Exploring Phantasms of the Living (1886) through Machine Learning: Topic Discovery with Latent Dirichlet Allocation
NOTE: Click to open graphics for an expanded and clearer view of the findings they contain
Phantasms of the Living, published in 1886 by the Society for Psychical Research (SPR), was a landmark study that presented the case for “telepathy” or thought transference from mind to mind. The study consisted of 702 cases spanning over 1400 pages that considered several varieties of spontaneous telepathic experiences collectively referred to “phantasms of the living”
- The case collection examined non-sensory and internalized impressions, many of which were presentiment experiences involving dreams, clairvoyance, visions, feelings or an awareness in connection with the deaths of family members or friends. These experiences often coincided with the approximate time of death
- Cases also considered
sensory and externalized impressions, in particular apparitional representations of living persons, who were perceived to be in moments of crisis or danger. These situations appeared evidential of shock-induced forms of thought transference from a distressed agent to a percipient in the form of telepathic hallucinations
As a follow-on to the earlier wordcloud project, we wondered whether unsupervised machine learning could discover main topics within Phantasms of the Living. For the project, two varieties of generative topic models were used: Latent Dirichlet Allocation (LDA) and probabilistic Latent Semantic Analysis (pLSA)
Both models view documents as having a latent semantic structure of topics that can be inferred from co-occurrences of words in documents. The mathematics underlying both models are beyond the scope of this post, but on an intuitive level there are key differences between the two methods
- pLSA views topics over probability distributions over words. Each word is generated by a single topic. Topics are seen as conditionally independent across the documents that produced them. Non-Negative Matrix Factorization (NMF) is a method for finding topic clusters used for pLSA
- LDA by contrast views documents as probability distributions over topics and topics as probability distributions over words. All documents share the same collection of topics, but each document contains those topics in different proportions
The project used various packages and libraries for natural language processing within the Python programming platform to include: the Natural Language ToolKit (NLTK) for processing the data set; Sci-Kit Learn to prepare and fit the LDA and NMF models; pyLDAVis was used to display the results and t-Distributed Stochastic Neighbor Embedding (t-SNE) to map topic distances
The end-to-end project pipeline involved: data set processing; conversion of words and documents into matrix and vector space; fitting the LDA and NMF models; and then displaying the results
Processing. The book was decomposed into several documents from its constituent sections, chapters and volumes for the data set. Stopwords were removed such as common prepositions and conjunctions using the wordcloud application
- Since telepathic experiences are spontaneous and can occur at any time or place, words conveying times and locations were removed as well as ordinal and cardinal types of rankings
- Nouns or titles representing persons were removed (e.g. man, woman, Mr., Mrs., etc.); however, interpersonal relationships were preserved (i.e. family, friends, acquaintances or strangers)
Conversion. Vector transformations converted the data set into a document-term matrix for mathematical processing
- The rows of the matrix correspond to documents with columns corresponding to the frequency of a term. Count vectorizers count word frequencies. Term Frequency-Inverse Document Frequency (TF-IDF) vectorizers normalize (divide) word counts by their frequency in the documents
- Both vectorizers converted words to lower case and removed non-word expressions. The vectorizers were also instructed to look for bigrams (or words that were often used together) such as “thought-transference” and “telepathic hallucination”
Model Fit/Display. The LDA and NMF models were fitted using ten topics. Words within topics were sorted and ranked with respect to their frequency in and relevance within a topic
- The LDA model was fitted with using Count and TF-IDF vectorization and ran with a maximum of 10 iterations. LDA model results were displayed using pyLDAVis and t-SNE to map topic distances
- The NMF model was fitted with TF-IDF vectorization only and ran with a maximum of 200 iterations. NMF model results were displayed via spreadsheet
In unsupervised machine learning data is unlabeled, hence the topics produced from both models were also unlabeled. However words within topics often can be woven into a coherent theme
The first two pyLDAvis graphs provide the top 30 words and bigrams in Topics 1 and 2 using Count vectorization
- Words in Topic 1 include: “dreams”; “visions”; “impressions”; and “experiences” in connection with the “death”(s) of family members and friends. This can be considered a “presentiment” topic. This topic contained 67% of the top terms. This mirrors results from the prior wordcloud project
- Words and bigrams in Topic 2 include: “thought-transference”, “hallucination(s)”, “phantasms”, “mind(s)”, “percipients”, “agent” and “telepathy.” This can be considered a “crisis apparitions” topic. This topic contained 27% of the top terms
The third pyLDAvis graph provides the top 30 words in Topic 1 using TF-IDF vectorization
- Topic 1 combines all the aforementioned words into one topic. This can be considered a “presentiment and crisis apparitions” topic.
