Mental imagery and the third dimension

What sort of medium underlies imagery for three-dimensional scenes? In the present investigation, the time subjects took to scan between objects in a mental image was used to infer the sorts of geometric information that images preserve. Subjects studied an open box in which five objects were suspended, and learned to imagine this display with their eyes closed. In the first experiment, subjects scanned by tracking an imaginary point moving in a straight line between the imagined objects. Scanning times increased linearly with increasing distance between objects in three dimensions. Therefore metric 3-D information must be preserved in images, and images cannot simply be 2-D "snapshots." In a second experiment, subjects scanned across the image by "sighting" objects through an imaginary rifle sight. Here scanning times were found to increase linearly with the two-dimensional separations between objects as they appeared from the original viewing angle. Therefore metric 2-D distance information in the original perspective view must be preserved in images, and images cannot simply be 3-D "scale-models" that are assessed from any and all directions at once. In a third experiment, subjects mentally rotated the display 90 degrees and scanned between objects as they appeared in this new perspective view by tracking an imaginary rifle signt, as before. Scanning times increased linearly with the two-dimensional separations between objects as they would appear from the new relative viewing perspective. Therefore images can display metric 2-D distance information in a perspective view never actually experiences, so mental images cannot simply be "snapshot plus scale model" pairs. These results can be explained by a model in which the three-dimensional structure of objects is encoded in long-term memory in 3-D object-centered coordinate systems. When these objects are imagined, this information is then mapped onto a single 2-D "surface display" in which the perspective properties specific to a given viewing angle can be depicted. In a set of perceptual control experiments, subjects scanned a visible display by (a) simply moving their eyes from one object to another, (b) sweeping an imaginary rifle sight over the display, or (c) tracking an imaginary point moving from one object to another. Eye-movement times varied linearly with 2-D interobject distance, as did time to scan with an imaginary rifle sight; time to tract a point varied independently with the 3-D and 2-D interobject distances. These results are compared with the analogous image scanning results to argue that imagery and perception share some representational structures but that mental image scanning is a process distinct from eye movements or eye-movement commands.     

Mental imagery and pictorial memory

Previous research has failed to show consistent effects upon memory performance of individual differences in the use of mental imagery. A test of pictorial memory was devised which varied the ease with which the stimulus patterns could be verbally encoded. A factor analysis related performance in this task to a variety of other individual characteristics. The recall of material which could not be readily verbalized defined a factor within the solution which showed significant loadings of age and performance in the Progressive Matrices, but not of subjective ratings of the vividness of experienced imagery. The recall of material which could be readily verbalized did not contribute to the factorial structure of the results. It was concluded that the two sorts of pictorial material are remembered in quite different ways.     

Mental imagery: in search of a theory

It is generally accepted that there is something special about reasoning by using mental images. The question of how it is special, however, has never been satisfactorily spelled out, despite more than thirty years of research in the post-behaviorist tradition. This article considers some of the general motivation for the assumption that entertaining mental images involves inspecting a picture-like object. It sets out a distinction between phenomena attributable to the nature of mind to what is called the cognitive architecture, and ones that are attributable to tacit knowledge used to simulate what would happen in a visual situation. With this distinction in mind, the paper then considers in detail the widely held assumption that in some important sense images are spatially displayed or are depictive, and that examining images uses the same mechanisms that are deployed in visual perception. I argue that the assumption of the spatial or depictive nature of images is only explanatory if taken literally, as a claim about how images are physically instantiated in the brain, and that the literal view fails for a number of empirical reasons--for example, because of the cognitive penetrability of the phenomena cited in its favor. Similarly, while it is arguably the case that imagery and vision involve some of the same mechanisms, this tells us very little about the nature of mental imagery and does not support claims about the pictorial nature of mental images. Finally, I consider whether recent neuroscience evidence clarifies the debate over the nature of mental images. I claim that when such questions as whether images are depictive or spatial are formulated more clearly, the evidence does not provide support for the picture-theory over a symbol-structure theory of mental imagery. Even if all the empirical claims were true, they do not warrant the conclusion that many people have drawn from them: that mental images are depictive or are displayed in some (possibly cortical) space. Such a conclusion is incompatible with what is known about how images function in thought. We are then left with the provisional counterintuitive conclusion that the available evidence does not support rejection of what I call the "null hypothesis"; namely, that reasoning with mental images involves the same form of representation and the same processes as that of reasoning in general, except that the content or subject matter of thoughts experienced as images includes information about how things would look.     

