Chapter 11 Notes – Credibility & Evidence

Introduction

Chapter focuses on the interdependence of (1) you as a speaker, (2) your ideas, and (3) evidence you borrow from others.
Main through-line: The degree of trust audiences place in your points is a product of BOTH personal credibility and quality of support.
Real-world vignette: Arnold Schwarzenegger’s March 17 2022 video to Russian soldiers illustrates strategic use of ethos (friendship to Russians, personal stories) + strong evidence (stats, examples) to raise worldwide awareness of the Ukraine invasion.

Learning Outcomes (p. 249)

Explain why source credibility matters.
Apply the four credibility dimensions to shape audience perceptions.
Build a research strategy for powerful support.
Recognise and employ eight kinds of supporting material.
Demonstrate correct attribution (spoken + written).
Follow ethical guidelines when presenting evidence.

Defining & Valuing Source Credibility

You are the primary “resource” that convinces or alienates listeners.
Source credibility = audience’s perception of your qualifications, honesty, and goodwill.
NOT a possessed trait; it is granted by listeners, context-dependent, and can fluctuate pre-, during-, and post-speech.
Six self-diagnostic questions for subtle credibility cues:
• Motives? • Qualifications? • Verification of info? • Audience benefit? • Reason for chosen structure? • Omitted content/bias?
Beginning speakers may have little expertise but can project sincerity & goodwill.

Four Dimensions of Credibility

Competence: Seen as skilled, informed, authoritative.
• Improve by minimal note reliance, translating complex ideas, mastering tech, polished delivery.
• Credibility killers (John Bowe): reading slides, announcing Google searches, fillers (“uh”), jargon, hedging words.
Trustworthiness: Honest, fair, friendly.
• Show balanced info, cite reliable sources, maintain eye contact, confident tone.
• Study: Lower male pitch tends to raise perceived trust; effect weaker for females.
Dynamism: Bold, energetic, emphatic delivery.
• Conveyed via vocal variety, purposeful movement, facial expression, gestures.
• Example: Oprah Winfrey, Magic Johnson.
Common Ground: Shared understanding or experience (past, present, future).
• Build by connecting topic–audience–self triangle (Fig 11.1). • Mary Sue Coleman speech to budding scientists—future shared identity.

Tactics to Boost Credibility

Sleeper Effect: Over time, message & source separate; low-credibility messages can gain influence if argument is strong, so craft clear logic.
Self-Disclosure: Appropriate personal sharing raises connection; over-sharing feels unprofessional.
Perceived Age: Dress professionally if youthfulness undercuts expertise.
Two-Sided Presentation: Address opposing views to avoid bias perception.
Language Tone: Highly emotive partisan wording can erode credibility.
Power Types: Use referent (rapport) + expert power (knowledge) for higher competence/trust.
Delivery Cues: Fluency, gestures, moderate pace.
Evidence Interaction: $\text{Credibility}\uparrow \text{ when } (\text{Evidence}\uparrow) \land (\text{Topic Importance}\uparrow) \land (\text{Perceived Competence}\uparrow)$ (Reinard & Myers).
COVID-19 research: Experts viewed as higher in expertise, not necessarily more trustworthy; citizens’ narratives valuable for trust.

Recognising (Dis)Information

Disinformation = intentional distortion; Misinformation = unintentional inaccuracy.
Wardle’s spectrum (Fig 11.2): Satire → Misleading → Imposter → Manipulated → Fabricated.
IMVAIN Test (Stony Brook): Independent, Multiple, Verify, Authoritative/Informed, Named.

Principles for Effective Research

Refine Topic: Specific thesis prevents info overload.
Iterative Process: Research-write-research cycle.
Source Variety: Personal, interviews, journals, books, reputable web, etc.
Evaluate: Apply IMVAIN + extra criteria—clarity, relevance, currency.
Heuristics Caveat: Reputation, endorsements, consistency, expectancy violation, persuasive intent, aesthetic appeal—use as quick filters, not final judgment.

Locating Information

Personal Experience: Ask if typical, relevant, comfortable to share, ethical to disclose.
Interviews: Be upfront, prep questions, respect time, note‐take/record with permission, cite orally.
Library: Start at reference desk; know source types (Table 11.3) – academic journals, trade mags, gov docs, etc. Use multiple databases (Academic Search Premier, Lexis-Nexis, MEDLINE, Opposing Viewpoints).
Internet Strategy:
• Use multiple portals (Google Scholar, YouTube, TED, Visually).
• Boolean & advanced search operators: "exact phrase", OR, AND, –exclude, wildcard * (Table 11.4).
• Judge by server extensions (.gov, .edu, .com, etc.) (Fig 11.3).

Eight Types of Supporting Material

Examples – hypothetical vs. factual; brief vs. extended. Must be plausible & typical.
Narratives – human stories that (a) reveal missing pieces, (b) evoke emotion, (c) inspire new possibilities. E.g., Brené Brown.
Surveys – public-opinion data; vet reliability, sample size, representativeness, motive.
Testimony – lay, expert, celebrity; watch for biases & paid endorsements.
Numbers & Statistics – simplify, round, compare, pair with visuals (pie/line/bar), e.g. >!300,000 grads ~ size of Lancaster.
Analogies – compare dissimilar items for clarity; not proof on their own.
Explanations – step-by-step clarification combining multiple supports (e.g., Sanjay Gupta medical demos).
Definitions – convey meaning via description; avoid jargon (e.g., “subcutaneous hematoma = bruise under skin”).

Mixing Support Wisely

Balance forms; align with topic emotion vs. controversy; pair supports (stat + explanation); avoid over-reliance on one type.
Visual identification of sources (photo + title) increases perceived source & speaker credibility.

Citation Mechanics

Bibliographic References: Full citations in outline refs/works cited.
Internal References: Parenthetical or footnote inside outline showing source-to-content link.
Verbal Citations: In speech give (who + qualification + recency). See Table 11.5.
Cite webpage creators/orgs, not bare URLs (unless audience needs link).

Ethics in Credibility & Evidence

Honest objectives; ends must not justify unethical means.
Avoid deception, scare tactics, selective omission.
Respect impact on listeners; present full picture.
Plagiarism: Using another’s words/ideas without credit. Incremental plagiarism = failing to signal extent of quoting/paraphrasing.
AI Generated Content: If AI output forms part of speech, verify facts, rewrite in own style, and cite prompt usage per instructor/style guide.
Cultural Credibility Tips (AMA): Recognise biases, self-regulate, build common ground, observe & adapt, show empathy, flexibility, curiosity.

Developing Expertise (Beyond Classroom Credibility)

Expertise requires thousands of hours + deliberate practice + immediate feedback + continual goal setting.
Self-awareness and calibrated improvement distinguish true experts.

Chapter Take-Aways (condensed)

Credibility stems from competence, trustworthiness, dynamism, common ground.
Strong arguments + quality evidence amplify ethos.
Research is iterative; use varied, high-quality, verified sources; guard against mis/disinformation.
Eight support types each serve unique rhetorical functions—blend strategically.
Cite everything orally & in writing; ethics demand honesty, accuracy, respect for sources & audience.
Continual skill/knowledge development turns classroom credibility into professional expertise.

Useful Formulae & Notation

Credibility–Evidence Interaction (Reinard & Myers): $\text{Ethos}_{\text{perceived}} \propto f(\text{Evidence},\,\text{Topic Importance},\,\text{Speaker Competence})$
Margin of Error concept (surveys): $MoE = z\times \sqrt{\dfrac{p(1-p)}{n}}$ (not in text but implied basis for sample-size discussion).