Index of Phonetic Complexity (IPC)

The Index of Phonetic Complexity (IPC) scores each word on eight phonetic parameters and sums them into a single complexity score. Higher scores indicate phonetically more complex productions. The analysis scores both the IPA Target and IPA Actual transcripts for each aligned word, allowing target and actual complexity to be compared directly.

The implementation follows Jakielski (2022), The Index of Phonetic Complexity: At-a-Glance Scoring System, Terminology, Instructions, & Data Forms.

Data Preparation

Session data is queried by word for each IPA Target and IPA Actual tuple. Proper syllabification is required for accurate results, as several parameters depend on syllable count and structure. All participants should have unique names/identification numbers and a speaker should be assigned to all records.

Complexity Parameters

Each word is scored on eight parameters. A point is awarded each time the corresponding pattern is observed in the transcript (most parameters are counts; word shape and word length contribute at most one point each). The total IPC score is the sum of the eight parameter scores.

Table 1. IPC Parameters
Code Parameter Scoring
D Place One point for each dorsal segment.
M Manner One point for each fricative, affricate, or liquid.
V Vowels One point for each rhotic vowel.
S Word shape One point if the word ends with a consonant.
L Word length One point if the word contains three or more syllables.
P Place variegation One point each time consecutive singleton consonants (separated by a vowel) differ in place of articulation.
C Contiguous clusters One point for each consonant cluster (sequence of contiguous consonants).
T Cluster type One point for each cluster whose consonants vary in place of articulation (a heterorganic cluster).

Report Output

The report opens with a short Readme describing the analysis, followed by the IPC results table and a Breakdown section.

IPC Table

The IPC table lists one row per aligned word. The first columns identify the result; the remaining columns report each parameter for both transcripts. Following Jakielski's notation, a trailing t denotes the IPA Target score and a trailing a denotes the IPA Actual score for the same parameter.

When orthography is available for the analyzed words, an additional Orthography column appears between the identifying columns and the parameter columns, showing the orthographic form of each word.

Table 2. IPC Table Columns
Column Description
Session Corpus and session containing the result.
Speaker Participant assigned to the record.
Record # Record number within the session.
IPA Target Target transcription of the word.
IPA Actual Actual (produced) transcription of the word.
Dt, Da Place (D) score for target and actual.
Mt, Ma Manner (M) score for target and actual.
Vt, Va Vowels (V) score for target and actual.
St, Sa Word shape (S) score for target and actual.
Lt, La Word length (L) score for target and actual.
Pt, Pa Place variegation (P) score for target and actual.
Ct, Ca Contiguous clusters (C) score for target and actual.
Tt, Ta Cluster type (T) score for target and actual.
IPCt Total IPC score for the target transcript (sum of the eight target parameters).
IPCa Total IPC score for the actual transcript (sum of the eight actual parameters).
Δ Difference between the target and actual totals (IPCt − IPCa).

Breakdown

The Breakdown section lists, for each word, the individual segments and structures that contributed to each parameter score. This makes it possible to verify how a word's total complexity score was derived.

Report Outline

A sample table of contents is displayed below. Bold level elements are section headers while italic items are tables.

  • Index of Phonetic Complexity

    • Readme

    • IPC (one row per aligned word, target and actual scores for each parameter)

    • Breakdown (per-word explanation of each parameter score)