Mental imagery and chunks: Empirical and computational findings

To investigate experts' imagery in chess, players were required to recall briefly presented positions in which pieces were placed on the intersections between squares (intersection positions). Position types ranged from game positions to positions in which both the piece distribution and the location were randomized. Simulations were run with the CHREST model (Gobet & Simon, 2000). The simulations assumed that pieces had to be centered back, one by one, to the middle of the squares in the mind's eye before chunks could be recognized. Consistent with CHREST's predictions, chess players (N = 36), ranging from weak amateurs to grandmasters, exhibited much poorer recall for intersection positions than for standard positions (pieces placed on the centers of the squares). For the intersection positions, the skill difference in recall was larger for game positions than for the randomized positions. The participants recalled bishops better than they recalled knights, suggesting that Stroop-like interference impairs recall of the latter. The data supported both the time parameter in CHREST for shifting pieces in the mind's eye (125 msec per piece) and the seriality assumption. In general, the study reinforces the plausibility of CHREST as a model of cognition.     

Mental imagery,reasoning, and blindness

Although reasoning seems to be inextricably linked to seeing in the “mind's eye”, the evidence is equivocal. In three experiments, sighted, blindfolded sighted, and congenitally totally blind persons solved deductive inferences based on three sorts of relation: (a) visuo-spatial relations that are easy to envisage either visually or spatially, (b) visual relations that are easy to envisage visually but hard to envisage spatially, and (c) control relations that are hard to envisage both visually and spatially. In absolute terms, congenitally totally blind persons performed less accurately and more slowly than the sighted on all such tasks. In relative terms, however, the visual relations in comparison with control relations impeded the reasoning of sighted and blindfolded participants, whereas congenitally totally blind participants performed the same with the different sorts of relation. We conclude that mental images containing visual details that are irrelevant to an inference can even impede the process of reasoning. Persons who are blind from birth—and who thus do not tend to construct visual mental images—are immune to this visual-impedance effect.     

Mental scanning in auditory imagery for songs

Four experiments examined how people operate on memory representations of familiar songs. The tasks were similar to those used in studies of visual imagery. In one task, subjects saw a one-word lyric from a song and then saw a second lyric; then they had to say if the second lyric was from the same song as the first. In a second task, subjects mentally compared pitches of notes corresponding to song lyrics. In both tasks, reaction time increased as a function of the distance in beats between the two lyrics in the actual song, and in some conditions reaction time increased with the starting beat of the earlier lyric. Imagery instructions modified the main results somewhat in the first task, but not in the second, much harder task. The results suggest that song representations have temporal-like characteristics.     

Mental imagery, reasoning, and blindness

Although reasoning seems to be inextricably linked to seeing in the “mind's eye”, the evidence is equivocal. In three experiments, sighted, blindfolded sighted, and congenitally totally blind persons solved deductive inferences based on three sorts of relation: (a) visuo-spatial relations that are easy to envisage either visually or spatially, (b) visual relations that are easy to envisage visually but hard to envisage spatially, and (c) control relations that are hard to envisage both visually and spatially. In absolute terms, congenitally totally blind persons performed less accurately and more slowly than the sighted on all such tasks. In relative terms, however, the visual relations in comparison with control relations impeded the reasoning of sighted and blindfolded participants, whereas congenitally totally blind participants performed the same with the different sorts of relation. We conclude that mental images containing visual details that are irrelevant to an inference can even impede the process of reasoning. Persons who are blind from birth—and who thus do not tend to construct visual mental images—are immune to this visual-impedance effect.     

Bilingual comparative judgments: Evidence against the switch hypothesis

The notion that bilinguals possess a language-switching mechanism was examined. Subjects made comparative judgments about concrete concept pairs (e.g., cow-panther) and abstract concept pairs (e.g., joy-sorrow), which were presented either unilingually or in mixed language. There was no significant difference in latencies for unilingual and mixed language concept pairs, whether the pairs were concrete or abstract. The results substantiate neither the general switch hypothesis nor the notion that between-language and within-language associative networks have different transition probabilities.This research was based in part on the author's master's thesis, submitted to the University of Guelph.     

