Illusion Paradigm Research Articles

Memory monitoring failure in confabulation: Evidence from the semantic illusion paradigm

Several prominent models of confabulation characterize the syndrome as a failure in controlled aspects of memory retrieval, such as pre-retrieval cue specification and post-retrieval monitoring. These models have been generated primarily in the context of studies of autobiographical memory retrieval. Less research has focused on the existence and mechanisms of semantic confabulation. We examined whether confabulation extends to the semantic domain, and if so, whether it could be understood as a monitoring failure. We focus on post-retrieval monitoring by using a verification task that minimizes cue specification demands. We used the semantic illusion paradigm that elicits erroneous endorsement of misleading statements (e.g., "Two animals of each kind were brought onto the Ark by Moses before the great flood") even in controls, despite their knowing the correct answer (e.g., Noah). Monitoring demands were manipulated by varying semantic overlap between target and foils, ranging from high semantic overlap to unrelated. We found that semantic overlap modulated the magnitude of semantic illusion in all groups. Compared to controls, both confabulators and non-confabulators had greater difficulty monitoring semantically related foils; however, elevated endorsement of unrelated foils was unique to confabulators. We interpret our findings in the context of a two-process model of post-retrieval monitoring.

Patients with Alzheimer's disease use metamemory to attenuate the Jacoby–Whitehouse illusion

Patients with Alzheimer's disease (AD) relying predominantly on familiarity for recognition, research has suggested that they may be particularly susceptible to memory illusions driven by conceptual fluency. Using the Jacoby and Whitehouse [Jacoby, L.L., & Whitehouse, K. (1989). An illusion of memory: False recognition influenced by unconscious perception. Journal of Experimental Psychology: General, 118, 126-135] illusion paradigm, we extended these findings and found that AD patients were also sensitive to perceptually driven false recognition. However, AD patients were equally able to disregard perceptual fluency when there was a shift in the sensory modality of the study and test stages. Overall, these findings support the notion that patients with AD can be susceptible to fluency-based memory illusions but these patients can strategically control the fluency attribution following their metamemory expectation in exactly the same way as elderly adults and young adults.

The Role of Hand Size in the Fake-Hand Illusion Paradigm

When a hand (either real or fake) is stimulated in synchrony with our own hand concealed from view, the felt position of our own hand can be biased toward the location of the seen hand. This intriguing phenomenon relies on the brain's ability to detect statistical correlations in the multisensory inputs (ie visual, tactile, and proprioceptive), but it is also modulated by the pre-existing representation of one's own body. Nonetheless, researchers appear to have accepted the assumption that the size of the seen hand does not matter for this illusion to occur. Here we used a real-time video image of the participant's own hand to elicit the illusion, but we varied the hand size in the video image so that the seen hand was either reduced, veridical, or enlarged in comparison to the participant's own hand. The results showed that visible-hand size modulated the illusion, which was present for veridical and enlarged images of the hand, but absent when the visible hand was reduced. These findings indicate that very specific aspects of our own body image (ie hand size) can constrain the multisensory modulation of the body schema highlighted by the fake-hand illusion paradigm. In addition, they suggest an asymmetric tendency to acknowledge enlarged (but not reduced) images of body parts within our body representation.

The relational determination of length illusions and length aftereffects.

When two lines were presented simultaneously, in an illusion paradigm, the judged length of one of the lines (the focal line) assimilated toward the length of the contextual line. When the lines were presented sequentially, in an aftereffect paradigm, the apparent length of the focal line was displaced away from the length of a previously presented contextual line (i.e. contrast). The largest effects obtained at inverse contextual-to-focal length ratios: 1.67:1 for contextual lines longer than the focal line and 0.60:1 for contextual lines shorter than the focal line. Overestimation of focal length was larger than underestimation for both illusions and aftereffects despite the fact that identical stimuli produced effects in opposite directions in the two paradigms. Results were discussed in terms of a neural length-coding model and were related to visual size constancy.

Masking, aftereffect, and illusion in visual perception of curvature

Masking, aftereffect, and illusion paradigms were used to establish the spatial selectivity of curvature detectors in human vision. Arcs with the same chord orientation mask each other maximally when they are identical in radius and direction of curvature. There is gradual reduction in masking over an extensive spatial range as arcs diverge in curvature. The transition from convexity to concavity does not produce discontinuity in the masking function. The extent to which a straight line appears curved also depends on the curvature of arcs shown previously (aftereffect) or at the same time (illusion). It is suggested that these effects could occur through selective adaptation of detectors responsive to either global curvature or the orientation of local straight-line approximations within an arc. Evidence is reviewed in support of the latter interpretation.