Subjective ratings revealed a perceptual advantage for 3D images which were rated more realistic and received some higher ratings of emotion than 2D images. Conversely, there were no differences in psychophysiological responding (i.e. skin conductance and electromyography) between 2D and 3D images. The implications of these results and future directions are discussed.

Summary for Lay Audience

In order to generate an emotional reaction within a research setting, most psychology and neuroscience studies use emotional 2D images (e.g. kittens to induce pleasant emotions, spiders to induce fear). However, recent research suggests there are differences in the way the human brain respond to 2D images versus actual, physical objects. Real objects are better remembered, attended to, and are more highly valued than 2D images. This raises the question as to how well findings from studies which use 2D images can generalize to real world situations. In the laboratory, it is often difficult to mimic the impact of emotions in the real-world because emotional responses to images tends to weaken significantly when they are presented repeatedly. The present study aims to determine whether effects of emotion can be improved by using 3D images as they more closely resemble real objects. This study compared photorealistic 2D and 3D images of insects and arachnids of varying degrees of pleasantness (e.g. butterflies, scorpions). We predicted that 3D images would be perceived as more realistic and generate more intense emotional reactions compared to 2D images. To measure this, we explicitly asked participants to rate how realistic, pleasant, arousing, approachable, and dangerous they found each image. We also measured participants’ bodily responses to the images as specific patterns of bodily responses are associated with different emotional reactions. The startle eye blink response is differentially affected by emotional images; positive images decrease the magnitude of the startle and negative images increase the magnitude of the startle. Skin conductance (SC) measures minute changes in the amount of sweat present on the skin. SC increases in response to emotionally arousing images, whether positive or negative. Our study found that 3D images showed greater subjective ratings for realism, arousal, and danger, but these same 3D images did not result in significant differences in visceral emotional reactions compared to 2D images. Before a definitive judgement can be made on whether there are differences in visceral reactions between 2D and 3D images, future research should compare these two image types using more arousing images, more bodily measures, and less repetitions.

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