Academic Department of Psychiatry, University of Sheffield, UK
Correspondence: Dr Sean A. Spence, Reader in General Adult Psychiatry, Academic Department of Psychiatry, University of Sheffield, The Longley Centre, Norwood Grange Drive, Sheffield S5 7JT, UK. Tel: +44 (0) 114 22 61519; fax: +44 (0) 114 22 61522; e-mail: S.A.Spence{at}Sheffield.ac.uk
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ABSTRACT |
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Aims To examine the definition and application of thought insertion in psychiatric and allied literatures.
Method A semi-structured literature review and conceptual analysis.
Results When narrowly defined, thought insertion is reliably identified but not specific to schizophrenia. There is a range of related phenomena (alienated, influenced, made and passivity thinking), less consistently defined but also not specific to schizophrenia. Whether thought insertion is solely an abnormal belief (or may also be an experience) is open to question. Nevertheless, the symptom has been used to explain schizophrenia, predict dangerousness and advance theories of normal agency. Most applications have been subject to critique.
Conclusions Despite its widespread occurrence and diagnostic application, thought insertion is an ill-understood and underresearched symptom of psychosis. Its pathophysiology remains obscure.
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INTRODUCTION |
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METHOD |
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RESULTS |
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But when they shall lead you, and deliver you up, take no thought beforehand what ye shall speak, neither do ye premeditate; but whatsoever shall be given you in that hour, that speak ye: for it is not ye that speak, but the Holy Ghost. (Authorised King James Version)
Some contemporary authors have argued that first-rank symptoms are non-pathological in the context of spiritual experience. In their first case (Simon), Jackson & Fulford (1997) describe thought insertion but discount its pathological nature because Simon appears otherwise well and is professionally successful. His experiences seem congruent with his religious beliefs. Yet, he clearly describes household appliances affecting his thinking: the things that come are not the things that I have been thinking about... They kind of short circuit the brain, and bring their message.
Thought sharing
There are, of course, natural means by which one person's thoughts can be
known to another: for example, we can deduce what others think from their
manifest behaviours. However, in pathological states there is a subjective
breach of a perceived psychological border, conceptualised as the
ego-boundary, which is described concretely
(Sims, 1991). In some way, the
victim's mind/ego seems (to him or her) to become permeable, and abnormal
influence passes into or out from the
ego according to the symptom type. Hence, Fish
(1967) describes the
ego-boundary losing its normal integrity in schizophrenia:
[The] patient knows that his thoughts and actions have an excessive effect on the world around him, and he experiences activity, which is not directly related to him having a definite effect on him.
Although most authors emphasise those symptoms in which influence encroaches upon the ego (Appendix), Stanghellini & Monti (1993) delineate an experience of activity. Patients could believe that they can breach the ego-boundaries of others: for example, one stated that her thoughts could fly to others, who could catch them. Without this sense of activity or volition such an experience might resemble thought broadcast (Pawar et al, 2002).
Hence, the ego-boundary can be permeable in both directions (inwards and outwards) and specific first-rank symptoms could preferentially implicate such directional permeability. In thought insertion the permeation is inwards: another's thoughts breach the ego-boundary. In thought withdrawal and broadcast the permeation is outwards: the patients' own thoughts pass externally (Table 1).
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Thought insertion
The experience of thought insertion has two components:
A much-quoted example is provided by Mellor (1970):
I look out of the window and I think the garden looks nice and the grass looks cool, but the thoughts of Eamonn Andrews come into my mind. There are no other thoughts there, only his...He treats my mind like a screen and flashes his thoughts on to it like you flash a picture.
Earlier descriptions of thought insertion are found in Jaspers (1963). In one case a patient describes such thoughts as com[ing] at any moment like a gift...I do not dare to impart them as if they were my own (Gruhle, in Jaspers, 1963). Jaspers refers to these thoughts as implanted, coming like an inspiration from elsewhere and remarks that no one speaks them to the patient nor are the thoughts "made",... the thoughts are not his own (italics added).
Jaspers seems to distinguish such surprising or incongruous inserted/implanted thoughts from those that are made by others, by which he seems to mean thoughts that emerge under the perceived influence of an external agent (so-called passivity thinking; Appendix).
Patients think something and yet feel that someone else has thought it and in some way forced it on them. The thought arises and with it a direct awareness that it is not the patient but some external agent that thinks it. The patient does not know why he has this thought nor did he intend to have it. He does not feel master of his own thoughts and in addition he feels in the power of some incomprehensible external force (pp. 122-123).
Hence, the patient with passivity thinking reports: Some artificial influence plays on me; the feeling suggests that somebody has attached himself to my mind and feeling... (Jaspers, 1963: p. 123; italics added).