Mental imagery as an emotional amplifier: application to bipolar disorder

Cognitions in the form of mental images have a more powerful impact on emotion than their verbal counterparts. This review synthesizes the cognitive science of imagery and emotion with transdiagnostic clinical research, yielding novel predictions for the basis of emotional volatility in bipolar disorder. Anxiety is extremely common in patients with bipolar disorder and is associated with increased dysfunction and suicidality, yet it is poorly understood and rarely treated. Mental imagery is a neglected aspect of bipolar anxiety although in anxiety disorders such as posttraumatic stress disorder and social phobia focusing on imagery has been crucial for the development of cognitive behavior therapy (CBT).In this review we present a cognitive model of imagery and emotion applied to bipolar disorder. Within this model mental imagery amplifies emotion, drawing on Clark's cyclical panic model [(1986). A cognitive approach to panic. Behaviour Research and Therapy, 24, 461–470]. We (1) emphasise imagery's amplification of anxiety (cycle one); (2) suggest that imagery amplifies the defining (hypo-) mania of bipolar disorder (cycle two), whereby the overly positive misinterpretation of triggers leads to mood elevation (escalated by imagery), increasing associated beliefs, goals, and action likelihood (all strengthened by imagery).Imagery suggests a unifying explanation for key unexplained features of bipolar disorder: ubiquitous anxiety, mood instability and creativity. Introducing imagery has novel implications for bipolar treatment innovation - an area where CBT improvements are much-needed.     

Mental imagery and the distinction between primary and secondary memory

Previous research has shown that the imageability of stimulus material affects the secondary memory (SM) component of free recall, but not the primary memory (PM) component, and that a negative recency effect is only observed for material of high imageability. It was found that interactive imagery instructions affected the SM component, but not the PM component; separative imagery instructions led to an increased PM component and a reduced SM component. A negative recency effect can be observed in an initial, delayed recall test. However, it is removed by imagery mnemonic instructions. This supports the idea that the negative recency effect is caused by the fact that subjects do not normally image the last few words presented in a free-recall task.     

Test of the neurolinguistic programming hypothesis that eye-movements relate to processing imagery

Bandler and Grinder's hypothesis that eye-movements reflect sensory processing was examined. 28 volunteers first memorized and then recalled visual, auditory, and kinesthetic stimuli. Changes in eye-positions during recall were videotaped and categorized by two raters into positions hypothesized by Bandler and Grinder's model to represent visual, auditory, and kinesthetic recall. Planned contrast analyses suggested that visual stimulus items, when recalled, elicited significantly more upward eye-positions and stares than auditory and kinesthetic items. Auditory and kinesthetic items, however, did not elicit more changes in eye-position hypothesized by the model to represent auditory and kinesthetic recall, respectively.     

Mental imagery and creativity: A meta‐analytic review study

The reports of many creative individuals suggest the use of mental imagery in scientific and artistic production. A variety of protocols have tested the association between mental imagery and creativity, but the individual differences approach has been most frequently employed. This approach is assessed here through a range of meta‐analytic tests. Database searches revealed 18 papers employing the individual differences approach that were subjected to a conservative set of selection criteria. Nine studies (1,494 participants) were included in the final analyses. A marginal, but statistically significant, Fisher's Z‐transformed correlation coefficient was revealed. Further analyses showed little difference between form and type of self‐reported imagery and divergent thinking. Explanations for the failure to account for more than 3% of the variance in the data sets are discussed in the context of anecdotal reports, task validity, and design problems.     

Mental imagery of visual motion modifies the perception of roll-vection stimulation

When viewing a wide-angle visual display, which rotates in the frontoparallel plane around the line of sight, observers experience an illusory shift of the direction of gravity; this shift leads to an apparent tilt of the body and displaces allocentric space coordinates. In this study, subjects adjusted an indicator to the apparent horizontal while viewing a rotating display. To determine whether top down processes could affect the illusion, the subjects were asked to visualize a rotating configuration of dots onto a blank central portion of the moving visual field. Visualizing dots and actually viewing the dots deflected the spatial judgment in very similar ways. These results demonstrate that top down processing can affect allocentric space coordinates.     

