Our starting point is a 2008 study by Brébion et al. The researchers present a theory of source-memory deficits as possible etiological explanation for VH in individuals with schizophrenia. The Source Memory deficit theory argues that VH essentially arise from a lack of intact reality testing. In this paradigm, VH are a result of the individual’s inability to differentiate between imagination and perception—similar to the theory that auditory hallucinations arise from externalization of internal speech (Allen et al., 2004). The authors, therefore, designed a reality monitoring perception test that would measure an individual’s ability to distinguish perceived from imagined images. The researchers hypothesized that clients with VH would exhibit a greater tendency to falsely remember seeing pictures that had in fact been presented as words only.
The present study contained 41 patients with schizophrenia and 43 healthy individuals for the control group. There was no significant difference of age, gender, education, ethnicity or verbal IQ between the two groups. Verbal IQ was assessed by administration of the National Adult Reading Test (NART). Positive symptoms were assessed by administration of the Assessment of Positive Symptoms (SAPS).
The researchers employed the Battig and Montague set (1969). An invaluable tool for researchers across multiple disciplines, this instrument is a categorical norming set which purports to present exemplars and prototypes of various culturally conditioned objects. Sixteen categories from the Battig and Montague set were presented. Only common objects were used—for instance, “elephant” and “tiger” for the category of animal. Participants were shown two cards for each instance within a category. One card displayed only the word defining the object; the other card provided the picture of the object with an accompanying verbal label. The experimenter indicated the category name (“types of animals”) before presenting both cards. In order to ensure encoding, the participants were required to verbally name the two objects, as well as provide a third example. Unfortunately, participant examples were not included in their research. After an approximately 5 minute pause, a recognition test was administered. As the experimenter read aloud the list of objects as well as distractor items, the participants were required to indicate whether each item had been presented as a word, a picture, or not at all. Immediately following the recognition test, a reality-monitoring test was given. As the experimenter read the list of the 32 target items, participants were required to indicate whether a picture of the word had been displayed or merely the word. Participants were informed that all items in this test had been previously presented.
Data analysis seems to confirm the misattribution theory. The researchers found a significant interaction of subgroups and misattribution. Specifically, they found that those participants reporting VH made significantly more misattributions to pictures than the other patients, t(39) = 2.79, p < .01.
The authors note the limitations characteristic of a study on VH in individuals with schizophrenia—namely, a small sample size. They further note that, procedurally, the presentation of images and words categorically (“type of animals”) is limiting insofar as it may provide memory cues, and urge that future replication studies consider employing a non-systematic presentation of images.
Two further limitations may be equally noted. First, the researchers employed the Battig and Montague set (1969) to categorically delineate everyday objects, which itself is an updated version of the Connecticut Category Norms originally published in 1957 by Cohen, Bousfield, and Whitmarsh (Overschelde, Rawson, and Dunlosky, 2004). More than 40 years after its creation, the Battig and Montague set should most likely have been substituted for a more current standard. The Battig and Montague set, for example, includes such anachronisms as “rubbers” for shoes, and the “waltz” for a popular style of dance. A replication of Brébion’s above work using the Overschelde et al. instrument, which boasts new categories, new measures, as well as latencies for generated responses, would be highly desirable.
Second, with respect to the aforementioned epistemological framework, it is not clear to me why the researchers required participants to verbalize the image on the card. While the integration of contemporary cognitive theory into the research is laudable, the difficulty with this method is that it produced both an internal and external vocalization. Although still self-generated, this external vocalization could be disruptive to the process of understanding how only internal events (whether words or images) relate to misattributions.
A less unique, but particularly relevant study for the purposes of this paper, concerns the role of affect and intentionality as predisposing factors for a hallucinatory experience. Based in part on previous work by Gauntlett-Gibert and Kuipers (2005), that indicated the activating role of affect in hallucinatory experiences, this 2012 study by Oorschot et al., employed the Experience Sampling Method (ESM). The ESM purports to provide first person empirical feedback on emotional states by means of a structured, self-report likert scale. While proponents of the ESM method argue that it offers the advantage of providing real-time responses, instead of relying on recall and the possibility of memory deficiencies, opponents readily cite the inherent difficulties in any self-report measure, perhaps especially in patients with psychotic disorders.
Nonetheless, in this study, 184 participants (71% male) with psychosis spectrum disorder were provided a digital stop watch and assessment booklets that were collected daily. Ten times daily for six consecutive days, the programmed stop watch would signal at random intervals ( = 90 minutes) between 7:30 am and 10:30 pm, alerting the participant to begin the assessment. The ESM assessment consists of open-ended questions and a 7-point Likert scale questions aimed at measuring the participant’s emotional state, psychopathology, and environment. Likert scale questions aimed at capturing psychopathology included statements such as, “I hear voices” and “I hear phenomena”. Similarly, likert scale questions to assess emotional state were based on mood adjectives such as “I feel cheerful/satisfied/relaxed” and “I feel guilty/anxious/sad.” During pre-testing instructions, participants were required to complete a single ESM assessment to gauge their task comprehension. The experimenters regularly contacted the participants throughout the trial in order to assure compliance, and participants who responded to less than one third of the emitted signals were not included in the study. Finally, Oorschot et al. report literature citing the validity of the ESM measurement, in both normal control groups as well as psychotic populations.
Analysis revealed that, of the commendably large sample size for this population, 30% reported AH and 25% reported VH. Further, of the 1,111 instances of reported hallucinatory events, there were 196 VH and 399 AH. Participants reported 117 moments of cannabis use out of 7,399 total reported instances (9 instances were related to VH, and 31 instances related to AH).
In terms of the relationship of emotional state to hallucinatory experiences, Oorschot et al.’s predictable results found that participants expressed significantly higher negative affect (and subsequently significantly lower positive affect) during a hallucinatory event. More specifically, patients reported that VH were preceded by a decrease in positive affect. Accordingly, future research in this domain would be highly improved by the use of emotionally charged stimuli. The previously discussed Brébion (2008) article, for instance, would seem more successful if the pedestrian words and images presented (for instance, “elephant” for type of animal) were replaced with more emotionally relevant stimuli (religious or personally relevant words seem applicable).
The limitations of self-report nature of this study notwithstanding, the relationship of anxiety to the onset (and duration) of both AH and VH is significant insofar as it intersects and confirms prior research on the role of intentionality and affect in hallucinatory experiences. Prior research has already well-documented the relationship between affect and hallucinations (Gauntlett-Gilbert and Kuipers, 2003; Birchwood and Chadwick, 1997), specifically implicating anxiety and depression in the genesis of hallucinations (Freeman and Garety, 2003).
Still, observing a correlation between the variables of anxiety and hallucinations is one thing—accounting for the cognitive processes underlying this relationship is quite another. The limitation of the absence of a theory of knowledge guiding this research is reflected in the inability of researchers to construct experimental procedures with which to test specific cognitional theories. That is, as was noted above, the vast and steadily growing literature on cognitional theories of hallucinations seems primarily to confirm previous similar studies. More recent literature, failing to provide an epistemological foundation and focusing instead on new measures, different instruments, or higher sample sizes, has thus far only been able to replicate previous findings. Scientific progress, at least in a Kuhnian perspective, will require explication and unification of a theory of knowledge from which more accurate experimental models can be produced.
By Phillip J. Kuna, PhD (abd)for John G. Kuna, Psy.D. and Associates Counseling
www.drjohngkuna.com
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