Jaspers' distinction between implanted thoughts and passivity thinking is, therefore, a subtle one. It seems to hinge upon whether the thought came spontaneously (i.e. was implanted) or emerged under the perceived influence of another (made, passivity thinking). In modern parlance, the former has been described as a narrowly defined thought insertion, whereas the latter, influenced (or controlled) thinking, has been seen as comprising a broader category, with possible diagnostic implications (O'Grady, 1990; cf. Peralta & Cuesta, 1999).
Taylor & Heiser (1971) also draw a distinction between the ownership of a thought and the process of thinking it. These authors (and Koehler, 1979) distinguish the experience of influence (in which the process of thinking is controlled from outside) from the experience of alienation (in which a thought belongs to another agency; i.e. is inserted). Hence, the influence/alienation distinction equates to that of passivity/implantation. In each dichotomy it is the second term that satisfies the contemporary definition of thought insertion (Appendix). Koehler is explicit that although the influenced patient owns his or her thoughts, the thought insertion patient does not.
Other terms
As Jaspers' subtlety illustrates, there is a potential for confusion at the
boundaries of the thought insertion concept, and multiple terms have been used
in describing similar (non-thought insertion) phenomena:
influenced, made and passivity
thinking (Appendix). Although these three terms appear equivalent, problems
arise when others are applied inconsistently. For instance, when Taylor &
Heiser (1971) use the term
alienation (to indicate thought insertion), they contradict
Fish's (1967) use of the term
(to indicate influenced/made thinking):
[The patient's] thoughts are under the control of an outside agency... others are participating in his thinking (Fish, 1967: p. 39; italics added).
Fish differentiates this form of alienation from thought insertion, which he describes thus:
[The patient] knows that thoughts are being inserted into his mind, and recognises them as being foreign and coming from without (Fish, 1967: p. 39).
Hence, the term thought alienation is probably best avoided, as it means different things to different authors.
Elsewhere, Schneider (1959) uses another term, thought intrusion, when describing external influence, attributed to hypnosis by a woman with schizophrenia. Although his precise meaning is uncertain, intrusion (in this context) appears equivalent to influence.
The act of thinking: agency
The perceived process of thinking seems to be important when making some of
the above distinctions (e.g. between influenced and
inserted thoughts). During influence the process
of thinking has been noticeably altered, whereas during
insertion it is reportedly absent; the thought
arrives de novo. Indeed, Mellor
(1970) states that inserted
thoughts are forced upon passive minds and Jaspers
(1963) comments that
the patient does not oppose them in any way. The common feature
that has been stressed is a loss of volition. In this state (thought
insertion), the subject is the passive recipient of alien thoughts that are
the products of alien thinking.
The philosophers Stephens & Graham (1994), conceptualise thought insertion as a problem of agency, which they define as consist[ing] in regarding one's mental episodes or thoughts as expressions of one's own active doing: as things one does rather than things that happen to one. Hence, they differentiate influenced thinking from thought insertion on the basis of whether or not the alien performs the thinking. The merely influenced subject believes that someone else has caused him to think the thought... In thought insertion, by contrast, the subject believes that someone else has actually done the thinking for him. He has not been manipulated into thinking something; rather his agency has been bypassed completely (italics added).
Hence, the concept of agency helps us to disambiguate thought insertion from influenced/made thinking (Table 1). An influenced thought emerges when the alien other interferes with the subject's agency but the subject owns the ensuing thought. In thought insertion the subject's own agency is absent and an alien thought is inserted. In this account, patients retain ownership of a made thought whereas thought insertion thoughts (by definition) are experienced as alien.
Again, these distinctions are rather subtle, and may be difficult to fully elucidate clinically. Stephens & Graham's definition of influenced thinking may go further than that of Jaspers (1963). The latter's account does not state explicitly that influenced thinking permits (self-) ownership of the ensuing thought. However, some of our own patients have made such a distinction:
A man said that great forces were being used against his thinking, but that his thoughts were still his own (Spence et al, 1997).
Thought insertion and attribution
Some subjects attribute their loss of agency to an identified other (e.g.
Eamonn Andrews, above) but this is not universal. Similarly, patients describe
various modes of causation. Influencing machines were described
before the first-rank symptoms were first ranked by Schneider.
Air-loom machines, reported by James Tilly Matthews (1800), were
said by him to have the power to make ideas or to steal
others... (Haslam, 1810, in Porter,
1991: p. 146; italics added). Tausk's
(1988) patient with
schizophrenia described her thoughts as being produced by an electrical
machine controlled by others, at a distance. A patient of Jaspers
(1963) also described the
experience of electricity: one evening the thought was given to
me electrically that I should murder Lissi (original italics).
Again, some of our own patients bear out this experiential quality, prompting
explanations of aetiology:
One man said that thoughts were being put into his mind and that they "felt different" from his own; another said that the television and radio were responsible for different thoughts, which were "tampered with electrically" and always felt the same way (i.e. recognisably different from his "own") (Spence et al, 1997).