This topic contained 95% of the top terms, rendering all other topics comparatively insignificant in generating the documents
The spreadsheets compare LDA and NMF model runs using TF-IDF vectorizations, however, with results limited to the 10 top words. Although topic weights and distances are not available, some topics appear more meaningful and cohesive, and are likely more impactful than others
- There is considerable overlap between topics 6 and 7 in the LDA model and together they form the presentiment and crisis apparitions topic. Topics 0 and 1 in the NMF model respectively appear to correspond to presentiment and crisis apparitions topics
- The bigram “thought-transference” arises in both the LDA and NMF results and is associated with the “Society” for “Psychical” Research and the late F.W.H. “Myers” who invented the term “telepathy”
This project had an extended preparation and production pipeline. However, results clearly show that unsupervised machine learning using LDA and NMF effectively and comprehensively summarized topical content in Phantasms of the Living. Moreover, the topics approximately corresponded to the types of internalized and externalized telepathic experiences described in the book
This project demonstrates the usefulness of topic generation models for finding meaningful patterns in masses of unlabeled or unstructured data. Moreover, visualization and graphing tools are essential for fully comprehending these patterns. Elsewhere in parapsychology LDA or NMF could also be applied to survey data, case collections, web or social media content of interest.
Anaya, L. A. Comparing Latent Dirichlet Allocation and Latent Semantic Analysis as Classifiers. University of North Texas, 2011.
Blei, D. M., Ng, A. Y., & Jordan, M. I. (2003). Latent dirichlet allocation. Journal of machine Learning research, 3(Jan), 993-1022.
Christou, D. (2016). Feature extraction using Latent Dirichlet Allocation and Neural Networks: A case study on movie synopses. arXiv preprint arXiv:1604.01272.
Deerwester, S. (1988). Improving information retrieval with latent semantic indexing.
Gurney, E., Myers, F. W., & Podmore, F. (1886). Phantasms of the Living (2 vols.). London: Trübner. Reprinted at the Esalen Center.
Pedregosa, F., Varoquaux, G., Gramfort, A., Michel, V., Thirion, B., Grisel, O., … & Vanderplas, J. (2011). Scikit-learn: Machine learning in Python. Journal of machine learning research, 12(Oct), 2825-2830.
Sievert, C., & Shirley, K. (2014). LDAvis: A method for visualizing and interpreting topics. In Proceedings of the workshop on interactive language learning, visualization, and interfaces (pp. 63-70).
pyLDAvis Graph of Topic 1 (Count Vectorization) from Phantasms of the Living Corpus. (2018, Mar 24). © Maryland Paranormal Research ®. All rights reserved.
pyLDAvis Graph of Topic 2 (Count Vectorization) from Phantasms of the Living Corpus. (2018, Mar 24). © Maryland Paranormal Research ®. All rights reserved.
pyLDAvis Graph of Topic 1 (TF-IDF Vectorization) from Phantasms of the Living Corpus. (2018, Mar 24). © Maryland Paranormal Research ®. All rights reserved.
Top Words List: Latent Dirichlet Allocation (TF-IDF Vectorization) from Phantasms of the Living Corpus. (2018, Mar 24). © Maryland Paranormal Research ®. All rights reserved.
Top Words List: Non-Negative Matrix Factorization (Frobenius) from Phantasms of the Living Corpus. (2018, Mar 24). © Maryland Paranormal Research ®. All rights reserved.