Understanding Time Estimation

• Imagine that “Real Time” is measured by a physical clock, that ticks once a second.

• We can plot psychological time (on the ordinate) as a function of physical time (on the abscissa).

• Psychophysics! – A psychophysical function

Some Vocabulary• Veridical Perception

• “Truthful”- corresponding to a known standard.• Indexed by a physical measurement, e.g., stop watch, light meter.

• Accuracy • The extent to which an observation matches a standard.

• Indexed by PSE (mid-point) on psychometric functions.• Precision

• The fineness (“smallness”) of a measurement.• Indexed by the slope of psychometric functions.

• Representation• A correspondence between two systems, such that the state of

one system provides information about the other system.• Can be analogical or symbolic; often used in memory research.

Understanding Time Estimation

Physical Time 8th Notes

On THC Agonist:Physical time seems slow

by comparison, as ifyour psyc clock ticks quickly!

Psyc Clock 16th Notes (Leftward PSE shift)

On Music or THC Antagonist:Physical time seems fast

by comparison, as ifyour psyc clock ticks slowly!Psyc Clock Quarter Notes

(Rightward PSE shift)

Understanding Time Estimation• Theories about PSE Shifts in Time Estimation

– Internal Clock • A biological pace-maker speeds or slows• The PSE shift reflects this speeding or slowing

– Music or THC antagonist would slow the pace-maker; THC agonist would speed it up.

– Memory Bias• A sample duration is retrieved from LTM, and compared to accumulated pulses• The PSE shift reflects longer versus shorter LTM samples

– Music or THC antagonists have us draw longer sample-durations from LTM; we need more ticks to accumulate before the present stimulus matches the LTM sample. We draw briefer LTM samples under THC agonists.

– Attention• The “pulses” from the biological pace-maker accumulate• The failure to select (attend to) a pulse will lead to an under-estimate of the number of

accumulated pulses.– We almost always fail to select (fail to attend to) some of the pulses; our attention to the

number of pulses is enhanced by TCH agonists, and impaired by music or TCH antagonists.

Time Perception Schematic

Decision:

If Accumulator > LTMthen “Longer”,else “Shorter”.

Internal ClockOr

Pacemaker

(emits pulses)

Accumulator

(counts pulses)

Long TermMemory(LTM)

Time Perception Schematic

Decision:

If Accumulator > LTMthen “Longer”,else “Shorter”.

Internal ClockOr

Pacemaker

(emits pulses)

Accumulator

(counts pulses)

Long TermMemory(LTM)

Internal Clocks & PharmacologyDopamine Agonists

(Methamphetamine)Reduce PSE

(speed the clock)

Internal Clocks & Pharmacology

Dopamine Antagonists(Haloperidol)

Increase PSE(slow the clock)

Time Perception Schematic

Decision:

If Accumulator > LTMthen “Longer”,else “Shorter”.

Internal ClockOr

Pacemaker

(emits pulses)

Accumulator

(counts pulses)

Long TermMemory(LTM)

Memory Biases & PharmacologyAcyetylcholine

Agonists(Physostigmine)Reduce PSE

(by shortening “remembered

time”)

Memory Biases & Pharmacology

Acyetylcholine Antgonists

(Atropine)Increase PSE

(by lengthening “remembered

time”)

Time Perception Schematic

Decision:

If Accumulator > LTMthen “Longer”,else “Shorter”.

Internal ClockOr

Pacemaker

(emits pulses)

Accumulator

(counts pulses)

Long TermMemory(LTM)

Attn

Attention & Time Estimation• Theories about Attention & Time Estimation

– Attentional Gate Latency• There is a delay (latency) in the time at which the participant selects

(attends to) pulses.• The PSE is increased because the first few internal-clock-pulses do not

“register”. – Predicts that the PSE-shift will be the same absolute size regardless of the

interval to be timed.

– Attentional Flickering• The participant’s selection of pulses waxes and wanes, missing some

pulses across the entire interval to be timed. • The PSE is increased because a fraction of the internal-clock-pulses do

not “register”. – Predicts that the PSE-shift will be proportional to the interval to be timed.