Diverse mechanisms are reported, including hypnotism in Schneider's case (above) and that of Reiter (1926): while experiencing schizophrenia, a woman believed that she was hypnotised by Professor C., who transferred his thoughts to her and made her do as he wanted.
Beliefs regarding the mechanism through which another usurps agency have assumed little importance in modern diagnostic criteria. The significance of such additional psychopathology has not been elaborated. Does it matter whether a machine, a spirit or an agent unknown to the subject inserts a thought? According to Berrios (1997), such content is of little explanatory interest; delusions are empty speech acts. However, it is conceivable that beliefs and attributions could help determine whether the subject seeks, or is brought to, psychiatric attention. If subjects experience a spiritual dimension to thought insertion, and are not behaviourally compromised, then they might seek religious or spiritual contexts (Jackson & Fulford, 1997).
Is thought insertion solely a belief?
Subjects experiencing thought insertion were included in Nayani &
David's (1996)
phenomenological survey of auditory hallucinations. These subjects'
descriptions of their alien thoughts varied quite widely:
internal hallucinators (i.e. those who heard voices
inside their heads) described inserted thoughts in terms of bad
impulses or unpleasant visual images (e.g. to maim or kill) whereas
external hallucinators described them in terms of unpleasant
internal voices. Other authors have described patients whose inserted thoughts
feel different (e.g. Spence
et al, 1997), and in Cahill & Frith
(1996), a patient identified
the exact point of entry of an inserted thought into his head. As well as
being alien, the thought could be felt to enter. Hence thought
insertion might not be solely a belief: in some (if not all) patients it can
incorporate abnormalities of perception. This is also implied by those authors
who distinguish experiences of alienation from
experiences of influence
(Taylor & Heiser, 1971;
Koehler, 1979).
The applications of thought insertion
Diagnosis
The centrality of first-rank symptoms to the diagnosis of schizophrenia,
although controversial (Crichton,
1996), is apparent in the standard diagnostic manuals (e.g.
ICD10). Thought insertion, on its own, is sufficient for a diagnosis of
schizophrenia to be made, if present for 1 month in the absence of an organic
or mood disorder (F20, ICD10; World
Health Organization, 1992). Hence, a simple definition of thought
insertion can appear to simplify practice for clinicians attempting to
diagnose a complex disorder in the absence of a biologically validated
pathognomonic marker. Also, first-rank symptoms can be reliably agreed upon by
different examiners (e.g. McGuffin et
al, 1984).
Consistent with this view, O'Grady (1990) reported that narrow definitions of first-rank symptoms (as a group) might be more specific to schizophrenia (cf. psychotic depression). Hence, thought insertion might be more schizophrenic than is influenced thinking. However, relatively few patients in his sample exhibited first-rank symptoms and these symptoms were not investigated individually.
A later and larger study of people with psychoses (Peralta & Cuesta, 1999) found thought insertion and other first-rank symptoms to be distributed across psychotic diagnoses and not specific to schizophrenia; the study utilised phenomenological definitions comparable with those of Mellor, 1970). Thought insertion was elicited in 19% of people diagnosed with schizophrenia (19.7% in Mellor's study), 7.2% of those with mood disorder and similar percentages of those with brief reactive (8%) and atypical psychoses (6%). The figures for made thoughts were 35.8, 27.7, 32 and 18%, respectively (Peralta & Cuesta, 1999). The authors concluded that first-rank symptoms are symptomatic of psychosis generally, and not schizophrenia specifically.
Explaining schizophrenia
Notwithstanding the above findings, although schizophrenia has lacked a
pathognomonic biological marker, its characteristic symptoms (such as thought
insertion) have been used by some to explain the syndrome. Hence, Nasrallah
(1985) proposed that thought
insertion is an indicator of defective interhemispheric integration, thoughts
from the right hemisphere being interpreted as alien by the
left. Crow (1998) has likewise
focused upon first-rank symptoms, in advancing the theory that schizophrenia
is the price humans pay for language. Again, deficits in
hemispheric integration/asymmetry are invoked to explain first-rank symptoms.
Also, Frith's (1992) cognitive
neuropsychological account of thought insertion and other first-rank symptoms
has been generalised into a model of disordered internal
monitoring. Hence, inserted thoughts are experienced as such because
the subject/patient is unaware of his or her own intentions (to think).
Thoughts arising unbidden are therefore perceived as alien.
Critique of this elegant and influential theory is beyond the scope of this
paper but rehearsed extensively elsewhere
(Campbell, 1999;
Spence, 2001;
Thornton, 2002).