Activation of the opioid and nonopioid analgesic systems: evidence for a memory hypothesis and against the coulometric hypothesis

It has been suggested that the magnitude and form of hypoalgesia elicited by an aversive event can be predicted from its coulometric product (Intensity X Duration). According to this hypothesis, small products elicit opioid hypoalgesia, and large products elicit nonopioid hypoalgesia. This suggests that increasing the duration of an aversive event should heighten the nonopioid hypoalgesia. Contrary to this prediction, in Experiment 1 I found that increasing the duration of a mild shock attenuated the nonopioid hypoalgesia. In Experiment 2 I tested another implication of the coulometric hypothesis, namely, that mild shocks that have the same coulometric product should elicit equivalent hypoalgesia. The results did not support this prediction. We discuss how these findings are consistent with an alternative theory, the "working memory hypothesis." According to this theory, the representation of an aversive event in working memory elicits hypoalgesia. In Experiment 3 a novel prediction of this theory was tested, namely, that displacing the representation of intense shock from working memory, by following the intense shock with a weak shock "distractor", should attenuate hypoalgesia. The results support this prediction. I conclude by discussing the relation of this work to other findings in the analgesia literature.     

Mental abilities and school achievement: A test of a mediation hypothesis

This study analyzes the interplay of four cognitive abilities - reasoning, divergent thinking, mental speed, and short-term memory - and their impact on academic achievement in school in a sample of adolescents in grades seven to 10 (N = 1135). Based on information processing approaches to intelligence, we tested a mediation hypothesis, which states that the complex cognitive abilities of reasoning and divergent thinking mediate the influence of the basic cognitive abilities of mental speed and short-term memory on achievement. We administered a comprehensive test battery and analyzed the data through structural equation modeling while controlling for the cluster structure of the data. Our findings support the notion that mental speed and short-term memory, as ability factors reflecting basic cognitive processes, exert an indirect influence on academic achievement by affecting reasoning and divergent thinking (total indirect effects: β = .22 and .24, respectively). Short-term memory also directly affects achievement (β = .22).     

Feedback interference and dissociations of classification: Evidence against the multiple-learning-systems hypothesis

Researchers have argued that different categorization problems are learned by separate and distinct cognitive systems. They propose that an explicit system is responsible for learning rule-based categories and that a separate implicit system learns information-integration categories. One source of supporting evidence involves experiments in which observers perform a concurrent memory-scanning task that interferes with the processing of feedback. Researchers have reported a dissociation in which this manipulation impairs learning of a rule-based category but not an information-integration category. In the present research, we test the hypothesis that the dissociation was the result of lowered perceptual discriminability in the rule-based structure in comparison with the information-integration one. We demonstrate an example of an alternate rule-based category with easy-to-discriminate stimuli in which performance is unaffected by the interfering memory-scanning task. Furthermore, we demonstrate that learning of an information-integration category with low perceptual discriminability is impaired by the memory-scanning task. These demonstrations of the reverse dissociation challenge the interpretation that rule-based and information-integration category structures are learned by separate cognitive systems.     

Motor imagery: the relation between age and imagery capacity

The imagination of motor actions forms not only a theoretical challenge for cognitive neuroscience but may also be seen as a novel therapeutic tool in neurological rehabilitation, in that it can be used for relearning motor control after damage to the motor system. However, since the majority of rehabilitation patients consist of older individuals it is relevant to know whether the capacity of mental imaging is compromised by age. Scores on the vividness of movement imagery questionnaire were obtained for 333 participants, divided in three age groups. Results showed that elderly participants were slightly worse in motor imagery capacity than younger participants, particularly in relation to motor imagery from an internal (first person) perspective. Furthermore, a possible relation between the level of physical activities and motor imagery capacity is discussed.     

The facilitation of aggression by aggression: evidence against the catharsis hypothesis.

Nnety male subjects were either attacked or treated in a more neutral manner by a male confederate. On a subsequent maze-learning task, one third of the subjects shocked the confederate, one third observed as the experimenter shocked the confederate, and one third waited for a period of time during which the confederate was not shocked. Finally, all subjects shocked the confederate as part of a code-learning task. Subjects who had been attacked and had shocked the confederate during the maze task delivered shocks of greater intensity on the code task did subjects in the other two conditions, and the former subjects also experienced a greater reduction in diastolic blood pressure than did the latter. The results contradict the hypothesis of aggression catharsis and are discussed in terms of feelings of restraint against aggressing that a subject experiences after committing an aggressive act.