Topic 15 Speed lab

*Rigor Mortis* by Richard Harris

Figure 15.1: Rigor Mortis by Richard Harris

PSYCH 490 The Reproducibility Crisis in Science

Background

Question

Prediction

We predict that the speed of conduction will be …

Between 40 and 60 m/s.

Method

  • Speed (\(s\)) = Distance (\(d\))/Time (\(t\)), then \(t=d/s\)
  • Chain of participants to make distance larger
    • If typical person ~ 1.5 m, then
    • at \(s=30\) m/s, \(t = d/s \rightarrow 1.5/30\) = 0.05 secs.
    • Helpful to have \(n\) participants, where \(n>20\) or so.

Condition 1 (ankle)

  • Squeeze (pull on) ankle
  • ankle_shoulder + shoulder_brain + brain_decide + brain_shoulder + shoulder_hand

Condition 2 (shoulder)

  • Squeeze (pull on) shoulder
  • shoulder_brain + brain_decide + brain_shoulder + shoulder_hand
  • Condition 1 - Condition 2
  • ankle_shoulder + shoulder_brain + brain_decide + brain_shoulder + shoulder_hand

Measure

  • sum(ankle_shoulder) for all participants -> Distance
  • mean(time(Condition 1)) - mean(time(Condition 2)) -> Time
  • Speed = Distance/Time

Materials

  • Stop watch (or phone app)
  • Tape measure

Decisions

  • Same hand or dominant?
  • Alternate ankle/shoulder or one condition before the other?
  • How many trials?
    • Fixed number = 3
    • When reach asymptote?
      • How decide asymptote?

Data files

  • Google Sheets Data file with body measurements
    • participant, ankleshoulder (cm)
  • Data file with reaction times
    • trial {1…n}, condition {ankle, shoulder}, time (s)

Results

Download data as CSV

  • CSV = “comma-separated value”
## File downloaded:
## • 'psych-260-bbh-203-2023-spring-distance'
##   <id: 1Kt9Fny1HKy35MUYje-8yeFahR3LiHVEdycGVqPvBhfI>
## Saved locally as:
## • 'csv/psych-260-bbh-203-2023-spring-distance.csv'
## File downloaded:
## • 'psych-260-bbh-203-2023-spring-time'
##   <id: 1ZVbAXhs3K6LFU62FfsXNpqGjsEHDXya6oRf12uhDkMU>
## Saved locally as:
## • 'csv/psych-260-bbh-203-2023-spring-time.csv'

Reimport data

## New names:
## Rows: 29 Columns: 4
## ── Column specification
## ──────────────────────────────── Delimiter: "," chr
## (1): comment dbl (2): participant.id, ankleshoulder lgl
## (1): ...3
## ℹ Use `spec()` to retrieve the full column
## specification for this data. ℹ Specify the column types
## or set `show_col_types = FALSE` to quiet this message.
## Rows: 34 Columns: 4
## ── Column specification
## ──────────────────────────────── Delimiter: "," chr
## (2): condition, comments dbl (2): trial, time
## ℹ Use `spec()` to retrieve the full column
## specification for this data. ℹ Specify the column types
## or set `show_col_types = FALSE` to quiet this message.
## • `` -> `...3`

Measuring distance

## Warning: Removed 27 rows containing non-finite values
## (`stat_bin()`).

Sum distance

##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##     119     127     131     133     140     147

The total distance is 931 cm.

Measuring time

## Warning: Removed 30 rows containing missing values
## (`geom_point()`).
## Warning: Removed 30 rows containing missing values
## (`geom_line()`).

Calculate time difference

Calculating speed

Plot time series of speeds

Discussion

  • We tested the mean speed of neural propagation in a sample of \(n\)=7 college-age adults.
  • The mean speed of neural propagation over 3 trials was 14.2903928 m/s with a range of [12.7534247, 16.625] m/s. However, the median was 13.4927536 m/s.
  • This value is not in the range we predicted. It is slower by a factor of 2-3.
  • These findings are not generally in accord with values we would expect from the literature.

Limitations

  • Small sample size of participants.
  • Timing was done by hand.
  • Inexperienced group of participants. There was only 1 warm-up trial.
  • Only did one ankle-shoulder measurement.
  • Stopwatch had beep, could have alerted participants to coming squeeze.
  • The reaction time of the person timing may have played a larger role because of the smaller number of participants.

How to replicate/extend/modify

  • Address measurement limitations.
  • Recruiting could be clearer about what’s involved.