Forensic psychiatry
A diagnostic symptom detectable on a single mental state examination might
be particularly useful for forensic psychiatrists having to perform
assessments under difficult conditions. Thought insertion appears useful
because of its perceived diagnostic significance and because it is relatively
reliable. Furthermore, there have been reports of its possible utility in
predicting dangerousness. Link et al
(1992) described the
threat/control-override syndrome after epidemiological studies
(initially replicated) suggested that the difference in previous
violence between former patients and controls could be accounted for by
the presence of specific symptoms, including persecutory delusions and thought
insertion. Such patients reported beliefs that involved either a perceived
threat to themselves or external control over their minds and actions. The
strength of the association with violence increased with the number of
delusions present (Link et al,
1992). However, subsequent prospective studies have failed to
replicate this finding, and it seems as if a number of confounding variables
could account for the original results: a retrospective design; reliance upon
self-report of symptoms; and failure to control for anger and impulsivity
(Appelbaum et al,
2000).
Philosophy of mind
Understanding the nature of unusual human experience has long been common
ground for psychiatry and philosophy. Recent interdisciplinary dialogue has
been realised (to a degree) through the mutual investigation of thought
insertion (e.g. Chadwick, 1994;
Fulford, 1995; Spence,
1996,
2001;
Gibbs, 2000;
Stephens, 2000;
Thornton, 2002). The
subjective experience of thought insertion appears to challenge a key
philosophical concept: immunity to subjective error. If a
subject is aware of a thought, how can she claim that the thought is not hers?
Assuming intelligibility, some philosophers have begun to tackle thought
insertion. Hence, to Stephens & Graham
(1994) a solution is the
distinction between subjectivity and agency: although the subject retains
awareness of her thoughts (subjectivity), she has lost the associated sense of
mental causation (agency). It is noticeable how similar these formulations are
to psychological models of unawareness of voluntary processes
(Angyal, 1936;
Feinberg, 1978;
Frith, 1992). However, what
remains unexplained is the distinction between inserted thoughts
and those everyday thoughts that come into our minds, apparently
spontaneously, and to which we do not attach any paranoid interpretation
(Spence, 1996). Invoking a
normal model of thinking, in which thoughts are preceded by
intentions to think (Frith,
1992), is open to critique (see
Campbell, 1999;
Spence, 2001;
Thornton, 2002). Among other
problems, it opens up an infinite regress: intentions to think would
themselves be preceded by intentions to think, ad infinitum.
Gaps in the literature
Our review has revealed no pathophysiological studies of thought insertion
per se and few that have reported findings of more than tangential
relevance. One case report suggests that symptoms resembling influenced
thinking can follow posterior right hemisphere lesions
(Mesulam, 1981). A study
comparing first-rank symptoms in people with idiopathic schizophrenia with
those occurring secondary to temporal lobe epilepsy found no difference in the
rates of thought insertion (implying that temporal lobe dysfunction might be
equally relevant to both; Oyebode &
Davison, 1989). A neuroimaging study of made
movements implicated the right parietal cortex but these data were not
examined for associations with thought insertion, or influenced thinking,
where present (Spence et al,
1997). It appears that the pathophysiology of thought insertion
awaits elucidation. However, there is some evidence that first-rank symptoms
(including thought insertion) could be partially heritable
(Loftus et al, 2000;
Cardno et al,
2002).
Other noticeable absences from our review include systematic studies of the phenomenology of thought insertion and any coping mechanisms adopted by those affected. One anecdotal report describes a patient who screamed to stop thoughts entering his mind (Spence, 1999).
These gaps in the literature could reflect the inherent difficulty of capturing such phenomena and also an assumption that thought insertion is solely an abnormal belief. Our review suggests that thought insertion is still little understood. Further research could assist in understanding both its emergence in the psychotic process and those related phenomena thought to affect the healthy mind (Jackson & Fulford, 1997).
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Clinical Implications and Limitations |
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LIMITATIONS
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APPENDIX |
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The subject experiences thoughts which are not his own intruding into his mind. The symptom is not that he has been caused to have unusual thoughts, but that the thoughts themselves are not his (Wing et al, 1983).
Same meaning applied by Fish (1967), Mellor (1970) and Landmark (1982).
Equivalent terms: implanted thoughts (Jaspers, 1963); experience of alienation (Taylor & Heiser, 1971); passive experience of alienation (Koehler, 1979).
Influenced thinking
The patient's OWN thoughts... are being controlled or influenced by
an outside force (Koehler,
1979; original capitals).
Same meaning applied by Landmark (1982) and O'Grady (1990).
Equivalent terms: made and passivity thinking (Jaspers, 1963); thought alienation (Fish, 1967); experience of influence (Taylor & Heiser, 1971); possibly thought intrusion (Schneider, 1959).
Experiences of activity
Patients... intentionally transmit their thoughts... [and]
intentionally exert control on objects and events of the outside world
(Stanghellini & Monti,
1993).
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Received for publication June 5, 2002. Revision received October 4, 2002. Accepted for publication October 21, 2002.